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Sequential modulation of cardiac autonomic control induced by cardiopulmonary and arterial baroreflex mechanismsBACKGROUND: Nonhypotensive lower body negative pressure (LBNP) induces a reflex increase in forearm vascular resistance and muscle sympathetic neural discharge without affecting mean heart rate. We tested the hypothesis that a reflex change of the autonomic modulation of heartbeat might arise during low intensity LBNP without changes of mean heart rate. METHODS AND RESULTS: Ten healthy volunteers underwent plasma catecholamine evaluation and a continuous recording of ECG, finger blood pressure, respiratory activity, and central venous pressure (CVP) during increasing levels of LBNP up to -40 mm Hg. Spectrum and cross-spectrum analyses assessed the changes in the spontaneous variability of R-R interval, respiration, systolic arterial pressure (SAP), and CVP and in the gain (alpha(LF)) of arterial baroreflex control of heart rate. Baroreceptor sensitivity was also evaluated by the SAP/R-R spontaneous sequences technique. LBNP began decreasing significantly: CVP at -10, R-R interval at -20, SAP at -40, and the indexes alpha(LF) and baroreceptor sensitivity at -30 and -20 mm Hg, compared with baseline conditions. Plasma norepinephrine increased significantly at -20 mm Hg. The normalized low-frequency component of R-R variability (LF(R-R)) progressively increased and was significantly higher than in the control condition at -15 mm Hg. CONCLUSIONS: Nonhypotensive LBNP elicits a reflex increase of cardiac sympathetic modulation, as evaluated by LF(R-R), which precedes the changes in the hemodynamics and in the indexes of arterial baroreflex control.
Document ID
20040088609
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Furlan, R.
(Universita degli Studi di Milano Italy)
Jacob, G.
Palazzolo, L.
Rimoldi, A.
Diedrich, A.
Harris, P. A.
Porta, A.
Malliani, A.
Mosqueda-Garcia, R.
Robertson, D.
Date Acquired
August 21, 2013
Publication Date
December 11, 2001
Publication Information
Publication: Circulation
Volume: 104
Issue: 24
ISSN: 0009-7322
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
Clinical Trial
Controlled Clinical Trial
NASA Discipline Regulatory Physiology

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