sood - performing a lung disability evaluation (2014)

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SUPPLEMENT

Performing a Lung Disability Evaluation

How, When, and Why?

Akshay Sood, MD, MPH

Objectives:The objective of this review is to present a case-based clinical

discussion on this topic. Methods:The article represents part of the proceed-

ings of the Occupational and Environmental Lung Disease conference held

by the American College of Chest Physicians at Toronto, Ontario, Canada, in

2013, and is based upon a nonsystematic review of the current literature by

the author.Results:Although the American Medical Association Guides to

the Evaluation of Permanent Impairment is the mainstay for evaluating respi-

ratory impairment, many other impairment schemata are currently available

in the United States. Impairment evaluation for a case with chronic respi-

ratory disease and a separate case with asthma is discussed. Conclusions:

Pulmonary function tests are the cornerstone for evaluating respiratory im-

pairment. Impairment values differ between various impairment schemata.

Impairment evaluation for asthma may be particularly difficult.

T he management of a patient with lung disease does not endwith its treatment. These patients often require additional assis-tance on issues related to respiratory impairment and disability. Yet,many physicians refrain from providing these services, often withdisastrous consequences for the patient. Multiple reasons underliethe general physician reluctance in addressing impairment. Theseinclude a lack of inclusion as a curricular milestone in fellowshiptraining,1 fear and poor understanding of the legal system, confusionabout various compensation systems, a mistaken notion that thosewho seek impairment assistance are malingerers,2, 3 and a desire toavoid potentially uncompensated efforts in the context of an already

burdensome clinical schedule.Although the terms impairment and disability are often

used interchangeably, they are not synonymous. In 1980, the WorldHealth Organization issued a statement defining impairmentas anyloss or abnormality of psychological, physiological, or anatomicalstructure or function anddisability as any restriction or lack, re-sulting from impairment, of ability to perform an activity within therange considered normal for a human being.4 The goal of respi-ratory impairment evaluation is the objective measurement of theextent of loss of respiratory function, primarily through the applica-tion of pulmonary function or exercise testing. The physician plays

From the University of New Mexico Health Sciences Center School of Medicine,Albuquerque, NM.

Supported by the National Institutes of HealthK23 HL094531-01A1;

1UL1RR031977; and 5 UL1 TR000041-05; Health Resources and ServicesAdministration (HRSA)1D33HP19042; Patient-Centered Outcomes Re-search Institute Contract # 7738152.

Although the Occupational and Environmental Lung Disease Conference 2013was sponsored by the American College of Chest Physicians, the content ofthe presentation as well as that of this article was not regulated or approved

by the College or by other presenters at the conference. The author of thismanuscript was the speaker on this topic at the above-mentioned conference

but not the organizer. Several other topics from that multispeaker conferenceare being published in the same special edition of theJournal of Occupationaland Environmental Medicine.

The author declares no conflict of interest.Address correspondence to: Akshay Sood, MD, MPH, University of New

Mexico Health Sciences Center Schoolof Medicine, Department of Medicine,1 University of New Mexico, MSC 10 5550, Albuquerque, NM 87131([email protected]).

Copyright C 2014 by American College of Occupational and EnvironmentalMedicine

DOI: 10.1097/JOM.0000000000000282

a key role in impairment evaluation. On the other hand, the impactof the respiratory impairment on a persons ability to perform day-to-day activities is called disability, which is typically determinedthrough the application of administrative and legal instruments byexperts in these areas who may be physicians or nonphysicians.These experts not only rely upon the impairment evaluation but alsotake into consideration other social and legal issues, as well as thespecific requirements of the job.

Patients seeking an impairmentevaluationin theUnitedStatescan be usually classified into three general types: (1) those withadvanced lung disease who apply for disability benefits under theUnited States Social Security Impairment program; (2) those with

work-related lung disease who usually apply under the WorkersCompensation System; and (3) those who develop lung disease asa consequence of active military service, such as the Veterans Ad-ministration. The most commonly used impairment guidelines inthe United States are the Social Security Impairment program andthe Workers Compensation System. Issues relevant to impairmentevaluation for lung disease are discussed using two examples in thetext below.

