Ask Dr. C. Lancer

What causes Decompression Sickness?

Some Facts & Myths

By Brian S. Pinkston, M.D. and Tracey E. Pinkston, M.D.*

Decompression sickness (DCS) is a complex disease process caused by nitrogen bubbles coming out of blood and body fluids following a dive. Two divers may have identical dive profiles and only one suffer DCS. Additionally, a diver may develop DCS after diving a profile he has dived many times before without any difficulty. While DCS may seem unpredictable, there are known predisposing factors, and although study continues to reveal the mechanisms of the disease, some commonly held beliefs have actually been proven false. A few of the most important facts and myths follow:

Myth #1 "Come on, it’s okay to go diving now. That twelve pack of beer was last night."

Fact: Dehydration is perhaps the number one risk factor. It is extremely important that a diver be well hydrated prior to a dive and rehydrate following a dive. This means that alcohol, drugs, caffeine, "water pills", and recent or current illness also put a diver at risk of DCS due to dehydrating effects.

Myth #2 "If you hear a beeping when we come up, don’t worry about it. It’s just my computer alarm – it always does that."

Fact: Rapid ascents are also known definitely to cause DCS. This is because the decreasing pressure causes the nitrogen to come out of body fluids, forming bubbles. A slow ascent rate allows time for the nitrogen to escape from the body without forming significant bubbles. That is why you should always follow the ascent rate recommended by the tables or computer you are using.

Ascents also include ascents to altitude. There is a very definite relationship between ascent to altitude and development of DCS due to the increase in release of nitrogen as the pressure is reduced to less than sea level. While people usually remember that they should not fly for at least 12 hours following a dive (and probably longer based on early data from a DAN study), they often forget that altitude includes driving to areas of more than 1000 ft elevation. For that reason, it is not a good idea to dive in the morning and take a leisurely drive to Haleakala in the afternoon!

Myth #3 "It always eases my aches and pains to go soak in the hot tub after a chilly night dive."

Fact: Temperature also affects DCS. Although cold temperatures tend to keep gases dissolved in liquids, diving in cold temperatures can contribute to DCS by reducing circulation to the skin and causing shivering. Nevertheless, a hot shower or dip in the hot tub is not the answer, either. Going into hot water leads to bubbles coming out of body fluids, often causing DCS. Similarly, strenuous exercise during or after a dive can also increase bubble formation, with the same result.

Myth #4 "Women have a higher risk of getting DCS than men."

Fact: Contrary to popular belief, gender has no effect on the development of the bends. Women are no more likely to suffer DCS than men. Studies are still ongoing to determine effects of menstruation and other physiologic changes that occur in women.

Myth #5 "Overweight people have a higher risk of getting DCS than thin people"

Fact: Obesity also plays no role in the development of DCS. Rates of DCS in thin, average, overweight and obese people showed no significant difference. Most likely this is because nitrogen takes a long time to absorb in and escape from fat. Nevertheless, fitness is an important part of diving health for many other reasons!

Clearly, many factors contribute to the development of DCS, many of which are not well understood and others may still be discovered. Ongoing research will hopefully continue to establish fact from myth in decompression sickness

* Drs. Pinkston are physicians, members of Undersea & Hyperbaric Medical Society, DAN Oxygen instructors, and PADI instructors. To submit questions or topics to appear in this column, email HonuDivers@aol.com or give to cashier on club nights. This column is for general information only and is not intended as medical advice. For medical advice, please see your physician.