Editing Decompression sickness (section)

=== Individual ===
[[File:Atrial septal defect-en.png|thumb|alt=Diagram of the four chambers of the heart. There is a gap in the wall between the upper-left and upper-right chambers|Atrial septal defect (PFO) showing left-to-right shunt. A right-to-left shunt may allow bubbles to pass into the arterial circulation.]]

The following individual factors have been identified as possibly contributing to increased risk of DCS:

* [[dehydration]]&nbsp;– Studies by Walder concluded that decompression sickness could be reduced in aviators when the serum surface tension was raised by drinking isotonic saline,{{r|Walder}} and the high surface tension of water is generally regarded as helpful in controlling bubble size.{{r|Fryer}} Maintaining proper hydration is recommended.{{sfn|Lippmann & Mitchell|p=71}} There is no convincing evidence that overhydration has any benefits, and it is implicated in [[immersion pulmonary oedema]].<ref name="UKDMC" />
* [[patent foramen ovale]]&nbsp;– a hole between the atrial chambers of the [[heart]] in the [[fetus]] is normally closed by a flap with the first breaths at birth. In about 20% of adults the flap does not completely seal, however, allowing blood through the hole when coughing or during activities that raise chest pressure. In diving, this can allow venous blood with microbubbles of inert gas to bypass the lungs, where the bubbles would otherwise be filtered out by the lung capillary system, and return directly to the arterial system (including arteries to the brain, spinal cord and heart).{{r|Moon}} In the arterial system, bubbles ([[arterial gas embolism]]) are far more dangerous because they block circulation and cause [[infarction]] (tissue death, due to local loss of blood flow). In the brain, infarction results in [[stroke]], and in the spinal cord it may result in [[paralysis]].{{sfn|Lippmann & Mitchell|p=70}}
* a person's age&nbsp;– there are some reports indicating a higher risk of altitude DCS with increasing age.{{r|38uhms | Fryer}}
* previous injury&nbsp;– there is some indication that recent joint or limb injuries may predispose individuals to developing decompression-related bubbles.{{r|38uhms | Karlsson}}
* [[wikt:ambient|ambient]] temperature&nbsp;– there is some evidence suggesting that individual exposure to very cold ambient temperatures may increase the risk of altitude DCS.{{r|38uhms | Fryer}} Decompression sickness risk can be reduced by increased ambient temperature during decompression following dives in cold water,{{r|Gerth2}} though risk is also increased by ingassing while the diver is warm and peripherally well-perfused, and decompressing when the diver is cold.<ref name="Pollock 2023" />
* body type&nbsp;– typically, a person who has a high body fat content is at greater risk of DCS.{{r|38uhms | Fryer}} This is because nitrogen is five times more soluble in fat than in water, leading to greater amounts of total body dissolved nitrogen during time at pressure. Fat represents about 15–25 percent of a healthy adult's body, but stores about half of the total amount of nitrogen (about 1 litre) at normal pressures.{{r|fatness}}
* alcohol consumption&nbsp;– although [[alcohol (drug)|alcohol]] consumption increases dehydration and therefore may increase susceptibility to DCS,{{r|Fryer}} a 2005 study found no evidence that alcohol consumption increases the incidence of DCS.{{r|leigh2005}}