Title: A pilot study to assess whether humidified oxygen is more effective than standard oxygen therapy in treating children with acute severe asthma
Funder: Department of Health (England)

Abstract: In asthma, viral respiratory infections or inhaled allergens irritate the airways. These cause the airway to become inflamed and produce more mucus, and the airway wall muscles to tighten. All these processes make it difficult to breathe. Normally, microscopic hairs move mucus and other inhaled particulate matter from the lower to the upper airways, where they are swallowed. This transport system is very sensitive. Thus, even the very small changes in humidity and temperature that happen in the lungs during chest infections, can cause profound effects on airway function. These effects become more pronounced the greater the deviation from normal and the longer the exposure. In animals exposed to different temperatures and humidities of air for variable amounts of time, significant changes are seen within 10 minutes of exposure to dry (unhumidified) air at 15-240C, and obvious airway damage is seen following 3-4 hours exposure (Supplement 2) . Recently, portable humidification devices have become more widely available in clinical practice but very few studies have examined their use in acute respiratory disease in either adults or children. One small study in children with acute asthma, looked at how lung function changed before and after nebulised bronchodilators driven by humidified oxygen, either at room temperature or at 400C. Lung function increased more in the heated, humidified oxygen group than in the room temperature group. In the UK, 30,000 children annually attend hospital with severe asthma with many needing oxygen, however there is no evidence to support the most effective oxygen treatment. In A&E departments around the country, oxygen is given straight from the wall at the patient bedside to children (and adults). Following transfer to medical wards, a survey of practice (Supplement 3) revealed considerable variation in whether oxygen is given warm, cold and/or humidified. The need for an evidence base to inform best practice has been identified as important by consumers, Asthma UK and clinicians. To determine the most effective treatment for children admitted to hospital with severe asthma, we propose a pilot, randomised controlled trial in which participants will receive either: standard oxygen therapy; warm humidified oxygen; cold humidified oxygen. A range of outcomes will be measured which have previously been assessed as relevant and important by consumers and clinicians. The pilot study will establish which outcome measures can be successfully measured, and provide estimates of effect sizes for these outcomes; a consensus exercise will establish which outcome measure(s) is most relevant and important to consumers and clinicians. A health economic assessment will investigate the feasibility of collecting the relevant data required to calculate differences in Quality Adjusted Life Years (QALYs) in a definitive study. This will enable us to plan a larger definitive multi-centre study with a definitive primary outcome measure, sample size and robust data to inform recruitment rate in the population and setting under study. In a previous feasibility study at Alder Hey Children's Hospital A&E between April 2008-March 2010, we confirmed that two of the study interventions could be delivered in the proposed setting following randomisation. During the two year feasibility study we also assessed the number of admissions with acute asthma: 1490 children attended the A&E department with acute asthma, of whom 253/1490 (17%) required oxygen therapy and needed admission to hospital. 137 (9%) were admitted between 8am-8pm. 80% of those approached agreed to be randomised. We estimate that it would take 24 months to be sure of recruiting sufficient numbers of children with severe asthma to this proposed pilot study (n=90).


Research activity codes: 6.7 PHYSICAL
Health categories: RESPIRATORY