frontline pulmonary procedures and interventions

Frontline Pulmonary Procedures and Interventions

WelcomeWelcome to the Snowdrift Frontline TreatmentMonographs. The authors welcome you to this series ofmonographs that aim to disseminate worldwide newknowledge about common pulmonary disorders. Weoffer our messages to anyone who will find them usefulin the diagnosis and treatment of the many pulmonarydisorders that continue to plague mankind around theworld. We invite you to download these monographsand use them in your teaching and practice of medicine.We feel a fraternal connection to all practitioners whoserve the suffering. We hope that we can move towardthe prevention of disease as an alternative to prematuremorbidity and mortality.

The Authors.

Mission StatementThe Snowdrift Pulmonary Conference is a not-for-profitcorporation that is dedicated to the dissemination ofknowledge about the lungs and lung diseases.Composed of both private practice pulmonologists andacademicians, the conferees have launched a consumer-oriented program for primary care practitioners and thepatients they serve. As a result, the following conciseand authoritative monographs have been written.

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Books in the Frontline Series

Frontline Treatment of COPD, 2000*

Frontline Treatment of Asthma, 1997

Frontline Treatment of Common RespiratoryInfections, 1998

Frontline Treatment of Venous Thromboembolism,1999

Frontline Assessment of Common PulmonaryPresentations, 2000*

Frontline Assessment of Lung Cancer and Occupational Pulmonary Diseases, 2001*

Frontline Pulmonary Procedures and Interventions,2001*

Frontline Cardiopulmonary Topics / Dyspnea, 2001*

Frontline Advice for COPD Patients, 2002*

* Available on the web for downloading

A Monograph for Primary Care Physicians

FrontlinePulmonaryProceduresandInterventionsThe Authors

David D. Collins, md Winston-Salem, NC

Dennis E. Doherty, md Lexington, KY

J. Roy Duke, Jr., md West Palm Beach, FL

James T. Good, Jr., md Denver, CO

Leonard D. Hudson, md Seattle, WA

Michael D. Iseman, md* Denver, CO

Thomas L. Petty, md* Denver, CO

Charles H. Scoggin, md Boulder,CO

*Co-Editors

iii

Copyright ©The SnowdriftPulmonaryFoundation, Inc.2001

The SnowdriftPulmonaryConference is afunction of TheSnowdrift PulmonaryFoundation, Inc.A NonprofitCorporation

The SnowdriftPulmonaryConference,899 Logan,Denver, CO 80203

All rights reserved.No part of this bookto which theSnowdrift copyrightlegally applies may bereproduced or copiedin any form or by anymeans withoutwritten permission ofThe SnowdriftPulmonaryFoundation, Inc.Printed and bound inthe United States ofAmerica.

ISBN 0-9671809-6-1

Contents Preface / ix

Pearls/ 1

A. Spirometry / 4

B. Lung Volume Studies / 17

C. Arterial Blood Gases (abg’s) and Pulse Oximetry / 28

D. Chest X-rays / 41

E. Special Thoracic Imaging Techniques / 50

F. Ultrasound Procedures / 57

G. Cardiac Catheterization / 63

H. Sputum Studies / 69

I. Bronchoscopy / 75

J. Sleep Studies / 80

K. Mechanical Ventilatory Support and Weaning From Mechanical Ventilation / 93

L. Internet Applications / 104

M. Medicolegal Issues / 123

N. The National Lung Health Education Program(nlhep) / 128

O. The Snowdrift Pulmonary Conferences / 129

P. Postscript and Biographical Sketches of Authors / 131

Index / 143

Frontline Pulmonary Procedures and Interventionsv

Tables

vi

Table 1. / page 7Common Obstructive Ventilatory Disorders

Table 2. / page 7Common Restrictive Ventilatory Disorders

Table 3. / page 8Diseases with High Risk Associated with SpirometricAbnormalities

Table 4. / page 8When to Perform Spirometry

Table 5. / page 18Causes of Restrictive Lung Disease

Table 6. / page 24Factors Affecting the Diffusing Capacity

Table 7. / page 34Criteria of Acidemia and Alkalemia

Table 8. / page 34Major Causes of Metabolic Acidosis According toMechanism and Anion Gap (ag)

Table 9. / page 38Major Clinical Applications of Pulse Oximetry

Table 10. / page 38Limitations of Pulse Oximetry

Table 11. / page 42Diagnosis from Patterns and Evolution of Infiltrates

Table 12. / page 47Mediastinal Masses by Location

Table 13. / page 51Imaging Techniques

Table 14. / page 58Echocardiographic Techniques and Their Advantages

Table 15. / page 76Overall Indications for Bronchoscopy

Table 16. / page 82Patients at Risk for Sleep Apnea


Table 17. / page 82The Epworth Sleepiness Scale

Table 18. / page 86Diagnostic Criteria for the Obstructive Sleep Apnea-Hypopnea Syndrome (osahs)

Table 19. / page 88Treatment of Sleep Apnea

Table 20. / page 98Complications of Mechanical Ventilation

Table 21. / page 106Important Events in Early Internet Development

Table 22. / page 107Glossary of Internet Terms

Table 23. / page 109Frequently Visited Consumer Healthcare Websites

Table 24. / page 110Consumer-oriented Pulmonary Websites

Table 25. / page 113Questions to Ask When Evaluating Internet Healthcare Sites

Table 26. / page 114Pulmonary Websites for Physicians

Table 27. / page 118Issues to Consider in Using e-mail With Patients

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viii

Figures Figure 1. / page 9Normal Flow-volume

Figure 2. / page 9Mild Obstruction

Figure 3. / page 10Moderate Obstruction

Figure 4. / page 10Severe Obstruction

Figure 5. / page 11Moderate Restriction

Figure 6. / page 11Severe Restriction

Figure 7. / page 12Algorithm for Interpreting Spirometry Results

Figure 8. / page 20Lung Volumes

Figure 9. / page 22Interpretation of Pulmonary Function Tests

Figure 10. / page 32Ventilation-Perfusion (v· /q· )Mismatch and Intrapulmonary Shunt

Figure 11. / page 36The Oxyhemoglobin Dissociation Curve

Figure 12. / page 66Measuring Pulmonary Artery (pa) Pressure

Preface This is the seventh monograph in the Frontlineseries. It is written for frontline physicians whoencounter a wide array of common pulmonary

problems in daily practice. Each Section brieflydescribes the indications, uses, misuses, and abuses ofvarious techniques and procedures that may beemployed by frontline physicians. In today's economicclimate, it is wise for both frontline practitioners andconsultants to develop pragmatic approaches todiagnosis and treatment. Basic diagnostic techniquessuch as spirometry, arterial blood gases (abg’s) andchest x-rays are appropriately ordered by all physiciansinvolved in either primary or specialty care. But, otherprocedures and therapeutic interventions generally arebest utilized in conjunction with a pulmonologist orother specialists.

The purpose of this monograph is to update thefrontline, primary care physician on a wide variety ofspecialized procedures, their applications, and how bestto employ them. Although medicolegal implicationsmay be a consideration in the selection of proceduresand interventions, the primary consideration is what isappropriate for the optimal care of the patient.

In keeping with the statements made in our previousmonographs, we aim to provide primary carepractitioners with both contemporary and conciseinformation about pulmonary procedures that shouldbe of value in daily practice. The Sections in thismonograph were written by both academic and privatepracticing pulmonologists, using a consensus format.We hope that you will profit from the clinical andacademic experience compiled in this monograph and that this information will assist you in the care of your patients. ■

The Authors

Frontline Pulmonary Procedures and Interventionsix

1

Pearls ● Pulse oximetry may overestimate the true arterialoxygen saturation when carboxyhemoglobinemia ispresent, including that seen in heavy cigarettesmokers.

● Pulse oximetry alone is inadequate in the initialassessment of patients with acute respiratory dis-tress due to asthma or exacerbations of chronicobstructive pulmonary disease (copd). Arterialblood gases (abg’s) are needed to determine adequacy of ventilation.

● Spirometry can now be performed in the primarycare practitioner’s office using widely available,inexpensive, user-friendly, portable, and accurateoffice spirometers.

● Fully inflated normal lungs empty in six seconds orless. This is why the fev6 can be used as a surrogatemarker of fvc.

● A pulmonary artery (pa), balloon-tipped cathetershould be removed when therapeutic decisions areno longer being made on the basis of data providedby the catheter.

● Before any protocol is initiated to wean a patientfrom the ventilator, the practitioner should firstdetermine whether the patient can simply beextubated. A 30-minute trial on oxygen deliveredby T-piece will be helpful.

● Non-invasive ventilation techniques, such as bi-levelpositive airway pressure (bipap), may be effective ineliminating the need for intubation and mechanicalventilation in some patients with respiratoryinsufficiency.

● Attention to the patient being weaned frommechanical ventilation is more important than themethod being used.

● All who snore do not have obstructive sleep apnea-hypopnea syndrome (osahs); but, all who haveosahs snore.

● To achieve high rates of adherence (compliance)with nasal continuous positive airway pressure(cpap) for patients with sleep apnea, one mustachieve proper fit of the nasal mask or pillows.

● A routine chest radiograph should generally beobtained before specialized thoracic imaging studiesare obtained.

● The ventilation-perfusion (v· /q· ), lung scan is the initial study of choice for the diagnosis of pulmonary emboli (pe) in patients with a normalchest radiograph.

● Sputum cytology studies have a high yield inpatients with large, central tumors on chest x-rays.However, they also are highly useful in the earlydetection of bronchogenic carcinomas in patientswith normal chest x-rays but smoking-inducedchronic airflow obstruction.

● Flexible fibrotic bronchoscopy should be performedpromptly on patients with recurrent hemoptysis,localized inspiratory wheezing, and/or unresolvingpulmonary infiltrates.

● Community-acquired pneumonia (cap) can betreated empirically in most adults. However, forpatients with complicating diseases or special riskfactors, an aggressive search for the etiologic agentis indicated.

(continued)

Frontline Pulmonary Procedures and Interventions2

3

● Interstitial lung disease may be mistaken forrecurrent pneumonia or heart failure on chestradiography.

● Pneumonia involving bullous lesions in emphysemapatients can mimic lung abscesses or cavities.

● e-mail is not like using the telephone. We must consider both confidentiality and the risk of misinterpretation before using e-mail to communi-cate with patients.

● Physicians can help their patients seek informationon the Internet by being proactive “navigators” todirect them to credible, responsible sources ofinformation. ■

Pearls (continued)


A. Spirometry

The Basis ofPulmonaryMechanics

Spirometry is one of the most useful, yetunderutilized diagnostic techniques in all ofmedicine. Although introduced in the mid-

1800’s by John Hutchinson, a surgeon, spirometry has been reluctantly accepted in the day-to-day practiceof both general and specialty medicine. This hesitancyseems related to misconceptions and poorunderstanding of the technique, which continue tocloud its value, and the expense and complexity ofpreviously-used instruments.

Spirometry primarily measures expiratory airflow fromfully inflated lungs. Spirometry can also measureinspiratory airflow (See below).

To take a large breath, individuals must create anegative pressure in the pleural space. This is achievedby the descent of the diaphragms and enlargement ofthe rib cage by the action of the thoracic and neckmuscles. This negative pressure creates the force forairflow to fill the lungs to the point of maximuminflation. Expiratory airflow may be passive or, for thepurposes of testing, may be initiated by forceful effort.Much of the expiratory airflow is a function of theelastic recoil of the lung tissue and the conductance ofair through small and large airways. Following theinitiation of forced exhalation, the alveoli empty intosmall airways, and small airways empty into largeairways. As the air rushes out of the lungs through themouth, the airflow is recorded by a spirometer. Theforced expiratory volume in one second (fev1), is a flowtest. The entire forced expiration (forced vital capacityor fvc) is a volume test. Recently, new terminology hasbeen added to simple spirometry. Since normal lungsempty in six seconds, a recent convention hassubstituted the fev6 (also known as fev6 for the fvc) tomake testing more convenient for both the patient andthe spirometer technician. Normally, the patient expiresapproximately 70% of his/her vital capacity in the firstsecond. Thus, the normal ratio of the fev1 to fvc is

4

5

Obstructive LungDiseases

RestrictiveVentilatoryDisorders

Inspiratory FlowDisorders

70% or more. The same is true for fev1/fev6 A lowratio of fev1 to fvc identifies patients who are at riskfor accelerated losses in absolute fev1 over time.

Table 1 lists the common diseases characterized byexpiratory airflow obstruction. In obstructive diseasesthe fev1/fvc (fev6 ) is less than 70% and the absolutefev1 is usually less than 80% of predicted. Examples ofthe normal volume-time and flow-volume curves arepresented in Figure 1. Both expressions present thesame data, but in a different format. The advantage ofthe volume-time convention is that the fev1 and fvccan be directly visualized. The advantage of the flow-volume display is that the peak flow can be directlyvisualized as an indication of a good expiratory effort.Clinicians should be comfortable using either form ofexpiratory airflow recording. Examples of mild,moderate and severe expiratory airflow obstruction areshown in Figures 2, 3 and 4.

In restrictive ventilatory disorders, the lungs are “stiff”which results in increased elastic recoil pressure. Thistypically limits the amount of air drawn into the lungs,but produces higher than normal expiratory flowratios. Thus, the fvc (or fev6) is less than 80% ofpredicted and the ratio of fev1/ fvc is usually muchhigher than 70%, often 80%, 90% or even more. Examples of moderate and severe ventilatoryrestriction are presented in Figures 5 and 6.The common restrictive ventilatory defects are listed in Table 2.

Most respiratory disorders result in disturbance ofexpiratory airflow. By contrast, disorders such as vocalcord dysfunction, tracheal tumors or tracheal stenosisresult in impaired inspiratory flow. This may not bedetected on simple spirometry, but requires specializedstudies. When such conditions are believed to bepresent, consultation with a pulmonologist and/or anotolaryngologist is advised.

A. Spirometry (continued)

A simple algorithm for identifying restrictive andobstructive ventilatory disorders is shown in Figure 7.Lung volume measurements may be needed toadequately evaluate restrictive pulmonary disease state(See Section B).

It should be stressed that spirometric measurements donot make a clinical diagnosis. Rather, spirometricabnormalities indicate a physiological impairment fromwhich the physician must derive the diagnosis. It hasbeen traditional to label reversible airflow obstructionas asthma and irreversible airflow disorders as chronicobstructive pulmonary disease (copd). Overlaps arecommon. Responses to therapy, including the use ofbronchoactive drugs, i.e., bronchodilators,corticosteroids and other new agents, will helpdetermine how to establish the diagnosis of reversibilityor irreversibility. Consultation is advised in complexsituations.

Spirometric abnormalities are predictive of increasedrisk of many diseases and all cause mortality. Themajor diseases associated with spirometricabnormalities are listed in Table 3. Note that not onlylung diseases such as lung cancer or copd are included,but also ischemic heart disease and cerebrovascularaccidents are associated prognostically withspirometric dysfunction.

No doctor would prescribe antihypertensive agentswithout blood pressure measurements, antiarrhythmicswithout evidence of cardiac rhythm disturbances,insulin without measurements of blood sugar orCoumadin® without prothrombin measurements.Analogously, it is not appropriate to treat obstructiveor restrictive lung diseases without spirometry.Spirometry is as fundamental to the diagnosis andmanagement of pulmonary diseases as thesphygmomanometer is to the assessment andmanagement of hypertension.(continued)


Algorithm forInterpretation ofSpirometry

Spirometry andClinicalDiagnosis

Prognostic Value

Conclusion

7 A. Spirometry (continued)

Table 1 Common Obstructive Ventilatory Disorders

Asthma

Asthmatic bronchitis

Chronic obstructive bronchitis

Chronic obstructive pulmonary disease (COPD)1

Cystic fibrosis

Emphysema

1 COPD is a generic term that includes asthmatic bronchitis, chronic bronchitis, bronchiectasis andemphysema. These states commonly overlap.

Source: Petty TL. Simple Spirometry for Frontline Practitioners. Fairfield, NJ: Laennec Publishing, Inc.;1998. p 18.

Table 2 Common Restrictive Ventilatory Disorders

Idiopathic fibrosing alveolitis

Interstitial pneumonitis and fibrosis1

Fibrotic residue of disseminated granulomas (e.g., tuberculosis, histoplasmosis)

Sarcoidosis

Thoracic deformities

Congestive heart failure

Neuromuscular disorders

1. May be associated with drug reactions, e.g., bleomycin (Blenoxane), or occupational exposures, e.g.,asbestosis, or collagen vascular diseases, e.g., rheumatoid arthritis.

Adapted from: Petty TL. Simple Spirometry for Frontline Practitioners. Fairfield, NJ: Laennec Publishing,Inc.; 1998. p 18.


Table 3 Diseases with High Risk Associated with Spirometric Abnormalities

Disease State Reference

Heart attack J Chron Dis 1987;40:849-856.Am J Respir Crit Care Med 1995;151:390-398.

Lung cancer Ann Intern Med 1986;105:503-507.Am Rev Respir Dis 1990;141:613-617.

Stroke BMJ 1991;302:84-87.

COPD Am Rev Respir Dis 1987;135:788-793.

All cause mortality Am J Epidemiol 1994;140:398-408.

Table 4 When to Perform Spirometry

In all smokers age 45 and over

In patients of any age with

dyspnea

cough

wheeze

mucus hypersecretion

Source: Ferguson GT, Enright PL, Buist AS, et al. Office spirometry for lung health assessment in adults:A consensus statement from the National Lung Health Education Program. Chest 2000;117:1147, 1152.


Figure 1 Normal flow-volume Figure 2 Mild Obstruction

Normal Flow-volume (A) and volume-time (B)curves in a normal individual. LLN indicates lowerlimit of normal. Notice that the expiratory time canbe visualized from the volume-time curve, but thepeak flow can only be visualized from the flow-volume curve. Thus, both curves are useful. Adapted from: Enright PL, Hyatt PE: Office spirometry (A practical guide to the selectionand use of spirometers). Lea & Febiger,Philadelphia, 1987.

Mild Obstruction Flow-volume (A) and volume-time (B) curves in a patient with mild airflowobstruction.

Flo

w,

L/se

cV

olum

e, L

A

B

Exhaled flow-volume, L(BTPS)

Volume-time, sec

Result5.003.7976%

LLN(3.88)(3.12)(71%)

FEV1

FVCFEV1

FEV1/ FVC%

Flo

w,

L/se

cV

olum

e, L

A

B


Volume-time, sec

FEV1

FVCFEV1

FEV1/ FVC%

Result4.602.7459%

LLN(3.88)(3.12)(71%)


Figure 3 Moderate Obstruction Figure 4 Severe Obstruction

Moderate Obstruction Flow-volume (A) andvolume-time (B) curves in a patient with moderateairflow obstruction.

Severe Obstruction Flow-volume (A) and volume-time (B) curves in a patient with advanced airflowobstruction from emphysema.

Flo

w,

L/se

cV

olum

e, L

A

B


Volume-time, sec

FEV1

FVCFEV1

FEV1/ FVC%

Result3.612.0557%

LLN(3.88)(3.12)(71%)

Volume-time, secB

Vol

ume,

L

Exhaled flow-volume, L(BTPS)A

Flo

w,

L/se

cFEV1

FVCFEV1

FEV1/ FVC%

Result3.200.8928%

LLN(3.88)(3.12)(71%)

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11

Figure 5 Moderate Restriction Figure 6 Severe Restriction


Moderate Restriction Flow-volume (A) and volume-time (B) curves in a patient with amoderate restrictive ventilatory disorder. Noticethat FEV1/FVC is nearly 90%. A ratio this high maysuggest a restrictive disorder; however, normalindividuals can often empty most of the lung in onesecond.

Severe Restriction Flow-volume (A) and time-volume (B) curves in a patient with a severerestrictive ventilatory disease due to idiopathicpulmonary fibrosis. Notice the FEV1 /FVC is 99%

Volume-time, sec Volume-time, secB B

Vol

ume,

L

Vol

ume,

L

Exhaled flow-volume, L(BTPS) Exhaled flow-volume, L(BTPS)A A

Flo

w,

L/se

c

Flo

w,

L/se

c

FEV1

FEV1

FVCFEV1

FEV1/ FVC%

Result3.202.6489%

LLN(3.88)(3.12)(71%)

FVCFEV1

FEV1/ FVC%

Result1.801.7899%

LLN(3.88)(3.12)(71%)

Figure 7 Alogorithm for Interpreting Spirometry Results


Algorithm for interpretingspirometry results. COPD (chronic obstructivepulmonary disease); FEV1 (forced expiratoryvolume in one second);FVC (forced vitalcapacity).Source: Petty TL. Simplespirometry for frontlinepractitioners. LaennecPublishing, Inc. Fairfield,NJ 1998 p 19.

1. If clinical correlation is present.2. Some COPD may have a reversible component.

Acceptable Spirometry

Is FEV1/ FVC ratio low?

Is FVC low?

Is FVC low?

Yes No

Yes

Yes

Yes

No

No

No

Hyper-inflation versus

combined defect

Restrictive defect

Pure obstruction

Obstructive Defect

Further

testing1

Reversible with useof beta

agonist?

Further testing

(lung volumemeasure-ments)

Asthma1

COPD1,2

Normal spirometry

results

12


According to the Spirometry Committee of the NationalLung Health Education Program (nlhep), all smokersage 45 and over, and individuals of any age withsymptoms of cough, dyspnea, mucus hypersecretion orwheeze should have spirometry (See Table 4). Thenlhep aims to identify copd and related disorders intheir early stages in primary care physicians’ offices.There are fewer than 10,000 board certifiedpulmonologists in North America, but there areapproximately 220,000 primary care providers. Everyyear these professionals see at least 70% of the45,000,000 smokers in the United States for somemedical problem. All smokers should be stronglyadvised to stop. Spirometric abnormalities may bepersuasive evidence to assist in this difficult task.

Early identification of patients with spirometricabnormalities not only indicates an increased risk of thefour common causes of death noted above, it alsosignals increases in all cause mortality. Smokers withspirometric abnormalities have an urgent need to stop.Spirometry will not only guide responses to therapy inboth obstructive and restrictive disorders, but will helpto predict the patient's long-term progress. ■


Early identification of patients withspirometricabnormalities notonly indicates anincreased risk of thefour common causesof death noted inthe text, it also signalsincreases in all causemortality.

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15

References

Anthonisen NR, Connett JE, Kiley JP, et al. Effects ofsmoking intervention and the use of an inhaledanticholinergic bronchodilator on the rate of decline offev1. The Lung Health Study. JAMA 1994;272:1497-1505. This landmark study showed an improvement infev1 following stopping smoking, and a reduced rate ofdecline in fev1 over five years. Continuing smokers lostfev1 at a much faster rate.

Burrows B, Knudson RJ, Camilli AE, et al. The “horse-racing effect” and predicting decline in forcedexpiratory volume in one second from screeningspirometry. Am Rev Respir Dis 1987;135:788-793. Thisstudy demonstrated that a rapid rate of decline in fev1

was predictive of premature mortality from copd.

Ferguson GT, Enright PL, Buist AS, et al. Officespirometry for lung health assessment in adults: Aconsensus statement from the National Lung HealthEducation Program. Chest 2000;117:1146-1161. Thisnlhep consensus statement recommends testing allsmokers over the age of 45, and anyone with dyspnea,cough, mucus hypersecretion or wheeze.

Hankinson JL, Odencrantz JR, Fedan KB. Spirometricreference values from a sample of the general U.S.Population. Am J Respir Crit Care Med 1999;159:179-187. This article provides normal spriometric valuesfrom the largest population thus far. It gives evidencethat the fev6 is an excellent surrogate for the fvc.

Lange P, Nyboe J, Appleyard M, et al. Ventilatoryfunction and chronic mucus hypersecretion aspredictors of death from lung cancer. Am Rev RespirDis 1990;141:613-617. This is one of several studieswhich documents on an increased prevalence of lungcancer in smokers with airflow obstruction.(continued)



Rodriguez BL, Masaki K, Burchfiel C, et al. Pulmonaryfunction decline and 17-year total mortality: TheHonolulu Heart Program. Am J Epidemiol1994;140:398-408. This report relates abnormal lungfunction to premature deaths from all causes.

Skillrud DM, Offord KP, Miller RD. Higher risk of lungcancer in chronic obstructive pulmonary disease. Aprospective, matched, controlled study. Ann Intern Med1986;105:503-507. This study documents a muchhigher prevalence of lung cancer in smokers withairflow obstruction compared with smokers of equalintensity, the same occupational risk and family historyof lung cancer who have normal airflow.

Sorlie P, Lakatos E, Kannel WB, et al. Influence ofcigarette smoking on lung function at baseline and at follow-up in 14 years: The Framingham Study. J Chron Dis 1987;40:849-856. This study demonstratesa relationship between spirometric abnormalities andpremature death from coronary artery disease.

Strachan DP. Ventilatory function as a predictor of fatalstroke. BMJ 1991;302:84-87. This summary documentsan increased risk of stroke in smokers with airflowobstruction.

Tockman MS, Pearson JD, Fleg JL, et al. Rapid declinein fev1. A new risk factor for coronary heart diseasemortality. Am J Respir Crit Care Med 1995;151:390-398. This article shows evidence that rapid decline offev1 is predictive of excess risk of death from coronaryartery disease.

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17

B. Lung VolumeStudies

Introduction

Methods ofMeasuring LungVolumes

Measurement of lung volumes plays an integralrole in the evaluation of patients with knownor suspected lung disease. As discussed in the

previous Section, spirometry can establish the presenceor absence of obstructive pulmonary dysfunction.Spirometry may also document restrictive pulmonarydysfunction characterized by a reduction in total lungvolumes, but frequently additional techniques tomeasure total lung volumes are needed. Restrictivedysfunction is defined as a reduction of the total lungcapacity (tlc) and is associated with a wide variety ofdisorders involving the lung parenchyma, the thorax,the diaphragms and neuromuscular diseases (See Table5). Lung volumes can be measured by a variety ofmethods. The two most commonly used are the inertgas dilution and the body plethysmography techniques,which are discussed below.

Inert Gas Dilution Method: In this method, an inert gas,usually helium, is inspired from a closed-circuitspirometer. After a period of time, the concentration ofhelium equilibrates between the spirometer and thelungs. Oxygen is added to the system and carbondioxide is removed. The inert gas is neither absorbednor metabolized. The frc is then calculated and the rvis determined by subtracting the frc from the erv.

