Al­so known as The Bends and Cais­son Dis­ease, De­com­pres­sion Sick­ness is an ill­ness that can af­fect divers or oth­er peo­ple (such as min­ers) who are in a sit­u­a­tion that in­volves pres­sure rapid­ly de­creas­ing around the body. DCS, as it is com­mon­ly known, is caused by a build up of ni­tro­gen bub­bles in the body. When we breathe, ap­prox­i­mate­ly 79 per cent of the air we're breath­ing is ni­tro­gen. As we de­scend in wa­ter, the pres­sure around our bod­ies in­creas­es, caus­ing ni­tro­gen to be ab­sorbed in­to our body tis­sues.

This is not ac­tu­al­ly harm­ful and it's quite pos­si­ble for the body to con­tin­ue to ab­sorb ni­tro­gen un­til it reach­es a point called sat­u­ra­tion, which is the point at which the pres­sure in the tis­sues equals the sur­round­ing pres­sure. The prob­lem aris­es when this pres­sure needs to be re­leased. In or­der to re­lease the ni­tro­gen slow­ly from the body, a div­er must as­cend slow­ly and car­ry out de­com­pres­sion stops if nec­es­sary. This al­lows the ni­tro­gen to slow­ly seep out of the body tis­sues and ei­ther im­me­di­ate­ly re­vert to be­ing a gas, or to be­come tiny harm­less bub­bles which will even­tu­al­ly re­vert to gas.

This process is called "Off-gassing" and is nor­mal­ly car­ried out through the lungs.

If a div­er as­cends too fast and the ni­tro­gen es­capes the body tis­sue too quick­ly it be­comes bub­bles in the body and this leads to De­com­pres­sion Sick­ness. The bub­bles must nor­mal­ly be on the ar­te­r­i­al side of the cir­cu­la­to­ry sys­tem to be harm­ful-they are usu­al­ly harm­less on the ve­nous side.

Types of de­com­pres­sion sick­ness

Type I De­com­pres­sion Sick­ness is the least se­ri­ous form. It nor­mal­ly in­volves on­ly pain in the body and is not im­me­di­ate­ly life threat­en­ing. It is im­por­tant to note that symp­toms of Type I De­com­pres­sion Sick­ness may be warn­ing signs of more se­ri­ous prob­lems.

Type II De­com­pres­sion Sick­ness is the most se­ri­ous and can be im­me­di­ate­ly life-threat­en­ing. The main ef­fect is on the ner­vous sys­tem.

Oth­er forms of de­com­pres­sion sick­ness

Ex­treme tired­ness is very com­mon in cas­es of De­com­pres­sion Sick­ness and can some­times be the on­ly symp­tom present. It is not known what caus­es this, but you should be aware that ex­treme fa­tigue could be a sign of more se­ri­ous prob­lems. It is al­so pos­si­ble for De­com­pres­sion Sick­ness to oc­cur in the in­ner-ear. This is caused by bub­bles form­ing in the cochlea's per­i­lymph dur­ing de­com­pres­sion. The re­sult can be hear­ing loss, dizzi­ness, ring­ing of the ears, and ver­ti­go.

Risk fac­tors

Every div­er has a dif­fer­ent lev­el of risk of De­com­pres­sion Sick­ness. Many risk fac­tors are still not ful­ly un­der­stood, but there are a few ba­sic fac­tors that doc­tors agree in­crease the chance of de­vel­op­ing De­com­pres­sion Sick­ness:

• Body­fat: The the­o­ry is that ni­tro­gen ab­sorbs more eas­i­ly in­to fat, so an over­weight div­er is at a greater risk of de­com­pres­sion sick­ness.

• Ex­er­cise: In­ter­est­ing­ly, ex­er­cise has both a pos­i­tive and neg­a­tive ef­fect. Ex­er­cise at least 12 hours be­fore a dive seems to pro­duce pro­teins that pro­tect the body and de­crease the risk of De­com­pres­sion Sick­ness. On the oth­er hand, ex­er­cise less than 12 hours be­fore a dive can raise the num­ber of gas mi­cronu­clei on which bub­bles form and this in­creas­es the risk of De­com­pres­sion Sick­ness. Ex­er­cise im­me­di­ate­ly af­ter a dive in­creas­es the risk of bub­bles form­ing as blood pres­sure is in­creased, and bub­bles can more eas­i­ly be trans­ferred from the ve­nous to the ar­te­r­i­al side of the cir­cu­la­to­ry sys­tem.

• Gen­der: The­o­ret­i­cal­ly women should have a high­er risk of De­com­pres­sion Sick­ness due to the fact that women typ­i­cal­ly have a high­er body-fat con­tent. How­ev­er, this has not been proven in stud­ies and it's pos­si­ble that gen­der does not af­fect the chances of suf­fer­ing from De­com­pres­sion Sick­ness.

• Fit­ness: Fit­ness def­i­nite­ly de­creas­es the risk of De­com­pres­sion Sick­ness. A fit­ter body is able to tol­er­ate more phys­i­cal stress.

• De­hy­dra­tion: De­hy­dra­tion caus­es less blood to be avail­able for gas ex­change, which makes it more dif­fi­cult for the body to off-gas, in­creas­ing the risk of De­com­pres­sion Sick­ness.

• Al­co­hol: Con­sum­ing al­co­hol be­fore or af­ter a dive ac­cel­er­ates cir­cu­la­tion, which helps tis­sues to load with gas. Al­co­hol al­so di­lates cap­il­lar­ies which can in­crease the rate of ni­tro­gen re­leased.

• Car­bon Diox­ide: Im­prop­er breath­ing can lead to el­e­vat­ed lev­els of car­bon diox­ide which in­ter­feres with the bod­ies abil­i­ty to trans­port gas.

• Patent Fora­men Ovale (PFO) - Hole in the Heart: It has been found that a large pro­por­tion of divers who suf­fered from De­com­pres­sion Sick­ness had a PFO.