Neurally adjusted ventilatory assist vs pressure support ventilation for noninvasive ventilation during acute respiratory failure: A crossover physiologic study

Abstract

Background: Patient-ventilator asynchrony is common during noninvasive ventilation (NIV) with pressure support ventilation (PSV). We examined the effect of neurally adjusted ventilatory assist (NAVA) delivered through a facemask on synchronization in patients with acute respiratory failure (ARF). Methods: This was a prospective, physiologic, crossover study of 13 patients with ARF (median PaO2/FIO2, 196 [interquartile range (IQR), 142-225]) given two 30-min trials of NIV with PSV and NAVA in random order. Diaphragm electrical activity (EAdi), neural inspiratory time (T I n), trigger delay (Td), asynchrony index (AI), arterial blood gas levels, and patient discomfort were recorded. Results: There were significantly fewer asynchrony events during NAVA than during PSV (10 [IQR, 5-14] events vs 17 [IQR, 8-24] events, P = .017), and the occurrence of severe asynchrony (AI > 10%) was also less under NAVA(P = .027). Ineffective efforts and delayed cycling were significantly less with NAVA(P < .05 for both). NAVA was also associated with reduced Td (0 [IQR, 0-30] milliseconds vs 90 [IQR, 30-130] milliseconds, P < .001) and inspiratory time in excess (10 [IQR, 0-28] milliseconds vs 125 [IQR, 20-312] milliseconds, P,.001), but T I n was similar under PSV and NAVA. The EAdi signal to its maximal value was higher during NAVA than during PSV (P = .017). There were no significant differences in arterial blood gases or patient discomfort under PSV and NAVA. Conclusion: In view of specific experimental conditions, our comparison of PSV and NAVA indicated that NAVA signifi cantly reduced severe patient-ventilator asynchrony and resulted in similar improvements in gas exchange during NIV for ARF. Trial registry: ClinicalTrials.gov; No.: NCT01426178; URL: www.clinicaltrials.gov. © 2013 American College of Chest Physicians.