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Practice sessionHEALTHCARE & MEDICAL EXAMSMEDICAL LICENSING

USMLE (United States Medical Licensing Examination) Practice Exam 12

Practice exam for USMLE (United States Medical Licensing Examination).

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Question 1 of 1000%
Time remaining120:00
Attempts allowedUnlimited
Difficulty mixE • M • H
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Question 1

MEDIUM

A 24-year-old woman comes to the clinic because of episodic wheezing and chest tightness for 6 months, worse at night and after exposure to cats. She uses an albuterol inhaler several times per week with partial relief. She has no smoking history. Vital signs are normal. Spirometry shows an FEV1/FVC ratio of 0.62 that improves to 0.74 after inhaled bronchodilator. Which of the following is the most likely physiologic mechanism responsible for the improvement in airflow after bronchodilator use?

Beta-2 agonists relax bronchial smooth muscle, increasing bronchiolar radius and thereby markedly decreasing airway resistance (Poiseuille relationship). Reduced surfactant would worsen compliance, and diffusion capacity changes are not the primary driver of rapid reversibility in asthma.

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