Problems with this method include the following. Inpatients with chronic obstructive pulmonary disease(copd), the frc may be underestimated due to unevenventilation and the presence of air spaces that do notcommunicate with the bronchial tree (e.g., bullae). Agas leak in the system will falsely increase the rv. Theinability of the patient to maintain a tight seal on themouthpiece connected to the spirometer is a commoncause of erroneously high values for the rv.

Body Plethysmography Method: In this method, thesubject sits in an airtight chamber and performsmaneuvers to expand and compress the lung volumes. (continued)


Table 5 Causes of Restrictive Lung Disease

Pulmonary

Idiopathic pulmonary fibrosis

Lung resection

Atelectasis

Pneumonia

Hypersensitivity pneumonia

Congestive heart failure (can have a restrictive

and obstructive pattern)

Alveolar proteinosis

Bronchiolitis obliterans with organizing pneumonia (BOOP)

Pneumoconiosis (coal workers’ pneumoconiosis, asbestosis,

chronic beryllium disease)

Extrapulmonary

Pleural effusion

Pneumothorax

Pregnancy

Ascites

Morbid obesity

Chest Wall

Kyphoscoliosis

Ankylosing spondylitis

Neuromuscular

Guillain Barré syndrome

Myasthenia gravis

Amyotrophic lateral sclerosis

Poliomyelitis

Diaphragmatic paralysis

Adapted from: Hyatt RE, Scanlon PD, Nakamura M. Interpretation ofPulmonary Function Tests: A Practical Guide. Philadelphia, PA: LippincottWilliams & Wilkins; 1997. p107.

18

B. Lung Volume Studies (continued)

Lung VolumesDefinitions

DiffusingCapacity(Transfer Factor)2

By applying Boyle’s law1 lung volumes are calculated.Body plethysmography gives more accuratemeasurements of lung volumes than the inert gasmethod in patients with copd. Indeed, the tlc may be found to be substantially greater when measured by this technique. Another advantage of bodyplethysmography is that several measurements can be done over a few minutes. Occasionally, however,claustrophobic patients may not be able to tolerate the confines of the plethysmograph chamber.

(See Figure 8)1. Total lung capacity (tlc): Total volume of gas

in the lungs after maximal inspiration.2. Vital capacity (vc): The volume of gas expired

during a maximal effort.3. Residual volume (rv): The amount of gas

remaining in the lungs after maximalexpiration.

4. Functional residual capacity (frc): Theamount of gas remaining in the lungs at theend of a quiet expiration.

5. Inspiratory capacity (ic): The maximal amountof gas inspirable from frc.

6. Inspiratory reserve volume (irv): The maximalamount of gas inspirable after the end of aquiet inspiration.

7. Tidal volume (tv): The amount of gas movingin and out of the lungs with each respiratorycycle.

8. Expiratory reserve volume (erv): Theadditional volume of gas that can be expired atthe end of a quiet expiration.

Diffusion is the process of transferring oxygenmolecules from the alveolus, through the alveolar-capillary membrane, then across the red blood cell wall

1 Boyle’s law states that the product of the pressure (P) and volume (V)(PV)of a gas is constant under constant temperature (isothermal) conditions.

2 The term carbon monoxide diffusing capacity (DLco) is used in NorthAmerica. It is called the transfer factor in Europe.

19

Figure 8 Lung Volumes


Source: Comroe JH, Jr., Forster RE, Dubois AB, et al. The Lung: Clinical Physiology and PulmonaryFunction Tests. 2nd ed. Chicago, IL: Year Book Medical Publishers, Inc.; 1962. p 8.

TLC

VC

RV

IC

FRC

TV

ERV

RV

IRV

Total Lung Capacity (TLC)

Vital Capacity (VC)

Residual Volume (RV)

Functional Residual Capacity (FRC)

Inspiratory Capacity (IC)

Inspiratory Reserve Volume (IRV)

Tidal Volume (TV)

Expiratory Reserve Volume (ERV)

20

21 B. Lung Volume Studies (continued)

where it binds to hemoglobin. Quantifying this processin the pulmonary function laboratory is an importantelement of evaluating a patient with known orsuspected pulmonary disease, and in particular, thosecomplaining of dyspnea. Generally, the diffusingcapacity is conceptualized as a representation of theeffective surface or interface between the alveoli andthe capillary units of the lung. Multiple factorsinfluence the diffusion capacity, including the numberof functioning alveolar-capillary units, the volume ofblood in the pulmonary capillaries, matching ofventilation to perfusion and the thickness of thealveolar-capillary membrane.

In most clinical pulmonary function laboratories, thediffusing capacity is determined using the single breathcarbon monoxide method. Carbon monoxide has astrong affinity for hemoglobin and the diffusingcapacity for carbon monoxide (dlco) is a reliablesurrogate for oxygen transfer. In this test, the subjectmaximally inhales a gas mixture containing a traceconcentration of carbon monoxide and a suitableconcentration of helium from a closed system, andholds his or her breath for 10 seconds. The gas isexpired into a spirometer and is analyzed for theconcentration of carbon monoxide and helium. Heliumis used to calculate the lung volume. The changes incarbon monoxide concentration between inspirationand expiration estimates the amount of carbonmonoxide transferred to the red blood cells. The resultsare expressed as ml/min/mmHg. The normal value isusually in the range of 20 ml to 30 ml/min/mmHg.Corrections are made for the subject’s hemoglobinlevel. Subjects with small lung volumes and normaldiffusion can have a reduced dlco. Compensation forthis can be made on the basis of the ratio of thediffusing capacity to alveolar volume (d/va). In normalsubjects, the tlc approximates the alveolar volume(va) measured during the dlco measurement.(continued)

Methods ofMeasuring theDiffusing Capacity

Figure 9 Interpretation of Pulmonary Function Tests


Condition FVC FEV 1 FEV1/FVC TLC RV RV/TLC DLco D/VA

COPD N to�* � � N to � � � N� N�

Emphysema N to�* � � � � � � �

Asthma N to� N to� � N to� � � N to� N to �

IPF � � N to � � � N � �

PE N to� N to� N N to� N to� N � �

CHF N to� N to� N � N to� N to� � or � �

Polycythemia N N N N to� N N � �

N.M. N to� N to� N N to� N to� N N to� N

*Only in early stages of disease. In later stages of both, FVC decreases.

COPD=Chronic obstructive pulmonary diseaseIPF=Idiopathic pulmonary fibrosisPE=Pulmonary embolusCHF=Congestive heart failureN.M =NeuromuscularN =Normal�=Increased�=Decreased

Adapted from: Hyatt RE, Scanlon PD, Nakamura M. Interpretation ofPulmonary Function Tests: A Practical Guide. Philadelphia, PA: LippincottWilliams & Wilkins; 1997. pp104-105.

22


Interpretation ofPulmonaryFunction Tests

PharmacologicBroncho-provocationChallenge (PBC)

Normal values for the dlco are influenced by age, sizeand sex. Classically, the diffusion capacity is reduced inpatients with emphysema, interstitial lung disease andpulmonary vascular diseases. It is increased inpolycythemia, intra-alveolar hemorrhage such as is seen in Goodpasture’s syndrome, the supine positionand after exercise (See Figure 9). For a morecomprehensive list of diseases affecting the diffusingcapacity, refer to Table 6.

Measurement of the dlco is especially helpful inevaluating the dyspnec patient with normal spirometry,lung volumes and normal chest x-rays. Diminishingdlco in this setting may suggest to the clinician suchconditions as primary pulmonary hypertension,recurrent pulmonary emboli (pe) or obstructivevasculopathy. The diffusing capacity is also useful infollowing the course and response to treatment ofsarcoidosis, idiopathic pulmonary fibrosis and otherinterstitial diseases.

In 1962, the American Thoracic Society defined asthmaas a disease characterized by an increasedresponsiveness of the trachea and bronchi to variousstimuli, and manifested by a widespread narrowing ofthe airways that changes spontaneously or as a result oftherapy. Bronchial hyperresponsiveness is the hallmarkof asthma and can be demonstrated in virtually allpatients with asthma. A wide variety of stimuli canprovoke bronchial constriction including exposure tocold air, allergens, smoke, chemicals, dust and exercise.In the majority of patients, the history and physicalexamination and pulmonary function testing providessufficient evidence to support a diagnosis of asthma.However, in patients presenting with chronic cough orunexplained dyspnea, routine pulmonary functionstudies can be normal and pharmacologicbronchoprovocation challenge (pbc) can documentbronchial hyperreactivity. (continued)

Table 6 Factors Affecting the Diffusing Capacity

Increased Diffusing Capacity

Polycythemia rubra vera

Obesity

Pregnancy (first trimester)

Intra-alveolar hemorrhage (Goodpasture’s Syndrome)

Left to right intra-cardiac shunt

Supine posture

After exercise

Decreased Diffusing Capacity

Emphysema

Lung resection

Pulmonary emboli (PE)

Primary pulmonary hypertension

Anemia

Idiopathic pulmonary fibrosis

Sarcoidosis

Asbestosis

Alveolar proteinosis

Hypersensitivity pneumonia

Congestive heart failure (CHF)

Obstructive vasculopathy

Collagen vascular diseases

Drug induced interstitial lung disease (methotrexate,

amiodarone, nitrofurantoins, bleomycin)

Pregnancy, late

Carboxyhemoglobinemia (related to smoking)

Adapted from: Hyatt RE, Scanlon PD, Nakamura M. Interpretation ofPulmonary Function Tests: A Practical Guide. Philadelphia, PA: LippincottWilliams & Wilkins: 1997. p 45.



Indications forPharmacologicBroncho-provocationTesting

Contra-indications forPharmacologicBroncho-provocationTesting

PBC TestingMethods

1. To rule in or out asthma or to determine the severity of asthma in patients with chroniccough but normal spirometry,

2. Unexplained chest tightness, dyspnea and/ordecrease in exercise tolerance,

3. Recurrent episodes of bronchitis or pneumonia and/or,

4. Occupational asthma.

1. History of unexplained urticaria orangioedema,

2. Baseline fev1 less than 60% of predicted,3. Pregnancy,4. Unstable cardiac status and/or,5. Recent viral respiratory tract infection.

A number of substances and modalities have been usedin pbc testing including methacholine, histamine,hyperventilation, exercise and cold air. Methacholine isa cholinergic drug that stimulates muscarinic receptorsin the bronchial smooth muscles, provokingbronchoconstriction. It is the agent most commonlyused in the pbc for the following reasons: safety,availability, cost, ease of administering andstandardizing, is non-allergenic and non-sensitizing andit stimulates a natural asthma attack in susceptibleindividuals in a controlled manner.

Several protocols have been used, but all rely uponadministering incremental doses of methacholine byinhalation and sequentially measuring the fev1. Normal saline is administered as a control. The test isconsidered positive if the fev1 falls by 20% or moreafter the inhalation of methacholine, compared tonebulized normal saline. The lower the concentration ofmethacholine that provokes this reaction, the moresevere the asthma is deemed. By contrast, even“normal” persons will experience bronchoconstriction

Safety

at high concentrations (25 mg/ml). A fall of 16% to19% is said to be equivocal and the challenge should berepeated. A fall of less than 16% virtually rules outasthma. The reproduction of the symptoms such ascough, wheeze or chest tightness when present, ishelpful in interpretation of the test.

In two prospective studies with patients with chroniccough, the positive and negative predicative valueswere 60% and 100% respectively. In the evaluation ofpatients with unexplained dyspnea, the positive andnegative predictive values were 95% and 100%respectively. Irwin and colleagues advise that a positivetest must be correlated with a favorable response totherapy before concluding that the patient has asthma.False-positive responses can be seen in patients withrecent viral upper or lower respiratory infections(within up to six weeks of testing), sarcoidosis,hypersensitivity pneumonia, congestive heart failureand pulmonary eosinophilia.

In two studies of over 2,500 patients tested by the pbcthere were no instances of severe episodes ofbronchospasm requiring hospitalization. In patientswith a positive test, bronchospasm is usually reversedwith inhalation of a beta agonist bronchodilator withinfive minutes. Other symptoms such as chest tightness,sore throat, cough, dyspnea and dizziness are usuallytransient and resolve within 24 hours. ■


27

References

American Thoracic Society. Single-breath carbonmonoxide diffusing capacity (transfer factor).Recommendations for a standard technique–1995update. Am J Respir Crit Care Med 1995;152:2185-2198. Comprehensive review of methods, nomenclatureand standards for the measurement of the single breathdiffusing capacity for carbon monoxide.

Comroe JH, Jr., Forster RE, Dubois AB, et al. The Lung:Clinical Physiology and Pulmonary Function Tests. 2nded. Chicago, IL: Year Book Medical Publishers, Inc.;1962. pp 390. This is the classic primer relatingpulmonary physiology and lung function tests tovarious respiratory disorders.

Hyatt RE, Scanlon PD, Nakamura M. Interpretation ofPulmonary Function Tests: A Practical Guide.Philadelphia, PA: Lippincott Williams & Wilkins; 1997.pp 212. This monograph is recommended to theprimary care physician who is seeking a concise andpractical textbook on pulmonary function testing. Thechapter of illustrative cases is particularly useful inhelping the physician grasp the concepts of pulmonaryphysiology as it relates to clinical practice.

Irwin RS, Pratter MR. The clinical value ofpharmacologic bronchoprovocation challenge. MedClin North Am 1990;74:767-778. A comprehensivereview of pharmacological bronchoprovocation testingin the diagnosis of asthma.

Ries AL. Measurement of lung volumes. Clin ChestMed 1989;10:177-186. A review of the techniques ofdetermination of lung volumes and the clinicalclassifications of obstructive and restrictive lungdiseases.

B. Lung Volume Studies (continued)


Arterial blood gases (abg’s) measure what isperhaps the most important aspect of lung function, that of gas exchange and acid-

base balance. Interpretation of abg’s must beconsidered in perspective. In general, abnormalities in abg’s correlate with abnormalities in other aspectsof lung function. However, patients can have severelung disease and maintain normal or near normalabg’s. Likewise, relatively minor abnormalities in lungphysiology, as measured by other pulmonary functiontests such as spirometry, can be accompanied by severe abnormalities in abg’s. One must consider thepossible mechanisms causing the abnormalities tointerpret their meaning and clinical importance to theindividual patient.

Arterial puncture is a relatively easy procedure. Somepractitioners favor infiltrating around the artery from which the blood is to be drawn with lidocaine ora similar local anesthetic agent. However, usually the blood can be drawn with a minimum ofdiscomfort, similar to the initial skin needle puncturefrom injecting the lidocaine, such that a localanesthetic is unnecessary. The filling of the syringe bythe arterial pressure and the color of the blood usuallyindicates an arterial source. Obviously, the colorcannot be relied on in the presence of severehypoxemia and oxygen desaturation.

Commonly, prepackaged syringes containingpowdered heparin are used. If prepackaged syringesare not available, the syringe should be coated withheparin, but without any excess heparin solution in thesyringe. The syringe containing the arterial bloodshould be capped and placed on ice for transport to thelaboratory where the measurement should be made assoon as possible.(continued)

C. ArterialBlood Gases(ABG’s) andPulse Oximetry

Arterial BloodGases (ABG’s)

TechnicalAspects

28

29

The oxygen tension in the arterial blood (pao2) reflectsthe end result of the complicated process of transport ofoxygen from the inhaled air or gas mixture to thearterial blood. The causes of a low pao2 or hypoxemiainclude:

1. Breathing a gas mixture low in oxygen content,

2. Hypoventilation,3. Ventilation-perfusion lung scan

(v· /q· ) mismatch,4. Diffusion abnormality,5. Intrapulmonary or intracardiac shunt and/or,6. Altitude.

Usually, the possibility of breathing gas low in oxygencan be ruled out (or ruled in, e.g., at altitude with a lowbarometric pressure that is accompanied by the inspiredpressure of oxygen [p1o2] lower than that at sea level).A diffusion abnormality is rarely the sole or primarycause of hypoxemia and is almost always accompaniedby one of the other mechanisms of hypoxemia, which isconsiderably more important as the cause of the lowpao2. A low diffusing capacity, as discussed in Section B,is primarily a reflection of the amount of alveolar lungsurface which is approximated by capillary blood flow.The dlco correlates poorly with abnormalities in pao2.Therefore, for practical purposes, one can usually limitthe mechanisms of hypoxemia to three:hypoventilation, v· /q· mismatch and shunt.

Hypoventilation is defined by the arterial level of co2

(paco2). If the paco2 is elevated, then alveolarhypoventilation is present by definition, regardless ofthe amount of minute ventilation (the total air breathedin and out in one minute measured in liters/minute).Whether the remote ventilation is found to be low,normal or high, if the paco2 is elevated, hypoventilationis present and contributing, to some degree, to the

C. Arterial Blood Gases (ABG’s) and Pulse Oximetry(continued)

Interpretation ofArterial BloodGases (ABG’s)

Oxygenation

hypoxemia. The degree to which the hypoventilation iscontributing to the hypoxemia can be determined byusing the alveolar air equation.

The alveolar air equation states that the alveolarpressure of oxygen (pAo2) is determined by the p1o2

minus the alveolar pressure of co2 (pAco2) divided bythe respiratory quotient (rq), the difference in the ratesof oxygen uptake and co2 production. The equation isexpressed as follows: pAo2=p1o2–pAco2/rq. The p1o2

can be determined by multiplying the barometricpressure minus the water vapor pressure by the fractionof inspired oxygen (f1o2). Since inhaled gas iscompletely saturated by water by the time it reaches thealveolar level, the water vapor value is constant at 47mm Hg. For example, at sea level breathing ambient air,the p1o2 would be (760 to 47 mm Hg) x 0.21=150 mmHg. The pAco2 (alveolar) is assumed to be the same aspaco2 (arterial). Although the rq can vary, it is usuallyassumed to be 0.8. Thus if the paco2 is normal at 40 mmHg, the pAo2=150–40/.8=150–50=100 mm Hg. Next,the alveolar pAo2 is compared to the arterial pressure ofoxygen (pao2) and the alveolar to arterial oxygendifference, p(A-a)o2, is calculated. The normal range ofpao2 at sea level is approximately 75 to 90 mm Hg. Thenormal range of p(A–a)o2 while breathing air, therefore, is100 minus 75 to 90=10 mm to 25 mm Hg. This normalrange varies with age, increasing as we get older. Whenhypoventilation is the sole cause of hypoxemia, the p(A-a)o2 is normal. The low pao2 is caused by a reductionin pao2 associated with the hypoventilation.

If the p(A-a)o2 is increased, then either v· /q· mismatch orshunt is present and contributing to the hypoxemia.Blood flow has to be present out of proportion to areduction in ventilation, (i.e., �q), for v· /q· mismatch tocause a low pao2. An increase in v· /q· ratio would resultin wasted ventilation and perhaps increased work ofbreathing, but would not generally be accompanied



by hypoxemia. A classic example of a cause ofdecreased v· /q· would be an asthma attack with wide-spread narrowing of airways, resulting in decreasedventilation, but with continued perfusion of thehypoventilated areas.

Shunt can be thought of as an extreme form ofmismatch, i.e., no ventilation, but continued perfusion.v· /q· mismatch is separated or differentiated from shuntby the response to increasing the inhaled oxygen tension(See Figure 10). If v· /q· mismatch is present, eventuallythe increased oxygen mixture will wash out some of thenitrogen in the alveoli, since the airways are open tosome degree, and the resulting increase in pAo2 willincrease the arterial po2. If a shunt is present, i.e., noventilation, there will be no increase in oxygen in theclosed or fluid-filled alveoli, and thus, no change inoxygenation will occur in the blood flowing past thosealveoli. The only increase in arterial po2 will occur fromincreasing oxygen in the non-shunt areas of lung tissue.Since the oxygen saturation in these areas is usuallynearly complete already (approximately 95% orgreater) and thus, oxygen content is near maximum, theaddition of even 100% oxygen to these areas will resultin a relatively small increase in arterial oxygen content.

The use of increased f1o2 to differentiate between v· /q·

mismatch and shunt can be stated in practical terms. If asmall increment in inhaled oxygen is administered, e.g.,2 liters per minute o2 by nasal prongs, the pao2 willshow a measurable and clinically important increasewhen v· /q· mismatch is present, but virtually no changewhen shunt is present. If 100% oxygen (f1o2=1.0) isadministered, a very large increase in pao2 (usually to350 mm to 500 mm Hg) will result if v· /q· mismatch isprimarily present, but only a modest increase in pao2

will occur if shunt exists. (continued)

31

Figure 10 Ventilation-Perfusion (v· /q· ), Mismatch and Intrapulmonary Shunt


Ventiliation perfusion(V/Q), mismatch andintrapulmonary shunt.See text for descrip-tion of how these can be differentiated by administering oxygen.

32


Acid-BaseBalance

Arterial blood gases are necessary to determine the acid-base status of the blood. On abg’s, the pH and pco2 aredirectly measured, and the bicarbonate (hco3-)is calculated from the pH and pco2. If the calculatedhco3- is significantly different (e.g., ≥ 5) from themeasured serum hco3- from the blood chemistries, alaboratory error is possible, including the arterial pH,paco2 or venous co2 serum (hco3-).

In interpreting the acid-base status, first look at the pH.If the pH is low (<7.36), acidemia is present. If the pHis high (>7.44), alkalemia is present. If acidemia ispresent, the etiology can be respiratory, metabolic ormixed. Next, look at the paco2. If it is elevated, then arespiratory component of the acidemia exists. Anelevated paco2 will result in more dissolved hco3- (fromthe Henderson–Hesselbalch equation). Next look at thehco3-. If it is elevated, the acidemia is likely entirelyrespiratory in etiology. However, if the hco3- is normalor low, then a metabolic component is also likelypresent. If the paco2 is normal or low and the hco3- islow, then the acidemia is caused by a metabolicacidosis. It is common for a metabolic acidosis to bepartially compensated by a respiratory alkalosis(decrease in paco2). Likewise, if the pH is alkalemic,look at the paco2. If the paco2 is significantly decreased,then a respiratory cause of the alkalemia is present. Ifthe paco2 is normal or increased, look at the hco3-. If thehco3- is increased, then a metabolic alkalosis exists (See Tables 7 and 8).

Use of equations and formulas allow more precisecalculation of the degree of an acid-base abnormalityand the amount of correction necessary to result innormal or near normal acid-base balance. For practicalclinical purposes, however, an understanding of thephysiologic principles allow determination of theprimary abnormality and the amount of compensation.Then starting in the right direction with appropriate

33

Table 7 Criteria of Acidemia and Alkalemia1


Table 8 Major Causes of Metabolic Acidosis

According to Mechanism and Anion Gap (AG)

Mechanism of acidosis Increased AG Normal AG

Increased acid production Lactic acidosis

Ketoacidosis

Diabetes mellitus

Starvation

Alcohol-associated

Ingestions

Methanol

Ethylene glycol

Aspirin

Toluene (if early)

Loss of bicarbonate or Diarrhea or other intestinalbicarbonate precursors losses (e.g., tube drainage),

Type 2 (proximal), renal tubular acidosis (RTA), Posttreatment ofketoacidosis Toluene ingestion

Carbonic anhydrase inhibitors

Ureteral diversion (e.g., ileal loop)

Decreased renal Chronic renal failure Some cases of chronic acid excretion renal failure

Type 1 (distal), RTA

Type 4 RTA (hypoaldosteronism)

Source: Post TW, Rose BD. Approach to the patient with metabolic acidosis. In: UpTo Date, Rose BD (ed), January 8, 1999 Wellesley, MA.

Acidemia Alkalemia

pH < 7.36 >7.44

PaCO2 > 45 (respiratory) < 35 (respiratory)

HCO3- < 24 (metabolic) > 24 (metabolic)

1 Compensatory or mixed acid-base patterns are common.

34

therapeutic strategies and rechecking the abg’s, isadequate for managing most cases of acid-basedisturbance. Calculating the anion gap will be useful inconsidering the differential diagnosis of metabolicacidosis (See Table 8).

Pulse oximetry is a non-invasive method of measuringthe oxygen saturation of the blood. The oxygensaturation is related to the pao2 by the oxyhemoglobindissociation curve (See Figure 11). The oxygensaturation is calculated by shining light through tissueand measuring the light absorption on the other side ofthe tissue at two specific wavelengths. The tissue mostcommonly used is the fingertip, although the earlobe isalso used. The light source consists of twolight–emitting diodes (leds) that emit light at knownwavelengths, generally 660 nm and 940 nm. Thesewavelengths are used because oxyhemoglobin andreduced hemoglobin have different absorption spectraat these particular wavelengths. Pulse oximetry adds atechnical improvement to previously available oximetrymethods by helping to correct for light other tissues canabsorb in addition to the light absorbed by the blood.Pulse oximetry assumes that the only pulsatileabsorption between the light source and the photodetector is that of arterial blood. Pulse oximetrycorrects for absorption characteristic of substances notfound in pulsatile blood by separating the pulsatilealternating current component of the absorption signalfrom the non-pulsatile direct current component. Thedirect current component represents the absorbency ofthe tissue bed, including venous blood, capillary blood,and non-pulsatile arterial blood. The alternatingcurrent component represents the pulsatile expansionof the arteriolar bed with arterial blood. This results inmore accurate measurement of the arterial bloodoxygen saturation.


35

Pulse Oximetry


Figure 11 The Oxyhemoglobin Dissociation Curve

The oxygen-hemoglobin (O2-Hb) dissociation curve, relating the partial pressure of oxygen in arterial

blood (Pao2) to arterial O2 saturation (Sao2) and to the O2 content of arterial blood (Cao2). A normal Hb

concerntration in milliliters per deciliter is assumed. The curve descends steeply below Pao2 values of

50 mm Hg. indicating severely reduced O2 -carrying capacity of Hb below this PaO2. The lower line

represents O2 in solution in the blood; the middle line depicts O2 bound to the Hb at that Pao2; the upper

line shows O2 bound to Hb plus O2 dissolved. Note that dissolved O2 contributes little to Cao2 at a Pao2

in the normal range.

