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This Article Full Text Full Text (PDF) All Versions of this Article: 295/6/R1934    most recent 90475.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Van de Louw, A. Articles by Cottin, F. Search for Related Content PubMed PubMed Citation Articles by Van de Louw, A. Articles by Cottin, F.

NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Breathing cardiovascular variability and baroreflex in mechanically ventilated patients

¹Unité de Biologie Intégrative des Adaptations à l'Exercice (INSERM 902/EA 3872, Genopole), ZAC du Bras de Fer, Evry; ²Intensive Care Unit, Centre Hospitalier Sud-Francilien, Quartier du Canal, Courcouronnes, Evry; ³Institut National de Recherche en Informatique et en Automatique, Domaine de Voluceau, Rocquencourt, Le Chesnay, France

Submitted 5 June 2008 ; accepted in final form 9 October 2008

Heart rate and blood pressure variations during spontaneous ventilation are related to the negative airway pressure during inspiration. Inspiratory airway pressure is positive during mechanical ventilation, suggesting that reversal of the normal baroreflex-mediated pattern of variability may occur. We investigated heart rate and blood pressure variability and baroreflex sensitivity in 17 mechanically ventilated patients. ECG (RR intervals), invasive systolic blood pressure (SBP), and respiratory flow signals were recorded. High-frequency (HF) amplitude of RR and SBP time series and HF phase differences between RR, SBP, and ventilatory signals were continuously computed by Complex DeModulation (CDM). Cross-spectral analysis was used to assess the coherence and the gain functions between RR and SBP, yielding baroreflex sensitivity indices. The HF phase difference between SBP and ventilatory signals was nearly constant in all patients with inversion of SBP variability during the ventilator cycle compared with cycling with negative inspiratory pressure to replicate spontaneous breathing. In 12 patients (group 1), the phase difference between RR and ventilatory signals changed over time and the HF-RR amplitude varied. In the remaining five patients (group 2), RR-ventilatory signal phase and HF-RR amplitude showed little change; however, only one of these patients exhibited a RR-ventilatory signal phase difference mimicking the normal pattern of respiratory sinus arrhythmia. Spectral coherence between RR and SBP was lower in the group with phase difference changes. Positive pressure ventilation exerts mainly a mechanical effect on SBP, whereas its influence on HR variability seems more complex, suggesting a role for neural influences.

heart rate; blood pressure; baroreflex gain; hypoxemia; complex demodulation