Case 1:A 56-year-old man presents with a 5-year history ofprogressive moderate dyspnea on exertion (corresponding to NewYork Heart Association class II dyspnea) and daily cough productiveof white phlegm, meeting the clinical definition of chronic bronchi-tis. He gives a 42 pack-year history of smoking and an occupationalhistory of working in a foundry for 28 years. He gives a history of

sandblasting without adequate respiratory protection for the initial

12 years of this job. The foundry was shut down 2 years beforehis presentation when he was also laid off. His current medicationsinclude short-acting agonist and long-acting anticholinergic in-halers. His physical examination is significant for a height of 170 cmwithout shoes, a respiratory rate of 18 breaths per minute, a heartrate of 76 beats per minute, and an oxygen saturation of 92% onroom air. His chest wall is symmetric, and auscultation of his lungs

shows bilateral expiratory rhonchi. The rest of his examination isnormal. A two-view chest radiograph reveals hyperexpansion of bi-lateral lung fields. His pulmonary function tests are summarized inTable 1.

Question 1: What is the percent impairment of the wholeperson, on the basis of lung disease, assuming maximal medicalimprovement (MMI) and using the sixth edition of the American

Medical Association (AMA) Guides to the Evaluation of PermanentImpairment?

AMA GUIDES TO THE EVALUATION OFPERMANENT IMPAIRMENT (GUIDES)

There are six editions of the AMA Guides.5 Because thevarious editions of the AMA Guides contain markedly different setsof recommendations on impairment evaluation, the physician mustchoose the right edition, depending upon the requirement of thecompensation system that the patient is applying for. The use ofthe wrong edition may result in a different impairment rating.Generally speaking, the use of the sixth edition of the AMA Guidesresults in a lower impairment rating than the previous editions, whichmay translate to a lower financial compensation for the patient with

pulmonary injury or illness. Although the AMA Guides generally

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JOEM Volume 56, Number 10S, October 2014 S23
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TABLE 1. Summary of Pulmonary Function Tests for Case 1

Pulmonary Function Observed Percent Predicted

Parameter Value Value

Postbronchodilator FVC 3.48 L 80%

Postbronchodilator FEV1

1.60 L 45%

Post bronchodilator FEV1/

FVC Ratio

46%

DLCO 16.0 mL/min mm Hg

51%

DL CO, carbon monoxide diffusing capacity; FEV1, forced expiratory volume in 1second; FVC, forced vital capacity.

follow the American Thoracic Society (ATS) schema for evaluatingrespiratory impairment,6, 7 thereexist substantial differences betweenthe two guidelines. Furthermore, although other major guidelines areavailable on the Internet without charge, use of the web-based sixthedition of the AMA Guides carries a user fee.

Unlikeprevious editions, the sixth edition of the AMAGuidesuses a standardized grid that incorporates five classes of impairmentseverity, ranging from class 0 to class 4.5 The grids incorporate anobjective, test-based key factor for defining the impairment class,along with two non-key factors for fine-tuning the severity gradewithin a given class. There are five grades in each severity classexcept for class 0 where there are no grades. Among the variousobjective tests, the most severely affected test parameter is used todefine the impairment class.

Using the postbronchodilator forced expiratory volume in 1second (FEV1) value of 45%predicted (ie, the most severely affectedtest parameter); this patient meets the key factor criteria for class 3impairment (using the grid summarized in Table 2). The initial de-fault impairment rating is the central grade within the severity class,which corresponds to a severity grade of 3C or 32% impairment. For

the first remaining non-key factor, one determines the most appro-priate impairment class position and records the number differenceto the key factor impairment class. This step is repeated for the re-maining non-key factor. The history and physical examination status

(non-key factors) satisfy impairment class 2 criteria. Because theimpairment class for each of these non-key factors is one class level

below the key factor class, two grades should be subtracted from thedefault grade to identify the appropriate impairment severity grade.Thus, the final impairment rating corresponds to grade 3A or 24%,using the sixth edition of the AMA Guides.

