Preterm children are at increased risk for developing lung disease due to immature lungs. Non-invasive ventilation (NIV) support is increasingly used as treatment. Nasal continuous positive airway pressure (nCPAP) is the most common NIV-mode. Recently, high flow nasal cannulas (HFNC) have become an alternative NIV-mode. Both nCPAP and HFNC provide increased pressure in the airways aiming to keep the lungs open. With nCPAP it is common to use short binasal prongs that fill the nostrils completely and are pressed tightly over the nose. With HFNC oxygen/air is administered via two small, thin cannulas located just inside the nostrils, but the nostrils are not blocked.