FIO2 Delivery During Pediatric Heated High Flow Nasal Cannula Therapy

Abstract

Background: Heated high-flow nasal cannula (HHFNC) systems are used to treat children with hypoxemia and respiratory distress. These devices allow modification of flow and FIO₂. We evaluated the effect of different FIO₂ settings and the relationship between inspiratory and cannula flows on tracheal FIO₂. Methods: An anatomically correct orotracheal model of a 5 y old child was connected to a breathing simulator (frequency = 20 breaths/minute, tidal 180 mL, T_I 0.9 s, inspiratory flow 12 L/min), and an oxygen analyzer was interposed. A Fisher Paykel (FP) Optiflow Junior 2 XL cannula was used with the Fisher Paykel HHFNC system with a blender and the AIRVO 2 device with cannula flows of 6, and 12 L/min. Another oxygen analyzer was placed in-line with the circuit at the cannula connection. FIO₂ was set at 0.95, 0.70, 0.50 and 0.35. Circuit and tracheal FIO₂ was measured. Absolute difference between device and tracheal FIO₂ (Delta FIO₂) at different FIO₂ s, and Delta FIO₂ at 6 and 12 L/min were analyzed. Measurements were done in quadruplicate after 7 minutes of continuous operation. Results: See table. Conclusions: Delta FIO₂ was greater at higher FIO₂ settings. The effect of air entrainment was more evident at higher FIO₂ settings. The AIRVO 2 device was more effective than the FP device when cannula flow matched inspiratory flow.