RESTING PULMONARY FUNCTION TESTSPulmonary function tests are the cornerstone for evaluating

respiratory impairment and should be performed according to themost recent ATS standards.811 Spirometry and diffusing capac-ity are the key pulmonary function tests for assessing respiratoryimpairment for chronic respiratory conditions. Postbronchodilatorspirometry is used when airflow limitation is present. Although the

presence of hypoxemia on arterial blood gas analysis was used toevaluate impairment under the fifth edition of the AMA Guides,the sixth edition does not include hypoxemia in the evaluation ofimpairment.5 The sixth edition also endorses the use of specific Na-tional Health and Nutrition Examination Survey III reference stan-dards for spirometry for Caucasian Americans, Mexican Americans,and African Americans.5,12 For the remaining population subgroups,

no clear guidelines are provided. For corrected single-breath carbonmonoxide diffusing capacity (DLCO), Crapos reference standardsare used. The cut points for impairment classification, as suggested

by the AMA Guides, are set arbitrarily and may differ from thoserecommended for assessing the degree of lung disease severity byother professional organizations, such as the 2005 ATS statement9

or by the Global Initiative for Chronic Obstructive Lung Disease(GOLD).13 Some investigators have suggested that lung functionthresholds should be expressed as a z score, which converts a rawmeasurement on a test into a standardized score expressed in units ofstandard deviations.14,15 This strategy, although scientifically valid,is not currently used for impairment evaluation.

MAXIMAL CARDIOPULMONARY EXERCISE TESTSMaximal cardiopulmonary exercise tests are difficult to per-

form because of the need for specialized equipment and trainedpersonnel, are expensive and not readily available, and carry a riskto the patient. Test performance should strictly adhere to the 2003ATS-ACCP guidelines.16 A clear agreement on the role of exercise

TABLE 2. Summary of the Grid Used by the Sixth Edition of the AMA Guides to Determine the Class and Grade ofImpairment for Chronic Lung Disease*

Non-Key Factor

Key Factor Pulmonary

Function and Exercise Tests

History of Clinical

Presentation

Physical Examination

Findings

Severi ty class Class 3: 24%40% impa irment Cla ss 2: 11%23% i mpairment Cla ss 2: 11% 23% impairment

Severity grade, % A B C D E24 28 32 36 40

FVC 50%59% predicted Constant mild dyspnea despitecontinuous treatment

Constant mild physical findingsdespite continuous treatment

FEV1 45%54% predicted Intermittent moderate dyspneadespite continuous treatment

Intermittent moderate physicalfindings

DLCO 45%54% predicted

Vo2 max 1517 mL/kg/min

Vo2 max in 4.35.0 metabolicequivalent units

*FEV1 is the most severely affected test parameter in Table 1 and is used as the key factor for evaluating impairment. Even though the patients DLCO value falls in the

same impairment class as FEV1, the former is not used as a key factor because it is not the most severely affected test parameter.Theitalicizedtext shows the appropriate level of the rating factor in each column for case 1. Readers are advised to look up the complete tables in the AMA Guides.DLCO, carbon monoxide diffusing capacity; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; Vo2 max, maximum oxygen consumption.


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tests in the evaluation of respiratory impairment is lacking. Gener-ally, in cases in which subjective dyspnea is disproportionate to theresting pulmonary function test results, or when pulmonary functiontests are difficult to interpret because of submaximal performance,cardiopulmonary exercise tests may be considered. Exercise testingmay also be useful in determining whether an individual can per-form a specific job with a known energy requirement.5 Generally

speaking, per the AMA Guides, cardiopulmonary exercise testingis infrequently needed in the practical investigation of pulmonaryimpairment.5

