Van de Louw Andry, Médigue Claire, Papelier Yves, Cottin François
Unité de Biologie Intégrative des Adaptations à l'Exercise (INSERM 902/EA 3872, Genopole), ZAC du Bras de Fer, Evry, France.
Am J Physiol Regul Integr Comp Physiol. 2008 Dec;295(6):R1934-40. doi: 10.1152/ajpregu.90475.2008. Epub 2008 Oct 15.
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.
自主呼吸时的心率和血压变化与吸气时的气道负压有关。机械通气时吸气气道压力为正压，这表明正常压力感受器介导的变异性模式可能会发生逆转。我们对17例机械通气患者的心率和血压变异性以及压力感受器敏感性进行了研究。记录心电图（RR间期）、有创收缩压（SBP）和呼吸流量信号。通过复解调（CDM）连续计算RR和SBP时间序列的高频（HF）幅度以及RR、SBP和通气信号之间的HF相位差。采用交叉谱分析评估RR和SBP之间的相干性和增益函数，得出压力感受器敏感性指数。与采用负吸气压力模拟自主呼吸的通气周期相比，在所有通气周期中SBP变异性倒置的患者中，SBP与通气信号之间的HF相位差几乎恒定。在12例患者（第1组）中，RR与通气信号之间的相位差随时间变化，HF-RR幅度也发生变化。在其余5例患者（第2组）中，RR-通气信号相位和HF-RR幅度变化很小；然而，这些患者中只有1例表现出RR-通气信号相位差，模拟了正常的呼吸性窦性心律不齐模式。相位差发生变化的组中RR和SBP之间的频谱相干性较低。正压通气主要对SBP产生机械作用，而其对心率变异性的影响似乎更为复杂，提示神经因素发挥了作用。
