ABSTRACT

Life underwater exposes the diver to a major rise in ambient pressure of the environment, with physiological changes and problems from the direct effects of pressure on the body. In addition, the diver must be supplied with a mixture of gases to breathe at a pressure equal to ambient pressure, and this can also give rise to other problems. The vasoconstriction occurs in those organs that can utilize anaerobic metabolism such as the skin, muscle, kidneys and gastrointestinal tract. The brain requires a constant supply of oxygen as it relies on oxidative metabolism. The increased central blood volume stretches the atrial receptors and decreases vasopressin secretion and increases atrial natriuretic factor, resulting in diuresis. Gas-containing cavities in paranasal passages are bounded by rigid structures and cannot undergo any volume changes. Nitrogen narcosis can occur because the partial pressure of nitrogen increases when compressed air is used for breathing.