Under the 1986 ATS guidelines for the evaluation of impair-ment/disability secondary to respiratory disorders, the estimation ofimpairment from oxygen consumption at peak exercise (Vo2 peak)is based on the widely held, but untested, assumption that a workerinvolved in manual labor can comfortably work at 40% ofVo2 peak(corresponding to lower limit of generally accepted normal valuesfor anerobic threshold) for prolonged periods.7 This viewis based onfindings from several small exercise studies performed in controlledlaboratory settings on motivated volunteers, usually athletic men,that show that exercise endurance can be predicted from anaerobicthreshold.1720 This assumption is however inadequately tested in oc-cupational settings.Manyhave argued that 40%is a toolow thresholdvalue because anaerobic threshold occurs at a much higher percent-age of predictedVo2 peak in fit individuals.

17,19 Finally, none of themajor guidelines currently advocate the use of anaerobic thresholdover the Vo2 peak value to determine respiratory impairment.

Some laboratories lacking cardiopulmonary exercise testequipment often estimate METs (or metabolic equivalents or mul-tiples of basal oxygen consumption, which is approximately 3.5mL/min/kg) of activity based upon exercise speed and grade on atreadmill, duration of exercise, and heart rate or heart rate variabil-ity, instead of directly measuring oxygen consumption.2123 Thesemethods are not considered sufficiently accurate. The AMA Guidesand the ATS statements only use cardiopulmonary exercise testingfor this purpose.5, 7

Under the 1986 ATS guidelines for the evaluation of impair-

ment/disability secondary to respiratory disorders, it is further im-plied that Vo2 requirements can be assigned to specific occupationsand individuals whose Vo2 peak is 15 mL/kg/min or less would

be uncomfortable performing most jobs because they would findit difficult to travel back and forth to their place of employment. 7

Unfortunately, data on Vo2 requirements of most jobs in modernworkplaces are not currently available. Furthermore, jobs with thesame title may vary considerably in theirVo2requirements from onework site to another.

SCIENTIFIC RATIONALE FOR CHOICE OF TESTSUSED FOR IMPAIRMENT EVALUATION

The premise for the use of pulmonary function and exercisetests for evaluating impairment is that Vo2peak reasonably measures

ability to work, and that resting pulmonary function tests, such asFEV1 and DLCO, reasonably predict Vo2 peak values and thereforepredict ability to work.

OXYGEN CONSUMPTION AT PEAK EXERCISE ASTHE GOLD STANDARD FOR MEASURING ABILITY

TO WORKLimited available medical literature seems to support the view

that the Vo2 peak value, expressed as mL/kg/min, may be the goldstandard for assessing impairment.2426 With exercise on a cycle er-gometer, Vo2 increases linearly with external work,

16 andVo2 peakrepresents themaximal work an individual canperform duringa short

burst of activity. Some have advocated the use of percent predictedVo2 peak values (ie, loss of aerobic capacity), instead ofVo2 peakexpressedin mL/kg/min (ie, remaining aerobic ability) for evaluating

impairment in patients with respiratory disease, because the latterapproach overestimates impairment in older and obese subjects.27,28

In addition, some consider the value forVo2 at anaerobic threshold(Vo2 AT) as a better index for work ability than Vo2 peak.

28 Indi-viduals are unable to sustain work rates above anerobic thresholdvalues. Nevertheless, no major guidelines currently suggest the useof percent predictedVo2 peak values orVo2 AT to rate impairment.

COMPARISON OF RESTING PULMONARYFUNCTION TESTS WITH OXYGEN CONSUMPTION

AT PEAK EXERCISEFEV1 is linearly correlated with Vo2 peak levels,

29 but thereported correlations vary widely between studies, resulting in vari-ance (coefficient of determination orr2) values ranging from 0.25 to0.71.2934 The use of absolute versus percent predicted values yieldssimilar correlation measures.33 Although some studies demonstratethat FEV1 and forced vital capacity (FVC) have a similar predic-tive value forVo2 peak levels,

33 most report FEV1 to be a strongerpredictor than FVC. A 2005 ATS statement on interpretative strate-gies for pulmonary function testing indicated that percent predictedFEV1, rather than FVC, should be used to categorize the severity

of impairment for all respiratory diseases.9 The predictive abilityof FEV1 forVo2 peak increases if it is used in combination withanother variable, such as DLCO, minute ventilation (VE), or deadspace ventilation measure during exercise (VD/VT).

