Decompression sickness, or the bends, is caused by nitrogen bubbles forming in the body. As the pressure reduces during ascent, the volume of gas in the blood and tissues increases. If the ascent is too fast the bubbles may reach a dangerous size and prevent blood flow or damage tissues.

Normally associated with SCUBA diving, decompression sickness (DCS) is also be a risk for repetitive breath-hold diving. This was put forward as early as 1965 but is still not widely acknowledged.

A new study in the Research in Sports Medicine journal compared four groups of breath-hold divers: (1) Japanese and Korean amas and other divers from the Pacific area, (2) instructors at naval training facilities, (3) spear fishers, and (4) free-dive athletes. While the number of amas is likely decreasing, and Scandinavian Navy training facilities recorded only a few accidents, the number of spear fishers suffering accidents is on the rise, in particular during championships or using scooters. A number of free-diving athletes, training for or participating in competitions, are increasingly accident prone as the world record gets deeper and deeper.

The researchers – JD Schipke, E Gams, and O Kallweit of the University Hospital Duesseldorf – report some 90 cases in which DCS occurred after repetitive breath-hold dives. They suggest that breath-hold divers and their advisors and physicians be made aware of the possibility of DCS and of the appropriate therapeutic measures to be taken when DCS is suspected. Because the risk of suffering from DCS increases depending on depth, bottom time, rate of ascent and duration of surface intervals, some approaches to assess the risks are presented. Regrettably, none of these approaches is widely accepted. They propose the development of easily manageable algorithms for the prevention of avoidable accidents.

Journal Reference: Res Sports Med, 2006; 14(3): 163-78.

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