Decompression sickness in breath-hold divers: A review FRE ´ DE ´ RIC LEMAITRE 1 , ANDREAS FAHLMAN 2 , BERNARD GARDETTE 3 ,& KIYOTAKA KOHSHI 4 1 Faculty of Sport Sciences, University of Rouen, Mont-Saint-Aignan, France, 2 Department of Zoology, University of British Columbia, Vancouver, Canada, 3 COMEX SA, Marseille, France and 4 Division of Hyperbaric Medicine and Department of Neurosurgery, University Hospital of Environmental Health, Kitakyushu, Japan (Accepted 16 June 2009) 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. Keywords: Bubbles, mammal, human, N 2 , diving Introduction Snorkelling and breath-hold diving are enjoyed by millions of people around the world. Although most people dive to shallow depths for short durations, spear-fishermen and competitive breath-hold divers routinely perform repeated dives to depths greater than 30 m for more than a minute (Schipke, Gams, & Kallweit, 2006). While human breath-hold per- formances are well below those of marine mammals, depth and dive durations have been increased markedly in the last few years. The current depth record is 214 m and breath-hold durations of more than 10 min in static, shallow dives have been recorded. Elite breath-hold divers commonly per- form dives lasting 3–3.5 min, with very rapid descent and ascent rates. These factors raise questions about the health risks involved, as such dive practices may cause loss of consciousness from hypoxia during ascent, barotraumas, and decompression sickness (McCrory, Matser, Cantu, & Ferrigno, 2004). Decompression sickness arises mainly from gas phase separation in body tissues resulting in bubble formation. The bubbles can cause a variety of pathological signs and symptoms depending on the where they form. Arterial gas embolism occurs when lung tissue ruptures during ascent, allowing gas bubbles to enter the arterial circulation, and forming emboli that generally target the brain (Francis & Mitchell, 2002). While decompression sickness is to a large extent a function of the amount of inert gas taken up by tissues during a dive, arterial gas embolism is not necessarily associated with increased gas loading. The term ‘‘decompression illness’’, therefore, refers to any disease that occurs during decompression and includes decompression sick- ness, arterial gas embolism, and other gas-related forms of barotrauma of ascent. Despite performing bouts of repeated long and deep dives interspersed with short surface intervals, marine mammals have not been reported to experi- ence decompression sickness during natural dives Correspondence: F. Lemaitre, Faculte ´ des Sciences du Sport, CETAPS, EA 3832, Universite ´ de Rouen, Mont-Saint-Aignan cedex 76821, France. E-mail: frederic.lemaitre@univ-rouen.fr Journal of Sports Sciences, December 2009; 27(14): 1519–1534 ISSN 0264-0414 print/ISSN 1466-447X online Ó 2009 Taylor & Francis DOI: 10.1080/02640410903121351