Neurological aspects of diving

Abstract

The nervous system is exposed to many unfamiliar sensations in underwater diving, both from the external environment as well as from the body's internal environment. The underwater environment of a diver is very different from normal: the individual is surrounded by a low-gravity water environment, and the sense of touch is often dulled by a wet-suit and gloves. Sounds are strange and give little indication of direction or distance. The vestibular apparatus has to deal with continually changing body positions in three dimensions, and little sensation of gravity. Visual input is often distorted, reduced or even absent in low visibility diving. In addition to these sensations that can largely be anticipated, unexpected sensations can also arise if the function of the nervous system (e.g. the vestibular apparatus) is upset by changes in the surrounding pressure or temperature. The internal environment of the body is altered in diving because of the effects of breathing gases under pressure. Oxygen, nitrogen and the other gases in air are dissolved in the blood and tissues in larger amounts at increasing depths. The extra nitrogen may disturb normal brain activity. This effect should be anticipated on any deep dive. An effect of nitrogen that is not however usually anticipated is that of decompression sickness, when too rapid a return of the diver to the surface causes the extra nitrogen in solution to form bubbles within the tissues of the body.