Scuba Diving Illness: Decompression Sickness (DCS) while Scuba Diving

Scuba Diving Illness: Decompression Sickness (DCS) while Scuba Diving by Lilah Tusko

Getting decompression sickness while scuba diving is not an enjoyable experience. Decompression sickness was encountered when Brooklyn Bridge was being built. DCS affected the workers on the Brooklyn Bridge site who had to spend many hours near the bridge supports in compressed-air filled chambers (caissons) underwater. Upon surfacing, they suffered from abdominal cramps, joint pain, and in some cases death.

Let’s try and understand what causes decompression sickness while scuba diving. As the diver descends, he breathes in the nitrogen in the air through the tank. This nitrogen dissolves in the blood. While the diver is ascending, the lowered pressure causes the nitrogen to come out of the blood, forming small bubbles. To prevent these bubbles from becoming bigger, they need to be either re-absorbed into the blood stream or exhaled out through the lungs.

Decompression sickness is the result of a certain volume of these bubbles being formed.

A physics principle called Henry’s Law can explain this phenomenon technically. All basic diving courses teach this law to new scuba divers. What happens when a soda can is popped? Dissolved gases get released quickly out of the bottle as bubbles due to the quick pressure change. Similarly, each point of the dive determines how much gas is dissolved, and how quickly it will be released while ascending.

Decompression sickness is no laughing matter and all scuba divers are taught how to avoid it. Even if the diver survives, he can suffer permanent health damage. A scuba diver can avoid DCS by using a dive computer or a diving watch or dive tables.

While ascending, the scuba diver should spend time being neutrally buoyant at certain levels on the way up. Neutral buoyancy means the diver neither sinks nor floats. While the time spent at each stop varies with the specific nature of each dive, on average, he must stop for anywhere between one and three minutes every 9 m (30 feet) while coming up.

Scuba divers who take a short dive can safely ascend continuously. The thing to remember is that for any dive deeper than 20 feet; do not rise quicker than about 9 m (30 feet) per minute. For extra safety, stop at 10 to 20 feet in any case instead of rising continuously.

More stops of longer duration will of course be required in case of deeper dives. The factors that will influence the number of stops and their duration include the time spent at one depth, the diver’s general health, body type and age, the temperature during the dive etc. Body type makes a difference as nitrogen is stored more effectively by fat.

The mix of oxygen, nitrogen and helium contained in the tank air also affects the number of stops and allowable rate of ascent. A dive computer which is like a small wristwatch calculates all these complex factors to determine a safe rate of ascent and length of stops for the diver.

Since a dive computer gives an exact calculation, it is safer and more useful than mere experience or using tables printed on plastic-laminated cards. However, some divers continue to use these old methods.

The shortcoming of dive tables is the assumption of a 'square dive'. That is they assume the diver descends straight down and remains at one constant depth before starting to ascend. This makes dive tables only partially reliable.

Given the grave dangers of Decompression sickness, scuba divers should invest in a good dive computer and dive safely.

To obtain your 2 FREE Gifts: Special Report "Insider's Guide to Scuba Diving Gear" and Special Report "Top 10 Ways to Make Money while Scuba Diving", go to http://www.scubadivingsolutions.com and sign up for the FREE Gifts. Lilah Tusko is a writer who loves scuba diving!

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