Pulmonary Functional Tests

Question 1

Which volume cannot be measured by spirometry?

Answer 1

Residual volume

Question 2

resting volume of the lung-chest wall unit

Answer 2

functional residual capacity (FRC): tendency of chest wall to expand is balanced by the tendency of the lung to collapse

Question 3

Which lung volumes increase in obstructive versus restrictive, lung disease, respectively?

Answer 3

obstructive: residual, volume functional residual capacity, total long capacity, and tidal volume

Restrictive: none, all volumes, decrease

Question 4

how do obesity, kyphoscoliosis, and ankylosing spondylitis affect lung function?

Answer 4

decrease compliance of chest wall —> decrease lung volumes

Question 5

What is the most sensitive indicator of changes in expiratory airway resistance?

Answer 5

FEV1: volume air expelled in one second

Question 6

How does obstructive lung disease affect the flow – volume loop of pulmonary function?

Answer 6

flow is reduced during expiration due to premature airway closure —> curve appears “scooped out”

curve shift to the left due to air trapping that increases residual volume

Question 7

How does restrictive lung disease affect the flow – volume loop of pulmonary function?

Answer 7

in restrictive disease, flow is increased at low lung volumes

all lung volumes are reduced because the lung is stiff – the curve shifts right (however the shape looks the same, just smaller)

Question 8

Patients with diffusion problems through the alveolar capillary barrier will develop problems with which gas first oxygen or carbon dioxide?

Answer 8

Problems with oxygen diffusion will develop first because carbon dioxide diffuses much easier than oxygen through the alveolar capillary barrier

Question 9

which of the following gases is considered diffusion limited:
a. NO
b. O2
c. CO

Answer 9

nitrous oxide and oxygen are both perfusion limited (diffuse quickly, amount in blood depends on perfusion)

carbon monoxide has a slower transit across the alveolar capillary barrier, therefore is diffusion limited —> as CO content (alveolar) rises, partial pressure of CO does not

[this is why CO makes a good test of diffusion capacity, via DLCO]

Question 10

what DLCO result would you expect if a patient has emphysema?

Answer 10

inner walls of the lungs’ air sacs (alveoli) are damaged, causing them to eventually rupture. This creates one larger air space instead of many small ones and reduces the surface area available for gas exchange.

therefore, exhaled carbon monoxide will be greater than predicted