From Luce JM, Tyler ML. Pierson DJ: Intensive respiratory care. Philadelphia, PA: WB Saunders, Company, 1984. pg 345

36

37 C. Arterial Blood Gases (ABG’s) and Pulse Oximetry(continued)

The Uses of PulseOximetry

Limitations ofPulse Oximetry

The measurement of oxygen saturation can be useful ina variety of clinical circumstances. There are a numberof limitations based upon the technical aspects of themeasurement. The major conceptual limitation,however, has to do with understanding theoxyhemoglobin dissociation curve and the limitationthat oxygen saturation may not reflect importantchanges in pao2. Most oximeters claim a 95%confidence limit of ± 4% for sao2 readings above 80%.In fact, when the sao2 is greater than 90%, the accuracyin clinical tests has been somewhat better then ± 4%.However, if we use the 95% confidence limit of ± 4%,an oximetry reading of 95% could present a pao2

ranging between 60 mm Hg (sao2=91%) and 160 mmHg (sao2 = 99%). Even if the accuracy was better than4%, 95% confidence limit, an oxygen saturation thatoccurs in the flat part of the oxhemoglobin dissociationcurve will not give information about relatively largechanges in pao2. These changes could be physiologicallyand clinically important. The major clinical applicationsof pulse oximetry are presented in Table 9.

In addition to the issue of accuracy which was discussedabove, there are several clinical conditions listed inTable 10 which may affect the accuracy of pulseoximetry measurements. Abnormal hemoglobins cangive false readings. The two most common clinicalanomalous hemoglobins which affect pulse oximetryreadings when present in significant amounts arecarboxyhemoglobin (cohb), and methemoglobin(methb). The presence of carboxyhemoglobin (such asmight occur in accidental intoxication or even in heavysmokers) causes consistent overestimation of the truesao2. Methemoglobin causes the pulse oximetry tofalsely read approximately 85%. The treatment ofmethemoglobinemia is the administration of methyleneblue. Although methylene blue reverses the clinical signsof methemoglobinemia, including cyanosis, it alsocauses falsely low pulse oximetry readings, and cancause the reading to go as low as zero.

Table 9 Major Clinical Applications of Pulse Oximetry

1. Continuous monitoring of oxygen saturation in the clinic as either ascreen for lung disease that might cause oxygen desaturation ormonitoring patients with known lung disease.

2. Determining the oxygenation response to exercise in an outpatientsetting. Walking the patient in the clinic and determining if oxygendesaturation occurs, gives extremely important clinical information.

3. Continuous monitoring of hospitalized patients for episodes ofoxygen desaturation. This can be useful in a variety of pulmonaryconditions, including a screening evaluation for patients withsignificant sleep apnea.

4. Titration of oxygen therapy in the hospitalized patient or outpatientsetting. In patients receiving mechanical ventilation, F1O2 can bereduced as the patient improves. By following pulse oximetry, theneed for multiple ABG measurements can be reduced.

Table 10 Limitations of Pulse Oximetry

Limited information on PaO2 changes on the flat portion of the

oxyhemoglobin dissociation curve.

No information on acid-base status

Spurious data with anomalous hemoglobins

COHb causes overestimation of SaO2

MetHb causes SaO2 reading of ˜85%

Sickle cell anemia with venoocclusive crisis causes

underestimation of SaO2

Blue, green and black nail polishes cause falsely low readings

Dark pigmented skin may cause technical problems with

inaccurate readings

Low perfusion state may cause difficulty in obtaining an

interpretable signal


39 C. Arterial Blood Gases (ABG’s) and Pulse Oximetry(continued)

Anemia theoretically might affect the accuracy of pulseoximetry readings. While a study of patients with severeanemia but with normal oxygenation found pulseoximetry to be accurate in this situation, the combinedeffect of anemia and hypoxemia has not been studied.One study suggested that pulse oximetry underestimatesoxygen saturation in patients with sickle cell anemiapresenting with a venoocclusive crisis. Pulse oximetryhas been shown to be generally accurate in patients withhyperbilirubinemia.

Some nail polishes can cause inaccurate readings. Blue,green and black nail polish have been shown to causefalsely low pulse oximetry readings, although nodistortions were seen with red and purple nail polishes.This problem can be alleviated by mounting theoximetry probe side-to-side on the finger.

Darkly pigmented skin is a possible cause of aninaccurate reading. One study showed that technicalproblems in obtaining an interpretable reading occurredmuch more frequently in black patients than in whites.

Low perfusion states can make it difficult for theoximetry sensor to distinguish the true signal frombackground noise and can limit the usefulness of pulseoximetry in critically ill patients.

Finally, pulse oximetry alone, without an internal abgmeasurement, might give the clinicians false reassurancein some critically ill patients (such as those with acuterespiratory failure and copd) when oxygen saturationmight be satisfactory, but abnormalities of pH andpaco2 might be present. When any doubt exists aboutthe accuracy of oximetry, an abg is needed. ■


References

Adrogue HJ, Madias NE. Management of life-threatening acid-base disorders. New Engl J Med 1998;338; Part i: 26-34, Part ii: 107-111. This is a highlyrecommended article describing a useful approach toacid-base problems, written by a master clinician-teacher. It is a good review of management of lifethreatening acid-base problems.

Gold WM. 28. Pulmonary function testing. In: MurrayJF, Nadel JA. Textbook of Respiratory Medicine. 3rded. Philadelphia, PA: W. B. Saunders Company; 2000.pp 829-837. A standard textbook presentation aboutabg analysis and methods of sampling, determinationand interpretation.

Luce JM, Tyler ML, Pierson DJ. Intensive RespiratoryCare. Philadelphia, PA: W. B. Saunders Company;1984. pp 345. A good monograph on intensiverespiratory care principles in the 1980’s.

Post TW, Rose BD. Approach to the patient withmetabolic acidosis. In: UpToDate, Rose BD (ed),January 8, 1999 Wellesley, MA. A systematic approachto the classification and treatment of metabolicacidosis.

Tremper KK. Pulse oximetry’s final frontier. Crit CareMed 2000;28:1684-1685. A commentary on the newuse of pulse oximetry.

Weinberger SE, Schwartzstein RM, Weiss JW.Hypercapnia. New Engl J Med 1989;321:1223-1231.A review of the mechanisms of acute and chronichypercapnia.

40

41

D. Chest X-rays The chest x-ray is over a hundred years old andyet remains the cornerstone of chest imaging.The presence of abundant air in the lungs

provides many air-fluid interfaces in the chest that allowreasonably precise definition of many importantthoracic structures, and provides an opportunity toexamine the alveolar tissue of the lung for infiltrativeand nodular abnormalities. The chest x-ray initiallyprovided a much-needed breakthrough in tuberculosismanagement. The chest x-ray remains the initial studyof choice in anyone presenting with significant chestsymptoms and should always be obtained beforeconsidering more advanced chest imaging such ascomputed tomography (ct) scanning.

Reading abnormalities on chest x-rays requires a basicknowledge of normal thoracic structures and the basicprinciples of chest radiography. An air-fluid interfacedefines a border or contour, such as a heart border, orhemidiaphragm contour. On a normal chest x-ray, onesees two sharply defined hemidiaphragms extendingcentrally nearly to the spine, left and right heartborders, the aortic knob on the left and the hilarstructures. Absence of the normal contours occurs as aresult of a fluid density such as effusion, infiltrate oratelectasis obliterating a normal contour, the so-called“silhouette sign.” Absence of lung markings occurs as aresult of bullous lesions or pneumothorax. Infiltrates inthe lungs are the result of fluid density (e.g., white cells,edema fluid, blood or fibrosis) in or around the alveoli.Alveolar infiltrates are characterized by airbronchograms and the tendency of the infiltrates tocoalesce and silhouette out adjacent structures.Interstitial infiltrates are characterized by fine lines anddots (reticulo-nodular pattern) and often accentuateborders of adjacent structures. Patterns of infiltrates andevolution of infiltrates over time are important indifferential diagnosis (See Table 11).(continued)

Table 11 Diagnosis From Patterns and Evolution of Infiltrates


Diagnosis Pattern Resolution Interval

Pulmonary Edema Diffuse alveolar/interstitial Hours to days

Alveolar Hemorrhage Diffuse alveolar 3 to 5 days

Atelectasis Segmental, lobar, or whole lung Hours to days

Infectious Pneumonia Segmental to diffuse alveolar 10 to 30 days

Pulmonary Fibrosis Diffuse interstitia Persists indefinitely

Adapted from: Goodman N. Differential diagnosis of pulmonary alveolar infiltrates. Am Rev Respir Dis1967;95:681, 684-686.

42

43 D. Chest X-rays (continued)

The “routine” or “screening” chest x-ray was animportant part of tuberculosis surveillance and controlin the first sixty years of the twentieth century. More recently, we have rejected the concept andpractice of “routine” procedures and try to logicallyselect appropriate indications and intervals for chest radiographs. There are no systematic data aboutthe utility of “routine” chest x-rays in American adults. Arguably, the best practice is to obtain suchstudies only on the basis of cardiorespiratory symptomsor special risk factors. Preoperative chest x-rays prove useful as a baseline comparison in patients whomight develop postoperative respiratory problems.Preoperative chest x-rays should be obtained in older patients, those with significant cardiopulmonaryproblems and those undergoing extensive abdominal procedures.

Studies of the utility of chest x-rays for lung cancerscreening fail to support a yearly chest x-ray insmokers. However, we recommend a yearly chest x-rayin high-risk patients with 30 pack-years of smoking, asa chest x-ray is our only widely employed lung cancerscreening tool. Virtually all early-stage, asymptomaticlung cancers are discovered on “routine” chest x-ray orserendipitously during x-ray investigation of anotherproblem. Early diagnosis and more successful treatmentof lung cancer, the most common fatal cancer, remainsone of our greatest challenges and will require selectiveapplication of newer technologies (ct scanning orsputum cytology) in high-risk patients to achievesuccess.

Chest X-rayScreening

Is it Pneumoniaor Bronchitis?

Clinicians are faced with patients with acute respiratorysymptoms on a daily basis. A decision whether toobtain a chest x-ray must be made in every case. copdpatients with acute bronchitis are at higher risk forserious sequelae. They are generally sicker than arebronchitis patients without chronic lung disease.Pneumonia rather than bronchitis is more probablewith increasing numbers and severity of respiratorysymptoms. Temperature above a hundred degreesFahrenheit, new or increased shortness of breath,purulent sputum production, pleuritic chest pain andshaking chills can be signals of pneumonia. copdpatients with milder exacerbations may not require achest x-ray, but an x-ray is indicated for those requiringhospital admission, both to exclude the presence ofpneumonia, congestive heart failure and pneumo-thorax, and to provide a baseline if improvement is notrapid. Patients with normal lung function and clinicalsigns and symptoms of pneumonia should have a chestx-ray to define the absence or presence of pneumoniaand its extent, if present. Patients with more extensivepneumonia (i.e. greater than one lobe involved) eitherrequire admission or close follow-up to assure thatprogression to generalized involvement with respiratoryfailure does not occur in an uncontrolled setting.

Since the chest x-ray may suggest the presence of canceras a cause of the pneumonia, the x-ray should becarefully examined for mass lesions, and hilar ormediastinal adenopathy. Bronchoalveolar cellcarcinoma usually presents as a chronic non-resolvingpulmonary infiltrate and can mimic infectiouspneumonia.

Chest x-rays may reveal complications of pneumoniasuch as pleural effusion or lung abscess. Significantpleural effusion occurs in at least 20% of pneumonias.Signs of effusion can include silhouetting out of ahemidiaphragm, ground glass opacity at the lung base



DyspneaEvaluation

and fluid density with meniscus in the lower lung zone.Thoracentesis is indicated for large effusions, ifresponse to therapy is not rapid, and particularly if theeffusion increases in size with therapy. Examination andculture of pleural fluid can yield specific microbiologyand cytology information pertinent to the etiology ofthe pneumonia and effusion. Pleural ultrasoundexamination is more useful than a lateral decubitus x-ray in determining the presence, size and location of a pleural effusion, and is the preferred procedurewhen available. Early drainage of complicatedparapneumonic effusion can prevent formation oflocculated empyema.

Lung abscess should always be followed to resolution inorder to assure that the abscess is not a cavitarycarcinoma. Most patients with lung abscess should havea chest ct scan to size the cavity and to look for othersigns of malignancy. Bronchoscopy may be indicated inpatients with lung abscess to exclude malignancy andforeign body. Since simple infectious lung abscessesusually result from aspiration of periodontal debris inthe edentulous patient, the appearance of a cavitaryprocess with an air-fluid level may well represent abronchogenic carcinoma with central necrosis.

The chest x-ray is abnormal in as many as 40% of olderpatients presenting with isolated dyspnea, and is animportant part of the initial evaluation of all patientswith significant shortness of breath. Significant findingsinclude hyperinflation and bullous changes, interstitialinfiltrates, pleural effusion, cardiomegaly andcongestive heart failure. A normal study often suggeststhe need for more specialized testing, such as detailedpulmonary function testing, thromboembolic work-upor cardiology evaluation.

PulmonaryEmbolus (PE)

CardiovascularAbnormalities

The chest x-ray typically reveals subtle, non-specificabnormalities in patients with pe. Non-specific findingsinclude atelectasis, subtle elevation of a hemidia-phragm, pleural effusion and cardiomegaly. Morespecific findings include segmental or lobar oligemia(Westermark’s Sign) and peripheral wedge-shapedinfiltrate with rounded apex (Hampton’s Hump). Anormal chest x-ray in the dyspneic patient also shouldraise the possibility of pe. However, these findings arerarely distinctive enough to be clinically helpful. Theyoften are recognized only in retrospect after morespecific testing enables a diagnosis of pe.

The chest x-ray may reveal an enlarged cardiacsilhouette due to cardiac dilation or pericardial effusion.A prominent, muscular-appearing left ventricularcontour suggests hypertrophy due to hypertension oraortic valvular stenosis. Mitral stenosis is suggested bystraightening of the left heart border due to enlargementof the left atrial appendage, by a normal to small heartsize, and by pulmonary vascular engorgement withupper zone redistribution of flow. Marked non-specificcardiomegaly is typical of end stage cardiomyopathy,regardless of its cause. Enlargement of the centralpulmonary vasculature suggests primary or secondarypulmonary hypertension. Kerley-B lines indicateinterstitial edema due to heart failure or lymphaticengorgement from lymphangitic tumor spread to thelung. Ectasia of the thoracic aorta is common in theelderly, but focal dilation suggests atheroscleroticaneurysm or dissection of the aorta. Interstitial fibrosiscan be easily confused with congestive heart failure.Often more detailed testing is required to differentiatebetween the two.(continued)



Anterior mediastinum

Thymoma

Germ cell tumors

Lymphoma

Thyroid/parathyroid tumors

Mesenchymal tumors

Middle mediastinum

Benign and malignant lymphadenopathy

Lymphoma

Developmental cysts

Vascular aneurysms

Hiatal hernia

Posterior mediastinum

Neurogenic tumors

Esophageal carcinoma

Esophageal diverticulum

Adapted from: Park DR, Pierson DJ. Disorders of the mediastinum. Generalprinciples and diagnostic approach. In: Murray JF, et al. (eds). Textbook ofRespiratory Medicine, 3rd ed. Philadelphia, PA: W. B. Saunders Company;2000. p 2081.

Table 12 Mediastinal Masses by Location

PneumothoraxVersus BullousLung Disease

Mediastinal and HilarAdenopathy and Masses


The diagnosis of pneumothorax is made reliably withstandard x-rays in patients without intrinsic lungdisease. In patients with extensive bullous lung diseaseand acute dyspnea, it may be difficult to differentiatepneumothorax from large intraparenchymal bullouslesions. Placement of a chest tube into a bullous lesioncan be catastrophic. Caution is advised in theevaluation of possible pneumothorax in copd patients.Chest ct scan may be required for a certain diagnosis.

Asymptomatic bilateral hilar adenopathy is usually dueto sarcoidosis. Unilateral hilar adenopathy is due moreoften to tuberculosis or benign or malignant tumors.The presence of unilateral hilar and mediastinaladenopathy suggests unresectability in lung cancerpatients. However, further staging with ct imaging andbiopsy is required in most such patients. Othermediastinal masses are classified according to theirlocation in the anterior, middle or posteriormediastinum (See Table 12). ■(continued)

48


References

Felson B. A look at pattern recognition of diffusepulmonary disease. Am J Roentgenol 1979;133:183-189. Discusses pattern recognition and its importance inthe x-ray evaluation of diffuse infiltrative lung disease.

Kerr IH, Simon G, Sutton GC. The value of the plainradiograph in acute massive pulmonary embolism. Br JRadiol 1971;44:751-757. X-ray abnormalities arecommon in massive pe, but are non-specific and oftenapparent only in retrospect.

Muller NL. Imaging of the pleura. Radiology1993;186:297-309. This paper offers a good discussionof the x-ray diagnosis of pleural effusion.

Goodman N. Differential diagnosis of pulmonaryalveolar infiltrates. Am Rev Respir Dis 1967;95:681-686. A classic article illustrating the common causes ofacute and chronic alveolar infiltrates.

Park DR, Pierson DJ. Chapter 78: Disorders of themediastinum. General principles and diagnosticapproach. Murray JF, et al.(eds). Textbook ofRespiratory Medicine, 3rd ed. Philadelphia, PA: W. B.Saunders Company; 2000. pp 2095. A thoroughreview of diseases of the mediastinum in acontemporary textbook.

Multiple imaging techniques to better assesspulmonary anatomy, physiology andpathology are now available. Before any of

these more advanced techniques are used, a posterior-anterior (pa) and lateral chest x-ray should be obtainedto give an overview and to direct the order in whichother studies should be obtained. Imaging techniques tobe discussed include:

1. Computed tomography (ct)a. ct (with and without contrast)b. High resolution ct (hrct)c. Spiral ctd. Low radiation-dose ct

2. Ventilation-perfusion lung scanning (v· /q· scan)3. Diagnostic ultrasound4. Positron emission tomography (pet)5. Magnetic resonance imaging (mri)6. Pulmonary angiography

Physicians need to be aware of the local radiologydepartment’s areas of expertise as this too will influencethe type and sequence of the additional studies chosen.A summary of clinical indications for each study ispresented in Table 13.

The conventional ct scan gives an excellent anatomicalpicture of the thorax and its structures. The addition ofintravenous contrast allows blood vessels and othervascular structures to be differentiated from non-vascular structures such as mediastinal nodes, massesand soft tissue densities. Serial coronal images are takenevery 7 mm to 10 mm from the apices to the bases of thelungs. This may be visualized as slicing the lungs as aloaf of bread. Each cross-sectional image is then laid outfor inspection. Nodules, masses, infiltrates, atelectasis,pleural effusions and lymphadenopathy are identified inmuch greater detail than with the chest x-ray. Whenmore specialized versions of the ct scan, (See below),are employed without the basic ct scan, the above

E. SpecialThoracicImagingTechniques

ComputedTomography(CT)


51 E. Special Thoracic Imaging Techniques (continued)

Table 13 Imaging Techniques

Imaging Technique Clinical Indication for Study

Chest x-ray All patients should have a chest x-ray prior to other imaging techniques.

CT with contrast Evaluate lung masses, nodules, hilar andmediastinal structures (including aorta),pleural disease and pulmonary infiltrates.

CT without contrast Use if patient is allergic to contrast and for follow-up of lung nodules.

High resolution CT Evaluate parenchymal lung disease such asinterstitial lung disease, bronchiectasis andemphysema.

Spiral CT with contrast Evaluate for acute and chronicthromboembolic disease in patients with non-diagnostic lung scans, abnormal chest x-ray orchronic lung disease.

Low radiation-dose CT Screen high-risk patients (smokers with airflowobstruction), for lung cancer.

Ventilation- Current standard for evaluating patients with perfusion lung scan normal chestx-ray for thromboembolic disease(V·/Q· scan)

Diagnostic ultrasound Evaluate and localize pleural effusions.Evaluate lower extremities for deep veinthrombosis.

Positron emission Consider after chest x-ray and CT withtomography (PET) contrast to determine likelihood of malignancy

in a mass or nodule, to stage lung cancer, toevaluate cancer therapy and recurrence ofmalignancy.

Magnetic resonance Rarely used for imaging the thorax.imaging (MRI)

Pulmonary angiogram Traditional standard for diagnosis of PE whenother studies are non-diagnostic.

abnormalities can be missed. Once an abnormality such as a solitary pulmonary nodule is identified, 1 mm to 2 mm sections through the lesion should beobtained. Abnormalities can be evaluated forcalcification, density, contrast enhancement, cavitationand vascular supply.

High Resolution CT Scan (HRCT): This techniqueprovides extreme detail of the lung parenchyma and isparticularly helpful in diagnosing interstitial lungdisease and emphysema. While this technique gives anexcellent anatomical evaluation of the lung, it does notreplace the need for lung biopsy in most patients withinterstitial lung disease.

Spiral CT Scan: The spiral (or helical) ct technologyallows for direct visualization of the pulmonaryvasculature and is an excellent tool for assessingpatients for suspected acute and chronic thrombo-embolic disease. In contrast to conventional ct scanswhich produce a single axial image, the spiral techniqueresults in a helical volume of data over the entirethorax, in seconds. This allows for images to bereconstructed at overlapping intervals to furtherimprove resolution. Rather than viewing static images,radiologists are able to scan the software computerimages in a dynamic fashion. Thus, they may identifyemboli or thrombi at the segmental level of the lung.Patients with suspected pulmonary emboli (pe) andabnormal chest x-rays should have a spiral ct instead ofa v· /q· lung scan. However, this technique has been foundto lack sensitivity for small subsegmental emboli.Nonetheless, with recent improvements in equipmentand experience, this technique may become the imagingtechnique of choice for all patients suspected of havingacute thromboembolism.

Low Radiation-dose CT Scan: This method is deemedmost appropriate for serial studies to screen forbronchogenic carcinoma. Individuals at high risk of



developing lung cancer (smokers with airflowobstruction) are excellent candidates for this study. The spiral (helical) ct technique is used. Thin slicedimages through the thorax are obtained. Nodules andother abnormalities are identified much sooner thanwith chest x-rays, and appropriate management(observation or biopsy) can be initiated. This techniqueresults in lower doses of radiation exposure comparedto other ct studies. Guidelines for its use are undercurrent development.

Ventilation-Perfusion Lung Scan (v·/q· Scan):For years, v· /q· scans have been the most commonly usedinitial study to diagnose pulmonary embolism (pe). But,unless the lung scan is normal (excluding pe), or highprobability in conjunction with high clinical suspicion,the studies are regarded as equivocal or non-diagnostic.In the Prospective Investigation of PulmonaryEmbolism Diagnosis (pioped) study, 65% to 70% ofpatients had non-diagnostic scans. Combining v· /q·

scans with lower extremity ultrasound or impedanceplethysmography may improve the yield. But, untilspiral ct was available, pulmonary angiography wasnecessary to confirm pe. Individuals with chronic lungdisease and those with abnormal chest x-rays will haveabnormal lung scans, usually non-diagnostic, limitingthe usefulness of v· /q· scanning in these patients. Thus,the diagnostic algorithm for pe seems to be changing.Spiral ct imaging (when available) is becoming thediagnostic study of choice in pe suspects with abnormalchest x-rays or chronic lung disease.

Quantitative v· /q· scanning is helpful to determinedifferential lung function and is frequently used inpatients with severe underlying lung disease requiringpulmonary resection. This provides data on thepercentage of blood flow and ventilation to each lung,helping to stage for operability.

DiagnosticUltrasound

PositronEmissionTomography(PET)

MagneticResonanceImaging (MRI)

The best pulmonary use of ultrasound is to evaluatepleural effusions and to localize optimal location forthoracentesis or chest tube placement. Because of itsportability, the study can be done at the bedside.

Lower extremity ultrasound with color Doppler allowsfor the assessment of acute deep venous thrombosis,flow abnormalities and chronic venous insufficiency.This non-invasive technique is extremely helpful in theevaluation of lower extremity pain and swelling.

Positron emission tomography (pet) is a metabolicimaging technique that uses amino acids or glucose towhich positron emitting radionuclides are tagged. For thoracic pet scanning, the radiopharmaceutical, F-2-deoxy-D-glucose (fdg) is used and is labeled withfluorine-18. Because malignant cells metabolize glucose at a much higher rate than non-malignant cells,fdg injected intravenously is preferentiallyaccumulated in malignant cells. This is new technology,and guidelines have not been firmly established for itsuse. When combined with other imaging techniques, we anticipate that it may be helpful in evaluatinglocalized pulmonary lesions, characterizing hilar andmediastinal adenopathy, staging of lung cancer,evaluating recurrence of disease and measuringtreatment response. False-positives may be seen withactive granulomatous infection, such as seen in theMidwest (histoplasmosis) and Southwest(coccidiodomycosis).

While mri has revolutionized the diagnostic approachin the orthopedic and neurologic specialties, its use inthe thorax remains limited. Because of the continuouscardiac and respiratory motion, images are not as clearas in ct or x-rays. In general, the chest x-ray and ctscan provide more useful data. Magnetic resonanceimaging (mri), of the thoracic aorta is an accuratemethod for diagnosing aortic dissection, but spiral ct is



PulmonaryAngiography

quicker and as accurate. In special situations, mri maygive helpful additional information to ct scanning inevaluation of superior sulcus tumors, neurogenictumors and mediastinal masses. mri should not be usedfor the routine diagnosis of pe.

Pulmonary angiography remains the final definition testfor the diagnosis of pe. Numerous diagnosticalgorithms exist for diagnosing this disorder. But, whenv· /q· scanning, spiral ct, venous ultrasound or metabolicmarkers such as D-dimer fail to confirm a diagnosis,pulmonary angiography is utilized. Because it is moreinvasive and inherently hazardous, pulmonaryangiography should not be used first in the evaluationfor pe (See v· /q· scanning and spiral ct, above). ■

References

Erasmus JJ, Patz EF, Jr. Positron emission tomographyimaging in the thorax. Clin Chest Med 1999;20:715-724. A practical review of the use of this newtechnology in the diagnosis of staging of intrathoracicnodules, masses and lymph nodes.

Garg K, Welsh CH, Feyerabend AJ, et al. Pulmonaryembolism: Diagnosis with spiral ct and ventilation-perfusion scanning — correlation with pulmonaryangiographic results or clinical outcome. Radiology1998;208:201-208. Excellent discussion on the value of spiral ct in the diagnosis of pe with non-diagnosticlung scans.

McLoud TC. Imaging. Clin Chest Med 1999;20:697-874. An extremely well-written, comprehensive reviewof thoracic imaging techniques including spiral and highresolution ct scans, pet scans and mri.


