Which statement about altitude-related hypoxia and hyperventilation is true?

Which statement about altitude-related hypoxia and hyperventilation is true?

• A. Hyperventilation is likely below 10,000 ft.
• B. Hypoxia is likely below 10,000 ft.
• C. Cyanosis is common in hyperventilation.
• D. Hypoxia is never a concern above 10,000 ft.

Answer: (A)

As you climb, the availability of oxygen decreases, and the body responds by increasing ventilation to bring in more oxygen and remove CO2. This ventilatory response can begin as you approach moderate elevations, so hyperventilation is a common reaction to altitude exposure even before hypoxia becomes severe. Hypoxia itself becomes more likely as you rise further, especially beyond about 10,000 feet, but early in ascent the most immediate change you’ll notice is an increased breathing rate. Cyanosis is not a typical feature of hyperventilation; it’s a late sign of significant hypoxemia. And hypoxia can certainly be a concern above 10,000 feet, not never. So the statement that hyperventilation is likely below 10,000 feet best describes the initial ventilatory response to rising altitude.

As you climb, the availability of oxygen decreases, and the body responds by increasing ventilation to bring in more oxygen and remove CO2. This ventilatory response can begin as you approach moderate elevations, so hyperventilation is a common reaction to altitude exposure even before hypoxia becomes severe. Hypoxia itself becomes more likely as you rise further, especially beyond about 10,000 feet, but early in ascent the most immediate change you’ll notice is an increased breathing rate. Cyanosis is not a typical feature of hyperventilation; it’s a late sign of significant hypoxemia. And hypoxia can certainly be a concern above 10,000 feet, not never. So the statement that hyperventilation is likely below 10,000 feet best describes the initial ventilatory response to rising altitude.