Daily titration of neurally adjusted ventilatory assist using the diaphragm electrical activity.

PURPOSE: To determine the feasibility of daily titration of the neurally adjusted ventilatory assist (NAVA) level in relation to the maximal diaphragmatic electrical activity (EAdi(maxSBT)) measured during a spontaneous breathing trial (SBT) during pressure support ventilation (PSV).
METHODS: The study included 15 consecutive patients in whom mechanical ventilation weaning was initiated with the NAVA mode. EAdi(maxSBT) was determined daily during an SBT using PSV with 7 cmH2O of inspiratory pressure and no positive end-expiratory pressure (PEEP). If the SBT was unsuccessful, NAVA was used and the level was then adjusted to obtain an EAdi of ~60% of the EAdi(maxSBT). Arterial blood gas analyses were performed 20 min after each change in NAVA level.
RESULTS: Three patients were dropped from the study at day 4 because of worsening of their sickness. The median duration of NAVA ventilation was 4.5 days (IQR 3-6.5). From day 1 to extubation, EAdi(maxSBT) and EAdi increased significantly from 16.6 (9.6) to 21.7 (10.3) μV (P = 0.013) and from 10.0 (5.5) to 15.1 (9.2) μV (P = 0.026), respectively. The pressure delivered significantly decreased from 20 (8) to 10 (5) cmH2O (P = 0.003). Conversely, tidal volume, carbon dioxide tension, and pH values remained unchanged during the same period.
CONCLUSION: These results suggest that daily titration of NAVA level with an electrical goal of ~60% EAdi(maxSBT) is feasible and well tolerated. The respiratory mechanics improvement and increase in respiratory drive allowed for a daily reduction of the NAVA level while preserving breathing, oxygenation, and alveolar ventilation until extubation.