High-flow humidified oxygen as an early intervention in children with acute severe asthma: a feasibility randomised controlled trial.

Background: Treating children with acute severe asthma (ASA) who fail to respond to first-line inhaled bronchodilators is problematic: use of intravenous agents is inconsistent and side-effects are common. High-flow humidified oxygen (HiFlo) has shown promise in other respiratory conditions and is increasingly used in ASA, but with little evidence. Methods: We conducted a feasibility randomised controlled trial with deferred consent to assess early HiFlo in children aged 2-11 years with ASA not responding to "burst" therapy (high-dose inhaled salbutamol ± ipratropium). Children with Paediatric Respiratory Assessment Measure (PRAM) score 5+ after "burst" were randomised to commence HiFlo or follow standard care. Candidate primary outcomes assessed were treatment failure requiring escalation, and time to meeting hospital discharge criteria. Results: The target was met despite coronavirus disease 2019 pandemic disruption: 56 children were randomised across four sites, with deferred consent received in 50 out of 56 (89%), and mean recruitment rate 1.1 per site per month. 28 were allocated early HiFlo and 22 standard care. Data collection was complete for both candidate primary outcomes. Treatment failure requiring escalation occurred in 18 of 28 children (64%) in the HiFlo arm and in 19 of 22 (86%) in the standard care arm. Median (interquartile range) time from randomisation to meeting discharge criteria was 29.3 h (21.8-43.7 h) in the HiFlo arm and 36.8 h (24.1-46.3 h) in the standard care arm. Conclusions: HiFlo in childhood ASA is a potentially promising intervention whose use is increasing despite lack of evidence. A definitive randomised controlled trial to assess its effectiveness is required and appears to be feasible.