Download - Pulmonary Function Tests
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Pulmonary Function Tests
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O Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing (6-8 ml/kg)
O Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end-inspiratory tidal position.(1900-3300ml)
O Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( 700-1000ml).
O Residual Volume (RV): O Volume of air remaining in lungs after maximium
exhalation (20-25 ml/kg) (1700-2100ml)O Indirectly measured (FRC-ERV)O It can not be measured by spirometry
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• Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in lungs after maximum inspiration (4-6 L)
• Vital Capacity (VC): TLC minus RV or maximum volume of air exhaled from maximal inspiratory level. (60-70 ml/kg) (3100-4800ml)
• Inspiratory Capacity (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position. (2400-3800ml).
• Expiratory Capacity (EC): TV+ ERV
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Vital CapacityO Considered abnormal if <80% of
predicted value.O Physiological factors influencing VC: Height Sex Age Posture Strength of respiratory muscle
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Factors decreasing Vital Capacity:
① Alteration in muscle power.
② Pulmonary diseases.
③ Space occupying lesions in chest.
④ Abdominal causes.
⑤ Depression of respiration.
⑥ Posture – by altering pulmonary Blood volume.
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Different postures affecting VC
O POSITION
TRENDELENBERG LITHOTOMY PRONE RT. LATERAL LT. LATERAL
O DECREASE IN VC
14.5% 18% 10% 12% 10%
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Vital Capacity pre and post op.
Before epidural
1hr after epidural
24hrs after epidural
1. Upper Abdominal
35.2% 69% 83.2%
2. Lower Abdominal
55.5% 84.8% 94.7%
Vital capacity readings expressed as a % of pre op values.
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Functional residual capacity
O Functional Residual Capacity (FRC): O Sum of RV and ERV or the volume of air in the lungs
at end-expiratory tidal position.(30-35 ml/kg) (2300-3300ml).
O Measured with multiple-breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography.
O It can not be measured by spirometry)
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Functional Residual Capacity
• FRC INCREASES WITH• Increased height • Erect position (30% more than in supine) • Decreased lung recoil (e.g. emphysema)
• FRC DECREASES WITH• Obesity • Muscle paralysis (especially in supine) • Supine position • Restrictive lung disease (e.g. fibrosis, Pregnancy) • Anaesthesia
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Functions of FRC:• Oxygen store • Buffer for maintaining a steady
arterial po2 • Partial inflation helps prevent
atelectasis • Minimise the work of breathing • Minimise pulmonary vascular
resistance • Minimised v/q mismatch
- only if closing capacity is less than FRC.
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Maximum Voluntary Ventilation
O Also known as the Maximum Breathing Capacity (MBC)
O It is the largest volume of gas that can be moved into and out of the lungs in 1 minute by voluntary effort.
O Normal- 125-170L/min O Subject is asked to breathe as hard and fast as
possible for 10-15secs. The value obtained is converted to 60secs.
O Reflects the status of respiratory muscle, compliance of chest wall and airway resistance.
O Effort dependent test.O It can reveal diminished reserves of weak respiratory
muscles.
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What are pulmonary function tests?
O A group of studies or maneuvers that may be performed using standardized equipment to measure lung function.
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Bedside PFT’sO Sniders match blowing testO Forced expiratory timeO Saberazes single breath countO Saberazes breath holding testO Cough testO De bono’s whistle testO Wrights peak flowmeter
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Saberazes breath holding test
Ask the patient to take a full but not too deep breath & hold it as long as possible.
>25 SEC.-NORMAL Cardiopulmonary Reserve (CPR)
15-25 SEC- LIMITED CPR <15 SEC- VERY POOR CPR (Contraindication for
elective surgery)
25- 30 SEC - 3500 ml VC 20 – 25 SEC - 3000 ml VC 15 - 20 SEC - 2500 ml VC 10 - 15 SEC - 2000 ml VC 5 - 10 SEC - 1500 ml VC
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Saberazes single breath count
After deep breath, hold it and start counting till the next breath.
N- 30-40 COUNT Indicates vital capacity.
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Sniders match blowing test
Ask to blow a match stick from a distance of 6” (15 cms) with-
Mouth wide open Chin rested/supported No purse lipping No head movement No air movement in the room Mouth and match at the same level
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O Can not blow out a matchO MBC < 60 L/minO FEV1 < 1.6L
O Able to blow out a matchO MBC > 60 L/minO FEV1 > 1.6L
O MODIFIED MATCH TEST: DISTANCE MBC 9” >150 L/MIN. 6” >60 L/MIN. 3” > 40 L/MIN.
