A person moves to 4500 m altitude. Which cardiovascular change is seen during the first 24 hours of acute hypoxic exposure?
- A Decreased heart rate and decreased cardiac output due to hypoxic myocardial depression
- B Increased heart rate and increased cardiac output with unchanged or slightly reduced stroke volume ✓
- C Decreased heart rate and increased stroke volume, keeping cardiac output unchanged
- D Increased systemic vascular resistance with decreased cardiac output
Correct answer: B. Increased heart rate and increased cardiac output with unchanged or slightly reduced stroke volume
Explanation
Acute hypoxia activates peripheral chemoreceptors, increasing sympathetic outflow. Heart rate rises immediately, increasing cardiac output to maintain oxygen delivery despite reduced arterial oxygen content. Stroke volume is typically unchanged or slightly reduced. The myocardial depression option is wrong because acute hypoxia increases, not decreases, sympathetic drive to the heart.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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