LAUSR

Dear Editor, Though neurally adjusted ventilatory assist (NAVA) is known to improve patient-ventilator interactions in infants with bronchiolitis [1, 2], its impact on respiratory muscles unloading has not previously been studied. We conducted a secondary analysis (ethics committee approval CE_SRLF_18-48) of a prospective physiological study [3] which evaluated the impact of body positioning on work of breathing (WOB) in infants with severe bronchiolitis. Seven of the children included (median age 35 [27–63] days) had a respiratory recording during the transition from nasal continuous positive airway pressure (nCPAP; set at 7cmH2O [4]) to NAVA. Esophageal (Peso), gastric (Pga), and airway (Paw) pressures, as well as Electrical activity of the diaphragm (Edi), and flow were recorded simultaneously. Median NAVA level was set at 0.7 [0.7–0.9] cmH2O/μV and median positive end expiratory pressure at 5 [4–7] cmH2O. Twenty-five breaths during the last 2 min in nCPAP then during the first 2 min in NAVA were analyzed off-line. Metabolic cost of breathing was estimated by the Peso (PTPeso) and diaphragmatic (PTPdi) pressure time product, inspiratory effort by the Peso (ΔPeso) and diaphragmatic (ΔPdi) pressure swings, and respiratory drive by the Edi swing (ΔEdi). Data were expressed as median [IQR] and compared using Wilcoxon two-sample paired sign test. A p value < 0.05 was considered significant. As detailed in Table 1 and illustrated in Fig. 1, all indices of WOB (PTPeso, PTPdi, ΔPeso, ΔPdi, Edi swing, and inspiratory time to total time ratio (Ti/Ttot)) decreased significantly in every child with NAVA as compared to nCPAP (p < 0.05 in all instances), while the mean Paw was increased (p < 0.05).