Decompression sickness Guide, Meaning , Facts, Information and Description
Altitude-induced decompression sicknessDecompression sickness, DCS, the bends or caisson disease is an injury caused by bubbles of gas forming in the tissues of the body after breathing gas at high pressure and then reducing the ambient pressure.
DCS is most well known as an injury that affects divers. The ambient pressure due to the surrounding water increases as the diver descends and reduces as the diver ascends. The risk of DCS increases by diving long or deep without slowly ascending and making the decompression stops needed to eliminate the inert gases normally, although the specific risk factors are not well understood. Some divers seem more susceptible than others under identical conditions.
People flying in unpressurised aircraft at high altitude, such as stowaways in unpressurised parts of the aircraft or passengers after failure of the cabin pressure vessel, can suffer from decompression sickness. Likewise divers travelling in aircraft are at risk even in pressurised aircraft because the cabin air pressure is less than that at sea level.
The bends is a slang term describing a specific symptom of decompression sickness.
Arterial gas embolism and DCS have very similar symptoms and treatment because they are both the result of gas bubbles in the body. In a diving context, the two are often called decompression illness. Another term, dysbarism, encompasses decompression sickness, arterial gas embolism, and barotrauma.
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2 Avoiding decompression sickness 3 History 4 Helium 5 Signs and Symptoms 6 Treatment |
Cause
Two linked factors contribute to DCS, although the complete relationship of causes is not fully understood:
The physiologist J. B. S. Haldane studied this problem in the early 20th century, eventually devising the method of staged, gradual decompression, whereby the pressure on the diver is released slowly enough that the nitrogen comes gradually out of solution without leading to DCS. Bubbles form after every dive: slow ascent and decompression stops simply reduce the volume and number of the bubbles to a level at which there in no injury to the diver.
Repeated cases of decompression sickness can lead to the death of cells in long-bones and brittle bones. Severe cases can lead to death because large bubbles can impede the flow of oxygen-rich blood to the brain, central nervous system and other vital organs.
Decompression tables and dive computers have been developed that help the diver choose depth and duration of decompression stops for a particular dive profile at depth.
An alternative name is caisson disease; this term was used in the 19th century, when large engineering excavations below the water table, such as with the piers of bridges and with tunnels, required the work to be done in caissons under pressure to keep water from flooding the excavations. This was a major factor during construction of Eads Bridge, when 13 workers died from what was then a mysterious illness, and later during construction of the Brooklyn Bridge, where it incapacitated the project leader Washington Roebling.
Nitrogen is not the only breathing gas that causes DCS. Gas mixtures such as trimix and heliox include Helium, which can also be implicated in decompression sickness.
Helium both enters and leaves the body faster than nitrogen and for long dives, of around 3 hours or more, the body almost reaches saturation of Helium. For such dives, the decompression is shorter than for nitrogen based breathing gases (such as air).
There is some debate as to the decompression effects of helium for shorter dives. Most divers do longer decompressions, whereas some groups like the WKPP have been pioneering the use of shorter decompression times by including deep stops.
Helium decompression can be significantly accelerated by breathing Nitrox or pure oxygen, if in very shallow water, during the decompression phase of the dive.
Signs and symptoms of DCS range from skin rashes, extreme fatigue, joint pain, visual disturbances, balance disturbances, breathing difficulties, lack of strength, numbness, paralysis, unconsciousness and death. Symptoms indicating impairment of the central nervous system point to a serious injury. Joint pain, typically in the elbow or knee, pain is experienced from that joint. The pain may be reduced by bending the joint to find a more comfortable position. There are other terms describing other symptoms, such as, the "chokes", the "niggles" and the "staggers".
Recompression is the only effective treatment for severe DCS, although rest and oxygen applied to lighter cases can be effective. Normally this is carried out in a recompression chamber. A high-risk alternative is in-water recompression.
Oxygen first aid treatment is useful for suspected DCS casualties or divers who have made fast ascents or missed decompression stops. Most fully closed-circuit rebreathers can deliver sustained, high concentrations of oxygen- rich breathing gas and could be used as an alternative to pure, open circuit oxygen.
This is an Article on Decompression sickness. Page Contains Information, Facts Details or Explanation Guide About Decompression sickness Avoiding decompression sickness
decompression sickness is not an exact science. Accidents can occur after relatively shallow and short dives. To reduce the risks, divers should avoid long and deep dives and should ascend slowly. Also, dives requiring decompression stops and dives with less than a 16 hour interval since the previous dive increase the risk of DCS. There are many additional risk factors, such as, age, obesity, fatigue, use of alcohol, dehydration and a patent foramen ovale. In addition, flying at high altitude less than 24 hours after a deep dive can be a precipitating factor for decompression illness.
History
Helium
Signs and Symptoms
Treatment