Interaction between central-peripheral chemoreflexes and cerebro-cardiovascular control

Lucia Spicuzza, Cesare Porta, Alfina Bramanti, Mara Maffeis, Gaia Casucci, Nadia Casiraghi, Luciano Bernardi

Research output: Contribution to journalArticlepeer-review

Abstract

We investigated the interaction between hypoxia and hypercapnia on ventilation and on cerebro-cardio-vascular control. A group of 12 healthy subjects performed rebreathing tests to determine the ventilatory response to hypoxia, at different levels of carbon dioxide (CO2), and to normoxic hypercapnia. Oxygen saturation (SaO2), end-tidal CO2 (et-CO2), minute ventilation, blood pressure, R-R interval and mid-cerebral artery flow velocity (MCFV) were continuously recorded. The hypoxic ventilatory response significantly increased under hypercapnia and decreased under hypocapnia (slopes L/min/% Sa O2: -0.33 ± 0.05, -0.74 ± 0.02 and -1.59 ± 0.3, p <0.0001, in hypocapnia, normocapnia and hypercapnia, respectively). At similar degrees of ventilation, MCFV increased more markedly during normocapnic hypoxia than normoxic hypercapnia; the slopes linking MCFV to hypoxia remained unchanged at increasing levels of et-CO2, whereas the regression lines were shifted upward. The R-R interval decreased more markedly during normocapnic hypoxia than normoxic hypercapnia and the arterial baroreflex sensitivity was decreased only by hypoxia. Cardiovascular responses to hypoxia were not affected by different levels of et-CO2. We conclude that concomitant hypoxia and hypercapnia, while increasing ventilation synergistically, exert an additive effect on cerebral blood flow. Increased sympathetic activity (and reduced baroreflex sensitivity) is one of the mechanisms by which hypoxia stimulates cardiac sympathetic activity.

Original languageEnglish
Pages (from-to)373-381
Number of pages9
JournalClinical Autonomic Research
Volume15
Issue number6
DOIs
Publication statusPublished - Dec 2005

Keywords

  • Baroreflex
  • Cerebral circulation
  • Chemoreflex
  • Hypercapnia
  • Hypoxia

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)

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