What Causes the Bends When Diving?

The bends is a fundamental hazard for SCUBA divers, and it is tied to going deep. Many SCUBA divers like going deep, even if most of the interesting corals and fishes can be seen at a safe depth of 25 meters or less. Some dives, such as wreck dives, require going deep. Learning about the bends and how to prevent it is part of the basic training for every SCUBA diver.

  1. What is "the Bends?"

    • "The Bends" is better described as decompression sickness. For divers, this is what happens when a diver rapidly ascends from a deep dive to the surface.

    Pressure and Gases

    • According the Henry's Law, increasing pressure on a liquid allows it to absorb more gas at the same temperature. When a diver goes to substantial depths, the result is that the diver's body liquids absorb more inert gasses through respiration, the main one being nitrogen.

    Rapid Ascent and Decompression

    • When a diver rapidly ascends from a deep dive to the surface, they are going from a high pressure environment to a lower pressure environment. The result is that the nitrogen and other inert gasses that were absorbed into the body's liquids, especially the blood, during the time at higher pressure rapidly come out of solution, returning to a gaseous state and forming harmful bubbles.

    Symptoms

    • Mild cases of the bends result in the tell-tale warning signs of joint aches, rashes, and itchy skin. Severe cases result in sensory problems and paralysis and can lead to death.

    Prevention

    • Divers prevent the bends by limiting their time at the bottom on deep dives, using specially mixed gases, and planning for decompression stops on the return to the surface. The latter safety measure helps allow for the slow release of gasses from the body.

    Other Examples

    • Decompression sickness is also a problem when passengers on an airliner experience sudden decompression of the cabin.