Which of the following is a DCS prevention measure?

• A. Increasing cabin altitude above 25,000 ft
• B. No oxygen supply
• C. Pressurized cabin
• D. Rapid ascent

Answer: (C)

Preventing decompression sickness relies on keeping ambient pressure high enough so dissolved nitrogen in tissues doesn’t come out of solution and form bubbles. A pressurized cabin maintains the cabin at a moderate, stable pressure (roughly equivalent to 6–8 thousand feet), which minimizes nitrogen off-gassing during flight. This direct control of pressure is the most effective DCS prevention measure because it prevents the rapid pressure drop that would otherwise promote bubble formation. In contrast, increasing cabin altitude, having no oxygen supply, or ascending rapidly would all raise the risk by either lowering ambient pressure or creating conditions that promote bubble growth or insufficient oxygen.