Individual differences of cerebrovascular responses to gravitational stress — Prediction of orthostatic intolerance

Ueno, Toshiaki; Yoshimoto, Shunsuke; Mayanagi, Yoshiaki; Yumikura, Sei; Sekiguchi, Chiharu; Miyamoto, Akira; Yajima, Kazuyoshi

doi:10.1016/0094-5765(94)90134-1

Cited by 2 publications

(1 citation statement)

References 15 publications

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“…Zhang et al (26) also demonstrated a deterioration of dynamic CA during lower body negative pressure (LBNP) and suggested that these changes may contribute to presyncope. There are important differences between HUT and LBNP in terms of engagement of proprioceptor and vestibular reflexes (5,17,21,23). However, we observed a similar deterioration of dynamic CA in presyncopal subjects during orthostatic stress using HUT.…”

Section: Discussioncontrasting

confidence: 64%

Dynamic cardiorespiratory interaction during head-up tilt-mediated presyncope

Krishnamurthy

Wang

Bhakta

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

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In 28 healthy adults, we compared the dynamic interaction between respiration and cerebral autoregulation in 2 groups of subjects: those who did and did not develop presyncopal symptoms during 70 degrees passive head-up tilt (HUT), i.e., nonpresyncopal (23 subjects) and presyncopal (5 subjects). Airflow, CO2, cerebral blood flow velocity (CBF), ECG, and blood pressure (BP) were recorded. To determine whether influences of mean BP (MBP) and systolic SP (SBP) on CBF were altered in presyncopal subjects, coherencies and transfer functions between these variables and mean and peak CBF (CBFm and CBFp) were estimated. To determine the influence of end-tidal CO2 (ETco2) on CBF, the relative CO2 reactivity (%change in CBFm per mmHg change in ETco2) was calculated. We found that in presyncopal subjects before symptoms during HUT, coherence between SBP and CBFp was higher (P=0.02) and gains of transfer functions between BP (MBP and SBP) and CBFm were larger (MBP, P=0.01; SBP, P=0.01) in the respiratory frequency region. In the last 3 min before presyncope, presyncopals had a reduced relative CO2 reactivity (P=0.005), likely a consequence of the larger decrease in ETco2. We hypothesize that the CO2-mediated increase in resistance attenuates autoregulation such that the relationship between systemic and cerebral hemodynamics is enhanced. Our results suggest that an altered cardiorespiratory interaction involving cerebral hemodynamics may contribute in the cascade of events during tilt that culminate in unexplained syncope.

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Section: Discussioncontrasting

confidence: 64%