New setting of neurally adjusted ventilatory assist for noninvasive ventilation by facial mask: a physiologic study

Noninvasive ventilation (NIV) is generally delivered using pneumatically-triggered and cycled-off pressure support (PS P ) through a mask. Neurally adjusted ventilatory assist (NAVA) is the only ventilatory mode that uses a non-pneumatic signal, i.e., diaphragm electrical activity (EAdi), to trigger and drive ventilator assistance. A specific setting to generate neurally controlled pressure support (PS N ) was recently proposed for delivering NIV by helmet. We compared PS N with PS P and NAVA during NIV using a facial mask, with respect to patient comfort, gas exchange, 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) PS P , with an inspiratory support ≥8 cmH 2 O; (2) NAVA, adjusting the NAVA level to achieve a comparable peak EAdi (EAdi peak ) as during PS P ; and (3) PS N , setting the NAVA level at 15 cmH 2 O/μV with an upper airway pressure (Paw) limit to obtain the same overall Paw applied during PS P . We assessed patient comfort, peak inspiratory flow (PIF), time to reach PIF (PIF time ), EAdi peak , arterial blood gases, pressure-time product of the first 300 ms (PTP 300-index ) and 500 ms (PTP 500-index ) after initiation of patient effort, inspiratory trigger delay (Delay TR-insp ), and rate of asynchrony, determined as asynchrony index (AI%). The categorical variables were compared using the McNemar test, and continuous variables by the Friedman test followed by the Wilcoxon test with Bonferroni correction for multiple comparisons ( p < 0.017). PS N significantly improved patient comfort, compared to both PS P ( p = 0.001) and NAVA ( p = 0.002), without differences between the two latter ( p = 0.08). PIF ( p = 0.109), EAdi peak ( p = 0.931) and gas exchange were similar between modes. Compared to PS P and NAVA, PS N reduced PIF time ( p < 0.001), and increased PTP 300-index ( p = 0.004) and PTP 500-index ( p = 0.001). NAVA and PS N significantly reduced Delay TR-insp , as opposed to PS P ( p < 0.001). During both NAVA and PS N , AI% was <10% in all patients, while AI% was ≥10% in 7 patients (50%) with PS P ( p = 0.023 compared with both NAVA and PS N ). Compared to both PS P and NAVA, PS N improved comfort and patient-ventilator interaction during NIV by facial mask. PS N also improved synchrony, as opposed to PS P only. ClinicalTrials.gov, NCT03041402 . Registered (retrospectively) on 2 February 2017.