BACHb: Breathing Assistance in CHildren with bronchiolitis (BACHb): a group-sequential two-stratum multicentre open-label randomised clinical trial of respiratory support in infants with acute bronchiolitis

The aim of the BACHb trial is to evaluate the clinical and cost-effectiveness of the use of HFNC separately in two distinct populations, infants with moderate bronchiolitis and infants with severe bronchiolitis.

Bronchiolitis, a viral lower respiratory tract infection, is the most common reason for hospitalisation of infants under the age of one in the United Kingdom (UK). Between 40 and 50 per 1000 infants living in England require hospital admission for bronchiolitis each year, resulting in ~30,000 annual admissions; nearly 1000 need intensive care admission. Bronchiolitis also places an enormous burden on paediatric services every winter at a time of high clinical demand and staff shortages, leading to widespread bed shortages and elective surgery cancellations. Healthcare costs associated with bronchiolitis management have risen steadily over the past decade.

The management of bronchiolitis is mainly supportive: this mainly consists of oxygen supplementation for infants with hypoxaemia, respiratory support for breathing difficulties, and gastric (or intravenous) hydration for infants unable to feed orally.

There is a strong evidence base that LFNC should be used as the first-line mode of oxygen treatment for infants with mild bronchiolitis. The two main evidence gaps are in moderate bronchiolitis, i.e., infants who fail to respond to LFNC (~20-25% of infants started on LFNC) and severe bronchiolitis.

Although high-flow nasal cannula (HFNC) is used commonly in moderate bronchiolitis, no RCTs have directly compared HFNC with humidified standard oxygen (HSO). This is important because one of the reasons clinicians start HFNC is to provide humidified oxygen at flow rates >2 L/min. HSO can deliver flow rates up to 15 L/min, it is cheaper than HFNC, does not depend on availability of specialist equipment and, unlike HFNC, it is classified as a ward intervention (nurse-to-patient ratio of 1:4). On the other hand, in addition to humidification, HFNC can provide a degree of respiratory support (unlike HSO), which may help infants recover sooner.

Most infants with severe bronchiolitis are cared for in the paediatric emergency and ward settings, where there is a lack of RCT evidence to guide practice. The results from the most recent systematic review indicate that hospital length of stay (a secondary outcome) is lower with HFNC, an important finding that needs to be confirmed in a large RCT.