NAVA and PSV ventilation in neuromuscular and COPD difficult-to-wean patients

Aim of the study is to compare ventilatory parameters and diaphragmatic electromyography (EAdi) during pressure support ventilation (PSV) and neurally adjusted ventilatory assist (NAVA) in difficult to wean patients (DW). Five chronic obstructive (COPD) (4males, age 69.8±5.7y) and 5 neuromuscular (NMD) (2males, age 72.2±11.1y) DW underwent a sequence of progressive inspiratory support reduction in NAVA and in PSV, from baseline (BL) to the onset of dyspnoea or ventilator discomfort (FL), as assessed by Borg ≥ 6. Tidal volume (VT), minute ventilation (VE), peak EAdi (EAdipeak) and neural inspiratory time (TiNeur), Diaphragmatic effort (IEAdi) were computed from pressure, flow and EAdi signals derived from ventilator. Compared to COPD, in both ventilation modalities NMD showed at FL higher IEAdi (NAVA: 14.9±22.7 vs 9.7±12.0; PSV: 14.5±10.8 vs 11.2±11.1µV*s) and lower VT/EAdipeak (NAVA: 0.3±0.9 vs 0.9±3.2; PSV: 0.2±0.1 vs 0.7±0.7 ml/kg*µV) (P NMD showed an higher tolerance threshold compared to COPD. At FL, NMD ventilator pattern was characterized by higher IEAdi and TiNeur in NAVA compared to PSV. In this group, despite of a lower EAdipeak, an higher inspiratory effort effectiveness, as shown by VT/EAdipeak values, was observed in NAVA compared to PSV. These preliminary results require further investigations to confirm possible advantages of NAVA in NMD.