Abstract
A reciprocal relationship between the baroreflex and cerebral autoregulation (CA)
has been demonstrated at rest and in response to acute hypotension. We hypothesized
that the reciprocal relationship between cardiac baroreflex sensitivity (BRS) and
CA would be maintained during sustained central hypovolemia induced by lower body
negative pressure (LBNP), and that the strength of this relationship would be greater
in subjects with higher tolerance to this stress. Healthy young adults (n = 51; 23F/28M) completed a LBNP protocol to presyncope. Subjects were classified
as high tolerant (HT; completion of −60 mmHg LBNP stage, ≥20-min) or low tolerant
(LT; did not complete −60 mmHg LBNP stage, <20-min). R-R intervals (RRI), systolic
arterial pressure (SAP), mean arterial pressure (MAP), and middle cerebral artery
velocity (MCAv) were measured continuously. Cardiac BRS was calculated in the time
domain (ΔHR/ΔSAP) and frequency domain (RRI-SAP low frequency (LF) transfer function
gain), and CA was calculated in the time domain (ΔMCAv/ΔMAP) and frequency domain
(MAP-mean MCAv LF transfer function gain). There was a moderate relationship between
cardiac BRS and CA for the group of 51 subjects in both the time (R = -0.54, P < 0.0001) and frequency (R = 0.61, P < 0.001) domains; there was a stronger relationship in the HT group (R = 0.73) compared to the LT group (R = 0.31) in the frequency domain (P = 0.08), but no difference between groups in the time domain (HT: R = -0.73 vs. LT:
R = -0.63; P = 0.27). These findings suggest that an interaction between BRS and CA may be an
important compensatory mechanism that contributes to tolerance to simulated hemorrhage
in young healthy adults.
Keywords
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Article Info
Publication History
Published online: June 10, 2022
Accepted:
June 9,
2022
Received in revised form:
April 7,
2022
Received:
September 30,
2021
Identification
Copyright
© 2022 Elsevier B.V. All rights reserved.
