Medical Considerations Breathing Gas Mixtures
Air consists of approximately O,CO, and nitrogen gas N. When humans breathe gases that are not normally found in air, or in unique concentrations, the body may or may not be able to respond appropriately. Thus, breathing the gas mixture from a pressurized scuba tank presents unique stressors to the respiratory and circulatory systems of the body.
The term mixed gas refers to any breathing mixture other than air. Mixed-gas diving traditionally refers to diving with mixtures of helium and oxygen known as heliox, air enriched with oxygen known as nitrox, or a blend of oxygen, helium, and nitrogen known as trimix. Nitrogen and helium are not used by the body in respiration; they are inert gases. The two main purposes for using special mixed gases in diving are to be able to a change the inert gas and b control the level.
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Oxygen is always present in diving gases, but it may be a very small fraction of the mixture used for deep dives. It is imperative that the oxygen content of a gas mixture be appropriate for each dive, because is poisonous at high concentrations. Therefore, oxygen management is a major element of diving safety. Inert gases nitrogen, helium, neon, argon, hydrogen are added to scuba tanks to safely lower the oxygen content.
Seven clinical problems are associated with breathing mixed gases: hypoxia, oxygen toxicity, nitrogen narcosis, decompression sickness, bone necrosis, carbon dioxide toxicity, and breathing gas contamination. These medical conditions are described below.
Hypoxia refers to inadequate oxygen delivery to the body’s tissues; this impairs aerobic metabolism. Overwhelmingly, the greatest hazard pertaining to in mixed gases is not having enough of it. Although hypoxia is not a concern for most divers, or a major problem in air diving, mixed- gas diving introduces the possibility of getting a mixture without adequate O. This can result from breathing the wrong mixture, or from breathing the right mixture at the wrong pressure.
Hypoxia may cause debilitation, unconsciousness, and even death in extreme cases. Ironically, hypoxia can delude divers by making them euphoric and unconcerned about their welfare.