Pulmonary Engineering Group, Clinic of Anaesthesiology and Intensive Care Therapy, University Clinic Dresden, Germany.
Physiol Meas. 2012 Mar;33(3):503-19. doi: 10.1088/0967-3334/33/3/503. Epub 2012 Feb 29.
The physiological importance of respiratory sinus arrhythmia (RSA) and cardioventilatory coupling (CVC) has not yet been fully elucidated, but these phenomena might contribute to improve ventilation/perfusion matching, with beneficial effects on gas exchange. Furthermore, decreased RSA amplitude has been suggested as an indicator of impaired autonomic control and poor clinical outcome, also during positive-pressure mechanical ventilation (MV). However, it is currently unknown how different modes of MV, including variable tidal volumes (V(T)), affect RSA and CVC during anesthesia. We compared the effects of pressure controlled (PCV) versus pressure assisted (PSV) ventilation, and of random variable versus constant V(T), on RSA and CVC in eight anesthetized pigs. At comparable depth of anesthesia, global hemodynamics, and ventilation, RSA amplitude increased from 20 ms in PCV to 50 ms in PSV (p < 0.05). CVC was detected (using proportional Shannon entropy of the interval between each inspiration onset and the previous R-peak in ECG) in two animals in PCV and seven animals in PSV. Variable V(T) did not significantly influence these phenomena. Furthermore, heart period and systolic arterial pressure oscillations were in phase during PCV but in counter-phase during PSV. At the same depth of anesthesia in pigs, PSV increases RSA amplitude and CVC compared to PCV. Our data suggest that the central respiratory drive, but not the baroreflex or the mechano-electric feedback in the heart, is the main mechanism behind the RSA increase. Hence, differences in RSA and CVC between mechanically ventilated patients might reflect the difference in ventilation mode rather than autonomic impairment. Also, since gas exchange did not increase from PCV to PSV, it is questionable whether RSA has any significance in improving ventilation/perfusion matching during MV.
呼吸窦性心律失常（RSA）和心呼吸耦合（CVC）的生理重要性尚未完全阐明，但这些现象可能有助于改善通气/灌注匹配，对气体交换产生有益影响。此外，RSA 幅度降低已被认为是自主神经控制受损和临床预后不良的指标，在正压机械通气（MV）期间也是如此。然而，目前尚不清楚不同的 MV 模式，包括可变潮气量（V（T）），如何影响麻醉期间的 RSA 和 CVC。我们比较了压力控制（PCV）与压力辅助（PSV）通气，以及随机变量与恒定 V（T）对 8 头麻醉猪的 RSA 和 CVC 的影响。在相同的麻醉深度、整体血流动力学和通气下，RSA 幅度从 PCV 的 20ms 增加到 PSV 的 50ms（p < 0.05）。在 PCV 中有 2 只动物检测到 CVC（使用每个呼吸起始与心电图上前一个 R 波之间的间隔的比例香农熵），在 PSV 中有 7 只动物检测到 CVC。可变 V（T）对这些现象没有显著影响。此外，在 PCV 期间，心周期和收缩压波动与 PSV 期间呈相反相位。在相同的麻醉深度下，与 PCV 相比，PSV 增加了 RSA 幅度和 CVC。我们的数据表明，在猪中，与 PCV 相比，PSV 增加了 RSA 幅度和 CVC。在 PSV 中，中央呼吸驱动，而不是压力反射或心脏的机械电反馈，是 RSA 增加的主要机制。因此，机械通气患者之间 RSA 和 CVC 的差异可能反映了通气模式的差异，而不是自主神经损伤。此外，由于从 PCV 到 PSV 通气并没有增加，因此 RSA 是否对改善 MV 期间通气/灌注匹配有任何意义值得怀疑。
