German: Taucherkrankheit, Dekompressionskrankheit, DCS and Morbus Caisson Synonyms: Caisson disease, divers' disease and the bends
Decompression sickness is a disseminated trauma caused by bubbles of dissolved gases (nitrogen and helium) forming in various body tissues due to sudden pressure change (like rapid emergence from a deep dive).
Note: The neurological effects of nitrogen occurring in great depths, independent of the decompression disease, is termed nitrogen narcosis.
During dives with compressed air as breathing gas, nitrogen is increasingly stored in the tissues due to the water pressure on the body. The extent of the storage (as solution) is dependent on the depth and the duration of the dive.
Unlike oxygen or carbon dioxide, nitrogen is an inert gas that does not take part in metabolic processes. Stored nitrogen can therefore be eliminated from the body only through the lungs by way of gradual respiration. The distribution of the nitrogen in the various tissues is dependent, among others, on the blood supply and fat content of the tissues. In tissues well supplied with blood (brain and muscles), nitrogen is stored relatively quickly. In fatty tissues, nitrogen is stored slowly, but dissolved in clearly higher concentrations than in the "watery" muscle tissues.
When the pressure on the body lowers again (going up from the dive), the process takes place in a reverses order, i.e. the quickly stored nitrogen is quickly released, and the slowly stored nitrogen is slowly released. In addition, the dissolved nitrogen has to be transported through blood back to the lungs so as to exhale during the dive. The complex process of redistribution of the inert gas in the various areas takes time. This factor has to be countered by the maintenance of decompression time in different water depths. If the pressure change is sudden while going up from the dive, the solubility of nitrogen in the tissues is abruptly reduced. Thereby, gas bubbles form in the blood and other body tissues that may cause lasting damages to the structure of the tissues (see air embolism).
In regularly conducted dives, so-called "microbubbles" occur, which however do not lead to a destruction of the tissues.
The symptoms are divided into two groups:
In severe cases, decompression sickness can end in death.
The prognosis is dependent on the magnitude and localization of the tissue trauma. Minor cases heal without any consequences, but severe traumas under certain circumstances leave behind life-long disabilities.
The risk for decompression sickness increases when several dives are conducted one after the other. Every dive increases the plateau of dissolved nitrogen, because the total elimination of gases from the tissues is complete only after some days.
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