lung

[akimhaneul]

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There is a question in my kaplan book that I am confused about.

Idiopathic pulmonary fibrosis is a disease in which scar tissue forms in the alveolar walls, making the lung tissue significantly more stiff. Which of the following findings would likely be detected through spirometry in a patient with IPF?

I Decreased total lung capacity
II Decreased inspiratory reserve volume
III Increased residual volume

A I
B II
C I and II
D I, II, and III

The answer is B.

What I don't get is that the answer explanation said that the residual volume would decrease due to the scar. Why would this happen? If the alveoli become more stiff, doesn't that mean the lungs cannot breathe out air as easily as before, so shouldn't the residual volume increase?


Thanks!

 

[Domepiece]

Residual volume cannot be measured with a spirometer, thus any answer choices containing conclusions that involve the residual volume (C, as blatantly stated, and A, as TLC is vital capacity+residual volume) would NOT be measured by spirometry as the question specifies.