CIRCULATORY AND CEREBRAL CHANGES AND PROTECTIVE AIDS DURING EXPOSURE TO ACCELERATORY FORCES

Abstract

Acceleration of the heart rate on exposure to positive g forces shows a proportionality to the intensity and time of application of the force. Carotid (or brachial) blood pressure fell sharply and the femoral pressure rise was more abrupt. All arterial pressure changes showed a linear-relationship to g stresses. The carotid pressure of monkeys under g forces was affected significantly less than that of cats and dogs. A carotid sinus reflex response affecting arterial pressure appears to be initiated 6-8 sec. after starting exposure. Blood flow reductions in the carotid artery occurred within a sec. or so after starting the centrifuge, and showed a proportionality to the acceleration applied. On starting centrifugation, high-voltage low-frequency ("delta") brain waves appeared in 75% of monkeys tested witnin a sec. or so. Attempts to produce conditioned reflex responses and "exptl. neuroses" by exposure to high g forces applied frequently over several mos. were negative. Considerable protection against g forces was afforded by a belt or cuff around the abdominal area inflated usually up to 300 mm. Hg. pressure.