Enriched air
nitrox diving has been conducted to shorten
decompression time as well as to reduce risks of
decompression sickness. Nine volunteer divers served as subjects for
nitrox (-a: 60% N2 and 40% O2, and -b: 67.5% N2 and 32.5% O2) and air chamber dives of 20 m/60 min, 30 m/60 min and 40 m/60 min. Venous gas emboli (VGE) were examined after surfacing in a series of
nitrox dives and of air dives to compare the risks of
decompression sickness (DCS). Three divers as a group were compressed in a chamber for each dive.
Decompression was carried out according to the Norwegian Navy
nitrox decompression tables for the
nitrox dives, and for the air dives the Japanese Ministry of Labor tables were used.
Decompression time was much shorter in
nitrox diving than in air dives for the same dive profiles. All of
nitrox-a and air divers showed no VGE nor DCS symptoms after surfacing of 20 m dives. In case of 30 m dives, VGE appeared in one diver (33%) without DCS symptoms in
nitrox-a dive but no VGE nor DCS in
nitrox-b dive, whereas for the same air dives two subjects (66%) had VGE and DCS symptoms. When the depth was increased to 40 m in the
nitrox dive,
nitrox-b did not show both VGE and DCS, while the air dive showed one VGE and one DCS. These results suggest that the
nitrox dive with suitable
decompression schedule reduces the risks of DCS as well as shortening
decompression obligation.