TRANSIENT AND PERMANENT AFTER-EFFECTS OF EXPOSURE TO OXYGEN AT HIGH PRESSURE

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Abstract
Albino rats were exposed to O2 at 65 pounds pressure for periods of about 20 mins. singly or successively 3 times per day to study recovery reactions. The duration of each exposure and the total number of exposures were detd. by the severity of the reaction desired, and the individual susceptibility which varied widely. The possibility of bubble formation during decompression was eliminated. Successive exposures so spaced as to permit symptomatic recovery following each exposure had an additive effect which augmented and prolonged the subsequent acute reactions which were manifestations of C.N.S. involvement. This additive effect indicated the persistence of sub-symptomatic alterations after apparent recovery. Chronic effects, characterized by spastic motor dysfunction involving limbs and trunk, developed more gradually. The spacing of successive exposures was an important determinant in the induction of chronic effects, which frequently appeared after 6-10 exposures and rarely after 1 exposure. The chronic effects were predominantly permanent. The acute reactions appeared to be best explained as due to the influence of accumulated endogenous CO2 in the tissues, increased tissue acidity and a direct action of O2 at high pressure on tissue enzyme systems; the chronic effects as due to irreversible tissue damage induced by the above factors, particularly in the C.N.S.