Journal of Applied Physiology, Vol 63, Issue 5 1919-1925, Copyright © 1987 by American Physiological Society
Occurrence of high-pressure nervous syndrome at constant pressure during change of mixture
J. C. Rostain, M. C. Gardette-Chauffour and R. Naquet
Centre National de la Recherche Scientifique, Faculte de Medecine Nord, Marseille, France.
Three professional divers have performed a dive to 450 msw. From 200 msw
and during the first 64 h on the bottom, they breathed a H2-He-O2 mixture
with 54-56% H2. At this time a switch was performed to a mixture with 30%
H2, and 8 h later a second switch was performed to 0% H2. In the H2-He-O2
mixture the clinical symptoms of high-pressure nervous syndrome (HPNS) were
not present and the electroencephalogram changes were slight. The switch of
the mixture induced an isobaric HPNS of high intensity. Twenty-four hours
later the HPNS decreased, but the clinical symptoms persisted throughout
the stay in the He-O2 mixture. The appearance of isobaric HPNS during the
switch might be due to the disappearance of the narcotic substance which
suppressed or masked the clinical symptoms; it might also be due to the
sudden increase in the partial pressure of He, which was equivalent to a
fast compression.
