4. The Underwater World and Diving Physiology

Although considered relatively safe with modern technology, diving and underwater exploration went through perilous milestones from its practices in the early days. Today there are still a number of risks and health consequences associated with underwater exposure. Diving enforces a number of physiological alterations to the human body. Water clearly has different physical properties compared to the atmospheric conditions the human body is used to, and there are significant physiologic effects of both, pressure and immersion. In order to understand and subsequently investigate any physiological changes due to immersion, a fundamental knowledge of underwater physics is required. The physical laws governing the behaviour of gas under pressure are introduced. Nearly all physiological systems are subjected to changes due to the prevailing underwater physics. In this chapter, we discuss the physiology of immersion, high ambient pressure exposure, and exposure to individual gases. The physiology of immersion focuses on the effects of the diving reflex, respiratory implications and thermal considerations for a diver. While the physiology of high pressure exposure includes the effects of pressure on the volume of gas and air spaces in the human body, the physiology of exposure to individual gases has physiological and neurological consequences due to the narcotic and toxic effects of individual gases.