33 DLCO doesnot predict Vo2peak among healthy controls,

30 but it does so amongsubjects with chronic obstructive pulmonary disease (COPD) andthose with occupational lung diseases, where it may account for avariance (coefficient of determination orr2) of 0.25to 0.76in variousstudies.32,33,35

Despite the previously noted correlations in population stud-ies, resting pulmonary function tests cannot accurately predict Vo2

peak values among individuals, particularly those with occupationallung diseases. In a comparison study of impairment ratings obtainedusing simultaneous resting pulmonary function tests and exercise

tests conducted in 216 ambulatory patients with COPD, the twomethods resulted in similar impairment rating in only 30.1%.25 Rat-ings were similar between the two methods in the extreme sub-groups of normal or severely impaired individuals. Up to 61.1%were found to be less impaired according to exercise testing thanaccording to resting pulmonary function tests, and 8.8% were moreimpaired according to exercise testing than resting pulmonary func-tion tests. These data suggest that the use of resting pulmonaryfunction tests and exercise testing for evaluating impairment oftenyields discrepant results.

Question 2:Given the limited information available, can thelung disease in case 1 be attributedto his occupational inhalationalexposures?

Although not a part of impairment evaluation per se, physi-cians may need to confirm the validity of the clinical diagnosis and

may be asked to additionally render an opinion on causation andapportionment.Causationorattributionrefers to whether an expo-sure has been a substantial contributing factor in either causing orexacerbating lung disease. The level of certainty required in deter-mining causation for occupational lung disease is different from theusual standard of 95% certainty used in medical research. The com-monly accepted standard of certainty for occupational cases is thatthe illness is substantially caused, or exacerbated by, an occupationalexposure on a more probable than not basis, or a level of certaintygreater than 50%.

Any attempt to define causation or attribution must start witha comprehensive review of the existing medical literature on the as-sociation between the exposure and disease. For instance, relevantto case 1, COPD has been associated with inhalational silica ex-

posure, independent of smoking.3640 Studies from many different


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work environments suggest that exposure to working environmentscontaminatedby silicaat dust levels that seem notto cause roentgeno-graphically visible simple silicosis can cause chronic airflow limita-tion and/or mucus hypersecretion and/or pathologic emphysema.41

A meta-analysis of 13 studies among coal andgold miners confirmedan excess of bronchitic symptoms and obstructive physiology, evenamong nonsmokers.40 Furthermore, there may be an additive effect

between tobacco smoke and occupational pollutants in producingchronic bronchitis and airflow obstruction.41 Given the strength ofevidence that silica inhalational dust exposure is an independent riskfactor for COPD as well as the reported duration and latency ofexposure in this case, a level of certainty that is greater than 50%is reached. Therefore, this patients COPD can be attributed to hisoccupational inhalational exposures.

Apportionmentdescribes the relative contribution of multiplefactors to the total respiratory impairment. For instance, both chronicinhalational silica exposure and cigarette smoking are substantialcontributory factors to COPD. From a scientific perspective, it isusually difficult, if not impossible, to apportion their relative rolesin causation of COPD, a complex, multifactorial disease. Physiciansare asked to state their opinion on apportionment in the context of the

body of available knowledge in that area, which is usually very lim-ited. Furthermore, retrospective exposures are usually poorly quan-tified. It is the opinion of this author that specific percentages ofapportionment for dust versus cigarette smoke in causing occupa-tional lung disease in this case are best avoided.

