PFT DETAIL.pptx

PFT DETAIL.pptx

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  PULMONARY FUNCTION TEST DR. GANESH BR
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  PFT  Spirometry  –Before and after bronchodilator  – Sitting and supine  • Lung volumes  • Diffusion capacity (DLCO)  • Methacholine challenge  • Maximum voluntary ventilation (MVV)  • Maximum inspiratory and expiratory pressures (MIPS/MEPS)  • Pulse oximetry  • Arterial blood gases (ABGs)  • Six minute walk test  • Cardiopulmonary exercise test (CPET)  • Exhaled nitric oxide (FENO)
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  EQUIPMENT OF PFT
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  FLOW VOLUME LOOP
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  PARAMETERS  FVC: maximumamount of air exhaled after a maximal inhalation  If normal:  Elasticity is fairly normal (normal lung tissue)  Thoracic cage (configuration of thoracic spine/ribs) is normal  Respiratory muscles aren’t too weak  If low, suggests one or more of the above is a problem (restrictive disorder)
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   FEV1: amountof air exhaled in the first second as forcefully as possible from a full lung  Measuring the speed of the air being exhaled can provide a window to the airways -volume exhaled in the first second is a measure of speed (litres/second)  (FEV1) reduced speed indicates ‘obstructed’ or narrowed airways  FEV1/FVC ratio: identification of airflow obstruction:– <70% of predicted
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  WHATS NORMAL?  Gender,Age, Height, Race  Test data collected on a large number of ‘normal’ individuals:  – No history of lung disease  – No symptoms  – Normal chest X-ray  – Normal EKG  Pooled data used to relate lung function to characteristics most closely related to lung function
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   Predicted value(% of predicted): Age and height are entered into an equation to calculate the:-  average predicted value for an individual = middle of the normal range  Lower limit of normal (LLN): Another equation is used to define the ‘Lower Limit of Normal’ = lowest value considered normal for an individual
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  STEP BY STEP INTERPRETATION Step 1: FEV1/FVC ratio  FEV1/FVC <70% (or less than the LLN): Obstructive pattern (COPD, asthma)  ≥ 70%: Normal or Restrictive disease  Step 2:  Severity of obstruction (GOLD Criteria for COPD)  FEV1 80 - 100% predicted: Mild (Stage I)  FEV1 50 - <80% predicted: Moderate (Stage II)  FEV1 30 -<50% predicted: Severe (Stage III)  FEV1 < 30% predicted: Very severe (Stage IV)  FEV1< 50% with right side heart failure: Very severe (Stage IV)
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   Severity ofobstruction (ATS General Criteria): keep it simple  FEV1 over 70% predicted: MILD  FEV1 60-70% predicted: MODERATE  FEV1 50-60% predicted: MODERATELY SEVERE  FEV1 35-50% predicted: SEVERE  FEV1 < 35% predicted: VERY SEVERE
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   Step 3:Bronchodilator response:  ≥ 12% increase AND an absolute improvement of at least 200 ml after inhaling a beta agonist  FEV1, OR FVC is considered a significant response
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   Step 4:Total Lung Capacity (TLC) (Normal range: 80 - 120% of predicted)  TLC > 120% = Hyperinflation  TLC < 80% = Restrictive disease (ATS criteria for severity): keep it simple  70-80 % predicted: mild  60-70% predicted: moderate  50-60% predicted: moderately severe  < 50% predicted: severe  Step 5: RV/TLC ratio (Normal range: < 35% or < predicted)  RV/TLC > 35% or > predicted indicates Air trapping
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   Step 6:DLCO (Normal range: 80- 120% of predicted)  In obstructive disease:  Decreased in Emphysema  Normal in chronic bronchitis  Normal or increased in Asthma  In restrictive disease:  Decreased in parenchymal disease  Normal in non-parenchymal (e.g. chest wall) restriction
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  NORMAL EARLY ONCOAD FLAO ETLAO RES DISEASE