57

F. UltrasoundProcedures

TheEchocardiogram

Evaluation ofCardiacMurmurs

Evaluation ofCardiac Failure

The echocardiogram is one of the most widelyused and useful techniques in the evaluation ofthe patient with cardiopulmonary symptoms. It

is non-invasive. A normal echocardiogram excludes abroad range of potential cardiac problems. Newertechniques allow direct imaging of cardiac structures,generally accurate determination of various cardiacpressures and more sensitive imaging of valvularabnormalities. Unfortunately, lung interference oftenlimits the quality of the echocardiogram in patients withcopd. Table 14 summarizes available widely usedechocardiographic techniques.

The echocardiogram is helpful in the diagnosis ofcardiac murmurs and their severity and is performed asthe initial evaluation in most patients felt to have asignificant murmur. Abnormalities in aortic stenosisinclude bicuspid valve, thickening of valve leaflets,decreased leaflet excursion and increased pressuregradient across the valve. In aortic regurgitation, theechocardiogram provides an estimate of regurgitantflow, and may show premature closure of the mitralvalve in severe aortic valve regurgitation. In mitralstenosis, the echocardiogram shows thickening anddecreased excursion of the valve leaflets, left atrialenlargement and provides an estimate of the valve area.Findings in mitral insufficiency include regurgitant jetinto left atrium, abnormalities of the chordae andpapillary muscle, and mitral valve prolapse.

The echocardiogram provides an accurate estimate ofleft ventricular volume, contractility and ejectionfraction in most patients. It can reveal segmental wallmotion abnormalities that correspond to coronaryanatomy and suggest ischemic cardiomyopathy. Diffusehypokinesis is seen in non-ischemic congestivecardiomyopathy. Interventricular and interatrial septaldefects can be visualized and their diagnosis is enhancedwith bubble contrast and transesophageal techniques.The echocardiogram may reveal surprisingly goodventricular function and define unexpected valvular


Table 14 Echocardiographic Techniques and Their Advantages

Echocardiographic Technique Characteristics Advantages

M-Mode

(Motion-mode)

Visualizes motion of cardiac

structures by plotting one

dimensional “ice-pick” view of

heart against time.

Good visualization of mitral

and aortic valve pliability and

motion; accurate sizing of left

atrial and ventricular

dimensions.

Two-Dimensional (2-D) Ultrasound beam continuously

sweeps a pie-shaped sector.

Direct, spatially correct

visualization of cardiac

structures and motion.

Doppler Uses Doppler shift principle

to determine velocity of

blood flow and estimation

of pressures.

Good estimation of valvular

gradients and intracardiac

pressures.

Color flow Doppler Gated Doppler displays

spatially correct, colored

images of moving blood

superimposed on 2-D images.

Dynamic, spatially correct

visualization of abnormal

intracardiac blood flow.

Transesophageal 2-D probe passed into the

esophagus, allows placement

of transducer in close proximity

to heart.

Better visualization of valvular

structures/vegetations and

central, massive VTE.

Excellent visualization of

thoracic aortic disease and

cardiac shunt defects.

58

abnormalities that explain cardiac dysfunction. Stressechocardiography demonstrates inducible ventricularcontraction abnormalities in patients with activeischemia. The echocardiogram is essential to excludepericardial effusion in patients with non-specific“cardiomegaly” on chest x-ray.

Findings in right ventricular dysfunction are similar tothose in left ventricular dysfunction, but Dopplerestimates of right ventricular and pulmonary arterypressure are often inaccurate, and right heartcatheterization is frequently required to precisely definepressures in patients with suspected primary pulmonaryhypertension. Echocardiography is useful in evolvingpericardial effusions and with evidence of tamponade orpericardial restriction.

Frontline practitioners often see patients with dyspneathat remains unexplained after initial evaluationincluding physical examination, chest x-ray, pulmonaryfunction testing and the electrocardiogram. Theechocardiogram may be an appropriate next test tosearch for unexpected left or right heart disorders.

Diastolic dysfunction is a form of “functional” inflowobstruction to the left ventricle, with the stiff leftventricle causing decreased passive diastolic filling (“E”-wave) and an increased atrial wave (“A”-wave)seen in the mitral inflow velocity wave forms. Diastolicleft ventricular dysfunction can be worsened by suchstresses as volume overload, exercise-induced ischemiaand worsening of pulmonary status in patients withchronic lung diseases. Examination of mitral inflowvelocity patterns is an important part of theechocardiographic evaluation of any patient withunexplained dyspnea.

Unexpected right ventricular hypertrophy, dilation,tricuspid valve regurgitation and suggestion ofpulmonary hypertension may be found on examinationof the right heart.

59 F. Ultrasound Procedures (continued)

Evaluation of theDyspneic Patient


A normal echocardiogram study excludes most majorcardiac dysfunction. Further evaluation including stresstesting or catheterization may be required to excludemyocardial ischemia as a cause of dyspnea.

In most patients suspected of pe, other studiesenumerated above are performed for diagnosis.However, for patients who are too unstable to betransported to radiology or as an emergent screeningtechnique while awaiting other studies, the trans-thoracic echocardiogram may be suggestive of pe,showing right ventricular dilation and pulmonaryhypertension. Rarely, clot in the right ventricle can bevisualized. Paradoxical ventricular septal motion isreportedly a sign of massive emboli with acute rightventricular pressure overload. Occasionally, thetechnique allows direct imaging of large clots in thecentral pulmonary arteries.

Patients presenting with shock and no obvious sourcesuch as ruptured abdominal aneurysm or gastro-intestinal sepsis, often benefit from echocardiography.Transthoracic echocardiography may reveal severe left ventricular dysfunction, pericardial tamponade,acute mitral or aortic regurgitation, hyperdynamicventricle due to hypovolemia or sepsis or findingssuggestive of massive pe. Transesophagealechocardiography is a more sensitive test for thoracicaortic dissection, posterior mitral valve papillarymuscle rupture, thoracic aortic dissection, valvularvegetations from endocarditis, central pe and prostheticvalve dysfunction.

Duplex ultrasound is widely used in the diagnosis ofvenous thrombosis. The technique uses B-modescanning to evaluate the veins of the legs for patency,blood flow and the presence of thrombi. Thrombi aremost reliably diagnosed using the criteria of non-compressibility. Another criterion is abnormal or

VenousEmbolism (PE)

Evaluation of thePatient in Shock

DuplexUltrasonographyof Leg Veins

60

PleuralUltrasoundExamination

absent flow sounds. Echogenicity of clot is less reliableas acute clots are frequently non-echogenic.

Duplex ultrasonography is sensitive (~93%) andspecific (~95%) for the diagnosis of proximal leg veinthrombosis (popliteal and femoral veins) in symptomaticpatients. The technique is less sensitive for the diagnosisof calf vein thrombosis (~70%) and proximal veinthrombosis in asymptomatic patients (~50%). Serialstudies are useful to detect proximal extension of calfvein thrombosis.

Duplex ultrasonography is often the first test in patients with symptoms and signs of thrombophlebitisin the legs. The procedure is also useful in patients with suspected pe, as it increases the likelihood of pe,when positive.

Pleural ultrasound is not necessary for thoracentesis oflarge volume pleural effusions. However, it allowsprecise localization of small effusions, differentiatesextra- and intrapulmonary mass lesions from pleuralfluid, helps define loculations and guides optimallocation for catheter drainage of complicated effusions.For aspiration of pleural collections, it is preferred thatthe thoracentesis be performed at the time ofultrasonography since skin marks and fluid can shiftwith change in patient position and result in anunsuccessful procedure. ■

61 F. Ultrasound Procedures (continued)


References

Feigenbaum H. Echocardiography. 5th ed.Philadelphia, PA: Lea & Febiger; 1994. pp 695. Classicand comprehensive text on echocardiography.

Gelernt MD, Mogtader A, Hahn RT. Transesophagealechocardiography to diagnose and demonstrateresolution of an acute massive pulmonary embolus.Chest 1992;102:297-299. Case report and review oftransesophageal echocardiographic diagnosis ofmassive PE. In addition to findings of pulmonaryhypertension, the technique can provide directvisualization of a central clot.

Pearson SD, Polak JL, Cartwright S, et al. A criticalpathway to evaluate suspected deep vein thrombosis.Arch Intern Med 1995;155:1773-1778. Describes anappropriate clinical strategy for the use of venousultrasound in the diagnosis of above- and below-the-knee deep venous thrombosis.

Shapiro SM, Bersohn MM, Laks MM. In search of theHoly Grail: The study of diastolic ventricular functionby the use of Doppler echocardiography. J Am CollCardiol 1991;17:1517-1519. Excellent discussion ofthe complexities and controversies in the use ofDoppler measurement of left ventricular inflowvelocities to assess diastolic dysfunction.

62

63

G. CardiacCatheterization

Indications

Complicationsand RelativeContraindications

Cardiac catheterization is a procedure, or, moreaccurately, a group of procedures, in whichcatheters are introduced into the heart through

veins or arteries to provide information aboutcardiovascular anatomy and function. Although cardiaccatheterization is relatively safe, it does carry some risksand expense. Therefore, as with any procedure, therisk/benefit ratio must be considered before recommendingit. The benefit usually consists of important informationwhich will guide a therapeutic decision. The question,“How will the obtained data change the therapeuticplan?,” is always appropriate in considering whether ornot to recommend cardiac catheterization.

Cardiac catheterization can confirm the presence of aclinically suspected condition, define its anatomic andphysiologic severity and determine whether importantassociated conditions are present. It is usually indicatedwhen the patient is experiencing increasing orsignificant symptoms of cardiac dysfunction or whenother studies indicate a high risk for development of asignificant complication such as a myocardialinfarction. Cardiac catheterization is usually indicatedto define the anatomy when a cardiac surgicalprocedure is being considered. Exceptions include whendecisions regarding cardiac surgery can be made byclinical examination and non-invasive studies such asechocardiography (See Section F). Clinical examplesmight include uncomplicated patent ductus arteriosusor atrial septal defect.

The mortality rate associated with diagnostic cardiaccatheterization is quoted as being 0.1% or 1 in 1,000.Complications include myocardial infarction, perforationof the heart and great vessels, ventricular tachycardia orfibrillation, atrial arrhythmias or A–V block,thromboembolic complications including stroke,bleeding, infection and hypersensitivity reaction tocontrast agents.

Techniques

Relative contraindications include uncontrolledventricular irritability, hypokalemia, digitalis toxicity,uncorrected hypertension, decompensated heart failure(especially acute pulmonary edema), anticoagulatedstate with an elevated prothrombin time, known severeallergy to radiographic contrast agents and severe renalinsufficiency. The risk of complications with several ofthese relative contraindications can be reduced bytreatment. In addition to correction of metabolic andphysiologic abnormalities, this can include changingfrom an oral anticoagulant to heparin to facilitate rapidreversal, if necessary, or dialysis to remove fluid andlessen the risk of radiographic contrast load in thepresence of renal insufficiency.

Catheters can be introduced through a brachial arteryor vein, the subclavian or internal jugular veins, or afemoral artery or vein. Catheterization of either theright or the left heart can be accomplished depending on the suspected condition and the desired information.With the catheter in the heart or great vessels, pressuremeasurements as well as measurements of flow (cardiac output), can be obtained. Cardiac output canbe calculated or measured using the Fick principle:

Cardiac output=

vo2

Arterial O2 content – mixed venous O2 content

Cardiac output can also be measured using indicator–dilution techniques or angiography. Angiography usingcontrast agents can define the anatomy of the coronaryarteries, left ventricle or aorta. Angiography can alsoconfirm valvular regurgitation and the ventricularejection fraction. Pressure measurements, includingdetermination of pressure gradients across valves, canhelp define valvular stenosis and regurgitation,pulmonary hypertension, hypertrophic obstructive


65 G. Cardiac Catheterization (continued)

PulmonaryArtery (PA)Catheterization

cardiomyopathy, other cardiomyopathies and cardiac tamponade. Cardiac catheterization is usuallyperformed with the patient awake, but sedated(conscious sedation).

Pulmonary artery (pa) catheterization using a balloon-tipped flow-guided catheter (Swan-Ganzcatheterization, named for the cardiologists whodeveloped this technique), deserves special comment.This procedure is generally used in critically ill patientsin the Intensive Care Unit (icu). It may either be donefor a short period of time to obtain diagnosticinformation, or continued for a period of days for thepurpose of hemodynamic monitoring and guidance oftherapy over time.

By inflating the balloon with the catheter in thepulmonary artery, a segment of the pulmonary vascularsystem is changed to a state without flow, allowingmeasurement of an approximation of the pressure in the left atrium, the balloon occlusion pa wedgepressure. The pressure that is actually measured is thatat the most proximal point of the occluded pulmonaryvascular system where flow is present (See Figure 12) — a value which is very close to left atrial pressure.

A recent large retrospective study suggested that the useof pa catheterization may be associated with increasedmortality, even after attempting to control for severityof illness (a difficult task, especially in a retrospectivestudy). This has heightened the controversy over therole of pa catheterization. Currently, a number ofstudies are underway in North America and Europeinvestigating the use of pa catheterization and its effecton outcome in a variety of specific clinical circumstances.Pending the results of those studies, a prudent approachis to be particularly critical about the indications forplacing such a catheter, the quality of the data beingobtained, the clinical therapeutic response to those dataand the length of time the catheter remains in

Figure 12 Measuring Pulmonary Artery (PA) Pressure


Source: Shoemaker WC. Chapter 17: Physiologic monitoring of thecritically ill patient. Shoemaker WC (ed.) et al: Textbook of Critical Care.2nd ed. Philadelphia, PA: W. B. Saunders Company; 1989. p 155.

66

place. Regarding the last issue, it is useful to ask on adaily basis whether therapeutic decisions are beingmade on the data being collected. If not, the cathetershould be discontinued.

The primary monitoring uses of pa catheterizationinclude the following:

1. To assess the adequacy of intravascular volume.This may be warranted in patients withhypotension, oliguria or the high-risk surgicalpatient.

2. To assess the effect of changes in the pulmonarywedge pressure on pulmonary edema.

3. To assess therapy for shock. This includes: a. vasodilator and inotrope therapy in

cardiogenic shock,b. volume, vasopressor and inotrope therapy in

septic shock and c. volume therapy in hypovolemic shock.

4. To assess the effects of positive end-expiratorypressure (PEEP) on cardiac output in adultrespiratory distress syndrome (ards).

Ensuring high quality data requires a knowledge of thetechnical aspects of obtaining the data and anunderstanding of normal physiology and patho-physiology. This subject is beyond the scope of thisSection. The interested reader is referred to the reference list which follows. ■

67 G. Cardiac Catheterization (continued)

Indications

References

Connors AF, Jr., Speroff T, Dawson NV, et al. Theeffectiveness of right heart catheterization in the initialcare of critically ill patients. support Investigators.JAMA 1996;276:889-897. This article summarizes thesupport Study paper reporting a higher mortality incritically ill patients receiving a pa catheter.

O’Quin R, Marini JJ. Pulmonary artery occlusionpressure: Clinical physiology, measurement, andinterpretation. Am Rev Respir Dis 1983;128:319-326.An older reference, but still the best review describingthe assumptions and techniques involved in themeasurement of pa wedge pressure by the balloonocclusion technique. An excellent review of the effect of respiratory pressures on intrathoraciccardiovascular pressures.

Pepine CJ, Lambert CR. Chapter 56. Diagnostic andtherapeutic cardiac catheterization. In: Kelley WN, (ed).Textbook of Internal Medicine. 2nd ed. Philadelphia,PA: J. B. Lippincott Company; 1992. pp 298-306. Acomprehensive review of cardiac catheterization.

Shoemaker WC. Chapter 17: Physiologic monitoring ofthe critically ill patient. Shoemaker WC et al (ed.):Textbook of Critical Care. 2nd ed. Philadelphia, PA: W. B. Saunders Company; 1989. pp 1519.

Swan HJ, Ganz W, Forrester J, et al. Catheterization ofthe heart in man with use of a flow-directed balloon-tipped catheter. N Engl J Med 1970;283:447-451. Theoriginal article describing the use of a flow-directed pacatheter in humans by Swan, Ganz, et al.


69

H. SputumStudies

Respiratory TractInfections andSputum Studies

Sputum analysis is performed to aid with thediagnosis of a variety of respiratory disorders.Broadly speaking, the diseases for which sputum

studies have been employed can be classified asinfectious, neoplastic or other inflammatory conditions.Appropriate and efficient utilization of sputum studiesrequires a clear understanding of the indications andlimitations of these tests.

Sputum tests have historically been a primary diagnostictool in pneumonia. Specific methods are noted below.

The Gram Stain: Learned as a medical student, this testhas been a sentimental favorite of physicians for years,but its validity in identifying etiologic agents involved inbacterial pneumonia has been challenged. Indeed,recent guidelines of the American Thoracic Society(ats) and Canadian Thoracic Society (cts)/CanadianInfectious Diseases Society (cids) have emphasized“empiric” treatment for most cases of community-acquired pneumonia (cap) based on epidemiologicaland clinical features of the patient. By contrast, the newversion of the Infectious Diseases Society of America(idsap) places more emphasis on sputum Gram stain.All three of the current guidelines stratify the evaluationof cap by the facilities in which they are to be treated.For patients who are diagnosed in the office oroutpatient department and are to be treated at home,the ats and cts/ cids guidelines both advocateempirical therapy without bacteriological studies.However, the idsa statement makes sputum stain andculture optional. All groups advocate sputum studiesfor patients whose status requires hospital-basedtreatment.

To be a valid predictor, the test must be done on a“good specimen” and read by a competent observer. A“good” sputum specimen is denoted by a high numberof neutrophils (> 25 per low power field), and a lownumber of epithelial cells (< 10 per low power field),


with a consistently prominent pathogen (e.g., Gram-positive diplococci, Gram-negative rods, etc.). Onemight regard sputum Gram stain results in thefollowing manner: a clearly “positive” good specimenis useful in establishing the probability of variousbacterial pneumonias, but a negative study does nothave strong predictive value.

Special stains may be helpful in detecting “exotic”pneumonias due to mycobacteria, fungi, nocardia,legionella or pneumocystis. Thus, if clinical features,radiographic findings, epidemiological profiles and/orfailure to respond to conventional therapy suggest thepossibility of an unusual pathogen, “special stains”should be requested. This is particularly relevant topatients with immunosuppression.

Most patients can spontaneously expectorate lowerrespiratory tract secretions on request. However, forvarious reasons, some are unable to do so. “Induction”of cough and sputum by inhalation of heated orhypertonic saline via nebulizer may facilitate retrievalof useful specimens in these cases.

Culture Techniques: Cultivation of respiratorysecretions has variable utility in the diagnosis ofpneumonia. Particularly problematic is diseaseassociated with microbes which are part of the normalrespiratory flora, i.e., pneumococcus, haemophilus,moraxella, etc. Nonetheless, cultivation may beappropriate to both confirm the presence of thesuspected pathogen and to study in vitro susceptibility.The combined findings of a Gram stain demonstratingdominant organisms and a culture positive for suchorganisms are especially useful.

As with microscopy, cultivation of exotic organismsmay require specialized methods including selectivemedia, enrichments or incubating practices. Thus, ifexotic agents are suspected, specified cultures for

71 H. Sputum Studies (continued)

mycobacteria, nocardia, fungi, legionella or chlamydiamay be ordered. Routine sputum cultures for anaerobicbacteria are useless due to the inevitable exposure tooxygen in the upper airway.

Other Sputum Tests for Pneumonia: In addition tomicroscopy and culture, a variety of novelmethodologies are being used to identify pathogens insputum. For M. tuberculosis and other mycobacteriasuch as M. avium complex or M. kansasii, nucleic acidamplification (naa) techniques have proven to be rapid(24 to 48 hours), and reliable (85% to 95% sensitive,95% to 100% specific), but are currently recommendedonly in specimens which are positive on microscopy.

Direct fluorescent antibody tests have proven quitespecific (± 90%), but relatively insensitive (± 50%) forLegionella pneumophila. Urinary antigen is moresensitive for L. pneumophila but is limited to the mostcommon serovar, type 1. Preliminary data suggest apossible role for urinary antigen tests for invasivedisease due to pneumococci.

Empirical treatment of cap has become an endorsedand widely accepted practice in the United States and Canada. This is based on:

1. A high-probability of efficacy with agents suchas the newer fluoroquinolones, macrolides orazolides,

2. Mistrust of the accuracy of sputum studies,3. The observation that even aggressive

microbiological and serological testingidentifies an etiologic agent in less than 50% ofcases, and

4. The desire to curtail expenditures for testing.

The counter arguments, as framed by the idsa, includethis logic in support of microscopy, cultivation or othermeans to establish a specific etiologic agent:

1. It permits selection of an “optimal” agentagainst the specific pathogen,

2. Selection of a specific antibiotic will limit costs,the risk of acquired drug resistance and drug toxicity, and

3. There is epidemiological utility in identifyingpathogens such as legionella, Hantavirus orpenicillin-resistant pneumococci,

a. careful/improved studies should increasethe yield to above 50%,

b. inability to see/recover typical pathogensshould trigger earlier pursuit of atypicalpathogens,

c. the absence of particularly ominouspathogens such as Staphylococcus aureusor Gram-negative rods is reassuring to the clinician and

d. the average cost of standardmicrobiological studies is < 1% of the average hospital bill!

Overall, we conclude that empiric choice of antibioticsfor cap in a general adult population to be treated athome is a practical and appropriate strategy. While thearguments posed in the idsa guidelines are rational,there is no persuasive evidence documenting improvedoutcomes, lessened drug resistance or cost savings fromthis approach. However, clinicians should be moreaggressive in obtaining respiratory secretions formicroscopy, cultivation ± other special studies forpatients whose pneumonia is severe enough to merithospitalization, or those with special risk factors. Thesemight include recent hospitalization, nursing homeresidency, very poor dental hygiene, exotic exposures(birds, rabbits, rural rodents or travel to the southwestUnited States), underlying structural abnormalities ofthe lungs or immunodeficiency status.


73 H. Sputum Studies (continued)

Respiratory TractNeoplasms andSputum Studies

Cytologic examination of cells exfoliated from thetracheobronchial tree and lung parenchyma has provenhighly useful in the diagnosis of cancer involving these tissues.

Sputum cytology is an appropriate test for individualswith significant risk factors for respiratory tract cancerincluding smoking (≥ 30 pack-years), or exposure tocarcinogens including passive tobacco smoke, asbestosor uranium. However, the overall return for screeningsuch populations is too low to be justified. But, if weselect for persons with chronic airflow obstruction onsimple spirometry, the yield of positive findings mayreach 1% to 2%. Such a process appears to result inearly diagnosis and improved survival.

Other indications for sputum cytology studies amongindividuals with other risk factors include anunexplained protracted cough, hemoptysis orsuspicious findings on chest radiography. Sputumcytology is more likely to yield positive results amongpatients with larger or centrally located tumors.

Positive cytology for malignancy should be combinedwith bronchoscopy (See Section I), computedtomography, as well as careful history and physicalexamination and other laboratory studies to localizeand stage the neoplasm.

Overall, a single cytology is positive in roughly 50% ofpatients with bronchogenic cancers. Three sputumcytology examinations increase the yield modestly andshould be done in high-risk subjects.

Negative cytology results are common in patients withsmaller peripheral nodules. One might order cytologystudies in such patients hoping that “positive” findingswill preclude more invasive studies. If such tests arenegative, one must proceed to more aggressive studies. ■

References

Bartlett JG, Breiman RF, Mandell LA, File TM, Jr.Community-acquired pneumonia in adults: Guidelinesfor management. The Infectious Diseases Society ofAmerica. Clin Infect Dis 1998;26:811-838. The 1998idsa guidelines take a more microorganism-centeredapproach to management. They include excellentreviews of both typical and atypical respiratory pathogens.

Mandell LA, Marrie TJ, Grossman RF, Chow AW,Hyland RH. The Canadian Community-AcquiredPneumonia Working Group. Canadian guidelines forthe initial management of community-acquiredpneumonia: An evidence-based update by theCanadian Infectious Diseases Society and the CanadianThoracic Society. Clin Infect Dis 2000;31:383-421. Avery thoughtful and well-balanced review of this topic.

Mehta AC, Marty JJ, Lee FY. Sputum cytology. ClinChest Med 1993;14:69-85. A helpful review of theutility and limitations of sputum studies in the diagnosisof respiratory tract cancer.

Niederman MS, Bass JB, Jr., Campbell GD, et al.Guidelines for the initial management of adults withcommunity-acquired pneumonia: Diagnosis, assessmentof severity, and initial antimicrobial therapy. AmericanThoracic Society. Medical Section of the American LungAssociation. Am Rev Respir Dis 1993;148:1418-1426.The original guidelines for cap were written in 1993. Thedocument emphasizes an epidemiological or risk-factorapproach to diagnosis, hospitalization and treatment.

Saccomanno G. Diagnostic Pulmonary Cytology. 2nded. Chicago, IL: American Society of ClinicalPathologists Press; 1986. pp 211. A beautiful collectionof 90 color plates which illustrate normal and manyabnormal cytologic and histologic studies withemphasis on various types of primary and secondarycancers of the lung.


75

I. Bronchoscopy

Indications

ComplicationsandContraindications

Endoscopy of airways is a widely practiced, safeand effective modality of diagnosis and, lessoften, treatment. The original technique

employed a metal, open-tube device, the rigidbronchoscope (rb). Over the past 30 years, thisprocedure has largely been supplanted by the flexiblefiberoptic (ffb) method. The indications forbronchoscopy among patients seen in frontline practiceare delineated below and in Table 15.

Generally, bronchoscopy is performed bypulmonologists or, less frequently, thoracic or generalsurgeons. The major advantages of the flexibleendoscopy include ease of performance under topicalanesthesia, ability to directly examine more remoteairways and the capacity to pass biopsy forceps orculture brushes into the distal airways and lungparenchyma. The rigid, open-tube device is theinstrument of choice for the extraction of larger foreignbodies, evaluation and management of massivehemoptysis, dilation/stenting of stenotic or collapsibleairways and for laser or brachytherapy ofendobronchial neoplasms.

The risks of bronchoscopy can be compartmentalizedinto adverse reactions to the premedications or topicalanesthetic agent, mechanical trauma to the airways or lungs, bleeding and infectious or inflammatorysequelae of passage of the instrument and/or instillationof lavage fluids.

