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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.

BackgroundAcute severe asthma (ASA) is a leading cause of hospital attendance in children. Standard first-line therapy consists of high-dose inhaled bronchodilators plus oral corticosteroids. Treatment for children who fail to respond to first-line therapy is problematic: the use of intravenous agents is inconsistent, and side effects are frequent. High-flow humidified oxygen (HiFlo) is widely used in respiratory conditions and is increasingly being used in ASA, but with little evidence for its effectiveness. A well-designed, adequately powered randomized controlled trial (RCT) of HiFlo therapy in ASA is urgently needed, and feasibility data are required to plan such an RCT. In this study, we describe the protocol for a feasibility study designed to fill this knowledge gap. ObjectiveThis study aims to establish whether a full RCT of early HiFlo therapy in children with ASA can be conducted successfully and safely, to establish whether recruitment using deferred consent is practicable, and to define appropriate outcome measures and sample sizes for a definitive RCT. The underlying hypothesis is that early HiFlo therapy in ASA will reduce the need for more invasive treatments, allow faster recovery and discharge from hospital, and in both these ways reduce distress to children and their families. MethodsWe conducted a feasibility RCT with deferred consent to assess the use of early HiFlo therapy in children aged 2 to 11 years with acute severe wheeze not responding to burst therapy (ie, high-dose inhaled salbutamol with or without ipratropium). Children with a Preschool Respiratory Assessment Measure score ≥5 after burst therapy were randomized to commence HiFlo therapy or follow standard care. The candidate primary outcomes assessed were treatment failure requiring escalation and time to meet hospital discharge criteria. Patient and parent experiences were also assessed using questionnaires and telephone interviews. ResultsThe trial was opened to recruitment in February 2020 but was paused for 15 months owing to the COVID-19 pandemic. The trial was reopened at the lead site in July 2021 and opened at the other 3 sites from August to December 2022. Recruitment was completed in June 2023. ConclusionsThis feasibility RCT of early HiFlo therapy in children with ASA recruited to the target despite major disturbances owing to the COVID-19 pandemic. The data are currently being analyzed and will be published separately. Trial RegistrationInternational Standard Randomised Controlled Trial Number Registry ISRCTN78297040; https://www.isrctn.com/ISRCTN78297040 International Registered Report Identifier (IRRID)DERR1-10.2196/54081