Introduction: Acute asthma exacerbations account for over 74,000 annual hospitalizations, and asthma-related pediatric intensive care unit (PICU) admissions are rising. Heated high flow nasal cannula (HHFNC) is widely used to deliver continuous short-acting beta agonist (cSABA) therapy to pediatric patients with critical asthma. Literature suggests that flow rates of 4-6 liters per minute (L/min) are optimal for effective cSABA delivery; however, there is wide institutional variability in prescribed flow rates. This study aims to assess the impact of HHFNC flow rates on clinical outcomes. Methods: A retrospective cohort study was performed investigating PICU patients admitted to a tertiary children’s hospital between 2017-2025 using Virtual Pediatric Systems (VPS), LLC. Subjects 2-17 years who received cSABA via HHFNC were included. Subjects were divided into two groups based on the mean HHFNC flow rate used to deliver cSABA: low flow (≤5L/min) vs high flow (>5L/min). Demographics and outcome data (total duration of cSABA, total duration of advanced respiratory support, PICU and hospital length of stay (LOS)) were collected from manual chart review. Wilcoxon Rank-sum tests were used to assess statistical significance. Results: 108 patients were included. Low flow patients (n = 54) had a median flow rate of 4.0 L/min IQR: 3.89, 4.0. High flow patients (n = 54) had a median flow rate of 9.64 L/min IQR: 7.05, 14.85. These two groups had statistically significantly different flow rates (p < 0.001). Low flow patients had significantly shorter total duration of cSABA compared to high flow patients (p = 0.03) and significantly shorter duration of advanced respiratory support (p = 0.006). Similarly, low flow patients had significantly shorter PICU and Hospital LOS compared to high flow patients (PICU LOS: p < 0.001, Hospital LOS: p = 0.003). Conclusions: Lower flow rates seem to be associated with improved patient outcomes including shorter duration of cSABA, advanced respiratory support, PICU and hospital LOS. However, we are unable to determine causation in this retrospective study. Given the increase in HHFNC use in critical asthma, a future prospective study is needed to directly determine the effectiveness of HHFNC in patient outcomes.
Roy et al. (Sun,) studied this question.