Neurally adjusted ventilatory assist vs. pressure support ventilation in critically ill patients: an observational study

Abstract

Background: During neurally adjusted ventilatory assist (NAVA), the inspiratory support is controlled by the patients' respiratory drive influenced by an operator-controlled gain factor (NAVA level). The purpose of our observational study was to transfer patients from conventional pressure support ventilation (PSV) to NAVA safely. We compared two approaches to set the NAVA level and evaluated the effect of NAVA. Methods: We studied mechanically ventilated patients capable of spontaneous breathing. For the change of the ventilator mode, we used a NAVA level calculated to generate a peak inspiratory pressure equal to PSV. We compared this NAVA level with a NAVA level determined by a NAVA level titration. Ventilatory and haemodynamic data were recorded during an observational period of 6 h. Results: All 20 patients included in the study could be transferred from PSV to NAVA and completed the observation interval. Setting the NAVA level according to prior PSV settings proved to be a feasible approach, but in 75% of our patients, we modified the NAVA level according to the titration results. Gas exchange and ventilatory mechanics during the observation interval remained stable. Conclusions: The ventilator mode NAVA seems to be well tolerated in a heterogeneous group of critically ill patients. Pre-setting of the NAVA level during PSV can result in an overestimation of the required ventilator support. An additional titration of the NAVA level ads valuable information although difficult to interpret in some cases.