FAA Private Pilot Airplane (PAR)Aeromedical Factors and ADMHard
During a post-flight inspection, a mechanic discovers that the exhaust manifold on a pilot's aircraft has a small crack, allowing exhaust gases to leak into the cabin heating system. On a recent flight, the pilot reported a headache and mild confusion but no vision changes or cyanosis. This scenario is most consistent with which type of hypoxia, caused by exposure to carbon monoxide?
- AHypoxic hypoxia
- BHypemic hypoxia
- CStagnant hypoxia
- DHistotoxic hypoxia
Show answer & explanationAnswer & explanation
Correct answer: B. Hypemic hypoxia
Carbon monoxide binds to hemoglobin far more readily than oxygen, reducing the blood's oxygen-carrying capacity; this is classified as hypemic hypoxia, and symptoms include headache and confusion, often without the cyanosis seen in hypoxic hypoxia.
Why the other options are wrong
- A. Hypoxic hypoxia is caused by reduced ambient oxygen pressure at altitude, not by CO displacing oxygen in the blood.
- C. Stagnant hypoxia is caused by poor blood circulation, such as from shock, not from a chemical binding issue.
- D. Histotoxic hypoxia occurs when tissues cannot utilize oxygen properly, typically from alcohol or certain drugs, not from CO binding hemoglobin.
Hypemic Hypoxia (CO Poisoning)
A form of hypoxia caused by a reduction in the blood's ability to carry oxygen, commonly due to carbon monoxide binding to hemoglobin far more strongly than oxygen.
- CO binds hemoglobin ~200x more readily than oxygen
- Symptoms: headache, confusion, drowsiness
- Cabin heat exchangers cracked near exhaust are a common source
Memory trick: CO steals hemoglobin's seat from oxygen