Dysbarism

Dysbarism is a collective term for all illnesses resulting from changes in ambient pressure that occur at a rate exceeding the capacity of the person to adapt safely. Conditions such as decompression sickness (the bends), arterial gas embolism (AGE), and barotrauma may result.

Decompression illness is a broad term that refers to both decompression sickness and AGE. Although they may share common clinical characteristics and treatment strategies, they are distinct entities with different pathophysiologies.

Diagnosis of decompression sickness or AGE can usually be made on history and examination alone.

Gas coming out of solution and forming bubbles is the prime cause of decompression sickness, whereas gas contraction and expansion causes barotrauma. AGE is usually secondary to pulmonary barotrauma.

Any body tissue can be affected, resulting in a wide variety of clinical presentations.

The unpredictability of ultimate outcome at the onset of any decompression illness requires each case to be managed as a medical emergency.

Recompression is the mainstay of treatment for decompression illness and should be administered as early as possible.

Oxygen administration plays a key role in all cases of decompression illness, both as emergency treatment and during recompression.

Dysbarism broadly describes decompression sickness and barotrauma, including AGE.

Decompression sickness is a complex of symptoms and disease caused by the formation of an excess of bubbles in body tissues. This occurs after an exposure to breathing inert gases at increased pressure, followed by a reduction in environmental pressure, causing bubbles to form as the gas comes out of solution. AGE refers to the presence of gas bubbles in the arterial circulation, often secondary to pulmonary barotrauma. Barotrauma is damage to tissues caused by the pressure-induced expansion and contraction of gases in enclosed spaces. The term decompression illness encompasses decompression sickness and AGE.[1]Mitchell SJ, Bennett MH, Moon RE. Decompression sickness and arterial gas embolism. N Engl J Med. 2022 Mar 31;386(13):1254-64. http://www.ncbi.nlm.nih.gov/pubmed/35353963?tool=bestpractice.com

Nitrogen narcosis is a syndrome of reversible neurological and behavioural changes produced by an increased partial pressure of nitrogen in the body at depth. These changes are present only at depth (during diving) and resolve as the diver ascends.[2]Grover CA, Grover DH. Albert Behnke: nitrogen narcosis. J Emerg Med. 2014 Feb;46(2):225-7. http://www.ncbi.nlm.nih.gov/pubmed/24262058?tool=bestpractice.com ​ If a diver is persistently symptomatic at the surface, nitrogen narcosis is not the cause and alternative diagnosis should be sought.