Decompression sickness

What is it?

Decompression sickness, also called generalized barotrauma or the bends, refers to injuries caused by a rapid decrease in the pressure that surrounds you, of either air or water. It occurs most commonly in scuba or deep-sea divers, although it also can occur during high-altitude or unpressurized air travel. However, decompression sickness is rare in pressurized aircraft, such as those used for commercial flights.

When you scuba dive with compressed air, you take in extra oxygen and nitrogen. Your body uses the oxygen, but the nitrogen is dissolved into your blood, where it remains during your dive. As you swim back toward the surface after a deep dive, the water pressure around you decreases.

If this transition occurs too quickly, the nitrogen does not have time to clear from your blood. Instead, it separates out of your blood and forms bubbles in your tissues or blood. It is these nitrogen bubbles that cause decompression sickness. The condition is called the bends because the joint and bone pains can be so severe they double you over.

What happens inside your body during decompression sickness is similar to what happens when you open a carbonated drink. When you open the can or bottle, you decrease the pressure surrounding the beverage in the container, which causes the gas to come out of the liquid in the form of bubbles. If nitrogen bubbles form in your blood, they can damage blood vessels and block normal blood flow.

Factors that put you at higher risk of decompression sickness include:

• heart muscle birth defects, including patent foramen ovale, atrial septal defect, and ventricular septal defect
• being older than 30
• being female
• low cardiovascular fitness
• high percentage of body fat
• use of alcohol or tobacco
• fatigue, seasickness or lack of sleep
• injuries (old or current)
• diving in cold water
• lung disease.

Someone with an abnormal hole or opening in the heart from a birth defect is at especially high risk of developing serious symptoms from decompression illness. Because bubbles create high blood pressure in the lungs, blood and bubbles from your veins may flow more readily through the heart's opening. This means your blood can re-circulate into arteries without first getting oxygen. An opening in the heart can also allow a relatively large air bubble (called an air embolism) to circulate into your arteries. An air embolism can cause a stroke.

People with asthma or another lung disease may have thin-walled air pockets in their lungs called bullae. These pockets do not empty quickly when the persons exhales. As they return to the surface after a deep dive, air in the bullae may expand. If a bulla ruptures, it could cause a collapsed lung or allow a large air bubble (air embolism) to enter the arteries.

Symptoms

Symptoms of decompression sickness include:

• joint pain
• dizziness
• headache
• difficulty thinking clearly
• extreme fatigue
• tingling or numbness
• weakness in arms or legs
• a skin rash.

Diagnosis

Your diving history and symptoms are key factors in diagnosing decompression sickness. Blood tests and joint X-rays usually do not show any signs of the problem.

Expected duration

Joint pain, the most common symptom from decompression sickness, can last for days or weeks.

Prevention

To minimize the risk of decompression sickness while diving:

• Dive and rise slowly in the water, and don't stay at your deepest depth longer than recommended. Scuba divers typically use dive tables that show how long you can remain at a given depth.
• Do not fly within 24 hours after diving.
• Don't drink alcohol before diving.
• Avoid hot tubs, saunas or hot baths after diving.
• Make sure you are well hydrated, well rested and prepared before you scuba dive. If you recently had a serious illness, injury or surgery, talk to your doctor before diving.

Some people should avoid diving altogether, or should consider special risks. If you have a heart defect, it is not safe to dive. If you have asthma, a history of a ruptured lung at any time in your life or another lung disease, discuss diving safety with a doctor before deciding whether to dive. A person who requires insulin to treat diabetes may have wide swings in blood glucose levels during a dive, and caution is advised. Avoid diving if you have a groin hernia that has not been repaired, since expanding gas in the hernia can cause symptoms.

Treatment

Emergency treatment for decompression sickness involves maintaining blood pressure and administering high-flow oxygen. Fluids also may be given. The person should be placed left side down and if possible the head of the bed tilted down.

The optimal treatment is the use of a hyperbaric oxygen chamber, which is a high-pressure chamber in which the patient receives 100% oxygen. This treatment reverses the pressure changes that allowed gas bubbles to form in the blood stream. The treatment drives nitrogen back into its liquid form so that it can be cleared more gradually from the body over a period of hours.

It is not recommended that divers with decompression sickness attempt to treat themselves with deep diving.

When to call a professional

If you experience symptoms of decompression sickness after scuba diving or flying, get to a doctor as soon as you can. Hyperbaric treatment is most successful if given within several hours after symptoms start.

Prognosis

Most cases of decompression sickness respond well to a single treatment with hyperbaric oxygen. Your doctor may suggest repeated treatments if you continue to experience symptoms, especially neurological symptoms.

Additional info

Undersea & Hyperbaric Medical Society
https://www.uhms.org/