![]() On mixed-gas operations, strict attention must be paid to gas analysis, cylinder lineups and predive checkout procedures. In open-circuit scuba and helmets, hypoxia is unlikely unless the supply gas has too low an oxygen content. Because of its insidious nature and potentially fatal outcome, preventing hypoxia is essential. Details of treatment are covered in volume 3.ģ-5.1.4 Preventing Hypoxia. For surface-supplied mixed-gas divers, it involves shifting the gas supply to alternative banks and ventilating the helmet or chamber with the new gas. For scuba divers, this usually involves bringing the diver to the surface. If a victim of hypoxia is given gas with adequate oxygen content before his breathing stops, he usually regains consciousness shortly and recovers completely. Hypoxia's interference with brain functions produces not only unconsciousness but also failure of the breathing control centers. A diver suffering from severe hypoxia must be rescued promptly. Inability to perform delicate or skill-requiring tasksģ-5.1.3 Treating Hypoxia. Lack of concentration Lack of muscle control None of these symptoms, however, are sufficient warning and very few people are able to recognize the mental effects of hypoxia in time to take corrective action. If hypoxia develops gradually, symptoms of interference with brain function will appear. The same signs could be caused by prolonged exposure to cold water. This may not be noticed by the diver and often is not a reliable indicator of hypoxia, even for the trained observer at the surface. ![]() ![]() A general blueness (cyanosis) of the lips, nail beds and skin may occur with hypoxia. A small increase in breathing may also occur. When hypoxia develops, pulse rate and blood pressure increase as the body tries to offset the hypoxia by circulating more blood. He is much more fortunate than a diver who gradually uses up the oxygen in a closed-circuit rebreathing rig and has no warning of impending unconsciousness. A diver who loses his air supply is in danger of hypoxia, but he immediately knows he is in danger and usually has time to do something about it. It can occur unexpectedly, making it a particularly serious hazard. There is no reliable warning of the onset of hypoxia. Unconsciousness and death can occur from brain hypoxia before the effects on other tissues become very prominent. Brain tissue is by far the most susceptible to the effects of hypoxia. Refer to paragraph 3-7 for more information on hyperventilation and its hazards.ģ-5.1.2 Symptoms of Hypoxia. Extended breathholding after hyperventilation is not a safe procedure. Hyperventilation lowers the carbon dioxide level in the body below normal (a condition known as hypocapnia) and may prevent the control mechanism that stimulates breathing from responding until oxygen tension has fallen below the level necessary to maintain consciousness. ■ Hyperventilation followed by breathholding, which can lead to severe hypoxia. Edema can interfere with gas exchange at the capillary/tissue areas, and carbon monoxide poisoning can interfere with oxygen utilization at the cellular level. Physiological problems such as anemia and inadequate blood flow that interfere with blood transportation of oxygen. Pneumothorax or paralysis of the respiratory muscles from spinal cord injury.ĭecreased oxygen exchange at the alveoli/capillary membrane caused by accumulation of fluid in the tissues (edema), a mismatch of blood flow and alveolar ventilation, lung damage from near-drowning or smoke inhalation, or "chokes" or bronchospasm from lung irritation due to showers of bubbles in the circulation. For divers, interference of oxygen delivery can be caused by:Įquipment problems such as low partial pressure of oxygen in the breathing mix, inadequate gas flow, inadequate purging of breathing bags in a closed oxygen UBA like the LAR V, or blockage of the fresh gas injection orifice in a semiclosed-circuit UBA.īlockage of all or part of the pulmonary system air passages by vomitus, secretions, water, foreign objects, or pneumomediastinum. The causes of hypoxia vary, but all interfere with the normal oxygen supply to the body. On ascent, however, the diver would rapidly experience hypoxia if the oxygen percentage were not increased.ģ-5.1.1 Causes of Hypoxia. For example, 5 percent oxygen would render a ppO2 of 0.20 ata for a diver at 100 fsw. In diving, a lower percentage will suffice as long as the total pressure is sufficient to maintain an adequate ppO2. Consciousness is usually lost at about 0.10 ata and at much below this level, permanent brain damage and death will probably occur. If the ppO2 goes as low as 0.11 ata at the surface, most individuals become hypoxic to the point of being nearly helpless. Is ample, but a drop to 0.14 ata causes the onset of hypoxic symptoms on the surface. Oxygen Consumption and RMV at Different Work Rates.
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