If an occupant is suspected to have decompression sickness, what should the pilot do?

Administering 100 percent oxygen to an occupant suspected of having decompression sickness is the recommended action because it helps to alleviate the symptoms and accelerate the elimination of nitrogen from the body. Decompression sickness occurs when nitrogen bubbles form in the bloodstream or tissues due to a rapid reduction in atmospheric pressure, often after a dive or rapid ascent.

When a person breathes 100 percent oxygen, it increases the partial pressure of oxygen in the lungs and facilitates a faster reduction in nitrogen gas bubbles, helping to mitigate the effects of the condition. This approach enhances the body's ability to metabolize and remove the nitrogen more quickly than if the occupant were to breathe normal air or lower concentrations of oxygen. This is a critical step in treatment before further medical assistance can be provided.

In contrast, other options such as administering 50 percent oxygen or allowing the occupant to breathe normal air would not be as effective in managing the symptoms of decompression sickness. Descending to a lower altitude without providing oxygen may also not adequately address the condition, as it does not effectively assist in eliminating the nitrogen bubbles already present in the body.