Hyperbaric oxygen for decompression sickness: 2021 update

RATIONALE Decompression sickness (DCS, “bends”) is caused by the formation of bubbles in tissues and/or blood when the sum of dissolved gas pressures exceeds ambient pressure (supersaturation) [1]. This may occur when ambient pressure is reduced during: ascent from a dive; rapid ascent to altitude in an unpressurized aircraft or hypobaric chamber; loss of cabin pressure in an aircraft [2]; and during space walks. In diving, compressed-gas breathing is usually necessary, although occasionally DCS has occurred after either repetitive or very deep breath-hold dives [3,4]. DCS can rarely occur in hyperbaric tenders after decompression from standard hyperbaric treatment at 2.2-2.5 atmospheres absolute (ATA) [5]. Although arterial gas embolism due to pulmonary barotrauma can occur after a dive as shallow as 1 meter, the threshold depth for DCS in compressed-gas diving is around 20 feet of seawater (fsw) [6]. DCS after a dive can be provoked by mild altitude exposure, such as a commercial aircraft flight [7,8], but without a preceding dive the threshold altitude for DCS occurrence due to acute altitude exposure is generally 18,000-20,000 feet [9,10]. Most cases of altitude DCS manifest as limb pain [11-13]. More serious manifestations of altitude DCS (e.g., neurological, cardiorespiratory DCS: “chokes”) have been described but typically at altitudes greater than 25,000 feet for periods exceeding one hour [2,14- 18]. When neurological symptoms occur, cerebral manifestations seem to occur more frequently than after diving [19]. Acute neurological manifestations after altitude exposure to 5,000-8,000 feet in commercial aircraft have rarely occurred due to arterial gas embolism caused by expansion of pre-existing bullae [20].

DOI: 10.22462/03.04.2021.11