Arterial and cardiopulmonary baroreflexes in 60- to 69- vs. 18- to 36-yr-old humans

This study was designed to test the hypothesis that aging diminished baroreflex function during central hypovolemia. Eleven healthy young and eleven older (age 60-69 yr) individuals were assessed by using heart rate (HR) and mean arterial pressure (MAP) responses to neck pressure and suction during rest and lower body negative pressure (LBNP) of -15 Torr. The slope of forearm vascular resistance to central venous pressure during low-level LBNP was assessed as the index of cardiopulmonary baroreflex sensitivity. Baseline cardiovascular variables were not significantly different between the groups. In addition, there was no group difference in cardiopulmonary baroreflex (-3.6 vs. -3.7 units/mmHg for young vs. older, respectively) or carotid baroreflex (-0.39 vs. -0.35 beats.min-1.mmHg-1 and -0.26 vs. -0.35 mmHg/mmHg, for young vs. older, respectively) sensitivity. LBNP did not affect either HR or MAP, whereas it decreased CVP and increased FVR in both groups. LBNP significantly augmented the carotid-HR (-0....