New Setting of Neurally Adjusted Ventilatory Assist during Noninvasive Ventilation through a Helmet

Background: Compared to pneumatically controlled pressure support (PS_P), neurally adjusted ventilatory assist (NAVA) was proved to improve patient-ventilator interactions, while not affecting comfort, diaphragm electrical activity (EAdi), and arterial blood gases (ABGs). This study compares neurally controlled pressure support (PS_N) with PS_P and NAVA, delivered through two different helmets, in hypoxemic patients receiving noninvasive ventilation for prevention of extubation failure. Methods: Fifteen patients underwent three (PS_P, NAVA, and PS_N) 30-min trials in random order with both helmets. Positive end-expiratory pressure was always set at 10 cm H₂O. In PS_P, the inspiratory support was set at 10 cm H₂O above positive end-expiratory pressure. NAVA was adjusted to match peak EAdi (EAdi_peak) during PS_P. In PS_N, the NAVA level was set at maximum matching the pressure delivered during PS_P by limiting the upper pressure. The authors assessed patient comfort, EAdi_peak, rates of pressurization (i.e., airway pressure-time product [PTP] of the first 300 and 500 ms after the initiation of patient effort, indexed to the ideal pressure-time products), and measured ABGs. Results: PS_N significantly increased comfort to (median [25 to 75% interquartile range]) 8 [7 to 8] and 9 [8 to 9] with standard and new helmets, respectively, as opposed to both PS_P (5 [5 to 6] and 7 [6 to 7]) and NAVA (6 [5 to 7] and 7 [6 to 8]; P < 0.01 for all comparisons). Regardless of the interface, PS_N also decreased EAdi_peak (P < 0.01), while increasing PTP of the first 300 ms from the onset of patient effort, indexed to the ideal PTP (P < 0.01) and PTP of the first 500 ms from the onset of patient effort, indexed to the ideal PTP (P < 0.001). ABGs were not different among trials. Conclusions: When delivering noninvasive ventilation by helmet, compared to PS_P and NAVA, PS_N improves comfort and patient-ventilator interactions, while not ABGs. (Anesthesiology 2016; 125:1181-9).