Effect of G-Suit Protection on Carotid-Cardiac Baroreflex Function

摘要

To test the hypothesis that 0-suit inflation could increase cardiac chronotropic responses to baroreceptor stimulation and enhance baroreflex buffering of blood pressure, the carotid-cardiac baroreflex response of 12 subjects was measured across two levels of lower body negative pressure (LBNP = 0 and 50 mmHg) and two levels of 0-suit inflation (0 and 50 mmHg) in random order. Carotid-cardiac baroreflex stimulation was delivered via a silastic neck pressure cuff and responsiveness quantified by determination of the maximum slope of the stimulus-response function between R-R intervals (ms) and their respective carotid distending pressures (mmHg). Mean % SE baseline control baroreflex responsiveness was 3.8 + - 0.4 ms/mmHg. LBNP reduced the baroreflex response to 2.7 % 0.4 ms/mmHg (P <0.05), but 0-suit inflation, both with and without LBNP, restored the baroreflex response to 4.4 % 0.7 and 4.3 % 0.6 ms/ MMHg, respectively. These results suggest that, in addition to increased venous return and elevated peripheral resistance, 0-suit inflation may provide protection against the debilitating effects of blood distribution to the lower extremities during 0 acceleration by increasing cardiovascular responsiveness to carotid baroreceptor stimulation.