PFT Flashcards
purpose of lung function testing
diagnose respiratory disease
monitor progression and severity of disease
evaluate response to therapy
clarify diagnosis
spirometry
most fundamental lung function test
measures dynamic volumes relative to time
diffusing capacity
measures rate of transfer of carbon monoxide to hemoglobin
normal value for PFTs
80-120% of the predicted value is normal
how is spirometry conducted
patient maximally exhales (at least 6 seconds) from full inspiration to full inspiration
(very dependent on coach)
major data points obtained from spirometry
FVC
FEV1
FEV1%
FEF 25-75
how is obstruction diagnosed through spirometry?
looking at FEV1/FVC ratio, <0.7 is obstructive
flow volume loop will be squished down
what does FEF 25-75% measure
it reflects flows at “mid” lung volumes (forced expiratory flow at 25 and 75%)
characteristics of obstruction on PFT
low FEF 25-75
hyperinflation (high TLC, RV)
BD responsiveness
what is static lung volume measurement useful for
to discriminate between restrictive and obstruct defects
characteristics of restriction on PFT
TLC <80%
reduced FEV1 and FVC with normal ratio
early restrictionL reduced FRC, or RV
what causes restriction?
sarcoidosis
ILD
lobectomy
what causes obstruction
asthma COPD LAM CF sarcoidosis
what can lead to increased or normal TLC?
obstruction
what leads to decreased TLC?
restriction or combin restriction/obstruction
