A 26-year-old woman presents to the emergency department with an acute asthma exacerbation. She can speak only single words, respiratory rate is 32/min, heart rate is 116/min, SpO2 is 92% on room air, and peak expiratory flow is 35% of predicted. Arterial blood gas shows PaCO2 41 mm Hg. Which single feature, if present, would reclassify her exacerbation as life-threatening?
- A Peak expiratory flow of 28% predicted ✓
- B Heart rate of 122/min
- C SpO2 of 91% on room air
- D Inability to complete sentences
Correct answer: A. Peak expiratory flow of 28% predicted
Explanation
Life-threatening asthma is defined by PEF below 33% predicted, silent chest, feeble respiratory effort, cyanosis, exhaustion, bradycardia or hypotension, or a normal or rising PaCO2 indicating fatigue. Heart rate above 110, SpO2 below 92%, and inability to complete sentences all fall within the acute severe category, not life-threatening. The key discriminator between the two grades is the degree of airflow obstruction, so a PEF of 28% predicted is the correct answer.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.