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Reference: N Engl J Med 2018 Mar 22;378(12):1121 (level 2 [mid-level] evidence)
- Supplemental high-flow or standard-flow oxygen is given to infants with bronchiolitis with hypoxemia, but evidence comparing the two is limited.
- A randomized trial with 1,472 non-critical infants with bronchiolitis with hypoxemia compared high-flow (2 L/kg/min, max 25 L/min) vs. standard-flow (≤ 2 L/min) supplemental oxygen.
- High-flow oxygen had lower rates of escalated care than standard-flow oxygen (12% vs. 23%, p < 0.001). There were no significant differences between groups in time on supplemental oxygen or length of hospital stay.
Infants with bronchiolitis with hypoxemia are given supplemental oxygen as supportive management (Pediatrics 2014). Observational studies and a 200-patient randomized trial suggest that high-flow warm humidified oxygen may have better clinical and physiological outcomes than standard-flow oxygen (Pediatrics 2014, Lancet 2017); additional trials with consistent results may boost confidence in this outcome. Here, we highlight a recent trial in which 1,472 infants < 12 months old with a clinical diagnosis of bronchiolitis with hypoxemia were randomized to high-flow vs. standard-flow supplemental oxygen therapy. Target oxygen saturation (SpO2) levels were 92%-98% or 94%-98% (depending on the hospital) in both groups. High-flow oxygen therapy consisted of warm humidified oxygen given through age-appropriate nasal cannula at 2 L/kg/min (maximum 25 L/min). Standard-flow oxygen therapy consisted of oxygen given through nasal cannula at ≤ 2 L/min and could be humidified depending on the hospital. In both groups, therapy was stopped after target SpO2 levels were maintained for ≥ 4 hours at settings approximating unsupported breathing. Exclusion criteria included critical illness and home-based supplemental oxygen. The primary outcome was escalated care, defined as a transfer to the intensive care unit or an increase in respiratory support. Escalated care was triggered by either clinical judgement or the infant meeting ≥ 3 of 4 clinical criteria: a hospital-specific early warning tool (based on multiple physiological and clinical variables) or persistence of tachycardia, tachypnea, or hypoxemia. Outcome assessors were not blinded to treatment allocation.
High-flow warm humidified supplemental oxygen therapy had lower rates of escalated care than standard-flow oxygen therapy (12% vs. 23%, p < 0.001, NNT 9), with a similar difference in rates of escalated care based solely on having met ≥ 3 of 4 clinical criteria (7% vs. 16%, p < 0.001, NNT 12). The two treatment groups had similar mean durations on supplemental oxygen (about 1.9 days) and length of hospital stay (about 3 days). Rates of non-study treatments, such as use of steroids and nebulized saline, were similar between groups, as were adverse events (pneumothorax in 1 infant in each group and apnea in 3 infants in each group).
This study is somewhat limited by how the primary outcome of escalated care was specified. The use of clinical judgement as well as clinical criteria introduces a possible source of bias considering that outcome assessors were not blinded to treatment allocation. This concern is alleviated to some degree by similar results in the subanalysis based on clinical criteria alone. However, note that the clinical criteria included an early warning tool. The example tool provided by the authors includes pain assessments, which are subjective, and heart rate, breathing rate, and SpO2 levels, which are redundant with the other criteria. Even with these concerns, the lower rate of escalated care with high-flow oxygen in this trial is consistent with previous studies and suggests that it should be considered over standard-flow oxygen for supportive management in infants with bronchiolitis with hypoxemia.
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