Pulmonary Function Testing (Selby) Flashcards
What are the five components of PFT?
1) Spirometry w flow volume loops
2) Lung volumes and capacities
3) Diffusing capacity of CO (DLCO)
4) Bronchodilator therapy - 12% or more increase in FEV1 or FVC and an absolute volume increase o 200ml or more
–> Positive=Asthma, Negative=COPD
5) Bronchoprovocation - methacholine challenge
Positive: more than 20% reduction in FEV1
What is the purpose of pulmonary function testing (PFT)
- Evaluate sx’s and signs of lung disease (i.e., cough, dyspnea, wheezing, hyperinflation, etc.
- Assess progression of lung disease
- Monitor effectiveness of therapy
- Evaluate preoperative patients in selected situation
- Screen people at risk for pulmonary disease such as smokers or people with occupational exposure
- Monitor for potentially toxic effects of certain drugs/chemicals
Indications for PFT
DOE
Cough
Asthma
Suspected bornchiectasis or bronchiolitis
Suspected ILD
Suspected neuromuscular or chest wall disease
Pulmonary function tests are not indicated in which patients; may be confusing when what is present?
Not indicated in pt’s without sx’s
May be misleading when non-pulmonary diseases that effect the pulmonary system are active (i.e., CHF); pt may appear to have pulmonary disease
What are the 3 most important values measured during pulmonary function testing?
- FVC
- FEV1
- FEV1/FVC ratio
What is the FEV1/FVC ratio used to determine?
If pattern is obstructive, restrictive, or normal
Obstructive: < 0.70 of normal
Which gas is used to assess the diffusion capacity of the lungs (DLCO)?
Carbon monoxide
For obstructive disease, measurement of the RV and TLC can be used to demonstrate what?
Airway obstruction
Hyperinflation
What value is needed to confirm true restriction and to better quantitate the degree of restriction in a restrictive lung disease?
TLC
If the FEV1/FVC ratio is either normal or increased this may indicate restrictive disease or normal study, how can the FVC value be used for further interpretation?
If the FVC is NOT less than the lower limit of normal = normal study
If FVC is less than the lower limit of normal = restrictive pattern
What is the FVC like in an obstructive vs. restrictive pattern of disease?
Obstructive = decreased or normal
Restrictive = decreased
What is the FEV1 like in an obstructive vs. restricitve pattern of disease?
Obstructive = decreased
Restrictive = decreased or normal
What is the TLC like in an obstructive vs. restricitve pattern of disease?
Obstructive = normal or increased
Restrictive = decreased
Using the FEV1 as % of predicted value for classifying the severity of an obstruction which value indicates mild, moderate, moderately severe, severe, and very severe?
- Mild = >70%
- Moderate = 60-69%
- Moderately severe = 50-59%
- Severe = 35-49%
- Very severe = <35%
Air trapping will lead to an increase in which value of lung volume?
RV
What are 4 extra-parenchymal causes of restrictive lung disease?
Obesity
Neuromuscular disease
Chest wall deformities
Large pleural effusions
Pneumothorax
Which value can be used to distinguish between parenchymal vs. extraparenchymal causes of restrictive lung diseases?
Diffusing capacity of the lung
If below lower limit of normal after correcting for lung volumes = parenchymal disease likely
DDX for obstructive lung diseases?
COPD: Chronic bronchitis, Emphysema
Asthma
Bronchiactasis
Bronchiolitis
DDX for restrictive lung disease?
Chest Wall: Kyphosis, Scoliosis, Obesity, Chronic Pleural Effusion, Ankylosing Spnondylitis
Drugs
ILD
Neuromuscular: Amyotrophic lateral sclerosis (ALS) Guillain-Barr (GBS) Myasthenia Gravis (MG)
What are the PFT characteristics of obstructive lung diseases?
FEV1 < 80%
FVC may be normal or reduced
FEV1/FVC < 0.70
Scooped/concave chair on loop
RV and TLC insreased
DLCO normal (asthma) or low (emphysema)
Asthma will have positive bronchodilator response
COPD and others will have negaive response
If the FVC is less than normal, how can using the TLC and RV determine if there is a mixed pattern of obstructive/restrictive or if there is obstruction with air trapping?
If there is mixed pattern, the TLC will be decreased (<5 percentile of predicted) and the FEV1/FVC will also be low.
If air trapping is occurring then the TLC will be normal or elevated and the RV will be significantly increased
What are the PFT characteristics of restrictive lung diseases?
FEV1 normal or mildly reduced
FVC < 80%
FEV1/FVC normal to > 0.70
Peaked or “witches hat” loop
RV and TLC decreased
DLCO low (e.g. ILD) or normal (NMSK)
What is this flow-volume curve indicative of?
Vocal cord dysfunctions
What is this flow-volume curve indicative of?
Asthma
What do the curves of A-C represent?
A) Normal
B) Obstructive (i.e., asthma or COPD)
C) Restrictive