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Cough test
Deep breath followed by cough ABILITY TO COUGH STRENGTH EFFECTIVENESSINADEQUATE COUGH IF: FVC<20 ML/KG FEV1 < 15 ML/KG PEFR < 200 L/MIN.
VC should be 3 TIMES TV FOR EFFECTIVE COUGH.
A wet productive cough / self propagated paraoxysms of coughing :patient susceptible for pulmonary complication.
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Forced expiratory time
After deep breath, exhale maximally and forcefully & keep stethoscope over trachea & listen.
Normal FET – 3-5 SECS. OBS.LUNG DIS. - > 6 SEC RES. LUNG DIS.- < 3 SEC
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Wrights Peak FLowmeter
• Measures tidal volume, mv (15 secs times 4)
• Simple and rapid• Instrument- compact, light and portable.• Disadvantage: It under- reads at low
flow rates and over- reads at high flow rates.
• Can be connected to endotracheal tube or face mask
• Prior explanation to patients needed.• Ideally done in sitting positoin.
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Wrights peak flowmeter
• MV- instrument record for 1 min. And read directly
• Accurate measurement in the range of 3.7-20l/min.(±10%)
• USES: 1)BED SIDE PFT 2) ICU – Weaning patients from Ventilation.
Measures PEFR (Peak Expiratory Flow Rate) Normal – MALES- 450-700 L/MIN. FEMALES- 350-500 L/MIN. <200 L/ MIN. – INADEQUATE COUGH EFFICIENCY.
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De bono’s whistle test
MEASURES PEFR.Patient blows down a wide bore tube at the end of which is a whistle, on the side is a hole with adjustable knob.
As subject blows → whistle blows, leak hole is gradually increased till the intensity of whistle disappears.
At the last position at which the whistle can be blown , the PEFR can be read off the scale.
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Components of PFT
1.Tests of mechanical function: Spirometry Static lung
volumes Respiratory
Mechanics Respiratory
muscle strength
2.Tests of gas exchange: ABG, DLCO.3.Cardiopulmonary interaction:• Qualitative- stair
climbing• Quantitative-
6min walking test
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Indications for spirometry:
O Diagnostic: • evaluate symptoms and signs• Effect of disease on PFT• Screen individuals• Pre-op riskO Monitoring- to assess therapeutic
interventionsO Public health
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Contraindications• Hemoptysis• Pneumothorax• Recent MI, unstable angina pectoris• Thoracic, abdominal and cerebral
aneurysm• Recent abdominal or thoracic
surgical procedure.• H/o Syncope with forced exhalation• Recent eye surgery
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Pre-requisitesO Prior explanation to the patientO Not to smoke /inhale bronchodilators 6 hrs prior or oral
bronchodilators 12hrs prior.O Remove any tight clothings/ waist belt/ denturesO Pt. Seated comfortablyO Nose clip to close nostrils.O Minimum exhalation time of 6 seconds, but up to
15 secondsO Number of maneuvers: Minimum of 3 and
maximum of 8O Should not be interfered by coughing, glottic closure,
mechanical obstruction.
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Requirements of a good PFT.
O Lack of artifactO Satisfactory startO Satisfactory exhalation with six seconds of
smooth continuous exhalation.
O ATS Criteria for reproducibility after obtaining 3 acceptable spirograms:
1) Largest FVC within 0.15L of next largest FVC
2) Largest FEV1 within 0.15L of next largest FEV1
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Measurements obtained from the FVC curve:
O FEV1---the volume exhaled during the first second of the FVC maneuver
O FEF 25-75%---the mean expiratory flow during the middle half of the FVC maneuver; reflects flow through the small (<2 mm in diameter) airways
O FEV1/FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ratio from expected values is specific for obstructive rather than restrictive diseases
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Causes of restrictive PFT
O Lung parenchymal pathology
O Inter pleural pathology
O Neuromuscular problems
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Grading of severity of abnormality
O Based on TLC: Mild: predicted TLC is less than lower limit of normal
but >70% Moderate: predicted TLC is <70% and >60% Moderately severe: predicted TLC <60%
O Based on spirometry: Mild: Predicted VC is less than lower limit of normal but
>70% Moderate: Predicted VC <70% and >60% Moderately severe: Predicted VC <60% and >50% Severe: Predicted VC <50% and >34% Very Severe: Predicted VC <34%
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Causes of obstructive PFT
O Narrowing of airways due to bronchial smooth muscle contraction.
