Basic Aviation Physiology and Health Maintenance
What the domain tests
Physiology questions ask for mechanisms and operational consequences: hypoxia, gas laws, decompression, spatial disorientation and fitness to fly. Learn the numbers and the correct response, not only the name.
Core rules
- Hypoxia types: hypoxic (low alveolar PO2), hypemic (anaemia, carbon monoxide, blood loss), stagnant (G-forces, heart failure) and histotoxic (alcohol, cyanide). At altitude the usual type is hypoxic.
- Time of useful consciousness falls with altitude: about 30–60 s at FL350 and 15–20 s at FL400; rapid decompression shortens it further.
- Boyle's law explains barotrauma and gas expansion in ears, sinuses and gut; Henry's law explains decompression sickness (DCS) after diving. Treat DCS with 100% oxygen, descent, landing and hyperbaric care.
- Spatial disorientation: somatogravic illusion in acceleration (false climb), somatogyral/leans in prolonged turns, black-hole approach at night. Trust instruments.
- Dark adaptation takes about 30 minutes; use off-centre viewing at night. Hearing loss is cumulative, and noise and vibration add fatigue.
- Fitness: IMSAFE (illness, medication, stress, alcohol, fatigue, eating), plus hydration and smoking.
Worked example
A pilot dives to 30 m and flies 12 hours later. Under Henry's law, nitrogen dissolved in tissues comes out of solution as pressure falls; flying adds further pressure reduction and raises DCS risk. Standard guidance is no flying for 24 hours after normal diving, or 48 hours after decompression diving. With symptoms: 100% oxygen and urgent treatment.
Traps
Do not confuse hyperventilation with hypoxia - both cause dizziness, but hyperventilation responds to controlled breathing while hypoxia needs oxygen. Do not say oxygen 'cures' DCS. Do not treat G-suits as DCS treatment. Do not ignore medication or alcohol.