During an exercise stress test, a patient's cardiac output increases from 5 L/min to 20 L/min. Heart rate rises from 70 to 160 bpm. What is the approximate stroke volume at peak exercise?
- A 71 mL
- B 125 mL ✓
- C 160 mL
- D 200 mL
Correct answer: B. 125 mL
Explanation
Cardiac output = heart rate × stroke volume; rearranging, SV = CO/HR = 20,000 mL/min ÷ 160 beats/min = 125 mL per beat. During exercise, SV rises through enhanced venous return (Frank–Starling mechanism) and sympathetic-augmented contractility, plateau-ing at about 100–130 mL in trained individuals.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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