Spontaneous beat-by-beat fluctuations of total peripheral and cerebrovascular resistance in response to tilt

• DOI: 10.1152/ajpregu.00408.2003
• Publication Date: 2004-05-04T00:48:53Z
• Authors: Deborah D. O'Leary; J. Kevin Shoemaker; Michael R. Edwards; Richard L. Hughson
• Keywords: Supine position; Mean arterial pressure; Head-Down Tilt; Beat (acoustics)

Beat-by-beat estimates of total peripheral resistance (TPR) can be obtained from continuous measurements cardiac output by using Doppler ultrasound and noninvasive mean arterial blood pressure (MAP). We employed transfer function analysis to study the heart rate (HR) vascular response spontaneous changes in relationships systolic (SBP) HR (SBP-->HR), MAP cerebrovascular index (CVRi) (MAP-->TPR MAP-->CVRi), as well stroke volume (SV) TPR nine healthy subjects supine 45 degrees head-up tilt positions. The gain SBP-->HR was reduced with both low- (0.03-0.15 Hz) high-frequency (0.15-0.35 regions. In contrast, MAP-->TPR not affected tilt, but it did increase phase between were unaffected but, consistent an autoregulatory system, followed directionally similar TPR, just observed for MAP-->CVRi. SV-->TPR had high coherence a constant 150-160 degrees. Together, these data that showed preceded possible link SV are complex interactions component cardiopulmonary baroreflexes intrinsic properties such myogenic arteries.