# Diving - 1 SPORT DIVING I. PRESSURE EFFECTS Pressure of air...

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1 SPORT DIVING I. PRESSURE EFFECTS Pressure of air at sea level = one atmosphere or 760 mm Hg The weight of a column of water directly above a diver's body (hydrostatic pressure) increases directly with increasing depth. The pressure increases by one atmosphere for each additional 33 ft. of depth. 33 ft. = 2.0 atmosphere 66 ft. = 3.0 " Because the tissues of the body are largely water, they are non-compressible. However, the body contains air cavities - lungs, respiratory passages, sinus and middle ear spaces - where volume and pressure will change with increases or decreases in diving depth. Boyle's Law - the volume of any gas varies inversely with the pressure on it (ie) if the pressure is doubled, volume is halved. II. SNORKELING AND BREATH-HOLD DIVING A. Snorkeling There are limits to snorkel size because: 1. Pressure effects - when breathing through a snorkel, the diver must inspire air at atmospheric pressure. At a depth of only 3 ft., the compressive force of water against the chest cavity is so large that the inspiratory muscles are usually unable to overcome external pressure and expand the thoracic cavity. 2. Increase in pulmonary dead space: Normal anatomical dead space = 150 ml. Dead space of regular snorkel = 150 ml. V A = V T - V D At rest: 350 ml = 500 ml - 150 ml With snorkel: 350 ml = 650 ml - 300 ml

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2 As snorkel size increases, V D increases and it becomes more difficult to maintain V A . B. Breath Hold Diving As the skin diver descends, the air in the lungs is compressed Æ lung squeeze. When lung volume is compressed below residual volume Æ lung damage occurs as blood is sucked from the pulmonary capillaries into the alveoli "Normal" maximal breath holding time after a maximal inspiration of ambient
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## This note was uploaded on 02/01/2010 for the course KIN 142 taught by Professor Asmundson during the Spring '09 term at Simon Fraser.

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Diving - 1 SPORT DIVING I. PRESSURE EFFECTS Pressure of air...

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