Effects of Neurally Adjusted Ventilatory Assist (NAVA) levels in non-invasive ventilated patients: titrating NAVA levels with electric diaphragmatic activity and tidal volume matching

Abstract

BackgroundNeurally adjusted ventilatory assist (NAVA) delivers pressure in proportion to diaphragm electrical activity (Eadi). However, each patient responds differently to NAVA levels. This study aims to examine the matching between tidal volume (Vt) and patients’ inspiratory demand (Eadi), and to investigate patient-specific response to various NAVA levels in non-invasively ventilated patients.Methods12 patients were ventilated non-invasively with NAVA using three different NAVA levels. NAVA100 was set according to the manufacturer’s recommendation to have similar peak airway pressure as during pressure support. NAVA level was then adjusted ±50% (NAVA50, NAVA150). Airway pressure, flow and Eadi were recorded for 15 minutes at each NAVA level. The matching of Vt and integral of Eadi (ʃEadi) were assessed at the different NAVA levels. A metric, Range90, was defined as the 5-95% range of Vt/ʃEadi ratio to assess matching for each NAVA level. Smaller Range90 values indicated better matching of supply to demand.ResultsPatients ventilated at NAVA50 had the lowest Range90 with median 25.6 uVs/ml [Interquartile range (IQR): 15.4-70.4], suggesting that, globally, NAVA50 provided better matching between ʃEadi and Vt than NAVA100 and NAVA150. However, on a per-patient basis, 4 patients had the lowest Range90 values in NAVA100, 1 patient at NAVA150 and 7 patients at NAVA50. Robust coefficient of variation for ʃEadi and Vt were not different between NAVA levels.ConclusionsThe patient-specific matching between ʃEadi and Vt was variable, indicating that to obtain the best possible matching, NAVA level setting should be patient specific. The Range90 concept presented to evaluate Vt/ʃEadi is a physiologic metric that could help in individual titration of NAVA level.

Biomedical engineer’s guide to the clinical aspects of intensive care mechanical ventilation

“…NAVA was found to improve patient-ventilator interaction, reducing the number of asynchrony events [ 156 ], as well as increasing respiratory variability in Vt and flow related variables [ 157 ]. Studies on NAVA have reported on impact to the patients [ 158 – 160 ], and an optimal titration method [ 161 , 162 ]. Thus, the benefits of this approach are potentially more substantial for patients ventilated for long durations.…”

“…Thus, the benefits of this approach are potentially more substantial for patients ventilated for long durations. However, similar to other ventilation strategies, there is also limited guideline is setting the appropriate NAVA level [ 161 – 163 ] of pressure support, so its use is affected by this difficulty and its added cost.…”

La ventilation non invasive en mode NAVA (neurally adjusted ventilatory assist) en réanimation pédiatrique

“…L'adaptation du niveau NAVA pour cibler une valeur d'AEdi semble prometteuse, en visant soit des valeurs « normales » d'AEdi (qui restent à définir), soit un pourcentage de l'AEdi mesuré au cours d'une épreuve standardisée [45]. Une autre méthode a été récemment décrite par Chiew et al [46] chez 12 patients adultes de réanimation. Le niveau NAVA était d'abord réglé afin d'obtenir le même degré d'aide inspiratoire qu'en VNI conventionnelle, puis modifié à 50 % puis 150 % de cette valeur initiale.…”