PFT's Flashcards
Spirometry measures?
FEV1 and FVC
What is TLC
Total lung capacity
the volume of air in the lungs after full inspiration
Can TLC be measured by spirometry?
No, because there is residual volume left after the forced exhalation.
How do you calculate TLC?
FVC + RV
What % of FVC is FEV1?
75% of the air is exhaled in the first second.
PEFR
Peak expiratory flow volume
Liters/minute or second
Used to determine obstructive pathology (asthma)
What is considered a normal PFT?
Values that are within 80% of predicted.
What would you expect to see in the PFT’s with COPD?
FEV1 is reduced disproportionately to the FVC, resulting in an FEV1/FVC ratio less than 70-80%.
What does the loop like like with obstructive dz?
The descent off the peak is concave, volume is decreased.
FEF 25 - 75%
The middle half of the forced expiration.
The most accurate measurement of obstructive airway dz.
Which patients cannot undergo bronchoprovocation challenge?
Unstable CAD MI/stroke past 3 months Uncontrolled HTN Significant bronchospasm known Pregnant/nursing
What is a positive provocation test?
Decrease of at least 20% in FEV1
Which agent is usually used for the provocation?
Nebulized Methacholine
Asthma challenge spirometry
If 2/3 test post-bronchodilator show 10% improvement it can be said patient has reversible obstructive airway dz (asthma)
How do FEV1 and FVC change in restrictive lung dz?
FEV1 and FVC are both reduced PROPORTIONATELY.
This means the FEV1/FVC ratio is normal or increased.
