Hypoxic hypoxia is caused by which of the following conditions?

• A. Caused by insufficient oxygen in the lungs due to poor lung function.
• B. Caused by lack of inhaled oxygen.
• C. Caused by insufficient oxygen available to the lungs due to low ambient oxygen pressure.
• D. Caused by low blood sugar.

Answer: (C)

Hypoxic hypoxia happens when there isn’t enough oxygen available to the lungs because the surrounding air has a lower oxygen pressure. In aviation terms, that means at high altitude or in an environment with reduced ambient oxygen, the partial pressure of oxygen entering the lungs drops. Because the lungs can’t transfer as much oxygen into the blood, arterial oxygen content falls and tissues receive less oxygen, even if heart rate and blood flow are normal. That’s why the correct statement points to insufficient oxygen available to the lungs due to low ambient oxygen pressure.

The other ideas describe different problems: if the lungs themselves aren’t functioning well, that’s a issue with lung transfer, not the ambient air. If you’re simply inhaling air with less oxygen, that can cause hypoxia too but the classic description of hypoxic hypoxia emphasizes the low ambient oxygen pressure, such as at altitude. Low blood sugar isn’t related to oxygen transport at all.