New Setting of Neurally Adjusted Ventilatory Assist During Mask Noninvasive Ventilation

Non invasive ventilation (NIV) is generally delivered by pneumatically triggered and cycled-off Pressure Support (PSP) through a facial mask. Compared to PSP, Neurally Adjusted Ventilatory Assist (NAVA), which is the only ventilatory mode using a non-pneumatic signal, i.e., diaphragm electrical activity (EAdi), to trigger and drive ventilator assistance, improves patient-ventilator interaction. A specific setting to generate neurally controlled Pressure Support (PSN) was recently proposed for delivering NIV by helmet. The investigators here compare PSN with PSP and NAVA during NIV by facial mask, with respect to arterial blood gases (ABGs), patient comfort, and patient-ventilator interaction and synchrony. Three 30-minute trials of NIV were randomly delivered to 14 patients immediately after extubation to prevent post-extubation respiratory failure: 1) PSP, with an inspiratory support ≥8 cmH2O; 2) NAVA, adjusting the NAVA level to achieve a comparable peak EAdi (EAdipeak) as during PSP; 3) PSN, setting the NAVA level at 15 cmH2O/mcV with an upper airway pressure (Paw) limit such to obtain the same overall Paw applied during PSP. We assessed EAdipeak, ABGs, peak inspiratory flow (PIF), time to reach PIF (PIFtime), pressure-time product of the first 300 (PTP300-index) and 500 (PTP500-index) milliseconds after initiation of patient effort, patient comfort, inspiratory trigger delay (DelayTR-insp), and the rate of asynchrony, as assessed by the Asynchrony Index (AI%).