DEAR DOCTOR K: I’m planning a diving vacation. A friend told me it’s not safe to fly within 24 hours of diving. Why not?
DEAR READER: When you scuba dive, you breathe compressed air from a tank. That air contains high amounts of two gases, oxygen and nitrogen – higher than are normally in the air around us.
The deeper you dive, the more pressure you’re under. That causes the nitrogen to stop being a gas; it dissolves into your blood, becoming a liquid, where it remains during your dive. Your body slowly eliminates the nitrogen, primarily in your urine.
As you swim back toward the surface after a deep dive, the water pressure around you decreases. If this transition occurs too quickly, the liquid nitrogen forms bubbles in your tissues or blood that can damage the walls of blood vessels. These bubbles also can block normal blood flow in the same way that little blood clots can.
Decompression sickness can cause a variety of symptoms: joint pain, dizziness, headache, difficulty thinking clearly, extreme fatigue, weakness in the arms or legs, or rash. The symptoms you get depend on the organs in which blood flow is blocked.
Symptoms of decompression sickness can take up to 24 hours before they appear.
If you experience any of the symptoms of decompression sickness after scuba diving, get to a doctor as soon as you can. The key to treatment is the use of a hyperbaric oxygen chamber. This is a high-pressure chamber that provides 100 percent oxygen. The treatment drives nitrogen back into its liquid form so that it can be cleared from the body gradually, over a period of hours.
As a plane climbs higher, the surrounding air pressure gets progressively lower. Although the plane keeps cabin pressure higher than the real air pressure outside the plane, the cabin pressure still is lower than the air pressure on the ground. That encourages any remaining liquid nitrogen in your blood to form bubbles and cause decompression sickness. For that reason, you should wait 24 to 48 hours after diving before flying.