2. Pulmonary Function Tests Flashcards
the rate at which the lung deflates (exhales) is a function of what?
resistance, and elastic recoil.
elastic recoil is determined by what?
properties of the tissue, and the volume to which it is inflated
stiff balloon will empty more or less air in one sec than floppy?
more
balloon that is inflated to a higher volume will empty more or less air in one sec than a less-volume balloon?
more
low FEV1 comes from what 3 things/
- incr in airway resistance
- decr in recoil
- decr in volume
- any combo of these
diseases in which airway resistance is incr
asthma, bronchitis, tracheal tumor, aspiration
diseases in which recoil is decr
emphysema
diseases in which lung vol decr
restrictive disease
in restrictive disease, is the VC incr or decr?
decr
in obstructive disease, is the VC incr or decr?
normal or decr
how does pulm fibrosis have opposing effects on the FEV1?
elastic recoil incr -> incr FEV1
stiff lungs cannot be inflated very much -> decr FEV1
what measure distinguishes between obstructive and restrictive disease?
RATION of FEV1 to FVC.
PFTs in obstructive disease
FEV1 decr, FVC normal or decr, ratio decr
PFTs in restrictive disease
FEV1 decr, FV decr, ration normal or incr
since we can’t measure FRC or RV with spirometry, how do we measure them?
plethysmography (like Inyang did?)
VC + RV = what?
TLC.
what is FRC?
point at which the elastic recoil of lungs exactly balances the recoil of the chest wall
what is RV when does it increase?
RV = amt of gas left in lungs after max expiratory effort. incr in obstructive disease (air trapping)
what is a restrictive ventilatory defect?
expansion of the lungs is restricted. reduction in TLC. NOT a reduction in VC. caused by insp muscles being unable to fully inflate the lungs and rib cage.
examples of restrictive defect?
neuromuscular disease, chest wall problems, pleural disease, loss of lung, interstitial lung disease
when is the flow-volume loop most useful?
in dx problems with inspiration, exp extra-thoracic airflow obstruction.
what affects the diffusing capacity?
- partial pressure gradient of CO between alveolus and blood.
- total surface area avail for gas exchange
- hemoglobin
- thickness of diffusing surface
- lung vol (if can’t take deep breath, DLCO decr)
what happens to diff capacity in smokers?
in smokers, there is incr CO in blood, which decr the partial pressure gradient, and decr measured DLCO
combination of obstructive pattern and low DLCO suggests what disease?
emphysema
combination of restrictive pattern, incr ratio, and low DLCO suggests what disease?
interstitial lung disease