WORKERS COMPENSATION SYSTEMThis patient may also be eligible to apply under the Workers

Compensation system. The Workers Compensation system is a no-fault system of medical care and disability insurance in which pri-vate insurers or self-insured employers pay benefits to an employeesustaining an injury or illness because of workplace exposure. UnderWorkers Compensation rules, workers cannot sue their employer forinjury or illness. The rules for the Workers Compensation systemin the United States vary from one state to another, but they usuallyfollow one of the six editions of the AMA Guides to the Evaluationof Permanent Impairment. Although not relevant to case 1, dust-exposed coal miners may apply for total disability benefits underthe 1972 Black Lung Benefits Act.42

Case 2:A 50-year-old male chemist presents with adult-onsetsevere persistent asthma that has involved eight unscheduled physi-cian visits including four visits to the emergency department, allresulting in hospitalizations, in the previous 12 months. The patientcomplains of daily respiratory symptoms of cough, wheeze, and dys-

pnea even in between attacks along with frequent nocturnal awaken-ings. A laryngoscopy reveals no paradoxical vocal cord movement.The list of daily medications includes 10 mg of oral prednisone,combination of inhaled high-dose corticosteroid and long-actingagonist, frequent short-acting inhaled agonist, zafirlukast, and

monthly omalizumab infusions. Physical examination is significantfor a height of 158 cm, a BMI of 35 kg/m2, and persistent expiratorywheezes documented on lung auscultation at all clinic visits. Pre-and postbronchodilator spirometry results are shown in Table 3. Amethacholine bronchoprovocation test was not performed as the testwas deemed unsafe.

Question 3: What is the percent impairment of the wholeperson, based on lung disease, assuming MMI and using the sixthedition of the AMA Guides?

Unlike most chronic respiratory conditions, asthma is anepisodic disease, and impairment evaluation for asthma is partic-ularly difficult. Therefore, most impairment evaluation schemataincorporate guidelines for asthma that are separate from those forchronic lung disease. Impairment levels for asthma differ dramati-cally between various impairment evaluation schemata as well.

A methacholine bronchoprovocation test is useful for con-firming the diagnosis of asthma as well as in evaluating impairmentfrom asthma under the AMA Guides andATS guidelines.5, 6 The per-formance of methacholine bronchoprovocation tests should strictlyadhere to the relevant ATS guidelines.43 The methacholine PC20(ie,

provocative concentration of methacholine, expressed as mg/mL thatresults in at least 20% drop in FEV1 compared to the pretest base-

line) is a key factor for evaluating asthma impairment under thesixth edition of the AMA Guides.5 On the other hand, methacholinePC20 and the extent of FEV1 reversibility are given less weightthan are either minimum medication need or postbronchodilatorFEV1 in the multicomponent asthma impairment scoring schemerecommended by the 1993 ATS guidelines or by previous editions ofthe AMA Guides.5, 6 Unlike Social Security Impairment criteria, theAMA Guides and ATS guidelines do not incorporate frequency ofacute exacerbations in the impairment evaluation for asthma. Giventhe efficacy of currently recommended asthma therapies, frequentemergency department visits or hospitalizations generally reflect in-adequate treatment and failure to achieve the objectives of treatment.The AMA Guides and ATS guidelines instead use minimum medi-cation needed for asthma control as a better reflection of the severityof disease for the purpose of impairment assessment than frequencyof asthma exacerbations. Hence, it is easy to see why impairmentratings for the same patient with asthma might vary widely amongvarious compensation systems. Furthermore, the use of the sixth edi-tion of the AMA Guides may result in a lower impairment rating than

previous editions of the AMA Guides, which in turn may translateto a lower financial compensation for the patient with asthma.

In the event that methacholine PC20 is unavailable or cannotbe safely performed (as is the case for the patient above), the sixthedition of the AMA Guides accepts the postbronchodilator FEV 1

percent predicted value as a key factor. Using that approach, thispatient receives an impairment rating of the whole person becauseof asthma of 0% (Table 4). Although this scenario is uncommon,this case reflects the difficulties associated with asthma impairment,

particularly when there is a discrepancy between the minimum med-

ication need and postbronchodilator spirometry values.

