Bali Diving
Nitrox is mainly used in scuba diving to reduce the proportion of nitrogen in the breathing gas mixture. Reducing the proportion of nitrogen by increasing the proportion of oxygen reduces the risk of decompression sickness, allowing extended dive times without increasing the need for decompression stops. Nitrox is not a safer gas than compressed air in all respects: although its use reduces the risk of decompression sickness, it increases the risk of oxygen toxicity and fire.
Breathing nitrox is not thought to reduce the effects of narcosis, as oxygen seems to have equally narcotic properties under pressure as nitrogen; thus one should not expect a reduction in narcotic effects due only to the use of nitrox. Nonetheless, there remains a body of the diving community that insists that they feel reduced narcotic effects at depths breathing nitrox. This may be due to a dissociation of the subjective and behavioral effects of narcosis. However, it should be noted that because of risks associated with oxygen toxicity, divers tend not to utilize nitrox at greater depths where more pronounced narcosis symptoms are more likely to occur. For a reduction in narcotic effects trimix or heliox gases which also contain helium are generally used by divers.
There is anecdotal evidence that the use of nitrox reduces post-dive fatigue, particularly in older and or obese divers; however the only known double-blind study to test this found no statistically significant reduction in reported fatigue. There has, however, been some suggestion that post dive fatigue is due to sub-clinical decompression sickness (DCS) (i.e. micro bubbles in the blood insufficient to cause symptoms of DCS); the fact that the study mentioned was conducted in a dry chamber with an ideal decompression profile may have been sufficient to reduce sub-clinical DCS and prevent fatigue in both nitrox and air divers.
Further studies with a number of different dive profiles, and also different levels of exertion, would be necessary to fully investigate this issue. For example, there is much better scientific evidence that breathing high-oxygen gases increase exercise tolerance, during aerobic exertion. Though even moderate exertion while breathing from the regulator is a relatively uncommon occurrence in scuba, as divers usually try to minimize it in order to conserve gas, episodes of exertion while regulator-breathing do occasionally occur in sport diving. Examples are surface-swimming a distance to a boat or beach after surfacing, where residual "safety" cylinder gas is often used freely, since the remainder will be wasted anyway when the dive is completed. It is possible that these so-far un-studied situations have contributed to some of the positive reputation of nitrox.
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