Treatment of dental emergencies.

In sea water, for each 10-m (33-ft) increase in depth, the ambient pressure of a diver increases by 1 atm (760 mm Hg). Recreational divers may expose themselves to depths as great as 40 m (130 ft). Commercial and military divers may reach considerably greater depths, and experimental dives have been made in the open ocean to depths exceeding 500 m and in a hyperbaric chamber to a pressure equivalent to a depth of 701 m. 1,56,86 The changes in pressure to which a diver is subjected has four major effects that may cause pathophysiologic events: (1) changes in the volumes of gas-containing spaces in the body, causing barotrauma; (2) increased partial pressures of component gases, including contaminants, in the breathing mixture; (3) formation of gas bubbles in the blood and tissues; and (4) the effect of hydrostatic pressure per se on the central nervous system (CNS). These changes can be influenced further by the effects of immersion, which causes a redistribution of blood from the extremities into the central circulation. This engorges pulmonary vessels, causing a reduction in static lung volumes 2 and a promotion of airway closure. 32,126 Immersion also increases cardiac preload. 24,128