Respiratory Conditions · USMLE Step 1

A 7-year-old with asthma has a pulsus paradoxus during an acute exacerbation. What is the mechanism?

  1. Acute right ventricular failure
  2. Negative intrathoracic pressure swings
  3. Massive acute pulmonary embolism
  4. Severe aortic valve stenosis
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Correct answer: Negative intrathoracic pressure swings

Severe asthma increases intrathoracic pressure swings, causing exaggerated decrease in systolic BP during inspiration (pulsus paradoxus).

Difficulty: Medium Question 4 of 20

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