Journal of Applied Physiology, Vol 57, Issue 2 341-350, Copyright © 1984 by American Physiological Society
HPNS of baboons during helium-nitrogen-oxygen slow exponential compressions
J. C. Rostain, B. Gardette, M. C. Gardette-Chauffour and C. Forni
From the results obtained with the experimental series CORASIN (fast
compression with He-N2-O2), a method of compression has been developed for
the baboon (Papio papio) to dive deeper than 600 m. This method utilizes an
exponential compression profile with stages of 40 min every 100 m and with
the introduction of N2 before each stage from 200 m onward to maintain a
concentration of 5.5%. Between 0 and 800 m, this procedure did not produce
myoclonus or epileptic seizures; tremor appeared beyond 400 m (578 +/- 109
m) but remained slight. If N2 was not introduced, the tremor appeared
earlier (266 +/- 52 m) and became severe; between 600 and 800 m, muscular
hypertonus, myoclonus, and muscular cramps occurred. The modifications of
the electroencephalogram were slight; the increase in slow activity did not
exceed 300% with or without N2. Beyond 800 m, the compression procedure
with N2 injections revealed new phenomena. There was a general depression
of EEG activity starting at 800 m; from 1,000 m and deeper, there were
periods of motor disturbances (hypertonus, spasms, and shaking), palpebral
clonus, and eye movements associated with peak EEG activities localized in
the posterior region of the skull that sometimes evolved toward an
epileptic seizure localized in this region. These symptoms differed from
the classical description of high-pressure nervous syndrome, which
comprises an increase in tremor followed by convulsions. These differences
may perhaps be linked to our compression procedure using N2 injection, to
the effect of the pressure itself, or to a combination of the two.
