Asynchrony, neural drive, ventilatory variability and COMFORT: NAVA versus pressure support in pediatric patients. A non-randomized cross-over trial

de la Oliva, Pedro; Schüffelmann, Cristina; Gómez-Zamora, Ana; Villar, Jesus; Kacmarek, Robert M.

PURPOSE: To determine if neurally adjusted ventilatory assist (NAVA) improves asynchrony, ventilatory drive, breath-to-breath variability and COMFORT score when compared to pressure support (PS). METHODS: This is a non-randomized short-term cross-over trial in which 12 pediatric patients with asynchrony (auto-triggering, double triggering or non-triggered breaths) were enrolled. Four sequential 10-min periods of data were recorded after 20 min of ventilatory stabilization (wash-out) at each of the following settings: baseline PS with the ventilator settings determined by the attending physician (1-PS(b)); PS after optimization (2-PS(opt)); NAVA level set so that maximum inspiratory pressure (P (max)) equaled P (max) in PS (3-NAVA); same settings as in 2-PS(opt) (4-PS(opt)). RESULTS: The median asynchrony index was significantly lower during NAVA (2.0 %) than during 2-PS(opt) (8.5 %, p = 0.017) and 4-PS(opt) (7.5 %, p = 0.008). In NAVA mode, the NAVA trigger accounted on average for 66 % of triggered breaths. The median trigger delay with respect to neural inspiratory time was significantly lower during NAVA (8.6 %) than during 2-PS(opt) (25.2 %, p = 0.003) and 4-PS(opt) (28.2 %, p = 0.0005). The median electrical activity of the diaphragm (EAdi) change during trigger delay normalized to maximum inspiratory EAdi difference was significantly lower during NAVA (5.3 %) than during 2-PS(opt) (21.7 %, p = 0.0005) and 4-PS(opt) (24.6 %, p = 0.001). The coefficient of variation of tidal volume was significantly higher during NAVA (44.2 %) than during 2-PS(opt) (19.8 %, p = 0.0002) and 4-PS(opt) (23.0 %, p = 0.0005). The median COMFORT score during NAVA (15.0) was lower than that during 2-PS(opt) (18.0, p = 0.0125) and 4-PS(opt) (17.5, p = 0.039). No significant changes for any variable were observed between 1-PS(b) and 2-PS(opt). CONCLUSIONS: Neurally adjusted ventilatory assist as compared to optimized PS results in improved synchrony, reduced ventilatory drive, increased breath-to-breath mechanical variability and improved patient comfort. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00134-012-2535-y) contains supplementary material, which is available to authorized users.