To compare dependent lung ventilation (as assessed with EIT, vertical center of ventilation (CoV(v)) measure) between extremely preterm infants treated with NIV-NAVA and those treated with NS-NIPPV. To compare global ventilation homogeneity (as assessed with EIT, global inhomogeneity index (GI) measure) between extremely preterm infants treated with NIV-NAVA to those treated with NS-NIPPV To explore an association between regional lung ventilation (EIT, GI and silent space percentage (SS%) measure) at a single time point after extubation and subsequent extubation failure within 5 days of extubation among extremely preterm infants. To assess the safety and feasibility of performing electrical impedance tomography in a population of preterm infants on non-invasive respiratory support. The primary outcome to be compared is the vertical center of ventilation (CoV(v)), a marker of dependent lung ventilation. Additional measures to be compared between respiratory support type and extubation success outcome include global inhomogeneity index (GI) and tidal volume impedance (TVi) as measures of ventilation homogeneity.