This study is no longer recruiting participants.


Around 20,000 children are admitted to NHS paediatric critical care units each year. Many of these children need breathing support while in paediatric critical care. The most invasive form of breathing support is when a child has a tube inserted into their windpipe and is put on a ventilator.

To reduce the number of children needing invasive support, non-invasive breathing support methods like Continuous Positive Airway Pressure (CPAP) are used. CPAP provides oxygen or air through a face mask or into the nose. Although CPAP is beneficial, some children find it uncomfortable and some have complications.

A more recent alternative is called High Flow Nasal Cannula (HFNC). HFNC provides oxygen or air through tiny tubes inserted into the nostrils. There is little research on whether HFNC is beneficial or safe. However, many paediatric critical care units are starting to use HFNC instead of CPAP as it is easier to use, and some children appear more comfortable on it. This means that there is widespread variation across in the country in which methods are used. Before HFNC is adopted more widely, it is crucial that its role is closely studied.


We are studying whether HFNC is as effective as CPAP by carrying out two randomised clinical trials (RCTs) under one framework (FIRST-ABC). The RCTs included 1,200 children (600 in each), from around 25 paediatric critical care units, who required non-invasive breathing support in two distinct clinical scenarios:

1. for an acute illness (step-up RCT) or

2. within 72 hours of extubation following a period of invasive ventilation (step-down RCT)

In each RCT, children were randomly assigned to receive either CPAP or HFNC as the first-line method of non-invasive breathing support.

This trial ran from summer 2019 to late 2021.

More information about the FIRST-ABC Pilot Study can be found here.



Key information

Chief investigator(s)

Dr Padmanabhan Ramnarayan, Great Ormond Street Hospital for Children NHS Foundation Trust


Great Ormond Street Hospital for Children NHS Foundation Trust


National Institute for Health and Care Research (NIHR) – Health Technology Assessment (HTA) Programme

(Project Number: 17/94/28)

Trial registration(s)

ISRCTN Registry: ISRCTN60048867 

NIHR Central Portfolio Management System: 42112

Contact information

Trial Manager: Alvin Richards-Belle


Phone: 020 7269 9277

Trial protocol
Statistical analysis plan