Assistance Publique-Hôpitaux de Paris, Service de Pneumologie et Réanimation, Groupe Hospitalier Pitié-Salpêtrière, and Université Paris 6-Pierre et Marie Curie, Paris, France.
Anesthesiology. 2010 Mar;112(3):670-81. doi: 10.1097/ALN.0b013e3181cea375.
Neurally adjusted ventilatory assist (NAVA) is a partial ventilatory support mode where positive pressure is provided in relation to diaphragmatic electrical activity (EAdi). Central inspiratory activity is normally not monotonous, but it demonstrates short-term variability and complexity. The authors reasoned that NAVA should produce a more "natural" or variable breathing pattern than other modes. This study compared respiratory variability and complexity during pressure support ventilation (PSV) and NAVA.
Flow and EAdi were recorded during routine PSV (tidal volume approximately 6-8 ml/kg) and four NAVA levels (1-4 cm H2O/microVEAdi) in 12 intubated patients. Breath-by-breath variability of flow and EAdi-related variables was quantified by the coefficient of variation (CV) and autocorrelation analysis. Complexity of flow and EAdi was described using noise titration, largest Lyapunov exponent, Kolmogorov-Sinai entropy, and three-dimensional phase portraits.
Switching from PSV to NAVA increased the CV and decreased the autocorrelation for most flow-related variables in a dose-dependent manner (P < 0.05, partial eta for the CV of mean inspiratory flow 0.642). The changes were less marked for EAdi. A positive noise limit was consistently found for flow and EAdi. Largest Lyapunov exponent and Kolmogorov-Sinai entropy for flow were greater during NAVA than PSV and increased with NAVA level (P < 0.05, partial eta 0.334 and 0.312, respectively). Largest Lyapunov exponent and Kolmogorov-Sinai entropy for EAdi were not influenced by ventilator mode.
Compared with PSV, NAVA increases the breathing pattern variability and complexity of flow, whereas the complexity of EAdi is unchanged. Whether this improves clinical outcomes remains to be determined.
神经调节辅助通气（NAVA）是一种部分通气支持模式，其中正压与膈肌电活动（EAdi）相关。中枢吸气活动通常不是单调的，而是表现出短期可变性和复杂性。作者推断，NAVA 应该产生比其他模式更“自然”或可变的呼吸模式。本研究比较了压力支持通气（PSV）和 NAVA 期间的呼吸可变性和复杂性。
在 12 例插管患者中，在常规 PSV（潮气量约 6-8ml/kg）和 4 个 NAVA 水平（1-4cmH2O/微VEAdi）期间记录流量和 EAdi。通过变异系数（CV）和自相关分析量化流量和 EAdi 相关变量的逐拍可变性。使用噪声滴定、最大李雅普诺夫指数、Kolmogorov-Sinai 熵和三维相图描述流量和 EAdi 的复杂性。
从 PSV 切换到 NAVA 以剂量依赖性方式增加了大多数流量相关变量的 CV 并降低了自相关（P<0.05，平均吸气流量 CV 的部分 eta 为 0.642）。EAdi 的变化不太明显。始终为流量和 EAdi 找到正噪声极限。与 PSV 相比，NAVA 时流量的最大李雅普诺夫指数和 Kolmogorov-Sinai 熵更大，并且随着 NAVA 水平的增加而增加（P<0.05，部分 eta 分别为 0.334 和 0.312）。通气模式对 EAdi 的最大李雅普诺夫指数和 Kolmogorov-Sinai 熵没有影响。
与 PSV 相比，NAVA 增加了流量的呼吸模式可变性和复杂性，而 EAdi 的复杂性保持不变。这是否能改善临床结果仍有待确定。
