Respiratory Measurements Flashcards
Lung complience
At high pressure: lung stiffer: lower compliance
Lung bases are more compliant than the apex - better ventilation
Compliance is ensued by elastic recoil
For efficient ventilation, healthy people tend to
have:
High lung compliance
Low Alveolar surface tension due to surfacant
Tests to assess lung function
Mechanical condition of the lungs: pulmonary fibrosis
Resistance of the airways: asthma
Diffusion across the alveolar membrane: pulmonary fibrosis.
Tidal volume
volume of air entering and leaving the lung with each normal breath = 0.5l
Inspiratory reserve volume
Extra volume of air inspired above the normal tidal volume with full force
Expiratory reserve volume
Extra volume of air expired by forceful expiration at the end of normal tidal expiration
Vital capacity
Maximum amount of air expelled from the lungs after first filling the lungs to a maximum then expiring to a maximum
Residual volume
volume of air remaining in the lungs after the most forceful expiration
Functional residual capacity
amount of air that remains in the lungs at the end of normal expiration
Total lung capacity
the maximum volume of air the lungs can hold
FEV1
volume expired in first second
Lung function test - nitrogen washout
patient inspires 100% O2
expires into the spirometer system
procedure repeated until N2 in lungs is replaced with O2
FRC calculated from exhaled N2 and estimated alveolar N2
Vitalograph
Measures the ability to move air out of the lungs
Gas transfer - Diffusion conductance test
Patient inhales single breath of dilute carbon monoxide followed by breath hold of 10s
Diffusion capacity is calculated from the lung volume and the % of CO in the alveoli at the beginning and the end of the 10s breath hold
