2013-08-19 Pulm Function Tests Flashcards
Define V_t
Tidal volume - volume of air inspired and expired in relaxed breathing
Define ERV
expiratory reserve volume - the amount of air you could forcibly expire after the end of an un-forced normal exhale. lies between V_t and FRC
Define IRV
inspiratory reserve capacity - the amt of air you could forcibly inhale after the end of an un-forced normal inhale. lies between V_t and TLC
Define RV
reserve volume - the amt of gas left in the lungs after a maximal expiratory effort. incr most often in obstructive dz (air trapping)
Define IC
inspiratory capacity = V_t + IRV; can be calculated from spirogram
Define VC
vital capacity - capacity for largest breath cycle possible
Define TLC
Total lung capacity - the total amt of air the lung can hold; TLC = RV + VC cannot be calculated from spirogram
Define FRC
functional residual capacity - volume of the lungs at the point when elastic recoil of the lungs = elastic recoil of the chest wall
obstructive defect
decr EXPIRATORY flow rate
restrictive defect
inflation problem; a reduction in TLC
cominbed
obstructive + restrictive
FEV_1
Forced Expiratory Volume exhaled in the FIRST SECOND; can be decreased in either obstructive or restrictive defects; can be due to incr airway resist., decr in elastic recoil, and/or ∆s in lung vol.
FVC
Forced vital capacity: the determination of the vital capacity from a maximally forced expiratory effort; can be decreased in either obstructive or restrictive defects
FEV_1/FVC; when decr? nl? incr?
FEV_1/FVC ratio tells you which defect it is; decr in obstructive and combined; nl or incr in restrictive
When is TLC decreased?
TLC is decr when there is inspiratory muscle deficit or decr complicance of the lungs/chest wall
Give examples of dzs that cause obstruction?
COPD, asthma
give 5 categories of proglems that result in restriction patter on PFT
- neuromuscular, 2. chest wall problem, 3. pleural dz, 4. loss of lung, 5. interstitial dz
example of combined pattern
COPD and pneumonectomy
Label me


Diffusing capacity
how to measure? what affects it?
measure by having pt inhale known quantity of CO
DLCO is affected by: 1. thickness of alveolar wall; 2. surface area; 3. CO gradient (smokers have some in blood!), 4. [Hgb], 5. lung volume
What would you expect to find on the PFT of a pt w/ emphysema?
combo of obstruction and low DLCO
What would you expect to find on PFT of pt w/ interstitial lung dz?
combo of: restriction, incr FEV1/FVC and a low DLCO
What does the flow-volume loop help you dx?
extra-thoracic airway problems.
Why?!
How are the predicted values for PFTs calculated?
Those are population means in health subjects