P1.164: Quantifying the Impact of Nasal Prong Fit on PEEP Generation in a 3D Newborn Airway Model

Background: High Flow Nasal Cannula (HFNC) is increasingly used for noninvasive respiratory support, offering benefits like improved comfort and reduced nasal injury. However, HFNC-generated Positive End Expiratory Pressure (PEEP) is highly variable, influenced by nasal prong fit, leak, and gas flow rate. Consistent PEEP delivery is essential for preterm respiratory support and minimizing the risk of atelectasis or overdistension. Better PEEP monitoring could optimize care and outcomes, resulting in reduced tissue injury, enhanced neurodevelopmental outcome, and improved long-term respiratory health. This study aimed to quantify PEEP across varying flow rates, leak percentages, and prong sizes using a 3D printed model of the newborn airway. In addition, the effect of varying distances between the HFNC prongs and the nasal septum on resulting PEEP was measured.

Methods: A 3D newborn airway, derived from a clinically-performed CT scan in a 3.5 kg infant without structural pathology, was modeled using 3D Slicer and printed with semi-malleable silicon. HFNC devices were secured to the model according to manufacturer guidelines. Pressure was measured via a 1.1 mm catheter attached to clinically available pressure transducer (LP15, DRW Medical). Pressure measures were performed at a distance of 3 mm within the airway, with a range of nasal cannula sizes and at flow rates 1–11 L/min. A 5 French tube was added to simulate a clinical NG tube. To quantify the impact of septal distance on PEEP generation, pressure measurements were repeated with the prong crossbar at distances of 0-3 mm from the nasal septum.

Results: Pressure readings showed variable PEEP generation at all flow rates across varying levels of leak. Pressure from six devices at a range of flow rates are shown in Figure 1. Devices with lower leak percentages (determined by subtracting prong area from nares area) generated higher PEEP than those with greater leak, though this trend was not uniform. Figure 2 shows that PEEP generation varies somewhat as distance between the HFNC prongs and the septum changes, but variability in PEEP is generally < 1 cm H2O.

Conclusion: Gas flow rate and size of prongs relative to the nares are the primary drivers of PEEP generation on HFNC therapy. While pressure increased with increasing flow in all six devices this relationship was not linear, and varied significantly across the range of HFNC devices recommended for newborn use. This makes PEEP difficult for clinicians to predict in real-world practice highlighting the need for careful prong selection and real-time pressure monitoring to optimize lung recruitment while minimizing risks. Future studies should explore patient-specific variables and clinical outcomes to further refine HFNC strategies for neonatal respiratory support.