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Every Dive Is a Decompression Dive

By

three scuba divers descend from the surface.

Even recreational dives involve the release of compressed nitrogen from a diver's body upon ascent.

© istockphoto.com, strmko

Shifting the Way We View Recreational Scuba Diving:

Have you ever been on a decompression dive? Perhaps you have not engaged in technical diving or dives exceeding the recreational no-decompression limits, but if you dive at all, you have engaged in a dive involving decompression. Why? Because every dive involves some level of decompression, even if it does not require decompression stops. This may sound like mincing words, but changing the way that you look at recreational diving enforces safe diving guidelines and leads to more conservative dive practices.

Why Does Every Dive Involve Some Decompression?:

Underwater, the air a diver breathes is compressed by the pressure of the water and the atmosphere above him. A diver's body tissues absorb compressed nitrogen from the air (or other breathing gas). This absorbed nitrogen decompresses during the diver's ascent as he moves slowly upwards through a gradual decrease in pressure. The diver's body eliminates this decompressing nitrogen as he ascends. Even after surfacing, a small amount of nitrogen remains in the diver's system, and his body continues to eliminate nitrogen for hours after surfacing. Every dive involves the compression and absorption of nitrogen, and the decompression of nitrogen upon ascent and surfacing. Every dive involves a small amount of decompression.

Why Is Understanding That All Dives Involve Decompression Important?:

Realizing that even shallow, recreational dives involve decompression emphasizes the importance of maintaining a slow, safe ascent rate and making safety stops on every dive. Violating safe diving guidelines, even on dives that do not exceed or approach the no-decompression limits, can increase a diver's risk of decompression sickness because every dive involves the absorption of nitrogen. A quick ascent and violating other safe diving guidelines can lead to the nitrogen in a diver's body decompressing rapidly and forming bubbles in his body tissues or, becoming arterial embolisms (bubbles in his arteries).

Understanding that every dive involves some level of decompression also helps explain why, in rare cases, some divers get "undeserved" decompression sickness -- decompression sickness which manifests even though a diver followed safe diving guidelines.While "undeserved" decompression hits are unusual in recreational diving, they do occur. Why? Because for some reason the diver's body failed to eliminate decompressing nitrogen from his system efficiently enough to prevent the nitrogen from forming bubbles.

Take Safe Diving Guidelines With a Grain of Salt:

How is it possible that a diver can get decompression sickness while following safe diving practices? Consider that no-decompression limits, dive tables, and safe ascent rate guidelines are simply tools that a diver can use to avoid absorbing such a high quantity of nitrogen or ascending so quickly that his body can not efficiently eliminate the decompressing nitrogen. Divers should realize that these guidelines are created with the "average" diver in mind. They are based on experimental data, accident statistics, and mathematical algorithms.

No algorithm or rule will ensure that every diver who follows it is one hundred percent safe. Divers have different physiologies. Because all diving involves the absorption of compressed nitrogen and the release of decompressed nitrogen, divers with conditions that may predispose them to decompression sickness and those that have completed multiple days of intense diving would do well to dive more conservatively than the guidelines suggest.

How Might This Knowledge Change Your Diving?:

The take-away concept here is that it is possible to get bent on a 40 foot dive. It is possible to get bent on a 30 foot dive. Does this mean divers should panic and stop diving? Of course not! Diving, as far as adventure sports go, has a terrific safety record and is a relatively low-risk activity. However, understanding the basics of nitrogen compression, absorption, and decompression, and how the body works to eliminate nitrogen during and after ascent may encourage divers to dive more safely.

A wise diver will take personal responsibility for his diving safety. Owning a dive computer in order to monitor ascent rates is a great place to start. Implement multilevel dives or deep stops when diving to greater depths. Avoid exertion underwater, and be sure to master the art of the relaxed safety stop. Remain calm and motionless during your three to five minute stop at the end of each dive to facilitate the release of nitrogen.

A conservative and safe diver will consider his health and physical state before diving. Avoid hangovers before diving. Do not dive when sick, exhausted or extremely stressed as these states may affect the body's functioning. And most importantly, be sure to be well-hydrated before and after the dive (chugging a bottle of water immediately before descending does not count!).

Remember also, that although a dive ends once a diver reaches the surface, his body is still off-gassing nitrogen for hours, if not days, after the dive. Exertion, exercise, and dehydration immediately after diving may impede a diver's ability to release residual nitrogen after a dive, and exacerbate or (in extreme cases) cause a decompression hit that could have been avoided!

The Take Home Message About Decompression and Scuba Diving:

Are you going to get bent on your next recreational scuba dive? It's highly unlikely. However viewing every dive as a decompression dive leads to more conservative diving practices and explains many safe diving guidelines. Divers who understand the reasons behind the rules are more likely to follow them!

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