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Dynamic regulation of heart rate during acute hypotension: new insight into baroreflex functionTo examine the dynamic properties of baroreflex function, we measured beat-to-beat changes in arterial blood pressure (ABP) and heart rate (HR) during acute hypotension induced by thigh cuff deflation in 10 healthy subjects under supine resting conditions and during progressive lower body negative pressure (LBNP). The quantitative, temporal relationship between ABP and HR was fitted by a second-order autoregressive (AR) model. The frequency response was evaluated by transfer function analysis. Results: HR changes during acute hypotension appear to be controlled by an ABP error signal between baseline and induced hypotension. The quantitative relationship between changes in ABP and HR is characterized by a second-order AR model with a pure time delay of 0.75 s containing low-pass filter properties. During LBNP, the change in HR/change in ABP during induced hypotension significantly decreased, as did the numerator coefficients of the AR model and transfer function gain. Conclusions: 1) Beat-to-beat HR responses to dynamic changes in ABP may be controlled by an error signal rather than directional changes in pressure, suggesting a "set point" mechanism in short-term ABP control. 2) The quantitative relationship between dynamic changes in ABP and HR can be described by a second-order AR model with a pure time delay. 3) The ability of the baroreflex to evoke a HR response to transient changes in pressure was reduced during LBNP, which was due primarily to a reduction of the static gain of the baroreflex.
Document ID
20040112651
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Zhang, R.
(Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and University of Texas Southwestern Medical Center Dallas Dallas, Texas 75231, United States)
Behbehani, K.
Crandall, C. G.
Zuckerman, J. H.
Levine, B. D.
Blomqvist, C. G.
Date Acquired
August 21, 2013
Publication Date
January 1, 2001
Publication Information
Publication: American journal of physiology. Heart and circulatory physiology
Volume: 280
Issue: 1
ISSN: 0363-6135
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: HL-53206-03
Distribution Limits
Public
Copyright
Other
Keywords
Clinical Trial
NASA Discipline Cardiopulmonary
Non-NASA Center

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