PFTs Flashcards
What does spirometry measure?
FEV1 and FVC
What is required of the patient for spirometry to be effective?
patient needs to make a maximal inspiratory and expiratory effort
T/F As we age, the lungs lose their natural elasticity translating to smaller lung volumes and capacities
True
T/F When males and females are matched for height and weight, their lung sizes are equal
False. Males still have larger lungs than females even when matched for height and weight
How does obesity effect PFTs?
the abdominal mass prevents the diaphragm from descending as far as it could and the PFT results will demonstrate a smaller measured PFT outcome than expected
Why can’t TLC be measured by spirometry?
TLC = FVC + RV so it can’t be measured by spirometry because air remains in the lungs at the end of a maximal exhalation - i.e. the RV
Which of the following are ways to measure TLC: spirometry, helium dilution, nitrogen washout, body plethysmography, CXR/HRCT?
everything except spirometry. Body plethysmography is the gold standard
What percentage is the FEV1 of the FVC?
FEV1 is 75% of the FVC
Define FEF (Forced expiratory flow)?
the average forced expiratory flow during the mid (25 - 75%) portion of the FVC
Which test is a sensitive test for early obstructive disease?
FEF
Define PEFR (Peak expiratory flow rate)
measure of the highest expiratory flow rate during the PFT test
What is a useful test to see if treatment is improving obstructive disease?
PEFR
What values of FVC and FEV1 are considered in the normal range?
values that are > 80% of predicted based on age, height/size, gender, race
PFT results for obstructive airway disease
the FEV1 is reduced disproportionately more than the FVC, resulting in an FEV1/FVC ratio less than 70-80%.
What patient populations cannot have a bronchoprovocation test?
unstable cardiac dz, MI or stroke in last 3 months, uncontrolled HTN, pregnancy/nursing, bronchospasm already present
What qualifies as a positive bronchoprovocation test?
decrease of 20% in FEV1
What is used to determine if there is reversible airway obstruction?
Pre- and post- bronchodilator spirometry
PFT results for restrictive lung disease
both the FEV1 and FVC are reduced proportionately. presents with a normal or increased FEV1/FVC ratio
If a patient has a low FVC, how do you determine if their disease is restrictive or obstructive?
repeat the test after inhaling a bronchodilator. Improved FVC suggests obstructive pathology. If the FVC remains the same, it suggests restrictive pathology
Classification of mild, moderate, severe lung disease
Mild Disease: 65-85% of predicted values. Moderate Disease: 50-65 % of predicted values. Severe Disease: < 50 % of predicted values
What is a useful test to determine how well gases diffuse through the alveoli?
Diffusion capacity (DLCO)
T/F smoking substantially lowers the DLCO
True
Why is CO the preferred agent for DLCO tests?
normally not present in alveoli, transfer is diffusion limited rather than perfusion limited, avidly binds Hb, and its diffusion is less affected by other factors
What test is used to determine a patient’s functional aerobic excercise capacity?
VO2 testing.
