2013-08-19 Pulm Function Tests

Question 1

Define V_t

Answer 1

Tidal volume - volume of air inspired and expired in relaxed breathing

Question 2

Define ERV

Answer 2

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

Question 3

Define IRV

Answer 3

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

Question 4

Define RV

Answer 4

reserve volume - the amt of gas left in the lungs after a maximal expiratory effort. incr most often in obstructive dz (air trapping)

Question 5

Define IC

Answer 5

inspiratory capacity = V_t + IRV; can be calculated from spirogram

Question 6

Define VC

Answer 6

vital capacity - capacity for largest breath cycle possible

Question 7

Define TLC

Answer 7

Total lung capacity - the total amt of air the lung can hold; TLC = RV + VC cannot be calculated from spirogram

Question 8

Define FRC

Answer 8

functional residual capacity - volume of the lungs at the point when elastic recoil of the lungs = elastic recoil of the chest wall

Question 9

obstructive defect

Answer 9

decr EXPIRATORY flow rate

Question 10

restrictive defect

Answer 10

inflation problem; a reduction in TLC

Question 11

cominbed

Answer 11

obstructive + restrictive

Question 12

FEV_1

Answer 12

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.

Question 13

FVC

Answer 13

Forced vital capacity: the determination of the vital capacity from a maximally forced expiratory effort; can be decreased in either obstructive or restrictive defects

Question 14

FEV_1/FVC; when decr? nl? incr?

Answer 14

FEV_1/FVC ratio tells you which defect it is; decr in obstructive and combined; nl or incr in restrictive

Question 15

When is TLC decreased?

Answer 15

TLC is decr when there is inspiratory muscle deficit or decr complicance of the lungs/chest wall

Question 16

Give examples of dzs that cause obstruction?

Answer 16

COPD, asthma

Question 17

give 5 categories of proglems that result in restriction patter on PFT

Answer 17

1. neuromuscular, 2. chest wall problem, 3. pleural dz, 4. loss of lung, 5. interstitial dz

Question 18

example of combined pattern

Answer 18

COPD and pneumonectomy

Question 19

Label me

Answer 19

Question 20

Diffusing capacity

how to measure? what affects it?

Answer 20

measure by having pt inhale known quantity of CO

DL_CO is affected by: 1. thickness of alveolar wall; 2. surface area; 3. CO gradient (smokers have some in blood!), 4. [Hgb], 5. lung volume

Question 21

What would you expect to find on the PFT of a pt w/ emphysema?

Answer 21

combo of obstruction and low DL_CO

Question 22

What would you expect to find on PFT of pt w/ interstitial lung dz?

Answer 22

combo of: restriction, incr FEV₁/FVC and a low DL_CO

Question 23

What does the flow-volume loop help you dx?

Answer 23

extra-thoracic airway problems.

Why?!

Question 24

How are the predicted values for PFTs calculated?

Answer 24

Those are population means in health subjects