DETERMINANTS OF WORK ABILITY IN ASTHMADeterminants of work ability in asthma are inadequately stud-

ied. In one study of subjects with objectively confirmed asthma,factors associated with a lower self-reported work ability includethe lower PC20 value (ie, higher degree of airway hyperresponsive-ness), greater disease severityas definedby the minimum medicationneeded to control asthma, and the presence of respiratory symptomsat the workplace.44 Interestingly, work abilityin subjects with asthmais not related to baseline FEV1 or FVC in that study (even thoughFEV1 enters the impairment evaluation schema for asthma under

both the AMA Guides and the ATS guidelines).44 This finding isconsistent with another nonwork-related study that demonstratesthat FEV1percent predicted is inferior to standardized asthma ques-

tionnaires in predicting clinical asthma outcomes.45

COMPARISON BETWEEN RESPIRATORYSYMPTOMS AND PC20

For most subjects with asthma, greater breathlessness per-ceived during asthma attacks is not correlated with greater declinein the peak expiratory flow rate46 or with a lower PC20 value.

47

COMPARISON BETWEEN MINIMUM MEDICATIONNEED AND PC20

Almostall medications used to treat asthmaimprovePC20val-ues (ie, decrease bronchial hyperresponsiveness).4860 In one study,

patients with asthma with the minimum medication needed to con-trol symptoms were divided into four groups: (1) those who re-quired no medication; (2) those whorequired short-acting2agonist




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TABLE 3. Summary of Pulmonary Function Tests for Case 2*

Prebronchodilator Postbronchodilator Percent Change

Parameter Parameter Parameter Parameter

FVC 3.0 L (75%) 3.68 L (92%) 23%

FEV1

2.1 L (62%) 3.0 L (88%) 42%

FEV1/FVC ratio 71% 82%

*A methacholine bronchoprovocation test was not performed as the test was deemed unsafe.

FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity.

TABLE 4. Summary of the Grid Used by the Sixth Edition of the AMA Guides to Determine the Class and Grade ofImpairment for Asthma*

Non-Key Factor

Key Factor History of Clinical Minimum Medication

Criteria Methacholine PC20 Presentation Need

Severity class N/A Class 0: 0% impairment Class 4

Severity grade, % A B C D E

45 50 55 60 65

>80% postbronchodilator FEV1percent predicted despitecontinuous treatment

Asthma not controlledby treatment

*If methacholine PC20 is unavailable, postbronchodilator FEV1 percent predicted (otherwise a non-key factor) is used as a key factor.

Theitalicizedtext shows the appropriate level of the rating factor in each column for case 2. Readers are advised to look up the complete tables in the AMA Guides.

occasionally, but not daily; (3) those who required daily short-acting2 agonist; and (4) those who required additional inhaled corticos-teroiddosing. ThemeanPC20value was highest in group 1 andlowestin group 4; the differences between each group were significant.61

Minimum medication need in asthma is, therefore, an important

predictor for airway hyperresponsiveness as well as work ability.

COMPARISON BETWEEN PERCENT PREDICTEDFEV1 AND PC20

In a small clinical population of smokers and nonsmokers, aswell as in a population of subjects with asthma with concomitantstable bronchiectasis, baseline FEV1 has been shown to correlatewith methacholine PC20 values.

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Case 2(continuation):A review of the patients occupationalhistory revealed that this chemist had a new exposure to colophony

fumes at his workplace before the onset of symptoms. On direct ques-tioning, the patient stated that his symptoms were worse on the dayshe worked; and improved on weekends and vacations, with recur-rence of symptoms on returning to work. His serial peak expiratory

flow rate tracings were consistent with the diagnosis of work-relatedasthma. The material safety data sheet for colophony mentionedrosin, which is a sensitizer. A specific inhalational challenge couldnotbe performed because of thelack of clinical test availability in theUnited States. A diagnosis of occupational asthma was establishedand the patient was removed from workplace exposures.