Overall, the experience with the ffb technique in theUnited States has been quite benign. One surveyindicated minor complications in 0.2%, and majorproblems in 0.08% of patients undergoing theprocedure. It should be noted though, that these wereretrospective, self-reported events. An earlier 1976series described 12 deaths (0.02%), and “life

Condition/Problem Instrument Comments Of Choice

Chest x-ray suspicious FFB Bronchoscopy indicated all lesions except very small, for lung cancer peripheral nodules which cannot be reached.

Hemoptysis FFB or RB For minor hemoptysis the FFB allows more thoroughvisualization of airways, but, for massive bleeding, the RBpermits more effective aspiration of blood and airway control.

Diffuse interstitial or FFB Bronchoscopy with transbronchial lung biopsy and fibronodular lung disorders bronchoalveolar lavage is often the first step in the

diagnosis of diffuse lung disorders such as sarcoidosis,idiopathic pulmonary fibrosis, etc.

Cough FFB Endoscopy done for chronic cough but a normal chest x-ray has a very low yield. Evaluation to rule out morecommon causes of cough (sinusitis, esophageal reflux),is indicated prior to bronchoscopy.

Wheezing/stridor FFB “All that wheezes is not asthma”…but most is! Onceasthma has been excluded, other entities should beconsidered, (See Section A). Refractory, chroniclocalized wheezing should lead to endoscopy. One mayeither perform serial laryngoscopy, then bronchoscopy,or — if the operator is skilled at assessing both laryngealand lower airway anatomy and function — a singleendoscopy may be adequate to rule out tumors,strictures or foreign bodies.

Undiagnosed pneumonia, FFB Treatment of community-acquired pneumonia (CAP), is refractory or progressive most often empiric, (See Section H). In cases when the

patient does not respond to therapy as expected, FFBmay be indicated to rule out foreign body or tumor, obtaindiagnostic material and, occasionally, to removeinspissated secretions from airways.

Foreign body RB For patients observed or suspected to have aspirated aforeign object into their airways, examination andretrieval is indicated. If the object is large enough orplaced in a critical site where airway patency is seriouslycompromised (wheezing, choking, hypoxia, largospasm),emergent retrieval is indicated. The RB is clearly asuperior device in terms of removal of the object andcontrol of ventilation. For small, more remote objects, theFFB may be adequate in the hands of a skilledpractitioner.

FFB=Flexible fiberoptic bronchoscopy, R =Rigid bronchoscopy


Table 15 Overall Indications for Bronchoscopy

76

77 I. Bronchoscopy (continued)

Summary

threatening” cardiovascular events (0.5%) in 48,000endoscopies. A 1978 report noted major complicationsin 1.7% of patients and a mortality rate of 0.12%.

The few absolute contraindications to ffb arehemodynamic instability, life threatening arrhythmiasand severe hypoxia which in the non-intubated patient,if worsened, might be life threatening. A number offeatures increase the risks of morbidity and mortality.They include extensive bullous emphysema, severehypercapnia (paco2 > 60), unstable angina, recentseizure activity, labile asthma, significantcoagulopathy/thrombocytopenia and advanced airwaynarrowing. Obviously, the competency of the operator,the capabilities of support personnel and the adequacyof the facilities used, all influence outcomes. The moreominous sequelae of bronchoscopy include:

1. Premedications: hypoventilation, hypotension,2. Topical anesthetics: laryngobronchospasm,

seizures, arrhythmias,3. Endoscopy/biopsy/brushing: bleeding,

bronchospasm, hypoxia, arrhythmias, fever,pneumonia and pneumothorax,

4. Bronchoalveolar lavage (bal): Fever associatedwith release of cytokines due to perturbationof alveolar macrophages may occur in asubstantial portion of those undergoing bal.Careful observation is required to distinguishthis reaction from true infectious pneumoniasince bal typically results in retention of fluid in the air spaces and new shadows onchest x-ray.

Bronchoscopy is a useful and safe tool for diagnosis andmanagement of a variety of airway and lung parenchymaldisorders. Optimally, it should be performed by a well-trained endoscopist with adequate support staff andfacilities. A full appreciation of the limitations and risksis essential to selecting patients for this procedure. ■

References

Limper AH, Prakash UB. Tracheobronchial foreignbodies in adults. Ann Int Med 1990;112:604-609. Areport from the Mayo Clinic on their experience withboth ffb and rb in management of foreign bodies.

Pereira W, Jr., Kovnat DM, Snider GL. A prospectivecooperative study of complications following flexiblefiberoptic bronchoscopy. Chest 1978;73:813-816. Asmall but prospective study which recorded higher ratesof complications than earlier series.

Prakash UB, Offord KP, Stubbs SE. Bronchoscopy inNorth America: The accp Survey. Chest1991;100:1668-1675. The American College of ChestPhysicians sponsored this survey. While it is limited byretrospective self-reporting, it reflects wide sampling.

Prakash UB, Stubbs SE. The Bronchoscopy Survey.Some reflections. Chest 1991;100:1660-1667. Athoughtful analysis of the roles of ffb and rb by twohighly experienced practitioners from the Mayo Clinic.

Suratt PM, Smiddy JF, Gruber B. Deaths andcomplications associated with fiberoptic bronchoscopy.Chest 1976;69:747-751. A self-reported retrospectivequestionnaire involving over 48,000 procedures.

Zavala DC. Complications following fiberopticbronchoscopy. The “Good News” and the “Bad News.”Chest 1978;73:783-785. An editorial commentary by affb practitioner who favored endoscopy throughendotracheal tubes.


79

Nasal continuouspositive airwaypressure (CPAP), isthe most common andeffective therapyavailable for sleepapnea. The airpressure is adjustedso that it is justenough to preventairway collapseduring sleep. Apneaswill recur if thismodality is not in use,therefore 100%adherence to therapyis optimum.

J. Sleep Studies

Epidemiologyand Etiology ofSleep DisorderedBreathing (SDB)

Sleep apnea, first described in 1965, is a seriousand potentially life threatening disorder whichaffects an estimated 18 million Americans of

both sexes in all age groups. It is a breathing disordercharacterized by repeated collapse of the upper airwayduring sleep, culminating in apnea. It is more prevalentin the obese individuals, males, the elderly, ethnicminorities and those with systemic hypertension. Afamilial tendency for sleep disordered breathing (sdb)has been reported, raising the question of a genetic link.It is estimated that 4% of middle-aged men and 2% ofmiddle-aged women meet minimal criteria for sleepapnea syndrome. A detailed history, physicalexamination and standardized diagnostic testingtogether can establish abnormalities of sdb. AnAmerican Academy of Sleep Medicine Task Forcerecently outlined the diagnostic criteria and availablemeasurement techniques necessary to establish thediagnosis of the following sdb abnormalities:Obstructive Sleep Apnea-Hypopnea Syndrome (osahs),Central Sleep Apnea-Hypopnea Syndrome (csahs),Cheyne-Stokes Breathing Syndrome (csbs), and SleepHypoventilation Syndrome (shvs).

osahs, by far the most common sleep disorder, occurswhen airflow is blocked in the upper airway by physicalconstraints while efforts to breath continue. The throat,tongue and/or soft palate relax, fall back in the throatand block the airway. Obese patients have redundantposterior pharyngeal tissue which may contribute tothis airway blockage. Apneas result and lead to oxygendesaturation, hypercapnia and frequent arousals thatprevent the patient from entering restorative deep sleep.csahs occurs when the brain fails to send theappropriate signals to respiratory muscles to initiatebreathing. csbs occurs in patients with cardiacdysfunction, most commonly in association with severecongestive heart failure and central nervous systemdisorders. shvs is defined as an abnormal increase inpaco2 during sleep, which results in hypoxemia,erythocytosis, pulmonary hypertension and/or


J. Sleep Studies (continued)

ClinicalPresentation

respiratory failure. An overlap syndrome of copd andosahs is also common with a prevalence of 10% to20%, higher than that expected from multiplying theincidence of copd and osahs. This distinction is ofclinical importance. It has been demonstrated thatsleep-related hypoxemia is more pronounced in thisoverlap syndrome than in patients with either copd orosahs alone.

Recognition of signs and symptoms of sdb in theprimary care setting in conjunction with diagnostictesting by physicians with specialized training in sleepdisorders leads to early diagnosis of sdb and preventionof the serious sequellae of these disorders. Sleep apnea isoften characterized by habitual snoring associated withsnorting, gasping and choking sensations. Some 40% to60% of all adults report snoring. Of note, all patientswho snore do not have sleep apnea. Spouses or relativesare usually the first to recognize snoring and nocturnalapneas. Witnessed apneas are highly predictive ofosahs. Patients are often surprised or in denial of thesesymptoms. In fact, self-reported awakenings are oftennot indicative of sleep apnea, but rather a sign ofchronic heart failure, gastroesophageal reflux,nocturnal asthma, nocturia or panic disorder. Patientswith sleep apnea may also report early morningheadaches and dry mouth, excessive daytime sleepiness,decreased daytime concentration and performance/productivity, depression, irritability, sexual dysfunction,learning and memory dysfunction and falling asleep atwork, on the phone—or of great concern—whiledriving, (See Table 16).

A history of excessive daytime sleepiness should raise asuspicion for sleep apnea. The Epworth Sleepiness Scaleand the Stanford Sleepiness Scale are surveys widelyused for patient self-reporting of sleepiness, which aidin the diagnosis of sdb. The Epworth scale has beenvalidated in clinical studies and correlates with objective

81

Table 16 Patients at Risk for Sleep Apnea

Symptoms

Chronic, loud snoring

Gasping or choking episodes during sleep

Excessive daytime sleepiness (especially drowsy driving)

Automobile- or work-related accidents due to fatigue

Personality changes or cognitive difficulties related to fatigue

Signs

Obesity, especially nuchal obesity (neck size ≥17 inches in males and 16 inches in females), >120% ideal body weight, or body mass index (BMI),≥30 kg/m2

Systemic hypertension

Nasopharyngeal narrowing

Pulmonary hypertension or cor pulmonale (rarely)

Table 17 The Epworth Sleepiness Scale1

How likely are you to doze off or fall asleep in the following situations, in contrast to just feelingtired? This refers to your usual way of life in recent times. Even if you have not done some of thesethings recently, try to work out how they would have affected you. Use the following scale tochoose the most appropriate numbers for each situation.

0 = would never doze1 = slight chance of dozing2 = moderate chance of dozing3 = high chance of dozing

Situation Chance of Dozing

Sitting and reading _____Watching TV _____Sitting, inactive in a public place _____As a passenger in a car for an hour _____Lying down in the afternoon _____Sitting and talking to someone _____Sitting quietly after a lunch without alcohol _____In a car, while stopped for a few minutes in traffic _____

A score of 10 or greater is highly suggestive of daytime sleepiness.

1 Adapted from: Johns MW. Reliability and factor analysis of Epworth Sleepiness Scale. Sleep 1992:15:379.


83 J. Sleep Studies (continued)

measurements of sleepiness. A score of 10 or greater ishighly suggestive of daytime sleepiness (See Table 17),but is not specific for sleep apnea.

Although the exact link is unknown, the prevalence ofsystemic hypertension in patients with sdb is very high.Fifty percent of patients with sleep apnea have systemichypertension. Sleep apnea can also be associated withirregular heart beats, heart attacks and strokes.

Certain abnormalities in the physical examination can also be suggestive of sdb (See Table 18). Thephysical finding which is most predictive of osahs iscentral obesity. Sleep apnea occurs in individuals whoare overweight (Body Mass Index [bmi], > 30 kg/m2).Forty percent of individuals with a bmi ≥ 40 kg/m2

and 50% of individuals with a bmi ≥ 50 kg/m2

have significant sdb. Men and women with a neckcircumference of 17 or 16 inches respectively have a higher incidence of sleep apnea. Patients withanatomic abnormalities of the nose, throat or otherareas of the upper airway also have an increasedincidence of osahs.

Overnight PSG: is the gold standard for diagnosis ofosahs. An overnight psg includes recordings ofairflow, ventilatory effort, oxygen saturation,electrocardiogram, body position, electrooculography(eog), electromyography (emg) andelectroencephalography (eeg). In standard, laboratory-based psg, a technician is present for the entireovernight study. Patients with severe osahs can have asmany as 20 to 30 apneas per hour of sleep.Accordingly, the diagnosis of osahs can be made earlyin the study, and the second half of the evening can beused to titrate the treatment (nasal continuous positiveairway pressure [cpap]). When diagnosis and cpaptitration are done in a single night, the psg is called a“split night” study.

Diagnostic Tests

The eeg is the core measurement of psg, definingrelaxed wakefulness, stage 1 through 4 of non-rapid eyemovement (nrem) sleep and rapid eye movement (rem)sleep. Standard lead placement and interpretation is ofparamount importance. The identification ofcharacteristic eeg patterns can help diagnose specificsleep disorders: narcolepsy (occurrence of rem within15 minutes of sleep onset), sleep apnea (increasedfrequency of arousals and body movements, k complexes),alpha-delta sleep (alpha intrusion into rem sleep inpatients with psychiatric disorders) and transientarousals (daytime sleepiness or old age in the absence ofapneas). A summary of the amount of time spent ineach stage of sleep (rem and the 4 stages of nrem) isgenerated to evaluate sleep architecture, sleep latencies(elapsed time from lights out until 3 consecutive stage 1events or one event of any other stage occurs), cycles(nrem-rem descriptions) and the timing of events(apneas, hypopneas, oxygen desaturation, arrythmias,etc.) with rem or nrem sleep.

The eog records the cardinal sign of rem sleep, thephasic bursts of rapid eye movements. Thismeasurement is essential for sleep stage scoringcriterion. The emg measures activity in the mentalis and submentalis muscles located under the chin (used as a criterion for rem sleep), in the anterior tibialis(important in evaluating patients with periodic limbmovements in sleep, a.k.a., periodic limb movementdisorder [plmd]), in the masseter (to monitor bruxism) and occasionally in the intercostals (tomonitor respiratory effort). Airflow is measured with a thermocouple, thermistor, pneumotachometers orcapnography (infrared analysis of inhaled/exhaled co2). Ventilatory effort is monitored by string gauges,plethysmnography, magnetometers, emg or esophageal pressure.(continued)



The Apnea-Hypopnea Index (ahi) is the mostcommonly used criterion derived from psg testing toestablish the diagnosis of osahs. The ahi is defined asthe sum of apnea and hypopnea events divided by thehours of sleep. In adults, apnea is defined as thecessation or near cessation of airflow for 10 seconds orlonger which occurs despite continued ventilatoryefforts. The strict definition of hypopnea is morecontroversial. It is often described as a disturbancewhich causes a 50% reduction in airflow or a reductionin airflow that causes a physiologic abnormality i.e. a3% fall in oxygen saturation or an arousal. There is noconsensus on what constitutes a “normal” ahi. Adultsmay experience up to five events (apneas orhypopneas), per hour of sleep and be asymptomatic. Itis clear, however, that an increase in ahi closelycorrelates with the severity of symptoms. In general, theliterature supports that the ahi is diagnostic of sleepapnea when the index is ≥ 10, or if the ahi is ≥ 5 inconjunction with the self reporting of hypersomulenceor other symptoms of sdb. Another psg measurementis the Respiratory Effort-Related Arousal (rera) where an event is defined as a sequence of breathscharacterized by increasing respiratory effort leading to an arousal from sleep, but which does not meetcriteria for an apnea or hypopnea. Another consistentindex generated from psg testing is the oxygendesaturation index 4% (odi4), the number of 4%drops in oxygen saturation per hour. Furtherclassifications of the definitions and technologyavailable can be found in a summary statement of theAmerican Academy of Sleep Medicine (See Table 18).

Multiple Sleep Latency Test (MSLT): Physiologicalsleepiness can be thought of as the underlyingbiological drive to sleep. The primary index ofsleepiness is the speed with which an individual fallsasleep. This speed is therefore a measure of the intensityof one’s drive to sleep. The mslt measures the speedwith which an individual falls asleep. A mslt is a series

Table 18 Diagnostic Criteria for the Obstructive Sleep Apnea-Hypopnea Syndrome1

The individual must fulfill criterion A or B, plus criterion C

A. Excessive daytime sleepiness that is not better explained by other factors;

B. Two or more of the following that are not better explained by other factors;

Choking or gasping during sleep,

Recurrent awakenings from sleep,

Unrefreshing sleep,

Daytime fatigue,

Impaired concentration, and/or

C. Overnight monitoring demonstrates five or more obstructed breathing events per hour

during sleep. These events may include any combination of obstructive apneas/hypopneas

or respiratory effort related arousals.

1 Adapted from: American Academy of Sleep Medicine Task Force. Sleep-related breathing disorders inadults: Recommendations for syndrome definition and measurement techniques in clinical research.Sleep 1999;22:670.



Treatment

of “nap” opportunities presented at two-hour intervalsbeginning two hours after initial (morning) awakening.The patient is placed into an environment conducive to sleep. They are instructed to allow themselves to fallasleep and not to resist falling asleep. The time it takes the individual to fall asleep is monitored. eeg,eog, submentalis emg, airflow and sound (snoring)parameters are also monitored. Normal individuals will take between 10 and 20 minutes to fall asleep. If the time is 5 minutes or less, the patient is likely tohave a sleep disorder which requires treatment. Other measures of sleepiness include: pupillography,electroencephalography, Maintenance of WakefulnessTest, Vigilance Tests, Profile of Mood States and the two Sleepiness Scales (Epworth and Stanford)mentioned above. mslt is not generally indicated in the work-up of sdb.

Home Sleep Studies: Given the prevalence of sdb inadults and the fact that psg may not be readily availablefor all patients via a formal laboratory-based sleepcenter, considerable interest exists to developinexpensive, yet reliable portable screening devices forsleep disorders which can be used in the home. To date,these devices, which can measure airflow, ventilatoryeffort, heart rate, oxygen saturation and sleepparameters, have not been shown to save time or cost inthe diagnosis of sdg. An excellent review of availabledevices was recently published. While use of oximetryalone has been proposed to diagnose osahs, itssensitivity and specificity are controversial.

The goal for sleep apnea treatment includes bothphysiologic (eliminate sleep fragmentation, apneas,hypopneas and oxygen desaturation) and symptomatic(eliminate snoring and sleepiness, improving quality of life and reducing comorbidities) components (See Table 19). Therapy is individualized based onmedical history, physical examination and results of psg.(continued)


Table 19 Treatment of Sleep Apnea1

Modification of Behavioral Factors

Weight loss (including exercise program)

Avoidance of alcohol and sedatives before sleep

Avoidance of supine sleep position

Nasal CPAP

Non-invasive

Very effective

Patient adherence variable

Oral/Dental Devices

May be useful in mild to moderate cases

Not uniformly effective

Surgical Procedures

(UPPP, Tonsillectomy, LAUP, Nasal and Maxillofacial Surgery)

Invasive

Not uniformly effective

May carry risk

Repeat sleep study is necessary after each procedure

1 From: The National Heart, Lung, and Blood Institute Working Group onSleep Apnea. Sleep Apnea: Is your patient at risk? NIH Publication 95-3803, September, 1995, p 4.

88

89

Behavioral modification is essential: weight loss,avoidance of alcohol, tobacco, sleeping pills andsedatives and perhaps repositioning during sleep (ifapneas occur preferentially while patients lie in oneposition). Patients with sleep apnea should be advisednot to drive if untreated.

Nasal cpap is the most common and effective therapyavailable. The air pressure is adjusted so that it is justenough to prevent airway collapse during sleep. Apneaswill recur if this modality is not in use, therefore 100%adherence to therapy is optimum. However, manypatients use cpap intermittently. Some cpap use is betterthan none at all. Various devices and accessories areutilized to minimize the side effects of nasal irritationand drying, fascial skin irritation, abdominal bloating,mask leaks, sore eyes, rhinorrhrea or nasal congestionand headaches. In certain cases, dental appliances canaid in repositioning of the tongue and jaw for patientswho snore but do not have apneas.

Several surgical procedures have been developed toincrease the size of the upper airway, to reduce the redundancy of upper airway soft tissue and toreconstruct deformities of the nose and/or lower jaw. Some of the more common procedures include: removal of the adenoids and tonsils,uvulopalatopharyngoplasty (uppp), laser-assisteduvulopalatoplasty (laup), tracheostomy and surgicalprocedures to treat obesity. uppp success is in the rangeof 15% to 20%. laup, like uppp, may decrease oreliminate snoring, but not sleep apnea itself.Tracheostomy is definitive therapy and highly effective,bypassing the area of airway collapse. But it is anextreme invasive measure with known complicationsthat are poorly tolerated by the majority of patients.

Administration of supplemental oxygen may improvenocturnal desaturation, but does not primarily treatsleep disruption or daytime sleepiness. Oxygen should



be used in those patients with the “overlap syndrome”,osahs and copd, who have nocturnal desaturationsand indications for oxygen therapy based onconventional criteria.

Once effective therapy has been initiated, all patientsshould be periodically reevaluated for reoccurrence ofsymptoms such as snoring, daytime sleepiness andcomorbidities. The primary caregiver plays a key rolein determining if the patient is adhering to treatmentand in monitoring concurrent problems such assystemic hypertension (which may require lesstreatment if sleep apnea is controlled). If patients areadherent to therapy and symptoms of sleepinesspersist, the patient should be reevaluated andconsideration of diagnoses of other sleep disordersshould be entertained. ■(continued)

90

91

References

American Academy of Sleep Medicine Task Force.Sleep-related breathing disorders in adults:Recommendations for syndrome definition andmeasurement techniques in clinical research. Sleep1999;22:667-689. This report defines in detail thedefinitions and criteria for diagnosis of osahs, csahs,csbs, shvs and gives detailed descriptions andrecommendations for measurement techniques.

Davies RJ, Stradling JR. The relationship between neckcircumference, radiographic pharyngeal anatomy, andthe obstructive sleep apnea syndrome. Eur Respir J1990;3:509-514. Classic reference which correlatesincreased neck circumference with an increasedincidence of obstructive sleep apnea.

Johns MW. Reliability and factor analysis of EpworthSleepiness Scale. Sleep 1992;15:376-381. This articlepresents a commonly used grading system for daytimesleepiness.

Kryger MH, Roth T, Dement WC, (eds). Principals andPractice of Sleep Medicine, 3rd ed. Philadelphia, PA: W.B. Saunders Company; 2000. Chapter 100, pp 1197-1215 and Chapter 104, pp 1251-1257. These twochapters summarize the procedures for monitoring andevaluating sleep and sleepiness in the laboratory setting.

The National Heart, Lung, and Blood InstituteWorking Group on Sleep Apnea. Sleep Apnea: Is yourpatient at risk? nih Publication 95-3803, September,1995, pp 1-10. This monograph from nhlbi reviewsthe definition, prevalence and co-morbidities of sleepapnea. It summarizes how to identify patients, make thediagnosis and treatment options for sleep apnea.


Zubairi A, Phillips B. Chronic obstructive pulmonarydisease and the obstructive sleep apnea hypopneasyndrome (the overlap syndrome). J COPDManagement 2001;1:8-13. An excellent review of theepidemiology, pathogenesis, clinical presentation,diagnostic techniques and treatment options for theoverlap syndrome (copd/osahs).


The authors realize that while most frontline physiciansare not involved in the ventilatory management of theirpatients with respiratiory failure, they may closelyfollow this aspect of their medical care. The purpose ofthis Section is to familiarize primary care physicianswith concepts of mechanical ventilation, not to providespecifics of ventilatory management.

Mechanical ventilator therapy is a centralcomponent of critical care for patients withimpaired respiratory capacity due to various

acute and chronic disorders. Ventilator support isneeded when patients are not capable of maintainingadequate oxygenation (low pao2) or providing adequateventilation (high pco2). Multiple situations applyincluding ventilatory support of patients with acute andchronic lung disease, congestive heart failure,neuromuscular disease, acute trauma and postoperativestatus. Because of the wide array of conditionsrequiring mechanical ventilator support and thedifferent pathologic and physiologic processes that areinvolved, a comprehensive understanding of types ofventilator support is essential for physicians managingthese complex patients. More recently, non-invasivemechanical ventilatory techniques have offered a meansto support patients’ respiratory status withoutintubation and standard ventilation.

This discussion will cover the following modes ofventilatory support:

1. Volume ventilationa. Assist-control (ac) and continuous

mechanical ventilation (cmv)b. Intermittent mandatory ventilation (imv)

and synchronized intermittent mandatoryventilation (simv)

2. Pressure ventilationa. Pressure control ventilation (pcv)b. Pressure support ventilation (psv)

93

K. MechanicalVentilatorySupport andWeaning FromMechanicalVentilation


3. Positive end-expiratory pressure (peep) andcontinuous positive airway pressure (cpap)

4. Non-invasive ventilatory supporta. Continuous positive airway pressure (cpap)b. Bi-level positive airway pressure (bipap)c. Negative pressure chest wall devices,

(e.g., cuirass)

With both ac and cmv modes tidal volumes (tv’s) of 6to 12 cc/kg and respiratory rates (rr’s) of 10 to 14breaths per minute are selected. With cmv, the patientwill only receive the number of breaths and the volumechosen. The ventilator generates whatever pressure isnecessary to deliver the set tv. If the patient has a morerapid rate or pulls increased negative pressure, then theventilator is overridden and there is poor patient-ventilator interface. In contrast, the ac mode allowsfor the patient to add as many breaths per minute aswanted. Each breath delivers the preset tv. In criticalpatients who are heavily sedated, the ac mode allowsfor fine control of minute ventilation (mv=rr tv)while allowing the patient to add extra breaths asdesired. Typical settings for a 70-kg man would be a tvof 500–600 cc with a rr of 12.

