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A Journal on Sports Medicine

Official Journal of the Italian Sports Medicine Federation
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Medicina dello Sport 2002 June;55(2):131-6

language: Italian

Breath-hold diving

Schiavon M.

Servizio di Medicina dello Sport, Azienda ULSS 16, Padova


Ever since ancient times, man has engaged in underwater diving in conditions of apnea in the search for food or riches or for reasons of war. Quite apart from limitations involving the storage of oxygen (O2) while still on the surface, modifications related to underwater immersion (hyperbarism) and the variations that immersion produces from the physical and physiological points of view must be added. The body of the sub during his stay under water is compressed by an outside pressure equal to that of the environment (sum of the external and water pressures) and gaseous volumes vary in accordance with external and water pressures) and gaseous volumes vary in accordance with Boyles’ law (P×V=constant). The diminution in gas volume corresponds to a proportional increase in pressure in relation to the absolute pressure and percentage of gas in the mixture (Dalton’s law). The apnea breakage point depends on individual variables and arterial pressures (AP) of O2 and carbon dioxide. The black-out risk increases during the return to the surface owing to the drastic drop in the AP of in the final metres (shallow-water blackout) and wheter or not the apnea is preceded by hyperventilation. Study of the modifications induced on the human organis, including the higher intrathoracic blood volume (blood shift) and thez influence of compensation techniques, makes it possible to approach immersion in apnea with a greater degree of safety compared to the past, but prevention plays a fundamental role in the reduction of the risk and the rules of prevention must be thoroughly understood by both the sports physician and by the underwater swimmer too.

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