High pressure nervous syndrome: psychometric and clinico-electrophysiological correlations

The high pressure nervous syndrome (h.p.n.s.) was studied in man from clinical, electrophysiological and psychometric viewpoints during a variety of simulated dives to depths deeper than 300 m (between 300 and 610 m), which used different modes of compression and different gas mixtures (Heliox, Trimix). In particular we studied tremor, myoclonia, changes in electroencephalogram and psychometric performance. Three points stemmed from these results. Some h.p.n.s. signs are present whichever technique is used, while others depend on the technique, both in intensity and in quality; so there is a syndrome due to compression, whose effects diminish, and a pressure syndrome, which persists at depth. There are differences between the susceptibility of different individuals, not only concerning h.p.n.s. as a whole, but also each symptom and its evolution at a given constant depth. There are no close correlations between the different symptoms observed.