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NBME 24 Answers

nbme24/Block 2/Question#19 (25.7 difficulty score)
A 70-year-old man comes to the physician ...
Alveolar-arterial Po 2 difference🔍
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 +9  upvote downvote
submitted by neonem(500),
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yex  UW q id 7648 +2  
melanoma  uw id 1526 +  



 +1  upvote downvote
submitted by madojo(121),

The answer is not B because with interstitial fibrosis you have a decrease in the diffusing capacity because of the thickened alveolar membrane. The answer is not FRC because that will decrease in a restrictive lung disease such as fibrosis. FVC, RV, and TV are all expected to decrease.




I chose residual volume, but looking back, here's why its not (correct me if im wrong):

Restrictive lung disease is an issue with inspiring enough O2, not a problem with expiration (which is in obstructive lung disease like emphysema from floppy alveoli)

Also, a factor that influences A-a gradient is thickened membranes (decreased ability to diffuse across)

I think "Alveolar-arteriole PO2 difference" threw me off bc they didnt use the exact term of A-a gradient and I wasnt able to deduce that they're the same thing or felt like i was being tricked




I chose residual volume, but looking back, here's why its not (correct me if im wrong):

Restrictive lung disease is an issue with inspiring enough O2, not a problem with expiration (which is in obstructive lung disease like emphysema from floppy alveoli)

Also, a factor that influences A-a gradient is thickened membranes (decreased ability to diffuse across)

I think "Alveolar-arteriole PO2 difference" threw me off bc they didnt use the exact term of A-a gradient and I wasnt able to deduce that they're the same thing or felt like i was being tricked




Weird wording on the last sentence "Which of the following pulmonary function tests in this patient will most likely show a result greater than the predicted range?"

I mean, I was like this guy definitely has pulmonary fibrosis, so I'm predicting that his range of FVC, RV, FRC, TV, etc is low. It would be nice if it said 'greater than a normal patient'