Background To determine the prevalence of main inspiratory asynchrony events during non-invasive intermittent positive-pressure ventilation (NIV) for severe bronchiolitis in infants who failed to respond to nasal continuous positive airway pressure (nCPAP). Ventilator response time and asynchrony were compared in neurally adjusted ventilator assist (NAVA) and in pressure assist/control (PAC) modes.
Methods This prospective study in a university hospital’s paediatric intensive care unit included 11 children (aged 35.2 ± 23 days) with respiratory syncytial virus bronchiolitis with failure of nCPAP. Patients received NIV for 2 h in PAC mode followed by 2 h in NAVA mode. Diaphragm electrical activity and pressure curves were recorded for 10 min. Trigger delay, main asynchronies (auto-triggering, double triggering, or non-triggered breaths) were analysed, and the asynchrony index was calculated.
Results The asynchrony index (fig. 1) was lower during NAVA than during PAC (3 ± 3% vs. 38 ± 21%, p < 0.0001), and the ventilator response time was shorter (43.9 ± 7.2 vs. 116.0 ± 38.9 ms, p < 0.0001). Ineffective efforts were significantly less frequent in NAVA mode (0.54 ± 1.5 vs. 21.8 ± 16.5 events/min, p = 0.01). Patient Respiratory rates were similar, but the ventilator rate was higher in NAVA than in PAC mode (59.5 ± 17.9 vs. 49.8 ± 8.5/min, p = 0.03). The TcPCO2 baselines values (8.6 ± 1.6 kPa vs. 8.1 ± 1.2 kPa during NAVA, p = 0.36) and their evolutions during the study period (-0.8 ± 1.4 kPa vs. -1.6 ± 2.3 kPa during NAVA, p = 0.36) did not differ.