The Bends

The Bends (or more formally, decompression sickness) is a condition that affects divers who resurface too quickly. It is caused by bubbles of nitrogen forming in the blood. These bubbles prevents cells absorbing oxygen and lead to difficulty breathing; lips and skin turning blue, shock and eventually to death.

Nitrogen gas is five times more soluble [2] in fatty tissue than oxygen or carbon dioxide. Therefore, five times more nitrogen will be dissolved into fatty tissue than oxygen or carbon dioxide. This can be predicted by Henry’s Law. When the partial pressure of nitrogen equals the partial pressure of the liquids within the body nitrogen will start to become a gas causing the aforementioned bubbles to be formed. This is due to the partial pressure on the liquid side being proportional to that of the gas. Therefore, as pressure increases more bubbles are formed. Typical pressure changes required to cause this are 2 bars per minute [3]. This can be achieved at depths as low as 18 metres [4].

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