Dangers of scuba diving, by its nature, either with or without scuba, involves certain respiratory patterns that are potentially hazardous under water. Hyperventilation and breath holding, for example, may initiate cardioinhibitory and vasodepressor reflexes capable of causing syncope, cardiac arrhythmias, and arrest. Bradycardia, apparently more pronounced than might occur simply from breath- holding and the head-down position, and various cardiac arrhythmias have also been reported during breath-hold diving.
Vigorous hyperventilation by skin divers prior to a dive may lead to lowering of arterial Pco2 sufficient to abolish the stimulus to breathe and may allow dangerous levels of hypoxemia to develop. In addition, compression of air within the lungs during descent may maintain adequate alveolar Po2 levels despite a diminishing oxygen supply. Distress from air hunger may not occur because alveolar Pco2 has been reduced by prior hyperventilation. During ascent the expansion of the air remaining within the lungs results in a sharp reduction in Po2, possibly to levels that result in loss of consciousness before the diver is able to reach the surface, and he may drown unless help is available for prompt rescue and resuscitation.
Why Scuba Diving Hazards Is Painful,If you Don’t Care
Divers using properly functioning open-circuit scuba are unlikely to experience hypoxia if they restrict their dives to well within the limits of their air supply. The rate of air utilization increases in proportion to the increase in absolute pressure when using open-circuit scuba. Total duration of air supply is for example, only one-third as long at 66 feet as at the surface. Increased utilization from heavy exertion causes a proportionately greater expenditure of air.
The availability of scuba has enabled large numbers of untrained people to enter an unfamiliar and hostile environment previously restricted to trained professional divers. The increasing number of serious diving accidents attests to a general lack of understanding of basic underwater principles. As in any sport, accidents are unavoidable, but most scuba-diving casualties can be prevented.The greatest medical problem is education of those who participate in this sport. Physicians in almost any locality may now be called upon to manage a diving emergency. Excellent publications concerning this subject, such as the United States Navy Diving Manual and others, should be available for this purpose.