Baroreflex responsiveness during ventilatory acclimatization in humans

tested the hypothesis that the decline in muscle sympathetic activity during and after 8 h of poikilocapnic hypoxia (Hx) was associated with a greater sympathetic baroreflex-mediated responsiveness. In 10 healthy men and women (n 2), we measured beat-to-beat blood pressure (Portapres), carotid artery distension (ultrasonography), heart period, and muscle sympathetic nerve activity (SNA; microneurography) during two baroreflex perturbations using the modified Oxford technique before, during, and after 8 h of hypoxia (84 % arterial oxygen saturation). The integrated baroreflex response [change of SNA (SNA)/change of dia-stolic blood pressure (DBP)], mechanical (diastolic diameter/DBP), and neural (SNA/diastolic diameter) components were esti-mated at each time point. Sympathetic baroreflex responsiveness declined throughout the hypoxic exposure and further declined upon return to normoxia [pre-Hx, 8.3 1.2; 1-h Hx, 7.2 1.0; 7-h Hx, 4.9 1.0; and post-Hx: 4.1 0.9 arbitrary integrate