nbme 7 RESPIRATORY Q

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firstaid2012

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A healthy 40 year old woman inhales to total lung capacity and then exhales forcefully.The rate of expiratory airflow is highest at total lung capacity and decreases linearly as exhalation continues. Which of the following is the most likely cause of the observed decrease in expiratory airflow?

a. airway compression
b. decreased expiratory effort
c. decreased intrapleural pressure
d. doming of the diaphragm
e. increased elastic recoil

please explain all answer choice

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I would say A because what the question describes is obstructive pathology and option A is the closest answer.
Anyone feel free to add your 2 cents.
 
A healthy 40 year old woman inhales to total lung capacity and then exhales forcefully.The rate of expiratory airflow is highest at total lung capacity and decreases linearly as exhalation continues. Which of the following is the most likely cause of the observed decrease in expiratory airflow?

a. airway compression
b. decreased expiratory effort
c. decreased intrapleural pressure
d. doming of the diaphragm
e. increased elastic recoil

please explain all answer choice

to me, 'decreases linearly as exhalation continues' means that it's pretty much normal, not obstructive or restrictive. the decrease is toward the end of the expiration, so there is reduced lung recoil (not e). i imagine that part of the end of the expiration involves the diaphragm becoming more domed rather than flat like it is with inspiration, when expiration is most rapid and forceful.
thats what i answered, i got a 243 on nbme7 before i started reviewing biochem and immuno (DO student), idk if i reasoned correctly.
 
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to me, 'decreases linearly as exhalation continues' means that it's pretty much normal, not obstructive or restrictive. the decrease is toward the end of the expiration, so there is reduced lung recoil (not e). i imagine that part of the end of the expiration involves the diaphragm becoming more domed rather than flat like it is with inspiration, when expiration is most rapid and forceful.

D to me as well.
 
what was the answer?

The answer is A.

It's called dynamic compression. It's a normal phenomenon. It's the reason why max expiratory flow rates are effort independent at low volumes.
 
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