EEG and sleep disturbances during dives at 450 msw in helium-nitrogen-oxygen mixture.

To study the effects of nitrogen addition to the breathing mixture on sleep disturbances at pressure, two dives were performed in which helium-nitrogen-oxygen mixture was used up to 450 m sea water (msw). In total, sleep of 12 professional divers was analyzed (i.e.

Psychophysiological reactions in humans during an open sea dive to 500 m with a hydrogen-helium-oxygen mixture.

Six commercial divers were investigated for neurological and psychosensorimotor responses during an open sea dive to 500 m with a hydrogen-helium-oxygen mixture containing 49% hydrogen. Results showed only moderate neurological symptoms of high-pressure nervous syndrome, whereas the narcotic effect of hydrogen was detectable, as investigated by psychosensorimotor tests. Nevertheless, the divers successfully carried out the main purpose of the operational dive, which was to prove the feasability of such diving methods by connecting specific elements of an offshore oil installation.

Sleep organization in man during long stays at 30 and 40 bar in a helium-oxygen mixture.

Sleep organization was studied during 5 dives with long holds (from 6 to 15 days) at 30 and 40 bar in a helium-oxygen mixture. In total, 16 professional divers participated in these saturation dives; 337 nights were analyzed. Sleep was disrupted by compression and the stay at pressure, but the disturbances were greater at 40 bar than at 30 bar.

Effects of a H2-He-O2 mixture on the HPNS up to 450 msw.

A H2-He-O2 mixture with 54 to 56% hydrogen was studied with 6 subjects (professional divers) during 2 dives to 450 m. The 38-h compression was the same as that used with other types of breathing mixtures (He-O2 and He-N2-O2). The results obtained during compression and during the stay at 450 m in H2-He-O2 show that the EEG changes (increase of theta activities in the anterior regions of the skull, decrease of alpha activities) are similar to those found with other respiratory mixtures.

Sleep disturbances in man during different compression profiles up to 62 bars in helium-oxygen mixture.

Studies of sleep organization of 8 subjects were performed during 4 dives between 500 and 610 msw (51 and 62 bar) in a helium-oxygen mixture. The results of the 156 sleep records showed that sleep was disrupted from 30 bar: awake periods and stages I and II increased, stages III and IV and REM periods decreased. These disturbances, which were more intense with fast compression and recovered during decompression, can be considered as further symptoms of the high pressure nervous syndrome (HPNS).