How does increasing depth affect the partial pressure of gases in the body?

Increasing depth underwater leads to an increase in the pressure exerted on the body, which directly affects the partial pressure of gases dissolved in the body fluids, particularly nitrogen and oxygen. According to Dalton's Law, the pressure of individual gases in a mixture is proportional to their percentage in that mixture. As a diver descends, the ambient pressure increases due to the weight of the water above them, which in turn increases the partial pressures of the individual gases.

For instance, at sea level, the partial pressure of oxygen is about 0.21 ATA (atmospheres absolute), but as a diver goes deeper, the pressure increases, and so does the partial pressure of the gases. This increase in partial pressure influences how gases are absorbed into the bloodstream and tissues. Higher pressures can lead to more nitrogen being absorbed, increasing the risk of decompression sickness if a diver ascends too quickly after spending time at depth.

Understanding this relationship is crucial for dive safety and managing the risks associated with increased partial pressures, such as the need for controlled ascents and appropriate decompression stops during dives.