Clin Med Selby - Interpreting PFTs Flashcards
Who would get a PFT?
- Dyspnea at rest or on exertion
- Cough
- Asthma
- COPD
- Suspect bronchiectasis or bronchiolitis
- Suspect interstitial lung disease
- Suspect neuromuscular or chest wall disease
What is the FEV1/FVC ratio used for?
Normally about 0.80 and used to assess airway obstruction
What is the FEV1/FVC ratio in obstructive lung disease?
FEV1/FVC <0.70
What is diffusion capacity of lung for CO (DLCO)?
- measure of gas exchange through alveolar wall
- Pt inhales small amount of CO2, hold breath for 10 seconds and exhales quickly
- concentration of CO2 in exhaled air is calculated
What are DDX of obstructive lung disease?
- COPD (chronic bronchitis/emphysema)
- Asthma
- Bronchiectasis
- Bronchiolitis
What are DDX for restrictive lung diseases?
- Abnormalitis of chest wall/ Pleura (kyphosis, scoliosis, obesity, chronic pleural effusions, ankylosing spondylitis)
- Drugs
- Interstitial lung disease
- Neuromuscular disease (amyotrophic lateral sclerosis [ALS], Guillain-Barre, Myasthenia Gravis
What is the spirometry PFT pattern for Obstructive lung disease?
- FEV1/FVC <0.70
2. Flow volume curve has “concave or scooped pattern” (expiratory)
What would you expect to see on PFT for TLC and RV on obstructive lung disease?
- Increased TLC from Air trapping
2. Increased residual volume from air trapping
What would you expect to see on PFT for DLCO in obstructive lung disease?
DLCO can be low or normal
- Emphysema –> DLCO tends to be low causing destruction fo functional lung tissue
- Astma and Bronchitis–> DLCO tends to be normal
What is the Bronchodialator response in a patient with Asthma? COPD?
Asthma with show an improvement with bronchodilator response
COPD/ other obstructive diseases will not show improvement with bronchodilator tx
What is bronchodilator response?
Determine if obstructive sx resolve with therapy.
- positive response is >12% increase in FEV1 or FVC AND an absolute volume increase of >200ml
What would the FVC and FEV1/FVC numbers be on PFT in restrictive lung disease?
FVC in restrictive lung disease is <80% predicted
FEV1/FVC ration can be normal or >0.70
What does the flow volume curve look like in Restrictive lung pattern?
Peaked, steeple, or witch’s hat
How is the TLC and RV affected in restrictive lung disease?
- TLC decreases
- RV decreases
What is the DLCO in restrictive lung disease?
DLCO will be normal or low in restrictive lung disease
in ILD it tends to be low
in neuromuscular or chest wall abnormalities it tends to be normal