Supplemental Oxygen Use

Oxygen Requirements and Equivalent Altitudes

At altitudes up to 10,000 ft, breathing ambient air is generally sufficient for healthy individuals. Beyond this, the reduced partial pressure of oxygen means supplemental oxygen becomes necessary. Breathing 100% oxygen at mean sea level provides the maximum oxygen saturation, but as you climb, the effectiveness of oxygen delivery changes:

• At 10,000 ft: Breathing air is still usually adequate, but performance and cognition can decline.
• At 30,000 ft: Breathing 100% oxygen here is roughly equivalent to breathing ambient air at 10,000 ft.
• At 40,000 ft: Even 100% oxygen at normal pressure only matches the oxygen availability of ambient air at 10,000 ft. Above this, pressurised oxygen systems are required.

Oxygen Equipment and Pilot Actions

Aviation oxygen requirements dictate that pilots use oxygen masks and appropriate equipment above certain altitudes to prevent hypoxia. If cabin pressurisation is lost, immediate actions include donning oxygen masks, initiating an emergency descent, and landing as soon as possible. No further flight should be undertaken for at least 24 hours due to the risk of delayed decompression sickness symptoms.

Carbon Monoxide and Oxygen Transport

Carbon monoxide is produced by incomplete combustion, often from engine exhaust leaks. When inhaled, it binds to haemoglobin far more readily than oxygen, reducing the blood's oxygen-carrying capacity and causing anaemic hypoxia. This impairs tissue oxygenation even if supplemental oxygen is available.

Decompression Sickness and Treatment

Rapid decompression at altitude can lead to decompression sickness, as nitrogen comes out of solution in body tissues. Treatment involves immediate descent, administration of 100% oxygen, and seeking medical attention. Symptoms can appear up to 24 hours after exposure.

Haemoglobin Saturation and Altitude

As altitude increases, the oxygen saturation of haemoglobin drops due to lower partial pressure of oxygen, making supplemental oxygen essential for maintaining adequate tissue oxygenation and pilot performance.