As with the ac and cmv modes, tv’s of 6 to 8 cc/kgand rrs of 6 to 14 breaths per minute are selected. Thekey difference between imv-simv and cmv-ac is thatwhen the patient takes additional breaths, the tv isbased on the negative pressure generated by thepatient, not by the preset volume of the ventilator.Thus, with imv, the patient has a preset rate whichdelivers a set tv on a regular basis (e.g., for a rate of 10,one breath is given every 6 seconds). Because breathswith preset tvs are given without regard to thepatient’s spontaneous respirations, the patient couldreceive a much higher tv (the patient’s breath plus thatof the ventilator’s), potentially resulting in excessivevolumes. simv, on the other hand, not only allows thepatient to breathe spontaneously between mechanical

VolumeVentilation

Assist-Control(AC), andContinuousMechanicalVentilation(CMV)

IntermittentMandatoryVentilation(IMV) andSynchronizedIntermittentMandatoryVentilation(SIMV)

94

K. Mechanical Ventilatory Support and Weaning FromMechanical Ventilation (continued)

PressureVentilation

Pressure ControlVentilation (PCV)

Pressure SupportVentilation (PSV)

breaths, but also synchronizes any delivered mechanicalbreaths with the next spontaneous breath. In recentyears, simv has replaced imv in most hospitals. simvweaning consists of gradually reducing the rr overminutes to hours. When the simv rate is 0 to 2 and thepatient supports ventilation, extubation is performed(See Weaning From Mechanical Ventilation).

In patients with no spontaneous respirations who havethe same rr and tv settings, the ac and simv modesfunction in identical manners.

As with volume ventilation modes, a rr must beselected. In contrast to ac and cmv, a peak inspiratorypressure is chosen. The volume delivered is dependenton lung compliance (volume/pressure). Following acuteinjury, lungs become stiff and high pressures (>50 cmh2o) may result from delivery of the usual tv’s, 6 to 8cc/kg, when employing ac or cmv modes. Because highmean airway pressures may cause barotrauma withadditional lung injury, it is sometimes necessary to limitpeak pressures. Peak and mean airway pressures can belimited by use of a pressure control mode (pcv).Because delivered tv’s are lower, the rr is increased toprovide adequate mv. With this mode of ventilation,other more complicated ventilator adjustments arefrequently required. Such patients usually require heavysedation and neuromuscular blockers.

This form of ventilation is used in conjunction withsimv or as additional support to traditional weaning. Aset pressure is selected and delivered with everyspontaneous breath. Because the patient must initiate abreath to receive the pressure support, this should neverbe used alone in patients with significant apneas. Aswith pcv, the tv delivered depends on lung compliance(i.e., the stiffer the lung, the lower the tv for any givenpressure). The use of psv and simv allows for thepatient to receive a set tv from the simv setting andpressure support variable volumes with spontaneousrespirations (See Weaning From Mechanical Ventilation).

95


Both peep and cpap provide continuous airwaypressure and are used in conjunction with eithervolume or pressure modes of ventilation. The purposeis to improve oxygenation not ventilation. This isaccomplished by increasing the functional residualcapacity (See Section B) and recruiting atelectaticalveoli opening previously collapsed lung units.Generally, peep is the term used to describe the positiveairway pressure associated with both volume andpressure ventilation, and cpap is used in associationwith weaning (spontaneous breathing) and non-invasive ventilation. The physiologic effect is identicalsince there is positive airway pressure at all timesincluding end-expiration.

cpap has become an extremely important therapy forpatients with sleep disordered breathing (sdb),especially obstructive sleep apnea. A mask or nasalpillow device is placed over either the nose alone orboth the nose and mouth. The key component tosuccess is a good fit of this facial device. cpap isapplied, usually in the range of 5 cm to 15 cm h2opressure. More recently, this technique has been used in patients with acute pulmonary decompensation (e.g., pneumonia and copd) to prevent intubation andmechanical ventilation.

bipap represents a refinement of cpap. bipap not onlyprovides continuous positive airways pressure (cpap)at end-expiration, but it also provides a higher peakpressure which improves oxygenation and ventilationduring inspiration. bipap not only provides positiveairway pressure during inspiration, improvingventilation, it also provides continuous positive airwaypressure (cpap) at end-expiration, improvingoxygenation. As with cpap, a new family of improvedmasks that either cover the nose alone or both themouth and nose must be carefully fitted. Typical initialsettings might be an inspiratory positive airwaypressure (ipap) of 10 cm h2o and an expiratory positive

Positive End-ExpiratoryPressure (PEEP),and ContinuousPositive AirwayPressure (CPAP)

Non-InvasiveVentilatorySupport

ContinuousPositive AirwayPressure (CPAP)

Bi-level PositiveAirway Pressure(BiPAP)

96

airway pressure (epap) of 4 cm h2o. bipap can beadministered with a spontaneous setting where thepatient controls the rr, a timed setting where the rr ispredetermined, or both. The latter is similar to simvand cpap ventilation. As this form of respiratorysupport has become more available, it has generallyreplaced cpap as the preferred non-invasive positivepressure ventilation mode in treatment of acute and chronic respiratory insufficiency. Patients withsevere neuromuscular diseases who do not want a tracheotomy with volume ventilation support nowhave bipap as an option.

The development of these devices dates back to thepolio era and the use of the iron lung. Patients wereplaced in a metal tube with a rubber seal around theneck and negative pressure was generated to expandthe chest wall. Passive exhalation occurred and thecycle was repeated. Because these were large, bulky,non-portable devices, their use was limited. Currently,many refinements on this concept have produced small,portable devices that fit over the thorax. The originalcuirasses were made of firm plastic, which sometimesmade a tight seal on the chest wall difficult. Newmodels employ more flexible materials allowing forbetter comfort. Since bipap has become available, thesedevices are used less frequently.

The use of mechanical ventilation with an endotrachealtube or tracheostomy may be associated with manyunforeseen complications. These are brieflysummarized in Table 20, based on a prospective studyin a large number of patients.(continued)

K. Mechanical Ventilatory Support and Weaning FromMechanical Ventilation (continued)

97

NegativePressure ChestWall Devices

Complications

A. Complications attributable to intubation and extubation

1. Prolonged intubation attempt

2. Intubation of right mainstem bronchus

3. Premature extubation

4. Self extubation

B. Complications associated with endotracheal/tracheostomy tubes

1. Tube malfunction

2. Nasal necrosis

C. Complications attributable to operation of the ventilator

1. Machine failure

2. Alarm failure

3. Alarm found off

4. Inadequate nebulization or humidification

5. Overloading of inspired air

D. Medical complications occurring during assisted ventilation

1. Alveolar hypoventilation

2. Alveolar hyperventilation

3. Massive gastric distention

4. Pneumothorax

5. Atelectasis

6. Pneumonia

7. Hypotension

Source: Zwillich CW, Pierson DJ, Creagh CE, Sutton FD, Schatz E, PettyTL. Complications of assisted ventilation. A prospective study of 354consecutive episodes. Am J Med 1974;57:162.

Table 20 Complications of Mechanical Ventilation


99 K. Mechanical Ventilatory Support and Weaning FromMechanical Ventilation (continued)

Weaning FromMechanicalVentilation

Initial Evaluationof the PatientPrior to Weaning

The choice of a weaning modality remains one of themost controversial areas in pulmonary and critical caremedicine. There are many variations on the twocommon weaning methods. However, beforeconsidering “weaning,” the physician should determineif the patient continues to require mechanicalventilation. If support is no longer necessary, then thepatient should be extubated without a weaning process.

The first step in determining whether continuedmechanical ventilation is necessary is measuring thepatient’s spontaneous ventilation parameters. These include:

● Respiratory rate (rr)● Tidal volume (tv)● Minute ventilation (mv)● Negative inspiratory force (nif)● Vital capacity (vc)

Arterial blood gases identify the patient’s currentoxygenation (pao2 and sao2) and ventilation (paco2 and pH, See Section C). Frequently, though,measurements of o2 saturation and end-tidal co2

are sufficient. When most of the following guidelinesare met, the patient can usually be safely extubated:

rr=8 to 25 pao2 ≥ 55 mm hg breaths per minute with f1o2 ≤ 60%

tv=5 to 15 cc/kg sao2 ≥ 90% with fio2 ≤ 60%

mv=5 to 15 liter paco2 ≤ 45 mm Hg per minute (without chronic

co2 retention)

nif ≥-25 cm h2o pH ≥ 7.35

vc >1 liter

If the patient does not satisfy most of the above criteria,then continued ventilator support is presumablyneeded. Otherwise, the weaning process is initiated.

WeaningStrategies

T-Piece or 0-CPAP WeaningMode


The two most common forms of weaning are the T-piece or 0-cpap mode and the simv mode.Considerable controversy exists over which modality is superior and the underlying reason for respiratoryfailure (e.g., hypoventilation versus high oxygenrequirements).

The intubated patient may either be disconnected fromthe ventilator and placed on a T-piece or the ventilatormay be set in the 0-cpap mode which gives noadditional pressure or volume support to the patient’sspontaneous effort. At time 0 and after 30 to 60minutes of this weaning process, the patient istransiently removed from ventilatory support and theabove spontaneous parameters are measured. Once the above-noted extubation criteria are met, theendotracheal tube is removed. Patients who still requireventilatory support are again transitionally removed,initially for five to 60 minutes, three to four times per day. The duration and frequency of these weaningperiods may be increased until extubation criteria are met.

There are two additional support modes which can beadded to 0-cpap weaning. These will not work with T-piece weaning since the T-piece is strictly a flow-byoxygen delivery system. The first is the addition ofcpap, usually in the 5 to 10 cm h2o range, which mayimprove oxygenation and allows for reduction in f1o2,or pressure support (ps) may be added to deliverincreased tvs and to improve ventilation. The initialpressure selected should deliver an adequate tv of 6 to10 cc/kg. This pressure is then decreased over hours todays until the patient may be extubated. When ps andcpap are used together, the ventilatory mode isidentical to bipap. However, the patient is intubatedrather than using a facial or nasal mask. When patientsachieve settings of ps ≤ 10 cm h2o and/or cpap ≤ 5 cmh2o, most are ready for extubation.(continued)

100

101 K. Mechanical Ventilatory Support and Weaning FromMechanical Ventilation (continued)

SIMV Weaning

Pressure SupportVentilation (PSV)

Traditional simv weaning involves decreasing the rrfrom 12 to 14 breaths per minute to 0 to 2 breaths perminute over the course of hours to days. The concept isto support ventilation with an adequate number ofvolume-delivered breaths until the patient’s improvedstrength and medical condition allow for adequatespontaneous breathing. One potential problem with thismethod is prolongation of mechanical ventilation, sincesome patients may meet extubation criteria as theycontinue to be weaned with this model.

As with 0-cpap weaning, ps and cpap may be added to the simv mode. When ps is added, the patient stillhas a set number of volume breaths, but whenspontaneous breaths are taken, they are pressureaugmented to give higher tv’s. In this system the patientreceives both volume and pressure ventilation. Usuallythe simv is reduced to low levels of 0 to 4 breaths perminute before reducing ps. Initial ps settings should behigh enough to give tv’s of 6 to 10 cc/kg. In patientswhere oxygenation is still a problem, cpap may beadded to increase functional residual capacity and toallow for a lower f1o2.

In patients with adequate respiratory drive (e.g., noapneas), but marginal spontaneous respirations, theaddition of ps may allow them to breathespontaneously. The extra pressure gives just enoughsupport to prevent the patient from fatiguing. Overseveral hours to a few days strength may improveallowing the patient to be extubated.

Regardless of the mode of weaning, periodicmeasurement of the patient’s spontaneous ventilatoryparameters should be performed. When adequate values are obtained, weaning ceases, and the patient is extubated. ■

102 Frontline Pulmonary Procedures and Interventions

References

Butler R, Keenan SP, Inman KJ, et al. Is there apreferred technique for weaning the difficult-to-weanpatient? A systematic review of the literature. Crit Care Med 1999;27:2331-2336. Concludes that no one technique is superior to the other. How eachtechnique is used is probably more important than the technique itself.

Rabatin JT, Gay PC. Noninvasive ventilation. Mayo Clin Proc 1999;74:817-820. Concise reviewdiscussing the equipment, techniques and indicationsfor use of non-invasive positive pressure ventilation(bipap and cpap).

Stock MC, Perel A. Handbook of MechanicalVentilatory Support, 2nd ed. Baltimore, MD: Williams& Wilkins; 1997. pp 308. An excellent source for thebasics of both invasive and non-invasive mechanicalventilation and weaning techniques, with 24contributing authors.

Tobin MJ. Donald F. Egan Scientific Lecture. Weaningfrom mechanical ventilation: What have we learned?Respir Care 2000;45:417-431. A scholarly reviewabout the evolution of the techniques of weaning frommechanical ventilation and the pros and cons of each.

Zwillich CW, Pierson DJ, Creagh CE, Sutton FD,Schatz E, Petty TL. Complications of assistedventilation. A prospective study of 354 consecutiveepisodes. Am J Med 1974;57:161-170. This study was done in a single Intensive RespiratoryCare Unit a quarter of a century ago. Similarcomplications are encountered in the present era.

104 Frontline Pulmonary Procedures and Interventions

For many primary care physicians and specialists,stepping into an examination room to find apatient with a stack of printouts of information

gleaned from the Internet has become a frequentoccurrence. The Internet is changing all healthcarerelationships, including those between physicians andtheir patients. This Section discusses how the Internetevolved, how healthcare consumers and physicians areusing it, and concludes with a brief vision of futureInternet applications.

The roots of the Internet trace back to a DefenseDepartment program originally designed to providemilitary organizations with secure and reliable sharingof computer resources and information exchangeparticularly in the event of nuclear warfare. For anexcellent, although detailed, history of the Internet, seewww.isoc.org/internet-history/brief.html#origins.

J.C.R. Licklider of Massachusetts Institute ofTechnology is widely regarded as “The Father of theInternet.” In 1962, he envisioned a globally connectednetwork of computers through which data andprograms could be easily accessed from any site. Hetermed this, “The Galactic Network.” As the systemevolved, it was called “darpanet” after the sponsoringgovernmental agency (Defense Advanced ResearchProjects Agency). It was later renamed the “Internet” torecognize the concept of an open architecture ofmultiple computer networks. Table 21 summarizes keyevents in early Internet history. The development of theInternet has generated new terms to describe itsstructure and function. Some important terms aredefined in Table 22.

In less than half a century, the Internet has become asprawling collection of interconnected government,academic, military, commercial and private individualcomputers. The term “World Wide Web” (or “web”) isderived from a specialized management of electronictext called “hypertext” which provides a method to

L. InternetApplications

Brief History

The EarlyInternet

The Growth andImpact of theInternet

105 L. Internet Applications (continued)

create, access and transfer online documents. The web has grown because browser programs such asNetscape Navigator and Microsoft Explorer make itpossible to navigate the web by means of point-and-click graphic interfaces.

The Internet is regarded as having the fastest, mostwidespread adoption of any new technology. Forinstance, the telephone was invented by AlexanderGraham Bell in 1876 and first commercialized a fewyears later. However, it did not become a commonutility until after World War I. In contrast, it has takenless than three decades for an estimated 300 millionpeople worldwide to have easy access to the Internet.

“Cyberchondriacs”: A recent Harris Poll found that 98million people accessed the Internet in 1999 seekinghealthcare information. This is an increase of 44million since 1998. The proportion of those who usedthe web to look for health or medical informationincreased during the same period from 71% to 86%.Humphrey Taylor of the Harris Poll has termed thesepeople, “Cyberchondiacs.” Healthcare information isnot the most frequent reason people access the web, butit is among the most important. The rise of “consumerempowerment” in healthcare has been fed by the easeof access to information afforded by the Internet.

Consumers are using the Internet to find informationthey say they are not getting from the healthcaresystem.

People are becoming more actively involved indetermining their care: Only 5% of Americans overage 18 years, surveyed in 2000, report they wantdoctors to make their healthcare decisions for them.The remainder either want to actively share in thedecision-making process or to make all the decisionsthemselves.


Table 21 Important Events in Early Internet Development

1961 First paper on packet switching theory (necessary for the Internet to work).

1962 First recorded descriptions of implications of the Internet (“Galactic

Network”), by J.C.R. Licklider.

1965 First wide area computer network established allowing computers totalk together.

1966 Advanced Research Projects Agency Network (“ARPANET”),established.

1972 First public demonstration of ARPANET technology to the public.

1972 Introduction of e-mail.

1972 Concept of “open-architecture” developed by Bob Kahn, lead to thedevelopment of Transmission Control Protocol/Internet Protocol(TCP/IP), allowing widespread networking of computers.

1982 Required that all host computers convert simultaneously to the TCP/IP standard.

1992 Internet Society founded.

1994 World Wide Web.

106


Table 22 Glossary of Internet Terms

Bandwidth : The range of frequencies that can betransmitted over a communications channel. Thelarger the bandwidth, the greater the amount ofinformation that can be transmitted.

Baud : The rate at which data travels overtelephone lines.

BBS : Bulletin Board System, that can provideonline services, such as e-mails, chat groups andaccess to data bases.

Browser : Software, which allows navigation tovarious websites through a point-and-click graphicsystem.

Cashe : Storage, as for memory or web pages.

Chat : Online conferencing in real time.

Chat group : Online meetings where people log onto the same room at the same time to exchangeinformation.

Domain : A subset of the Internet. Domains areidentified by .gov for government, .org for non-profitorganizations, .edu for educational institutions, and.com for commercial ventures. New generic suffixes(e.g., .news, .info, .arts, .shop) are being proposedto increase the number of available web sites.

E-mail address : An Internet address where peoplecan receive e-mails.

FTP: File Transfer Protocol, an Internet protocol fortransferring files.

Flame : An angry, critical message sent from oneperson to another over the Internet. This process iscalled flaming and is often very verbally abusive.

Gopher : An Internet search and retrieval system.

Hacker : A person who specializes in unauthorizedaccess to Internet information and systems. This isa term of honor for some, and disdain for most.

Home page : The opening screen of a World WideWeb resource, such as documents.

Host : A computer on the Internet.

HTML: Hypertext Markup Language is the codes,which are used to construct web pages.

http : Hypertext Transfer Protocol, the softwarestandards that are necessary for functionality of theWorld Wide Web.

Internet : A global information system, linked byspecific protocols and standards, that makes highlevel services based upon computer networkedinteraction.

ISP: An Internet Service Provider.

Lurking : Logging on to a forum, but only as anobserver.

MeSH: The Medical Subject Headings indexingthesaurus of the National Library of Medicine,MEDLARS system.

Moderated : A forum, mail list or other electronicinformation exchange whose postings are reviewedand controlled to keep content relevant and toencourage cyber civility.

Mosaic : A pioneer web browser that spawnedNavigator and Explorer.

Newsgroups : The bulletin board discussionsgroups of USENET and the Internet.

Posting : A public accessible written message,usually to a forum, bulletin board, newsgroup ormail list.

Search engine : Software, which allows searchingon the web for particular information.

Server : A computer that provides programs,archives or other resources to other computers onthe network.

Shareware : Software distributed online with noinitial charge. You pay, on the honor system, only ifyou decide to keep the program.

TCP/IP: Transmission Control Protocol/InternetProtocol, the computer communications program ofthe Internet.

Thread : A series of messages or postings on asingle topic.

URL: Universal Record Locator, the Internetaddress necessary to find a particular web page.

USENET: A system of distributed computer bulletinboards on the Internet.

UserID : The code name or account nameassigned to an online user.

Virus : A computer program that travels fromcomputer to computer and destroys data. At best, itcan be a nuisance; at worst highly destructive anddisruptive.

World Wide Web : The hypertext-based protocolthat allows access to various resources on theInternet.

The Internet is a frequent source of consumerhealthcare information: Empowered by the Internet,consumers—whether patients or patients’ friends andloved ones—are going outside the traditionalhealthcare system to obtain the information that theywant. Seventy percent of persons searching for healthand medical information believe that the Internetempowers them by providing information before andafter visiting a doctor. Table 23 lists frequently visitedconsumer healthcare websites. Table 24 lists somewebsites that are related to pulmonary disease.

Quality of consumer healthcare information on the web is a concern: It is estimated that there are over15,000 healthcare-related sites on the web. The qualityof information on the Internet varies dramatically. TheInternet has been termed, “The world’s largest medicalgarbage dump.” While this may be an overstatement, it does underscore the variable quality of informationon the web.

Consumers commonly visit healthcare portals. Portalsare websites that aggregate many sources of electronicinformation that is then presented primarily in textform. There are non-profit sites, such as that supportedby the Mayo Clinic Foundation (www.mayohealth.org),and commercial sites, such as www.medscape.com. Thecommercial sites have not been financially successfulbecause of the unwillingness of consumers to pay forcontent information and the inability to generatesufficient advertising and sponsorship revenues.

Where consumers prefer to go for healthcareinformation is important: Some commercial sites havealso developed companion consumer-oriented sites.Such sites have been failures because consumers havevirtually ignored them. They prefer to visit physician-oriented sites. Consumers and physicians rely upon thesame online sources of clinical and researchinformation, such as the National Library of Medicine’sMedline service (www.nlm.nih.gov). It is clear that



(AOL) Health Channel (America on Line users only)

Drkoop.com www.drkoop.com

HealthAnswers www.healthanswers.com

InteliHealth www.intelihealth.com

Mayo Clinic Health Oasis www.mayohealth.org

Mediconsult www.mediconsult.com

Medscape www.medscape.com

Thriveonline www.thriveonline.com

Table 23 Frequently Visited Consumer Healthcare Websites


Topic Organization Web Address

Asthma Asthma, Allergy & Pulmonary www.asthmanews.com

News on the Net

Bronchiolitis obliterans Dynamics in Healthcare www.epler.comand sarcoidosis

COPD and lung cancer National Lung Health www.nlhep.orgEducation Program

Cystic fibrosis The Cystic Fibrosis Foundation www.cff.org

Emphysema and COPD The National Emphysema Foundation www.emphysemafoundation.org

Lung diseases American Lung Association www.lungusa.org

Lung diseases Australian Lung Association www.lungnet.org.au

Pulmonary hypertension The Pulmonary Hypertension Association www.phassociation.org

Sleep disorders National Sleep Foundation www.sleepfoundation.org

Table 24 Consumer-oriented Pulmonary Websites

110


consumers want to read the same information theirdoctors are reading. Physicians should remember thiswhen referring patients and family members tohealthcare information on the web.

Other sources of consumer information on the Internet:Other places consumers are going for information onthe web include Internet mailing lists such as CancerNet,sponsored by the National Cancer Institute. They mayalso seek information from e-commerce sites, such asInternet drug stores and sites that sell products forspecific disease conditions (e.g. www.gazoontite.com,an asthma and allergy products site). Internetnewsgroups or chat rooms are electronic “places”where people with similar interests can exchangemessages or meet online. There are healthcare specificareas of large websites such as Yahoo/health(www.yahoo.com). Computer-based, electronic linkagessuch as Comprehensive Health Enhancement SupportSystems (CHESS http://chess.chsra.wisc.edu/Chess/), areInternet-enabled interactive systems to assist patientswith chronic diseases such as aids, hiv infection andbreast cancer.

Search engines are commonly used, but have issues:Particular information can be sought on the web by theuse of search engines. Eighty-five percent of web usersrely upon search engines to find information. Recentstudies have shown that no single search engine coveredmore than 16% of the web content. Some enginesmerely covered 2.2%. Since it is estimated that in 1999the web encompassed three million servers hosting 800billion pages, an immense amount of information is notaccessed by individual search engines. Furthermore, thecombined 11 popular search engines which wereanalyzed covered less than half of the web. Searchengines may also be a source of bias. New searchtechnologies, such as Google and DirectHit, usemeasures of “popularity” to rank relevance of pagesthat they index.


If the growth of the Internet slows, then search enginesmay “catch up.” Meanwhile, to conduct exhaustivestudies, software tools like MetaCrawler that useseveral search engines should be used.

Consumer use of the web to access information is goingto continue to increase: While it is certain that use ofthe Internet for consumer healthcare information willincrease, so too will the volume and complexity ofinformation. This predictability will result inmisinterpretation and frustration. Consumers will befaced with sorting out information which is irrelevant,inaccurate and misleading. Less than one-third ofmedical sites on the Internet studied have been subjectto peer review. At least 6% of medical sites containerroneous information. Attempts are underway to monitor the quality of healthcare information on the web. However, much of the current informationwhich consumers are receiving is unstructured,unreviewed and unregulated. Table 25 lists somequestions to ask when evaluating Internet healthcareinformation sources.

Information specialists are emerging to assistconsumers: To help consumers, “navigators” whoprovide human-based assistance are starting to emerge.To illustrate, one of the problems in electroniccommerce on the web is frustrated shoppers abandoningtheir virtual shopping carts. In response to thisproblem, commercial Internet companies are givingconsumers the opportunity to access a customer servicerepresentative online to assist them. Such “navigators”may emerge to help healthcare consumers find thesuitable information on the Internet. Primary healthproviders can also serve this function for patients byhelping direct patients to websites which they believecontain responsible information that is pertinent totheir condition.


Table 25 Questions to Ask When Evaluating Internet Healthcare Sites

Is it sponsored by a trusted source? Most academic, professional and some commercial sitesreceive a high quality peer-review.

Are forums, chat rooms and bulletin Some sites allow anyone to post or to participate, rather boards moderated? than have a moderator who monitors content and quality.

How recently has the site been updated? Good sites give both dates of posting, electronic publicationand when the site was last updated. As with other forms ofinformation, Internet information becomes outdated.

Are “experts” identified and verifiable? Early in the history of the Internet there was an infamouscase of a 14-year-old giving advice over the Internet tobreast cancer patients.

Is there an issue with language? Since the Internet allows global participation, the possibilityexists for errors and misinterpretations to occur wheninformation is translated from one language to another.

What are the other potential This can include commercial advertising, sponsorship sources of bias? groups, institutional viewpoints, religious beliefs and

alternative approaches to healthcare.

Is there any risk of your Anytime you are asked to give personal information or confidentiality being compromised? you volunteer such information, there is the risk that such

information might fall into the wrong hands.


Table 26 Pulmonary Websites for Physicians

Alpha 1-Antitrypsin Deficiency Association www.alpha1.org

American Academy of Sleep Medicine www.asda.org

American Association for Respiratory Care www.aarc.org

Am. Assoc. of Cardiovascular & Pulmonary Rehabilitation www.aacvpr.org

American College of Chest Physicians www.chestnet.org

American Lung Association www.lungusa.org

American Thoracic Society www.thoracic.org

MDlinx.com www.mdlinx.com

Medscape; a commercial site with well-reviewed content www.medscape.com

National Heart, Lung, and Blood Institute (NHLBI) www.nhlbi.nih.gov

NHLBI Asthma Management Model System www/nhlbisupport.com/asthma/

National Jewish Medical & Research Center www.nationaljewish.org(many topics/services on pulmonary disease)

National Lung Health Education Program (NLHEP) www.nlhep.org

Resource for clinical trials involving pulmonary patients www.clinicaltrials.com

U.S. National Library of Medicine/Medline www.nlm.nih.gov

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Doctors have embraced the Internet and web: Likeconsumers, physicians have become major users of theInternet. A 2001 survey of 834 physicians conducted byHarris Interactive found that overall, 93% ofphysicians use the Internet with usage at their clinics(40%) and offices (56%) being considerably lower thanat home (87%). The average physician usage was 6hours per week. However, the majority of time (61%)was for personal use such as e-mail, shopping, financialtracking and accessing general information, such asnews. Other uses were for administration andmanagement of their practices.