Impairment evaluation for occupational asthma is even moreproblematic than nonoccupational asthma. In these cases, both tem-porary and long-term impairment evaluation should be performed.6

Temporary impairment for patients with sensitizer-induced occu-pational asthma should be performed after removing the workerfrom exposure. Early cessation of exposure improves prognosisin sensitizer-induced occupational asthma. Sometimes, physiologictests may be normal, and symptoms and need for treatment may sub-side after early cessation of exposure, resulting in 0% measureable

impairment. Nevertheless, such an individual should be consideredas100% disabled on a permanent basis from working in a job thatexposes him or her to the specific sensitizing agent.6 It is not nec-essary to wait for long-term impairment rating to initiate vocationalrehabilitation in such a case.6 The long-term impairment evaluation

is performed using the impairment evaluation systems devised fornonoccupational asthma, usually at least 2 years after thecessation ofexposure, when improvement has beenshown to plateau.5,6,6367 Thisrecommendation is based upon findings by Malo et al that improve-ments may be found 2 years or more after stopping exposure 68,69

and the systematic review by Rachiotis et al that demonstrated apooled estimate of 32% symptomatic recovery at a median durationof follow-up of 31 months after the cessation of exposure, with asignificant between-study heterogeneity.70

CONCLUSIONSThe following five steps often constitute the process of com-

pleting a respiratory impairment evaluation.The first step involves the confirmation of the diagnosis of

lung disease. Because of the medicolegal nature of the evaluation,the physician should have greater certainty of the medical diagnosisthan is sometimes used in clinical practice. In other words, objectiveconfirmation of the diagnosis is preferable.

The second step involves defining MMI. Maximal medicalimprovement occurs at the point when, after maximal therapy, nofurther clinical or physiological improvement is expected to occur(although deterioration might). If therapy has not been maximized,the physician should either delay impairment evaluation or give atemporary evaluation. A permanent impairment evaluation should

be performed only at, or after, MMI has been reached.The third step is identifying the correct guideline for eval-

uating impairment. As discussed previously, several compensationsystems exist, each with its own unique guideline. Therefore, identi-fication of the compensation system for which the patient is eligible


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is essential, and the evaluating physician must be familiar with thespecific guideline to be used. Of course, some patients may be eli-gible for more than one compensation program and may apply formore than one program contemporaneously.

The fourth step is to supplement the history and physicalexamination findings with appropriate objective tests. Performanceof these tests should strictly adhere to the ATS standards.811

The fifth and the most important step requires writing a com-prehensive report of the patients history, physical examination, andreview of objective tests. The assessment should provide clear andaccurate answers, in lay terms, to the questions asked. The evalua-tion should state the diagnosis and whether MMI has been reached,and it should make note of the presence and degree of respiratoryimpairment. The specific impairment scheme used, including thespecific page and table of the guideline used, should be referenced.In work-related respiratory disorders, causation, apportionment, andwork restrictions may also need to be addressed, as requested.

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2. Robinson KM, Monsivais JJ. Malingering? No evidence in a predominantlyHispanic workers compensation population with chronic pain. Pain Manag

Nurs. 2011;12:3340.

3. Demers RY, Fischetti LR, Neale AV. Incongruence between self-reportedsymptoms and objective evidence of respiratory disease among constructionworkers. Soc Sci Med. 1990;30:805810.

4. Wood PH. Appreciating the consequences of disease: the internationalclassification of impairments, disabilities, and handicaps. WHO Chronicle.1980;34:376380.

5. American Medical Association. The pulmonary system. In:Rondinelli RD,ed. Guides to the Evaluation of Permanent Impairment. American MedicalAssociation; 2008:7799.

6. Guidelinesfor the evaluation of impairment/disability in patients with asthma.American Thoracic Society. Medical Section of the American Lung Associa-

tion.Am Rev Respir Dis. 1993;147:10561061.7. American Thoracic Society. Evaluation of impairment/disability secondary

to respiratory disorders.Am Rev Respir Dis. 1986;133:12051209.

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