Sequential modulation of cardiac autonomic control induced by cardiopulmonary and arterial baroreflex mechanisms

Raffaello Furlan*, Giris Jacob, Laura Palazzolo, Alexandra Rimoldi, Andre Diedrich, Paul A. Harris, Alberto Porta, Alberto Malliani, Rogelio Mosqueda-Garcia, David Robertson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Background - 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 (αLF) 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 (αLF) 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 (LFR-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 LFR-R, which precedes the changes in the hemodynamics and in the indexes of arterial baroreflex control.

Original languageEnglish
Pages (from-to)2932-2937
Number of pages6
JournalCirculation
Volume104
Issue number24
DOIs
StatePublished - 11 Dec 2001
Externally publishedYes

Keywords

  • Baroreceptors
  • Hemodynamics
  • Nervous system, sympathetic
  • Pressure

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