Decompression sickness in breath-hold divers: A review

Abstract

Although it has been generally assumed that the risk of decompression sickness is virtually zero during a single breath-hold dive in humans, repeated dives may result in a cumulative increase in the tissue and blood nitrogen tension. Many species of marine mammals perform extensive foraging bouts with deep and long dives interspersed by a short surface interval, and some human divers regularly perform repeated dives to 30-40 m or a single dive to more than 200 m, all of which may result in nitrogen concentrations that elicit symptoms of decompression sickness. Neurological problems have been reported in humans after single or repeated dives and recent necropsy reports in stranded marine mammals were suggestive of decompression sickness-like symptoms. Modelling attempts have suggested that marine mammals may live permanently with elevated nitrogen concentrations and may be at risk when altering their dive behaviour. In humans, non-pathogenic bubbles have been recorded and symptoms of decompression sickness have been reported after repeated dives to modest depths. The mechanisms implicated in these accidents indicate that repeated breath-hold dives with short surface intervals are factors that predispose to decompression sickness. During deep diving, the effect of pulmonary shunts and/or lung collapse may play a major role in reducing the incidence of decompression sickness in humans and marine mammals.

Presumed Arterial Gas Embolism After Breath-Hold Diving in Shallow Water

“…6 These events are significantly correlated with the severity of dive exposure, including dive depth, dive time, and short surface intervals. 7,8 For unknown reasons a sparing of the spinal cord in cases of breath-hold diving related DCI has been observed. 5 Another characteristic of DCI after breath-hold diving was that neurologic symptoms typically resolved within several hours, even without treatment.…”

“…5 Possible pathomechanisms have been suggested with DCS rather than AGE being the most plausible etiology. 8,9 However, explanatory models do not satisfactorily apply to breath-hold diving in shallow water. 10 Therefore, different mechanisms or additional risk factors need to be assumed in our patients.…”

Acute Neurologic Changes in an Otherwise Healthy Young Adult

“…A spontaneous bleed would show rapid signs of deterioration. 1,2,4,7 DCS may be as subtle as unusual tiredness or aching joints (especially joints that have been previously injured) or a mottled skin rash. It may also present dramatically with unconsciousness, seizures, paralysis, shortness of breath, or death.…”

“…This practice displaces carbon dioxide and hyperoxygenates the brain. [1][2][3][4][5] Factors that contribute to the development of dysbarism include repeated dives that are greater than 70 ft, especially if subsequent dives are deeper; an ascent where too much energy is expended; shortened surface intervals between dives, which should be at least twice the dive length time; and predive hyperinflation. [1][2][3][4]6 Other questions to ask include activities over the previous 72 hours pre-and postdive (especially flying).…”

“…Paraplegia is not uncommon. 1,2,4 7. If symptoms are unrelieved by oxygen and intravenous fluids, consult with a diving medicine specialist at the closest hyperbaric chamber facility.…”