The Internet has yet to establish a compelling value fordoctors in their professional lives: Doctors are quick tograsp a new technology when it has a benefit for boththemselves and their patients. Advances in diagnosticimaging and new medical devices are examples. In thecase of the Internet though, a persuasive reason for useof the Internet in patient care has yet to be developed.While over 80% of doctors use cellular phones as partof their practice, only 8% of physicians use the Internetas a way to access clinical information. Just as accuracyof information is an issue for consumers accessinginformation on the web, so too is it for physicians.Table 26 lists some sites that physicians will findrelevant to pulmonary disease topics.

It is becoming increasingly popular for physicians tohave websites: One rapidly growing Internet area forphysicians is establishing websites to support theirpractices. Forty-two percent of physicians surveyedwork in practices with their own websites. This figure isprojected to continue to increase. Therefore, practicingphysicians should plan to develop websites as afundamental part of their practice.

e-mail is infrequently used for doctor-patientcommunication:The use of e-mail between physiciansand patients has both promise and problems. Fewer


than 5% of adults who have access to the Internetreport using it to communicate with their doctors. Only 13% of physicians report using e-mail to interactwith their patients and some doctors who haveattempted it have stopped doing so. This is despitestudies that have shown that patients would stronglyprefer doctors willing to communicate with them usinge-mail. The desire of patients to use e-mail involvesconvenience, but also reflects the decrease in both thefrequency and time for face-to-face encounters with their physicians.

Doctor-patient use of e-mail is not analogous to usingthe telephone: When the telephone first became widelyavailable, some doctors expressed concern about beingoverwhelmed by patients seeking over-the-telephonecare. They worried that the telephone would have anadverse effect on the traditional doctor-patientencounter. Similar issues are being raised with the useof e-mail. A critical difference between the telephoneand e-mail is that the telephone is a synchronous form of communication occurring in real-time, while e-mail is asynchronous, meaning patients andphysicians are not communicating in real-time.Consequently, an urgent e-mail might go unread for a critical period of time.

There are important issues with the use of e-mail inclinical practice: While e-mail may be an efficient wayto schedule appointments and request refills ofprescriptions (many states are now allowing e-mailprescriptions by physicians), serious issues exist aroundprivacy, identifying appropriate and inappropriate usesof the technology and compensation of physicians forthe time spent answering e-mails.

Privacy and confidentiality are important issues. Theprimary care physician using e-mail to communicatewith patients must avoid using computers and e-mailaccounts that could be accessed by others, including


patients’ family members. Similarly, patients should beadvised that if they are sharing resources and e-mailwith spouses and family, their medical information maybe accessible to them. The best solution is a medicalaccount address that is distinct from personal andprofessional accounts. Encryption using “public-privatekey” procedures might also protect against privacyviolations. However, such technology is not availablefor widespread use.

The medicolegal issues of the use of e-mail are alsomurky. At the least, medical e-mails should be linked toor otherwise included in the patient’s medical record.This represents a logistical challenge that will best beresolved with the widespread availability of anelectronic medical record. Unfortunately the electronicmedical record has been described as a constantlyemerging technology.

Perhaps the most vexing issue regarding e-mail is that of compensating physicians for their time. Untilphysicians receive fair payment for this form ofhealthcare delivery, all the anticipated benefits will notbe realized. Some payers have begun to appreciate that allowing patients to ask simple or importantquestions of their physicians via e-mail might welldecrease costly office or Emergency Room visits. Someare now experimenting with paying physicians forproviding such services. A few physicians are alsobeginning to offer subscription services, whereby, for amonthly fee, they will respond to their patients’ e-mails.Table 27 lists some things for primary care physiciansto consider when contemplating an e-mail system ofcommunication with their patients.


Table 27 Issues to Consider in Using e-mail With Patients

Is the information secure for both the physician and the patient? Can others access the sending machine and/or the e-mail account?

Are all e-mail addresses of patients treated as highly confidential, and only made available on a “need to know” basis? Most violations of the confidentiality of electronic data are committed by authenticated persons.

Providing patients with guidelines, and perhaps a template, for communication may decrease length andhelp triage messages received at a physician’s office. Categories could include prescription refill requests,appointment scheduling and questions that could be answered by an office nurse.

Consider having “office hours” during which time you will be online to answer e-mails.

Regulatory issues may limit your ability to request payment for e-mail and other online interactions with patients.

Electronic communication should become a part of the patient’s permanent medical record.

The use of e-mail has complex medicolegal implications. Electronic receive-and-read receipts will help assure that critical messages have been read. Documentation with e-mails is superior totelephone calls; but it may protect against or increase physician liability.

Source: Mandl KD, Kohane IS, Brandt AM. Electronic patient-physician communications: Problems andpromise. Ann Int Med 1998;129:495-500.

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The Internet and World Wide Web are at a nascentstage of development: Management guru, PeterDrucker, points out the first uses of new technology areto enhance existing systems. It is not until later thattruly revolutionary applications are developed. Forinstance, James Watt’s improved steam engine, whenapplied to the spinning of cotton, dramaticallyimproved the output and decreased the cost ofproducing cloth. But, a novel product, the steamboat,invented by Robert Fulton in 1807, had minimal initialimpact. Through the end of the 19th century, mostfreight on the world’s oceans was carried by sailingships. However, when the steam locomotive gave rise torailroads, a new, revolutionary product was born thatforever changed the economy and society.

The Internet and the web were totally unanticipatedand unprecedented: The Internet’s marvelous ability toshare information was first utilized by the military andacademic institutions and only later by the public. TheInternet is still in the stage of enhancing the pre-existingsystems, such as selling goods and communicating textinformation and simple images. The Internet has yet toreach the point of revolution where it changes howdecisions are to be made, and, like the early use ofsteam, is only beginning to change some parts of theeconomy and society. In healthcare, the use of theInternet for accessing information has becomecommonplace for consumers and doctors. Healthcareinformation has been democratized. Suppliers ofhealthcare supply chain products and services are nowusing the Internet to conduct their business, and as aconsequence, introduce efficiencies and cost saving intotheir products and services.

Emerging Uses ofthe Internet


Other uses for the web, including on-line counselingand second opinions, are in early stage use by bothcommercial and non-commercial organizations.There are also for-profit “cyber-physician” servicesthat will provide consultation and in some cases evenprescribe medications for patients, based upon onlyonline interactions. Such services raise both ethicaland legal issues.

New ventures are in early stages to use the Internetfor remote monitoring of patients with chronicconditions, such as congestive heart failure, diabetes,copd and asthma.

Many new Internet applications in healthcare mustawait technical advancements: Other applications,such as use of the Internet to transmit radiographicimages, pathology images, and ultrasound studies orfor telemedicine, await improvement in Internettechnology. These images are electronically dense andrequire both increased transmission speeds as well asbandwidth carrying capacity. There is currently anational initiative to develop a second generationInternet, termed “Internet-2” or “The Big Pipe.”Information about this project is available atwww.ccic.gov/ngi and www.ucaid.org. This mediumwill allow full-motion video and 3-dimensionalvirtual reality for medical education or training, andfor patient education. However, who ultimately willpay for these products and services enabled by theInternet is the question most are reluctant to ask.

The future is easy to imagine, but difficult to deliver:The biggest vision, as well as the biggest challenge,for the use of the Internet is to link together thewildly disparate systems for information exchangewithin the healthcare system. This includes clinical aswell as “referral, authorization, claims, eligibility andreporting” (racer) transactions. While the Internetmay be seen as a form of elixir that can somehow


work to provide the miraculous infrastructure linkingpatients, providers and others with a stake in thehealthcare process, there may be similarities to earlyvisions of a space station. It was easy for scientists toimagine the benefits and for engineers to produce thedesign. In reality, making it happen has taken animmensely long period of time, proven to besignificantly more complex than originally imaginedand considerably more costly. Companies proposing touse the Internet to widely “wire together healthcare”initially excited the investment community. Morerecently, enthusiasm has cooled as people have realizedthe enormity of the task and the fiscal constraints of thehealthcare system. The practitioner, faced daily with therealities of a complex, cumbersome and oftenunresponsive healthcare system, should not expecttechnological salvation for a number of years. ■

References

Coiera E. Guide to Medical Informatics, the Internetand Telemedicine. New York, NY: Oxford UniversityPress; 1997. pp 400. Very readable, with goodoverviews, not only on the Internet, but telemedicineand medical informatics.

Drucker PF. Beyond the information revolution. TheAtlantic Monthly 1999;284:47-57. Perspective on hownew technologies impact economies and societies withparticular attention to the electronic informationrevolution.

Graber MA, Bergus GR, York C. Using the World WideWeb to answer clinical questions: How efficient aredifferent methods of information retrieval? J FamPractice 1999;48:520-524. This article points out thepitfalls in searching for clinical information on the web,particularly the weakness of medical search engines.


Mandl KD, Kohane IS, Brandt AM. Electronic patient-physician communications: Problems and promise.Ann Int Med 1998;129:495-500. Excellent overview ofissues surrounding use of e-mail for communicationbetween physicians and patients.

Neuberger J. The educated patient: New challenges forthe medical profession. J Intern Med 2000;247:6-10.Nice discussion of necessity and strategies for establishingworking relationships with the new healthcareconsumer who is accessing information widely.

Smith RP, Edwards MJA. The Internet for Physicians.2nd ed. New York, NY: Springer Verlag; 1999. pp 206.Small and readable, with an extensive bibliography.

Stoll C. Silicon Snake Oil: Second Thoughts on theInformation Highway. New York, NY: DoubledayBooks; 1995. pp 247. A “classic” (in Internet time)perspective on both the promise, as well as hype aboutthe Internet. The author has been involved in computernetworks since their inception. Stoll tracked down aGerman spy ring working over the Internet and wroteabout it in his best-selling book, “The Cuckoo’s Egg.”

Wood MS, (ed). Health Care Resources on the Internet:A Guide for Librarians and Health Care Consumers.New York, NY: Haworth Information Press; 2000. pp 205. Reference that is useful for inquisitive patients.

123

M. MedicolegalIssues

Failure toDiagnose LungCancer

Failure toPrevent,Diagnose orTreat PulmonaryEmbolism (PE)

Acommon cause of medical malpractice claims isfailure to follow-up on chest x-rayabnormalities which later are found to

represent lung cancer. The delays involved may result inthe evolution of advanced disease, including locallyinvasive or metastatic cancer. Uncalcified solitarypulmonary nodules are more common than mostprimary care practitioners or specialists realize. All non-calcified solitary nodules need to be studied furtherunless a previous chest x-ray shows no change over twoor more years. New technologies, such as isotopeimaging (i.e., pet scans) are changing the approach todifferentiating benign from malignant lesions. Needlebiopsies and video-assisted thorascopic biopsies havereduced the need for exploratory thoracotomy.

Pulmonary infiltrates which persist after acutepneumonic processes, require assessment. Broncho-scopy should be ordered for an acute infiltrate that doesnot resolve within three months. However, it isimportant to note that resolution of pneumonicinfiltrates may take longer in patients with advancedemphysema. In some patients with very severe copdone may take a watchful rather than an aggressivestance in evaluating these residual infiltrates. This isbased on the relatively high risks for diagnosticprocedures (such as bronchoscopy or fine-needleaspiration), the likelihood that the copd—not thepotential neoplasm—will be the life-limiting condition,and the fact that persistent non-neoplastic densities aremore apt to occur in such patients.

Failure to provide prophylaxis for patients at high riskof pulmonary thromboembolism has increasinglybecome a cause for bringing malpractice actions. Thefact that anticoagulation can reduce the incidence of pe and mortality in various orthopedic procedures,including hip and knee replacements, is now well-established on the basis of controlled clinical trials.There have not been randomized, controlled, clinical

trials in abdominal operations such as appendectomy,cholecystectomy and bowel resection, butanticoagulation is strongly suggested for high-riskindividuals including those for whom immediateambulation is not possible. Clinical trials are pendingfor patients undergoing surgical procedures such asradical resection for carcinoma of the prostate. Untilresults from these studies are available or announced,we believe that it is appropriate that low-dose heparin(5,000 u.s.q. units twice daily or employing a lowmolecular weight heparin—lmwh) be given to allpatients (except those with the contraindication notedbelow) with major surgical procedures including canceroperations. This is particularly true when the period ofimmobility may be more than just a few days.Contraindications to this practice include patientsundergoing central nervous system or spinal surgery (in whom a hematoma might jeopardize vitalneurological function), those with a recent history ofpathological bleeding, or those with low plateletcounts. Of course, non-pharmacologic therapies such as ted hose or compression stockings carry essentiallyno risk and probably should be used in all surgicalpatients. Continuing prophylactic therapy until thepatient is fully ambulatory seems reasonable.

Another major reason for malpractice claims is failureto make the diagnosis of acute pulmonary embolism(pe) which subsequently results in a fatal event. Themost common symptom of a major pe is suddendyspnea. Thus, for those complaining of abrupt onsetof shortness of breath (particularly those with riskfactors including extended travel, recent lowerextremity imaging or trauma, women receiving oral contraceptives or persons with a family history of vte) studies to prove or to disprove pe are stronglyadvised.


125 M. Medicolegal Issues (continued)

Failure to DoSpirometry

Spirometry andLung CancerScreening

Failure to Referto Specialists

It is amazing that every year pulmonary experts areasked to defend physicians in malpractice actionsbecause of complications of steroid therapy for“asthma” when there is no documentation on themedical record of airflow obstruction. Such examplesmay be individuals who enter the Emergency Roomwith classical manifestations of asthma, such as acutewheezing and dyspnea, for whom steroids are deemednecessary. Unfortunately, if the patient continues toreceive corticosteriods and a complication such asaseptic necrosis of the femoral head occurs, a lawsuitfrequently follows. If there is no documentation ofairflow obstruction, the clinician may have substantiallegal exposure. The advent of new simple, accurate andinexpensive office spirometers under the National LungHealth Education Program (nlhep) today should makespirometer use as ubiquitous as blood pressure inphysicians offices, clinics and at the workplace.

It is now well-established that heavy smokers withairflow obstruction have 4 to 6 times the prevalence oflung cancer compared with those with normal airflow,but with equal smoking, occupational and familyhistories. Efforts are underway to encourage spirometrytesting in all smokers over the age of 45, and anyonewith chronic cough, excessive dyspnea on exertion,mucus hypersecretion or wheeze. Patients with 30pack-years of smoking and airflow obstruction have anapproximately 2% prevalence of lung cancer at the timeof initial screening, and 3% to 4% more lung cancer inthe five years that follow. The authors advise that thisgroup of patients should be screened for lung cancerwith spiral ct scans and sputum cytology.

Today, the public expects that all symptoms and signs ofdisease will ultimately result in a diagnosis. Whentroubling symptoms or signs like dyspnea, cough, chestpain, fever, weight loss or anemia cannot be readilydiagnosed or managed, the primary care physicianshould initiate referral to an appropriate specialist.

Failure to ClearlyDocument theMedical Record

Failure toAppropriatelyCommunicateWith the Family

Failure to beResponsible

Although insuring agencies or managed care systemsmay place impediments in the way of such referrals, we must not lose sight of our ethical responsibility toour patients.

A definitive diagnosis should be expected in all but self-limited symptoms and signs that present to theprimary care physician.

One of the most common problems that result inmalpractice action is failure to accurately document the medical record. “If it is not written down, it hasn’tbeen done,” has become a legal dictum. Sadly, this fails to recognize that a physician may be too busy towrite down everything done or considered in thedifferential diagnosis. But a clearly written note,whether or not it follows the style of the problem-oriented record, should be entered into everyhospitalized patient’s chart each day, no matter howbusy the practice. Records must be dated, timed andsigned. The same is true for each office visit.

One of the most common reasons for a lawsuit is whenthe family feels that they have been badly treated orignored. Detailed, honest communication is thefiduciary responsibility of every managing andconsulting physician. Covering up mistakes, altering themedical record or misrepresentations are predictablecauses for adverse medical malpractice judgmentsplacing the physician in great peril. Always tell thetruth. Communicate clearly with the family regularly.Document every visit.

Failure to respond to calls from medical personnel suchas nurses who are monitoring patients on the clinicalwards or in the icu are a common cause of unfavorablemalpractice judgments. The need to respond within areasonable time is one of the clearest precepts inmedicine. Coverage by another medical professionalmust be provided if you are unable to respond to calls,both on and off of your regular duties. ■


127 M. Medicolegal Issues (continued)

References

Austin JH, Romney BM, Goldsmith LS. Missedbronchogenic carcinoma: Radiographic findings in 27patients with a potentially resectable lesion evident inretrospect. Radiology 1992;182:115-122. This is acomprehensive analysis of the factors responsible for amissed diagnosis of a solitary nodule that proved to be lung cancer.

Ferguson GT, Enright PL, Buist AS, et al. Officespirometry for lung health assessment in adults: Aconsensus statement from the National Lung HealthEducation Program. Chest 2000;117:1146-1161. This statement recommends spirometric testing of all smokers age 45 and older and anyone with chronic cough, mucus hypersecretion, wheeze orinappropriate dyspnea.

Rosner F, Berger JT, Kark P, et al. Disclosure andprevention of medical errors. Committee on BioethicalIssues of the Medical Society of the State of New York.Arch Intern Med 2000;160:2089-2092. A gooddiscussion about the importance of disclosing medicalerrors to patients and families. A medical mistake doesnot necessarily imply negligence.

N. The NationalLung HealthEducationProgram(NLHEP)

Anew national healthcare initiative known as theNational Lung Health Education Program(nlhep) is directed at copd and related

disorders, including lung cancer, heart attack andstroke. Thus, this is a new initiative for improvedgeneral health in America. The key role of the primarycare physician and respiratory care practitioners isstressed by the nlhep. The nlhep is directed to allprimary care practitioners, the public, third partypayers and healthcare administrators. The nlhep urgesthat all primary care physicians and other healthcareproviders obtain simple, accurate, handheldspirometers for office and clinic use. Only the fev1 andthe fvc are required to assess patients with copd inincipient or advanced stages of diseases. “Test YourLungs, Know Your Numbers” is the battle cry of thenlhep.

The nlhep recommends that all smokers age 45 andover and individuals of any age with symptoms ofcough, dyspnea, mucus hypersecretion or wheezeshould be tested by spirometry. Early identification of patients with spirometric abnormalities indicates an increased risk of all-cause mortality and will guideearly diagnosis, therapy and a more positive prognosis. You are invited to view the nlhep web page at www.nlhep.org. ■


TESTYOUR

LUNGS-

KNOWYOUR

NUMBERS

128

129

O. The SnowdriftPulmonaryConferences The Snowdrift Pulmonary Conference, Inc. is a

not-for-profit corporation that is dedicated tothe dissemination of knowledge about the lungs

and lung diseases. Both private practice pulmonologistsand academicians have launched a program for primarycare practitioners and the patients they serve. This is aconsumer-oriented program. Already, concise andauthoritative monographs for the frontline practitionerhave been written on:

Frontline Treatment of COPD 2nd ed (1996and 2000)Frontline Treatment of Asthma (1997)Frontline Treatment of Common RespiratoryInfections (1998)Frontline Treatment of Venous Thromboembolism (1999)Frontline Assessment of Common Pulmonary Presentations (2000)Frontline Assessment of Lung Cancer and OccupationalPulmonary Diseases (2001)Frontline Pulmonary Procedures and Interventions (2001)

All of the Frontline series are being periodicallyupdated. They are available in hard copy or in a cd-rom format. They can be viewed on the Internetwebsite: www.FrontlinePulmonology.org.

Lung cancer, the most common fatal malignancy of men and women, presents the most challenging frontier.To help disseminate the new knowledge about the roleof early identification and intervention in lung cancer as a major new initiative, the Snowdrift PulmonaryConference has produced a newsletter, Lung CancerFrontiers (LCF). LCF now reaches the nearly 10,000board certified pulmonologists in North America. LCFis available on the Internet at:www.LungCancerFrontiers.org.

We believe that an enlightened and informed publicworking with their personal physician and consultantscan help guide the future of medicine as we aim toprevent, cure and diminish the number and severity oflung diseases which impact the health of our nation. ■


131

P. Postscript andBiographicalSketches ofAuthors

The evolution of technology in medicine fordiagnostic purposes began with the microscope,which was so critical to understanding the

pathology of lung diseases. It was key to the diagnosisof infectious diseases, such as tuberculosis. The firstinstrument for the evaluation of diseases of the chestwas the stethoscope, introduced by Laënnec in 1819.Shortly thereafter, John Hutchinson, a surgeon,introduced the concept of spirometry into medicine.Hutchinson coined the term, “vital capacity,” i.e., thecapacity to live. He recognized that a reduced vitalcapacity was related to all-cause mortality. He wasparticularly interested in the effects of tuberculosis andcoal mining on the vital capacity.

Oxygen was introduced by Priestly in 1774 and finallyfound application in clinical medicine, beginning withBarach’s use of oxygen in the treatment of pneumonia.Oxygen has revolutionized the management ofadvanced states of chronic respiratory insufficiency.Evolving mechanical ventilators offered new approaches to the management of acute respiratory failure.

Roentgen discovered x-rays in 1895—chest imaging hasevolved and is the cornerstone for many pulmonarydiagnoses.

The cuff sphygmomanometer was invented by Italianphysician, Scipione Riva-Rocci, in 1896. This simpledevice caught the eye of U.S. surgeon, Harvey Cushing,who believed he could use it in the measurement ofblood pressure, which would be useful in his ongoingstudies of cerebral perfusion. Cushing introduced thisinstrument at Johns Hopkins Hospital. Early supportersof this new method of blood pressure measurementswere Theodore Janeway in New York City and GeorgeCrile in Cleveland, Ohio. After only two years ofexperience on the wards of Johns Hopkins, Cushingand his surgical house officers set out to promote wider

use of the cuff. This was the foundation for the use ofblood pressure measurements in epidemiological studiesand for controlled clinical trials of antihypertensiveagents, which have so dramatically reduced thesocioeconomic impact of heart attack and stroke in the last 25 years. Perhaps the same may still happenwith spirometry, but progress has been painfully slow.

The ekg was introduced by Einthoven in 1903. Rigidtube bronchoscopy was originally introduced by Killian in 1898 and evolved into a flexible fiberopticbronchoscope, by Ikeda, in 1964. Cardiaccatheterization was first developed and studied byForssmann, a resident surgeon, in 1928. Cournand andRichards made a slight modification of Forssmann’svenous catheter and introduced this technique intomedicine in 1941. The three pioneers shared the Nobelprize for this momentous advance in 1956. The flow-directed catheter was later introduced by Swan andGanz. Video-assisted thoracotomy added a newapproach to making a tissue diagnosis.

During the past century, numerous blood tests,ultrasonic imaging, isotope scans, various forms ofcomputed tomography and magnetic resonance imaginghave continued to aid clinicians in diagnosing a host ofdisorders of the respiratory and cardiovascular systems.It took not only the invention and introduction of newtechnologies into medicine, but also an evolvingunderstanding of the advantages and disadvantages ofeach new technique and treatment to be able to trulybenefit from these advances. How each new technologycan be applied in a systematic and cost-effective manner,remains a challenge to medicine. No technology,however, can replace the history and physicalexamination in creating a concept that will lead to adiagnosis, which then can be confirmed by appropriatestudies. Systematic treatment requires the interface ofnew technologies with the judgment and skill ofexperienced physicians.


P. Postscript and Biographical Sketches of Authors(continued)

References

Barach AL. The therapeutic use of oxygen. JAMA1922;79:693-699. The first description of the use of oxygen via an oxygen tent in the treatment of pneumonia.

Cournand A. Cardiac catheterization, development ofthe technique, its contributions to experimentalmedicine, and its initial applications in man. Acta MedScand Suppl 1975;579:3-32. A complete review of thedevelopment of cardiac catheterization and itsintroduction into medicine.

Crenner CW. Introduction of the blood pressure cuffinto U.S. medical practice: Technology and skilledpractice. Ann Intern Med 1998;128:488-493. Acomprehensive description of how the blood pressurecuff was introduced into the United States and widely promoted for the improvement of the health of our nation.

Petty TL. Home oxygen — a revolution in the care ofadvanced copd. Med Clin North Am 1990;74:715-729. A state-of-the-art review of the use of homeoxygen in advanced chronic respiratory insufficiency.

Steckelberg JM, Vlietstra RE, Ludwig J, Mann RJ.Werner Forssmann (1904-1979) and his unusualsuccess story. Mayo Clin Proc 1979;54:746-748. Areview of the remarkable personal experiences and selfcatheterization by Forssmann, the father of cardiaccatheterization. ■

133


Michael D. Iseman, MDMike Iseman grew up in Fremont, Nebraska. Hereceived his undergraduate degree from PrincetonUniversity where he majored in history and playedfootball. He attended Columbia University's College ofPhysicians and Surgeons, receiving his md in 1965. He received his training in internal medicine and pulmonary medicine in New York City between 1965 and 1972.

Joining the faculty of the University of Colorado in1972, he spent ten years at Denver General Hospital.Then he moved to National Jewish Hospital in 1982 as Head of the Clinical Mycobacterial Diseasesprogram. His primary research interests relate to drug-resistant tuberculosis and disease due to the“atypical mycobacteria.” He currently is Professor ofMedicine in the Division of Pulmonary Medicine and Infectious Diseases. He is also Editor-in-chief of the International Journal of Tuberculosis and Lung Diseases.(continued)

Co-Editor

134

135 P. Postscript and Biographical Sketches of Authors(continued)

Thomas L. Petty, MDThomas L. Petty received his md at the University ofColorado in 1958. He interned at Philadelphia GeneralHospital and received his residency training at theUniversity of Michigan and the University ofColorado. His pulmonary training was at theUniversity of Colorado. He is a pulmonologist andProfessor of Medicine at the University of ColoradoHealth Sciences Center in Denver and at RushUniversity in Chicago. He was previously Head of theDivision of Pulmonary Sciences at the University ofColorado and Director of the Fellowship TrainingProgram. Dr. Petty was founding President of theAssociation of Pulmonary Program Directors (appd)and has served as President of the American College of Chest Physicians. He is a former member of theBoard of Governors of the American Board of Internal Medicine.

