PS-376 Non-invasive Ventilation In Neonates: Effect Of Nasal Cannula Size, Insertion Depth And Nares Diameter On Mean Airway Pressure - An In-vitro Study

Abstract

<h3>Background</h3> Increased neonatal Non-Invasive Ventilation (NIV) use, such as nCPAP and high flow nasal cannula (HFNC) prompted re-evaluation of nasal interface devices – specifically short bi-nasal prongs, and their size and fit relative to the nares. <h3>Objective</h3> To quantify the effect of nasal prong size and insertion depth on generated mean airway pressure (MAP) during NIV. <h3>Design/methods</h3> A Dräger traditional nCPAP interface, three sizes of RAM cannulae (Neotech, Valencia, CA, USA) and two Fisher and Paykel (FP) (Auckland, NZ) HFNC cannulae were tested with 8 simulated nares sizes. A simulated nasal airway was connected to an active lung model set at: Vt 8–10 ml, 60 b/m, Ti 0.35–0.40 s. A Dräger Evita XL ventilator delivered 4,5,6,7 and 8 cmH₂O to the RAM and the Dräger nCPAP cannulae and a FP HFNC system delivered 1–6 L/m flows. MAP was measured for open and closed-mouth conditions. <h3>Results</h3> MAP decreased progressively as the percent nares occlusion (%Occl) decreased. At one-half insertion and closed-mouth conditions, close fitting prongs with high% Occl yielded MAP’s of one-half of set CPAP levels. Delivered MAP’s were significantly lower during open-mouth condition using either HFNC or CPAP cannulae. MAP increased with both flowrate and%Occl. A rapid rise in pressure was associated with% Occl’s &gt;74%. Complete nares occlusions generated the highest pressures. Simulated closed-mouth produced 12 ± 7 SD higher MAP’s than open-mouth over all%Occl’s at HFNC flows &gt;1 L/m. <h3>Conclusion</h3> RAM ‘CPAP’ does not deliver MAP as effectively as standard nasal prong CPAP. Optimum delivered airway pressure is dependent on appropriate %Occl, insertion depth and NIV settings.