When scuba diving, more oxygen and nitrogen dissolve in body tissues. The extra oxygen is absorbed by the tissues, but the excess nitrogen must be washed out by the blood during decompression. During or after ascent, this excess nitrogen gas can form bubbles in the tissues just like the carbon dioxide bubbles that form when a carbonated beverage is opened. These bubbles can cause symptoms known as decompression sickness (“DCS” or “the bends”).
If gas is trapped within the lungs during ascent, bubbles may be forced into the bloodstream (“arterial gas embolism” or “AGE”). This is more likely to happen if the diver has a diseased lung or is holding his/her breath. An arterial gas embolism blocks the flow of blood or damages the lining of blood vessels that supply blood to critical organs such as the brain. AGE also can occur in non-divers if air enters the body during medical diagnostic or therapeutic procedures.
Symptoms of Decompression Sickness or Arterial Gas Embolism:
- Joint pain
- Skin rash
- Extreme fatigue
- Weakness of arms or legs
- Loss of hearing
- Complete paralysis or unconsciousness (in serious cases)
If DCS or AGE is suspected, it is important to give the person oxygen and to maintain the person’s blood pressure. Laying the patient down and providing fluid is helpful in maintaining blood pressure.
Hyperbaric Oxygen Therapy
Hyperbaric oxygen therapy is the recommended treatment for DCS or AGE. This involves administering 100% oxygen at increased atmospheric pressure in a hyperbaric chamber (typically at a pressure 2-3 times greater than normal atmospheric pressure). Success in relieving symptoms is greater if the hyperbaric oxygen therapy is administered within a few hours after the onset of symptoms. However, symptoms can be improved even after a day or more of delay, particularly in mild cases of DCS or AGE. Most patients only need one hyperbaric oxygen treatment to receive the greatest benefit. Repetitive treatments may be recommended until no further improvement can be observed. A small minority of divers with severe neurological injury may require 15-20 repetitive treatments.