PHOTOELECTRIC EARPIECE RECORDINGS AND OTHER PHYSIOLOGIC VARIABLES AS OBJECTIVE METHODS OF MEASURING THE INCREASE IN TOLERANCE TO HEADWARD ACCELERATION (+GZ) PRODUCED BY PARTIAL IMMERSION IN WATER. TECHN DOCUM REP AMRL-TDR-63-106.

Abstract : The protection against the effects of headward acceleration afforded the human by his immersion in water to the level of the xyphoid and to the third rib at the sternum has been assayed in 15 trained centrifuge subjects. Variations in ear opacity, ear opacity pulse, heart rate, respiration and reaction times to auditory and visual stimuli were recorded continuously in a series of 15 subjects during 15-second exposures to acceleration while seated in a steel tub mounted in the cockpit of the Mayo centrifuge. No systematic alterations in the general pattern, characterized by a period of failure during the first 5 to 10 seconds followed by cardiovascular compensation and recovery from visual symptoms during the latter part of the exposure were observed during immersion in water. The decrements in ear opacity associated with the various degrees of visual impairment were closely similar; however, the decrements in ear opacity pulse and increments in heart rate were significantly less during immersion in water than when in air. (Author)