Effect of changing NAVA levels on peak inspiratory pressures and electrical activity of the diaphragm in premature neonates

BACKGROUND: Neurally adjusted ventilator assist (NAVA) uses electrical activity of the diaphragm (Edi) to provide patient-directed ventilatory support. The NAVA level determines the proportional amount of ventilatory support. Systematically increasing NAVA level initially increases peak inspiratory pressure (PIP) while maintaining a constant Edi until a breakpoint (BrP) is reached. Further increases in NAVA level reduce the Edi, while the PIP plateaus. This study was performed to establish whether premature neonates have intact neural feedback systems allowing them to have a BrP. METHOD: NAVA level was increased by 0.5 cm H2O mu V-1 every 3 min from 0.5 to 4.0 cm H2O mu V-1. PIP, Edi, mean blood pressure, heart rate, respiratory rate, oxygen saturation and FIO2 were recorded. Statistics: Non-linear regression was done for PIP and Edi. Linear regression was done for the other variables. The data from the trials were combined by normalizing to NAVA levels above and below the BrP. RESULT: Nine neonates were studied on NAVA and 12 on non-invasive NAVA. PIP increased until the BrP was reached and then remained unchanged. Edi decreased after the BrP was reached. All other variables remained unchanged. CONCLUSION: Neonates demonstrated a BrP suggesting intact neural feedback mechanisms that may protect lungs from over distention with NAVA ventilation.