O Narrowing of airways due to inflammation and swelling of bronchial mucosa.
O Material inside the bronchial passage.
O Destruction of lung tissue with loss of elasticity.
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Severity of obstructive lung disease:
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Obstructive vs Restrictive diseases on spirometry
Obstructive disorders
Restrictive disorders
O FVC N or↓O FEV1 ↓O FEF25-75% ↓ O FEV1/FVC ↓O TLC N or ↑
O FVC ↓O FEV1 ↓ O FEF 25-75% N to ↓O FEV1/FVC N to ↑O TLC ↓
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Criteria for reversibility of small airway obstruction on PFT:
O 2 PFTs should be done one before and one after administration of bronchodilator.
O Drug used is usually beta-2 sympathomimetic.
O If 2 out of 3 measurements improve then patient has reversible airway obstruction.
1) FVC of 10% or more 2) FEV1 an increase of 200ml or 15% of baseline FEV1
3) FEF25-75% an increase of 25% or more
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Flow volume loopsO Helpful in evaluation of air flow limitation on
inspiration and expiration
O In addition to obstructive and restrictive patterns, flow-volume loops can provide information on upper airway obstruction:O Fixed obstruction: such as in tumor, tracheal stenosisO Variable extrathoracic obstruction: such as in vocal
cord dysfunction O Variable intrathoracic obstruction:as in malignancy or
tracheomalacia
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Measurement of other lung volumes
O Nitrogen washout technique
O Helium dilution technique
O Body plethysmography
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DLCO (diffusion lung CO)
O The diffusing capacity is a measure of the ability of the lungs to transfer gas.
O Measure of interaction of alveolar surface area, alveolar capillary perfusion and physical properties of the alveolar capillary interface.
O CO is rapidly taken up by haemoglobin, its transfer is therefore limited mainly by diffusion
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Causes of decreased DLCO:
Causes of increased DLCO:
O AnemiaO EmphysemaO ILDO Pulmonary edemaO Pulmonary
vascular disease
O ObesityO AsthmaO L to R shuntO Alveolar
hemorrhage
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DLCO- capacity of the lungs to transfer CO (ml/min/mmHg)DLCOc- DLCO corrected for Hb (ml/min/mmHg)DLVA- DLCO corected for volume (ml/min/mmHg/L)DLVC- DLCO corrected for both volume and Hb (ml/min/mmHg/L)
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Respiratory muscle function
O A number of diseases such as motor neuron disease can result in respiratory muscle weakness, which can ultimately lead to respiratory failure
O Inspiratory mouth pressure A measure of inspiratory muscle function in which subjects generate as much inspiratory pressure as possible against a blocked mouth piece .Values of 80 cm of water or more exclude any significant inspiratory muscle weakness O Expiratory mouth pressure A measure of expiratory muscle function in which subjects generate as much expiratory pressure as possible against a blocked mouth piece. Values of 80 cm of water or more exclude any significant expiratory muscle weakness
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Tests for cardiopulmonary reserve:
O Number of flights of stairs patient can climb: inability to climb 2 flights of stairs indicates increased risk of post-op cardiopulmonary complications.
O Six minute walking test (6 MWT)
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Anesthetic Implications
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COPD classification by GOLD
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ATS classification of severity of COPD
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Evaluation of patient for lung resection
GOALS:1) to identify patients at risk of increased post-
op morbidity & mortality2) to identify patients who need short-term or
long term post-op ventilator support.Lung resection may be followed by – inadequate
gas exchange, pulm HTN & incapacitating dyspnoea.
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EXAMPLE:Assuming pre op FEV1 to be 70%
ppoFEV1= 70 X (1-29/100)
ppoFEV1= 50%
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ReferencesO A practice of anesthesia by Wylie 5th editionO Millers 7th editionO Clinical Anesthesiology- Morgan 5th editionO Interpreting pulmonary function tests: Recognize
the pattern, and the diagnosis will follow. CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 70 • NUMBER 10
O SERIES ‘‘ATS/ERS TASK FORCE: STANDARDISATION OF LUNG
FUNCTION TESTING’’ 2005
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Thank YouTHE END