Supplementary Material for: Effect of changing NAVA levels on tidal ventilation in extremely preterm infants supported with NIV-NAVA

Introduction Non-invasive neurally adjusted ventilatory assist (NIV-NAVA) is used in preterm infants as a synchronized and proportional mode of non-invasive ventilation. Finding the ideal NAVA level to support preterm infants remains challenging. Methods A single-center prospective interventional study was conducted to study the effect of increasing NAVA levels on tidal ventilation measured with electrical impedance tomography (EIT). Preterm infants supported with NIV-NAVA were included. After a baseline registration and following a predefined titration protocol, NAVA levels were progressively increased by 0.5 cmH2O/µV up to a NAVA level of 3 cmH2O/µV. Before and during the titration procedure the evolution of (EIT) parameters (end-expiratory lung impedance (EELI), end-inspiratory lung impedance (EILI), silent spaces (SS) and center of ventilation (CoV)) and respiratory parameters (electrical diaphragm activity (Edi) peak and minimum (Edimin) and peak inspiratory pressure (PIP)) were measured. Results 16 patients with a mean (standard deviation (SD)) gestational age (GA) at birth 26.7 (1.2) weeks and birth weight (BW) of 838 (205) grams were included for analysis. EIT parameters did not change significantly with titration of NAVA levels. PIP increased significantly with each increase in NAVA level and Edi peak decreased significantly from NAVA level 1 tot 1.5 cmH2O/µV. Edi min and transcutaneous CO2 (TcCO2) remained constant during the titration procedure. Conclusion There was no effect of increasing NAVA levels on regional ventilation parameters. PIP increased with each increase in NAVA level, whereas Edi peak largely remained stable.