PMID: 8447471Feb 1, 1993Paper

Microgravity and orthostatic intolerance: carotid hemodynamics and peripheral responses

The American Journal of Physiology
P J LacolleyM E Safar

Abstract

A ground-based model [24 h of bed rest (BR) with head-down tilt (HDT)] was used to investigate the cardiovascular deconditioning responsible for orthostatic intolerance, frequently observed after weightlessness flights. This experimental deconditioning is shown to be distinguished by an increase of mean blood pressure (P < 0.05), with increased total peripheral resistances (TPRs). Systolic tangential tension of the carotid arterial wall, cardiac output and frequency (spectral analysis), and plasma norepinephrine and epinephrine were not significantly altered, while plasma dopamine was increased (P < 0.05). Cardiovascular homeostasis was challenged before and after 24 h of BR with HDT through -40 mmHg lower body negative pressure (LBNP). Systolic tangential tension of the carotid wall was decreased, with a decrease of systolic pressure and cardiac output; increased heart rate was likely due to an increase of sympathetic drive with a decrease of vagal braking. The overall picture was not changed after 24 h of BR with HDT, except for a lack of increase of TPRs: their increase (+13.7%, P < 0.05) before was no longer observed after (-2.6%) 24 h of BR with HDT. This apparent deficiency cannot be explained. However, a heterogeneity in...Continue Reading

Citations

Apr 6, 2000·Journal of Applied Physiology·R C Looft-Wilson, C V Gisolfi
Dec 17, 2008·American Journal of Physiology. Heart and Circulatory Physiology·Qi FuBenjamin D Levine
Dec 6, 2018·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Craig G CrandallBlair D Johnson

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