The causes, mechanisms and prevention of the High Pressure Nervous Syndrome(HPNS)
ASPECTS OF THE HIGH PRESSURE NERVOUS SYNDOME IN HUMANS
ETIOLOGY OF THE HIGH PRESSURE NERVOUS SYNDROME
INCREASED MASS OF DISSOLVED GAS
DIRECT EFFECTS OF HYDORSTATIC PRESSURE
PHARMACOLOGY OF THE HIGH PRESSURE NERVOUS SYNDROME
POSTPONING THE HIGH PRESSURE NERVOUS SYNDROME
The HPNS complex has the following characteristics in a variety of invertebrates and vertebrates, including man. It usually appears at depths somewhat greater than 500fsw. Its symptoms involve primarily the central nervous system, being manifested as neuromuscular disturbances with incoordination, fasciculations and tremors or as disturbances of higher cerebral functions with disorientation, microsleep, and in animals, convulsions. These neurological aberrations can be correlated to some degree with changes in the electroencephalogram. The development and intensity of HPNS is augmented by rapid compression to depth. This symptom complex seems to be manifestation of some aspect of hydrostatic pressure per se, rather than the result of other more indirect effects of increased ambient pressure. The use of excursion diving or anesthetic gases and anticonvulsants may offer some degree of protection against this phenomenon.
In 1965 the Royal Naval Physiological Laboratory(RNPL) Alverstoke, Great Britain, was conducting a series of deep chamber dives to depths of 600 to 800 feet of sea water(fsw). During the course of these dives the subjects were noted to develop coarse tremors involving the extremities or even the whole body, accompanied by nausea, occasional vomiting, dizziness, and vertigo. This condition led to a severe decrement in psychomotor performance, especially in any task requiring manual dexterity, as well as documented decrements in cognitive function (Fig. 1).
Hunter, W. L., Jr., and P. B. Bennett. 1974. The causes, mechanisms, and prevention of the high pressure nervous syndrome. Undersea Biomed. Res. 1(1): 1~28