(674) Effects of Flows During High-Flow Nasal Cannula for Neonates and Pediatrics: A Systematic Review

Introduction: Selecting the right flow is essential in maximizing the physiological effects and clinical outcomes of children treated with high-flow nasal cannula (HFNC) therapy. However, the initial flow settings and subsequent adjustments for pediatric patients vary in clinical practice. Thus, we aimed to perform a systematic review to synthesize the impact of different flows during HFNC treatment.

Methods: In this systematic review, two investigators independently searched PubMed, Embase, Web of Science, Scopus, and Cochrane for in vitro and in vivo studies investigating the effects of different flows in HFNC treatment published in English before April 30, 2023. We excluded studies enrolling adults (≥18 years) or those using a single flow. Data extraction and risk of bias assessments were performed independently by two investigators. The study protocol was prospectively registered with PROSPERO (CRD42022345419).

Results: 38,406 studies were identified, and 61 were included. In vitro studies evaluated the effects of flow settings on airway pressures, humidity and condensation, carbon dioxide (CO2) clearance and other parameters. These effects were flow-dependent. Animal studies and clinical observational studies in neonates and children ≤ 2yrs consistently reported that higher flow resulted in: 1) increased pressure in the upper airway and potentially increased lower airway pressure, especially in neonate population; 2) improved oxygenation; 3) reduced respiratory rate and work of breathing with increasing flows up to a certain range. Three randomized controlled trials did not find significant differences in treatment failure with high and low settings during HFNC therapy. However, higher flows may be beneficial for younger infants or sicker children. The impact of flows on different patients exhibited significant heterogeneity.

Conclusions: Individualizing flow settings during HFNC treatment based on the patient's peak inspiratory flow and other factors, such as respiratory rate, heart rate, tolerance, work of breathing, and lung aeration, may be a potential solution.