Faster ascents have what effect on decompression sickness risk?

• A. Increase risk
• B. Decrease risk
• C. No effect
• D. Depends on depth

Answer: (A)

Faster ascents increase the risk of decompression sickness because the rapid drop in ambient pressure doesn’t give dissolved inert gas (mostly nitrogen) time to offgas safely. At depth, nitrogen is dissolved in tissues and blood in amounts proportional to pressure and time. When you ascend quickly, the pressure falls quickly, so the gas you’ve absorbed comes out of solution faster than your tissues and circulation can carry it away. This can form bubbles in tissues and in the bloodstream, which is what causes decompression sickness.

Taking the ascent more slowly gives your body time to release the inert gas gradually and to vent it through the lungs after reaching the surface, reducing the chance that bubbles will form. This is why ascent rates are regulated and why a safety stop is recommended.

So, faster ascents increase decompression sickness risk.