When a diver ascends, what happens to dissolved gases in the blood?

As a diver ascends, the pressure surrounding them decreases. This drop in pressure affects the solubility of gases in the blood—a principle known as Henry's Law, which states that the amount of gas that can be dissolved in a liquid is directly proportional to the pressure of that gas above the liquid.

During a dive, divers breathe compressed air that contains nitrogen and other gases. At greater depths, these gases dissolve in the body’s tissues and blood due to higher pressure. When ascending, as the pressure decreases, the solubility of these gases also decreases. Consequently, dissolved gases may come out of solution and form bubbles. If the ascent is too rapid, these bubbles can result in decompression sickness or “the bends,” as they can disrupt circulation and cause significant harm.

This process of bubbles forming is critical for divers to understand as it emphasizes the importance of ascending slowly and employing safety stops to allow the body to gradually off-gas the nitrogen safely.