HIGH ATMOSPHERIC PRESSURES; PHYSIOLOGICAL EFFECTS OF INCREASED AND DECREASED PRESSURE; APPLICATION OF THESE FINDINGS TO CLINICAL MEDICINE

Abstract

The physiol. effects of increased pressure up to 16 atm. or pressure decreased to i atm. fall into 2 groups, (a) effects of pressure per se, and (b) phenomena associated with disturbances in gaseous equilibria. The primary pressure effects are observed if auditory tube and sinus openings are not patent. Obstruction creates a differential pressure between tissues and the adjacent air spaces. Pain is elicited as a diagnostic symptom and is associated with congestion and hemorrhage of membranes lining the occluded spaces. Of the gases absorbed under pressure, (a) atmospheric N2 exerts a narcotic effect, minimized or abolished by the substitution of He; (b) pure O2 at atmospheric pressure elicits symptoms of bronchial irritation or vasomotor spasm if breathed for 6 or 7 hrs., and at a pressure of 4 atm. induces convulsive seizures followed by apparently complete recovery. Observations are presented describing the effects of air emboli formed following decompression from high-pressure at mospheres, the emboli affecting those parts of the body having poor circulation. The clinical significance of the data is discussed particularly with reference to the use of a pressure chamber for diagnostic purposes, and to the value of certain aspects of oxygen therapy.