Critical Care in Diving MedicineMostafa Adbullah Mohammed Abdullah
AbstractSUMMARY I n all diving operations, safety is the primary consideration. One key to safety is a clear understanding of the physics of diving. Physics is the field of science dealing with matter and energy and their interactions. The principles of physics provide the keystone for understanding the reasons for employing various diving procedures and the operation of associated equipment. Some of the major physical hazards are related to the effects of pressure. At all depths, the diver must compensate for the pressure exerted by the atmosphere, by the water, and by the gases being used for breathing under water. This compensation must always be thought of in terms of attaining and maintaining a balance between the pressure inside the body and the external pressure. Gases are subject to three interrelated factors: pressure, volume, and temperature. A change in one results in a measurable change in the others. The relationships among these three factors have been defined as the gas laws. Knowledge of these laws is important to the diver because they influence the duration of the air supply and affect the gas containing spaces in the body such as the ears, sinuses and lungs. Body heat is a form of energy, the level of which can be estimated by measuring the body temperature. Heat energy flows from areas of high temperature to areas of low temperature. The heat transfer which is important to the diver is thermal conduction (or transfer of heat by direct contact), and may cause hypothermia (low body temperature). Since normal body temperature is 37°C and oceanic water temperature is commonly 12–20°C, the diver is almost always immersed in water at a lower temperature than his body. Usually the water temperature decreases with depth. Cold water creates a strong temperature gradient along which heat flows from the body, resulting in a continuous heat loss into the water. This process is assisted by water having a high capacity to conduct and absorb heat. Since the maintenance of normal body temperature is essential for physiological functioning. As a consequence, it is often necessary to employ a thicker suit, a dry suit, or a hot water suit to compensate for extended exposures to cold water. Water covers over 70% of the earth, has varying depths and temperatures and contains much of the earth’s resources. Head-out water immersion (HOWI) or submersion at various depths (diving) in water of thermoneutral (TN) temperature elicits profound cardiorespiratory, endocrine, and renal responses. The translocation of blood into the thorax and elevation of plasma volume by autotransfusion of fluid from cells to the vascular compartment lead to increased cardiac stroke volume and output and there is a hyperperfusion of some tissues. Pulmonary artery and capillary hydrostatic pressures increase causing a decline in vital capacity with the
|Other Titles||الحالات الحرجة في طب الغوص||Issue Date||2016||URI||http://research.asu.edu.eg/handle/12345678/2985|
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