Dr. Petty received the Distinguished Service Award ofthe American Thoracic Society (1995), was elected tothe Colorado Pulmonary Physicians’ “Hall of Fame”(1995) and received the annual award for excellenceby the American Association for Respiratory andCardiovascular Rehabilitation (1995) and the designa-tion of faarc in 1999. He was elected to MasterFellow of the American College of Chest Physicians(1995). He also received the Master Award of theAmerican College of Physicians in 1996. Dr. Petty hasbeen named Chairman of the National Lung HealthEducation Program (nlhep). Its goal is the early diag-nosis of copd and lung cancer. He is also Editor-in-chief of the newsletter, Lung Cancer Frontiers.

Today, Dr. Petty also remains active in teaching,patient care and research. He enjoys fishing, smallgame hunting and playing with his three “kids” andeight grandchildren.

Co-Editor


David D. Collins, MD

Dr. Collins is a pulmonologist who has practiced inWinston-Salem, North Carolina for eighteen years. Heis Medical Director of Respiratory Therapy andIntensive Care Medicine at Forsyth Medical Center. Heis on the clinical faculty of the Wake Forest UniversitySchool of Medicine. He is involved in ongoing clinicalresearch on techniques of non-invasive ventilation.

Dr. Collins is a graduate of the Duke University Schoolof Medicine, and did his residency, chief residency andpulmonary fellowship at the University of ColoradoHealth Sciences Center in Denver, Colorado.

Dr. Collins is married to Carole and has two high-school aged children, Michael and Julie. Hisrecreational interests include fly fishing, bicycling,cabinetmaking and cooking.(continued)

136

137 P. Postscript and Biographical Sketches of Authors(continued)

Dennis E. Doherty, MD

Dr. Doherty is Professor of Medicine and Chief of theDivision of Pulmonary and Critical Care Medicine andthe Medical Director of Respiratory Care Services at theUniversity of Kentucky, Chandler Medical Center, andthe Lexington Veterans Administration Medical Center.He completed his medical school and internal medicineresidency training at the Ohio State College of Medicinein Columbus, Ohio between 1977 and 1983. Hispulmonary and critical care fellowship was receivedfrom the University of Colorado Health Sciences Centerin Denver, Colorado, from 1983 to 1986, where heremained on the faculty for eleven years.

In 1996, Dr. Doherty relocated to the University ofKentucky to serve as Chief of Pulmonary and CriticalCare Medicine. He has been principal investigator onover 35 basic science and clinical grants and haspublished numerous articles and chapters on thesubjects of acute and chronic lung inflammation,obstructive lung disease and pulmonary fibrosis. Heserves as editor for three pulmonary journals (TheJournal of copd Management, Pulmonary Perspectives,for physicians, and BreatheWell, for copd patients) andtwo medical internet sites (airwaves.com andmedscape.com, critical care section). He is the Co-chairman of the National Lung Health EducationProgram, a Fellow of the accp, and is President of theKentucky Thoracic Society.

Dr. Doherty is an avid home winemaker, a formernational champion in handball and enjoys spendingtime with his wife, Kim, and two children, Erin and Collin.


J. Roy Duke, Jr., MDDr. Duke was born in Ocala, Florida and attendedTulane University School of Medicine in New Orleans,Louisiana, obtaining his medical degree in 1960. Aftera two-year stint in the U.S. Air Force, he completed hispostgraduate training in pulmonary medicine atTulane in 1967.

Dr. Duke joined the Palm Beach Medical Group inWest Palm Beach, Florida in 1967 and has practicedpulmonary medicine and internal medicine there to the present. He has served as Chief of Medicine andChief of Staff of Good Samaritan Hospital in WestPalm Beach.

He has an interest in hyperbaric medicine, which is an extension of his hobbies of scuba diving and under-water photography. He is also an avid fly fishermanand fly tier.

Dr. Duke is married to Bobbye Craig Duke and hastwo children, Denise and Christopher.(continued)

138


139

James T. Good, Jr., MD

Dr. Good received his md degree from the University ofKansas and completed a medical internship, residencyand chief medical residency at the University of Kansas.He then completed a three-year pulmonary and criticalcare medicine fellowship at the University of Colorado.The next four years he remained on the faculty at theUniversity of Colorado as an Assistant Professor ofMedicine and was Medical Director of both theRespiratory Therapy Department and the Critical CareUnit at Denver General Hospital. His scientific interestsinclude management of critical patients with acuterespiratory failure, pleural diseases and asthma. He is afellow of the American College of Physicians and theAmerican College of Chest Physicians (accp) andserved as the Governor for the states of Colorado andWyoming for the accp from 1988 to 1994.

He currently is in the private practice of pulmonary andcritical care medicine in south Denver and is MedicalDirector of the Swedish/Columbia Critical Care Unit.He remains actively involved in clinical research,teaching medical students and residents and incontinuing medical education programs.


Leonard D. Hudson, MD

Dr. Hudson received his b.s. from Washington StateUniversity in Pullman, Washington and his md from theUniversity of Washington in Seattle. He did hisinternship at Bellevue Hospital Center located in NewYork City, and his residency at New York Hospital,Cornell Medical Center (New York City), and at theUniversity of Washington, in Seattle. He did hispulmonary/critical care fellowship at the University ofColorado and stayed on the faculty there from 1971 to1973. In 1973, he moved to Seattle’s HarborviewMedical Center and the University of Washington.

In 1985, Dr. Hudson became Head of Pulmonary andCritical Care Medicine at the University of Washington.Since 1982, he has been a Professor of Medicine at theUniversity of Washington, Seattle.

Dr. Hudson’s honors include Outstanding Resident,Harborview Medical Center; American ThoracicSociety Fellowship in Pulmonary Diseases; Chair,Pulmonary Disease Subspecialty Board, AmericanBoard of Internal Medicine; and Chair, Critical CareMedicine Test Committee, American Board of InternalMedicine. He was President of the American ThoracicSociety from 1995 to 1996.

Hudson has four children, Sean, Sherry, Meg andKevin. His hobbies include wood-fired pottery, listeningto jazz and reading poetry. He is an amateur flyfisherman and plays soccer for the Seattle Flounders,older men’s division.(continued)

140


141

Charles H. Scoggin, MD

Dr. Scoggin received his medical degree from theUniversity of Colorado, training in internal medicine atDuke University and pulmonary medicine and criticalcare in the Division of Pulmonary Sciences at theUniversity of Colorado in Denver, Colorado. He alsotrained in molecular and cellular biology at theUniversity of Colorado and Eleanor Roosevelt Institute.

He has held the positions of Professor of Medicine,Clinical Director of the Department of Medicine,Director of the House Staff Training Program of theDepartment of Medicine and Head of the Adult HumanGenetics Section, all at the University of Colorado. Hewas also Senior Scientist and Vice President of theEleanor Roosevelt Institute.

During his academic career, Dr. Scoggin receivednumerous awards and recognitions. He was Teachingand Research Scholar of the American College ofPhysicians, a Fellow of the American College ofPhysicians, Research Scholar of the American LungAssociation and Fellow of the American College ofChest Physicians.

Dr. Scoggin is currently Chairman, President and ChiefExecutive Officer of Medrock, Inc., a Boulder, Coloradoand Cambridge, Massachusetts-based company focusedon providing assistance to family members and loved-ones of patients experiencing a medical crisis. He enjoysfishing, hunting, his family and good friends. ■

AAcid-base balance, 33-35Acidemia, criteria of, 34Acidosis, metabolic, 34Alcohol

avoidance of before sleep, with sleep apnea, 88metabolic acidosis associated with, 34

Algorithm, for interpretation of spirometry, 6Alkalemia, criteria of, 34Alveolar hypoventilation, 98Alveolar proteinosis, 18

diffusing capacity and, 24Alveolitis, fibrosing, idiopathic, 7American Lung Association, website, 110Amino-pregnancy, diffusing capacity and, 24Amyotrophic lateral sclerosis, 18Anemia, diffusing capacity and, 24Aneurysms, vascular, on chest x-ray, 47Angiography, pulmonary, 55Ankylosing spondylitis, 18Anterior mediastinum thymoma, on chest x-ray, 47America On Line (aol) health channel, 109Apnea, 2, 80, 82, 85, 86

central sleep, hypopnea syndrome, 80obesity and, 80, 82obstructive sleep, hypopnea syndrome, diagnostic

criteria, 86patients at risk for, 82snoring, loud, chronic, 82

Apnea-hypopnea Index (ahi), 85Arrhythmias, with bronchoscopy, 77Arterial blood gases, 28-40

acid-base balance, 33-35interpretation of, 29oxygenation, 29-31pulse oximetry, 35technical aspects, 28

Artery, pulmonarycatheterization, 65-67pressure, measuring, 66

Arthritis, rheumatoid, 7Asbestosis, 7, 18

diffusing capacity and, 24Ascites, 18Aspirin, metabolic acidosis with, 34Assist-control ventilation, 93, 94Asthma, 7Asthma, Allergy & Pulmonary News, website, 110Asthmatic bronchitis, 7

Index143


Atelectasis, 18, 98Australian Lung Association, website, 110Automobile-related accidents, due to fatigue, 82

BBeryllium disease, chronic, 18Bi-level positive airway pressure, 94, 96-97Biographical sketches, authors, 134-142Bleeding, with bronchoscopy, 77Blood gases, arterial, 28-40Bronchiolitis obliterans, with organizing pneumonia, 18Bronchitis 4, 7, 45

asthmatic, 7bronchiectasis, 7chronic obstructive, 7obstructive, chronic, 7pneumonia, distinguishing, chest x-ray, 44, 45

Bronchoalveolar lavage, fever with release of cytokines, 77Bronchoprovocation testing, pharmacologic

contraindications for, 25indications for, 25methods, 25, 26safety, 26

Bronchoscopy, 75-78contraindications, 75-77indications, 75

Bronchospasm, with bronchoscopy, 77Bullous lung disease, versus pneumothorax, chest x-ray, 48

Ccap See community acquired pneumoniaCarboxyhemoglobinemia, diffusing capacity and, 24Cardiac catheterization, 63-68

complications, 63-64contradictions, 63-64indications, 63pulmonary artery, 65-67techniques, 64-65

Cardiac failure, evaluation of, 57-59Cardiac murmurs, evaluation of, 57Cardiovascular abnormalities, chest x-ray, 46Central sleep apnea-hypopnea syndrome, 80Chest x-ray, 41-51

cardiovascular abnormalities, 46dyspnea, 45mediastinal, hilar adenopathy, 48patterns, evolution of infiltrates, diagnosis from, 42pneumonia, bronchitis, distinguishing, 44-45pneumothorax, versus bullous lung disease, 48pulmonary embolus, 46

144

Index (continued)

screening, 43Cheyne-Stokes breathing syndrome, 80Choking, during sleep, 82Chronic obstructive bronchitis, 7Chronic obstructive pulmonary disease (copd), 7, 8, 22Coal workers’ pneumoconiosis, 18Cognitive difficulties, related to fatigue, 82Collagen vascular diseases, diffusing capacity and, 7, 24Collins, David E., md, biographical sketch, 136Communication with family, legal issues, 126Community-acquired pneumonia (cap), 2, 69, 71, 72Comprehensive Health Enhancement Systems, 111Computed tomography (ct), 50-53

with contrast, 51high resolution, 51low radiation dose, 51spiral, with contrast, 51without contrast, 51

Congestive heart failure, 7, 18, 22, 24diffusing capacity and, 24

Consumer empowerment, in healthcare, 105Consumer healthcare websites, 109Continuous mechanical ventilation, 93, 94Continuous positive airway pressure (cpap), 2, 79, 88, 89, 96, 101

nasal, for sleep apnea, 88copd. See Chronic obstructive pulmonary diseaseCor pulmonale, sleep apnea and, 82cpap. See Continuous positive airway pressurect. See Computed tomographyCystic fibrosis, 7Cystic Fibrosis Foundation, website, 110Cysts, developmental, on chest x-ray, 47

DDaytime sleepiness, excessive, 82Dental devices, for sleep apnea, 88Developmental cysts, on chest x-ray, 47Diabetes mellitus, metabolic acidosis with, 34Diaphragmatic paralysis, 18Diffusing capacity, 19-21

factors affecting, 24methods of measuring, 21

Diverticulum, esophageal, on chest x-ray, 47Documentation, medical record, legal issues, 126Doherty, Dennis E., MD, biographical sketch, 137Drug induced interstitial lung disease, diffusing capacity and, 24Duke, J. Roy, Jr., MD., biographical sketch, 138Dynamics in Healthcare, website, 110Dyspnea, chest x-ray, 45Dyspneic patient, evaluation of, 59-60

145

Ee-mail, 106, 107, 115, 116, 118Echocardiogram, 57-60Echocardiographic techniques, 57, 58Embolus, pulmonary, 22, 24

diffusing capacity and, 24Emphysema, 7, 24

diffusing capacity and, 24Empowerment of consumer, in healthcare, 105Endotracheal tubes, complications associated with, 98Epworth sleepiness scale, 82Esophageal carcinoma, on chest x-ray, 47Esophageal diverticulum, on chest x-ray, 47Ethylene glycol, metabolic acidosis with, 34Exercise, diffusing capacity and after, 24Exercise program, for sleep apnea, 88Expiratory reserve volume, 20Extubation, complications, 98

FFatigue, automobile-related accidents, 82Fever

with bronchoscopy, 77with release of cytokines, bronchoalveolar lavage, 77

Fibrosing alveolitis, idiopathic, 7Fibrosis

cystic, 7interstitial, 7pulmonary, idiopathic, 18

diffusing capacity and, 24Fibrotic residue, of disseminated granulomas, 7Flow-volume, volume-time, 5, 9-11

mild obstruction, 5, 9moderate restriction, 5, 11normal, 9severe obstruction, 5, 10severe restriction, 5, 11

Fluorescent antibody tests, for Legionella pneumophila, 71

GGasping, during sleep, 82Germ cell tumors, on chest x-ray, 47Good, James T., Jr., MD, biographical sketch, 139Goodpasture’s syndrome, diffusing capacity and, 24Gram stain, sputum studies, 69Granulomas, disseminated, fibrotic residue of, 7Guillain Barré syndrome, 18


Index (continued)

HHealthAnswers, website, 109Healthcare information, accessing web for, 105Healthcare websites, consumer, 109Heart attack, 8Heart failure, congestive, 7, 18, 24

diffusing capacity and, 24Hemorrhage, intra-alveolar, diffusing capacity and, 24Hiatal hernia, mediastinum neurogenic tumors, on chest x-ray, 47

High resolution computed tomography, 51Hilar adenopathy, mediastinal, chest x-ray, 48Histoplasmosis, 7Home sleep studies, 87Hudson, Leonard D., MD, biographical sketch, 140Hypersensitivity pneumonia, 18

diffusing capacity and, 24Hypertension

pulmonaryprimary, diffusing capacity and, 24sleep apnea and, 82

sleep apnea and, 82Hypotension, with bronchoscopy, 77Hypoventilation

alveolar, 98with bronchoscopy, 77

Hypoventilation syndrome, in sleep, 80Hypoxia, with bronchoscopy, 77

IIdiopathic fibrosing alveolitis, 7Idiopathic pulmonary fibrosis, 18

diffusing capacity and, 24Ingestions, metabolic acidosis with, 34Inspiratory capacity, 20Inspiratory flow disorders, restrictive ventilatory disorders, 5-6Inspiratory reserve volume, 20InteliHealth, website, 109Intermittent mandatory ventilation, 93, 94-95Internet

applications, 104-122early development of, 104, 106emerging uses of, 120-122growth, impact of, 104-117healthcare sites, evaluating, 113

Interstitial pneumonitis, 7Intra-alveolar hemorrhage, diffusing capacity and, 24Intra-cardiac shunt, left to right, diffusing capacity and, 24

147

Intrapulmonary shunt, 32Intubation, complications, 98Iseman, Michael D., MD, biographical sketch, 134

KKetoacidosis, 34Kyphoscoliosis, 18

LLaryngobronchospasm, with bronchoscopy, 77Laser-assisted uvulopalato pharyngoplasty, 88, 89laup See Laser-assisted uvulopalato pharyngoplastyLeft to right intra-cardiac shunt, diffusing capacity and, 24Leg veins, duplex ultrasonography of, 60-61Legal issues, 123-127

communication with family, 126documentation, medical record, 126lung cancer

failure to diagnose, 123screening, 125

pulmonary embolism, failure to prevent, diagnose, treat, 123-124

referral to specialist, 125-126responding to medical personnel, of physician, 126-127spirometry

failure to do, 125screening, 125

Legionella pneumophiladirect fluorescent antibody tests for, 71urinary antigen, 71

Licklider, J.C.R., 104, 106Low radiation dose computed tomography, 51Lung cancer, 8, 123, 125

failure to diagnose, legal issues, 123screening

legal issues, 125medicolegal issues, 125

Lung Cancer Frontiers, 130Lung resection, 18

diffusing capacity and, 24Lung volume, 17-27

methods of measuring, 17-19Lymphadenopathy, on chest x-ray, 47Lymphoma, on chest x-ray, 47

MM-mode (motion-mode) echocardiography, 58Magnetic resonance imaging, 51, 54, 55, 132Mailing lists, Internet, 111Maxillofacial surgery, for sleep apnea, 88


Index (continued

Mayo Clinic Health Oasis, website, 109Mechanical ventilation, 93-102

complications of, 98continuous, 93, 94weaning from, 93-102

Mediastinal hilar adenopathy, chest x-ray, 48Mediastinal masses, by location, 47Mediastinum, neurogenic tumors, on chest x-ray, 47Medicolegal issues, 123-127

communication with family, 126documentation, medical record, 126lung cancer

failure to diagnose, 123screening, 125

pulmonary embolism, failure to prevent, diagnose, treat, 123-124

referral to specialist, 125-126responding to medical personnel, of physician, 126-127spirometry

failure to do, 125screening, 125

Mediconsult, website, 109Medscape, website, 109Mesenchymal tumors, on chest x-ray, 47Metabolic acidosis, causes of, 34Methanol, metabolic acidosis with, 34Methotrexate, amino-pregnancy, diffusing capacity and, 24MRI. See Magnetic resonance imagingMurmurs, cardiac, evaluation of, 57Myasthenia gravis, 18Mycobacteria, sputum studies, 71Mycobacteria avium complex, sputum studies, 71Mycobacteria kansasii, sputum studies, 71

NNasal continuous positive airway pressure, for sleep apnea, 88Nasal surgery, for sleep apnea, 88Nasopharyngeal narrowing, sleep apnea and, 82National Emphysema Foundation, website, 110National Lung Health Education (nlhep), website, 110, 114National Lung Health Education Program (nlhep),

8, 13, 110, 114, 125, 128National Sleep Foundation, website, 110Negative pressure chest wall devices, 97Neurogenic tumors, mediastinum, on chest x-ray, 47Neuromuscular disorders, 7nlhep See National Lung Health Education ProgramNon-invasive ventilatory support, 96Nucleic acid amplification, 71

149

OO-CPAP weaning from ventilation, 100Obesity

diffusing capacity and, 24morbid, 18sleep apnea and, 80, 82, 89

Obstructive bronchitis, chronic, 7Obstructive lung diseases, pulmonary mechanics, 5Obstructive pulmonary disease, chronic, 7Obstructive sleep apnea-hypopnea syndrome, 80

diagnostic criteria, 86Obstructive vasculopathy, diffusing capacity and, 24Oral devices, for sleep apnea, 88Oximetry, pulse, 28-40

clinical applications of, 38limitations of, 37-39uses of, 37

Oxygen-hemoglobin dissociation curve, 36

PParalysis, diaphragmatic, 18Parathyroid tumors, on chest x-ray, 47pcv See Pressure control ventilation peep. See Positive end-expiratory pressurePersonality changes, related to fatigue, 82pet. See Positron emission tomographyPetty, Thomas L., MD, biographical sketch, 135Pharmacologic bronchoprovocation challenge, 23Pharmacologic bronchoprovocation testing

contraindications for, 25indications for, 25methods, 25-26safety, 26

Pleural effusion, 18Pleural ultrasound examination, 61Pneumoconiosis, 18

coal workers’, 18Pneumonia, 18, 98

bronchitis, distinguishing, chest x-ray, 44, 45with bronchoscopy, 77hypersensitivity, 18

diffusing capacity and, 24organizing, bronchiolitis obliterans, 18sputum studies, 71

Pneumonitis, interstitial, 7Pneumothorax, 18, 98

with bronchoscopy, 77versus bullous lung disease, chest x-ray, 48

Poliomyelitis, 18Polycythemia rubra vera, diffusing capacity and, 24


151 Index (continued)

Polysomnography (psg), overnight, 83, 84, 87Positive end-expiratory pressure, 94, 96Positron emission tomography, 50, 51, 54, 123Posture, supine, diffusing capacity and, 24Pregnancy, 18

diffusing capacity and, 24Pressure control ventilation (pcv), 93, 95Pressure support ventilation, 93, 95-96, 100, 101Pressure ventilation, 93, 95Primary pulmonary hypertension, diffusing capacity and, 24Prognostic value, spirometry, 6Proteinosis, alveolar, 18

diffusing capacity and, 24psg See polysomnographyPulmonary angiogram, 51Pulmonary artery catheterization, 65-67Pulmonary artery pressure, measuring, 66Pulmonary emboli, 22

chest x-ray, 46diffusing capacity and, 24

Pulmonary embolism, failure to prevent, diagnose, treat, legal issues, 123, 124

Pulmonary fibrosis, idiopathic, 18diffusing capacity and, 24

Pulmonary function tests, interpretation of, 21-23Pulmonary hypertension

primary, diffusing capacity and, 24sleep apnea and, 82

Pulmonary mechanics, spirometry, 4, 5Pulmonary websites

consumer-oriented, 110for physicians, 114

Pulse oximetry, 28-40clinical applications of, 38limitations of, 37-39uses of, 37

RReferral to specialist, legal issues, 125, 126Resection, lung, 18

diffusing capacity and, 24Residual volume, 20Respiratory tract infections, sputum studies, 69-72Responding to medical personnel, of physician,

legal issues, 126-127Restrictive lung disease, causes of, 18Restrictive ventilatory disorders, obstructive lung diseases, 5Rubra vera, polycythemia, diffusing capacity and, 24


SSarcoidosis, 7, 24

diffusing capacity and, 24Sclerosis, amyotrophic, lateral, 18Scoggin, Charles H., MD, biographical sketch, 141Seizures, with bronchoscopy, 77Shock, evaluation of patient in, 60Shunt

intra-cardiac, left to right, diffusing capacity and, 24intrapulmonary, 32

SIMV weaning, from ventilation, 101Sleep apnea, 80-92. See also Apnea

hypopnea syndrome, obstructive, 80treatment of, 88

Sleep disordered breathing, epidemiology, etiology, 80-81Sleep hypoventilation syndrome, 80Sleep studies, 80-92

sleep disordered breathing, epidemiology, etiology, 80, 81Sleepiness, daytime, excessive, 82Snoring, loud, chronic, 82Snowdrift Pulmonary Conferences, 129, 130Spiral computed tomography, with contrast, 51Spirometry, 4-16

algorithm for interpretation, 6, 12clinical diagnosis, 6failure to do, legal issues, 125inspiratory flow disorders, 5, 6obstructive lung diseases, 5, 7, 9, 10prognostic value, 6pulmonary mechanics, 4, 5restrictive ventilatory disorders, 5, 11screening, legal issues, 125when to perform, 8, 125, 128

Spondylitis, ankylosing, 18Sputum studies, 69-74

culture techniques, 70Gram stain, 69pneumonia, 71respiratory tract infections, 69-72respiratory tract neoplasms, 73tuberculosis, 71

Starvation, metabolic acidosis with, 34Stroke, 8Supine posture

diffusing capacity and, 24sleep apnea and, 88

Surgical procedures, for sleep apnea, 88Synchronized intermittent mandatory ventilation, 93, 94, 95

152

153 Index (continued)

TT-piece weaning, from ventilation, 1, 100Thoracic deformities, 7Thriveonline, website, 109Thyroid tumors, on chest x-ray, 47Toluene, metabolic acidosis with, 34Tonsillectomy, for sleep apnea, 88Total lung capacity, 20Tracheostomy tubes, complications associated with, 98Tuberculosis, 7

sputum studies, 71

UUltrasound

diagnostic, 51, 54pleural examination, 61procedures, 57-62

Urinary antigen, Legionella pneumophila, 71Uvulopalatoplasty, laser assisted 88, 89uppp See UvulopalatopharyngoplastyUvulopalatopharyngoplasty 88, 89

V(v· /q· ) See ventilation-perfusion lung scanVascular aneurysms, on chest x-ray, 47Vasculopathy, obstructive, diffusing capacity and, 24Veins, leg, duplex ultrasonography of, 60, 61Venous embolism, 60Ventilation

medical complications occurring during, 98weaning from, 99

Ventilation-perfusion lung scan (v· /q· ) 2, 53intrapulmonary shunt, 32normal lung scan, 51

Ventilator, complications attributable to operation of, 98Volume-time, flow-volume

mild obstruction, 5, 9moderate restriction, 5, 11moderate obstruction, 5, 11normal, 9severe obstruction, 5, 10severe restriction, 5, 11

Volume ventilation, 94


WWeaning from mechanical ventilation, 93-102

0-cpap, 100pressure support ventilation, 101simv weaning, 101strategies, 100T-piece weaning, 1, 100

Websiteshealthcare, consumer, 109pulmonary

consumer-oriented, 110for physicians, 114

Weight loss, for sleep apnea, 88Work-related accidents, due to fatigue, 82World Wide Web, uses of, 106

XX-ray, chest, 41-51

cardiovascular abnormalities, 46dyspnea, 45mediastinal, hilar adenopathy, 48patterns, evolution of infiltrates, diagnosis from, 42pneumonia, bronchitis, distinguishing, 44, 45pneumothorax, versus bullous lung disease, 48pulmonary embolus, 46screening, 43

YYahoo/health, 111

154

frontline pulmonary procedures and interventions

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