High-flow nasal cannula therapy versus continuous positive airway pressure for non-invasive respiratory support in paediatric critical care: the FIRST-ABC RCTs.

Background: Despite the increasing use of non-invasive respiratory support in paediatric intensive care units, there are no large randomised controlled trials comparing two commonly used non-invasive respiratory support modes, continuous positive airway pressure and high-flow nasal cannula therapy.

Objective: To evaluate the non-inferiority of high-flow nasal cannula, compared with continuous positive airway pressure, when used as the first-line mode of non-invasive respiratory support in acutely ill children and following extubation, on time to liberation from respiratory support, defined as the start of a 48-hour period during which the child was free of respiratory support (non-invasive and invasive).

Design: A master protocol comprising two pragmatic, multicentre, parallel-group, non-inferiority randomised controlled trials (step-up and step-down) with shared infrastructure, including internal pilot and integrated health economic evaluation.

Setting: Twenty-five National Health Service paediatric critical care units (paediatric intensive care units and/or high-dependency units) across England, Wales and Scotland.

Participants: Critically ill children assessed by the treating clinician to require non-invasive respiratory support for (1) acute illness (step-up randomised controlled trial) or (2) within 72 hours of extubation (step-down randomised controlled trial).

Interventions: High-flow nasal cannula delivered at a flow rate based on patient weight (Intervention) compared to continuous positive airway pressure of 7-8 cm H₂O pressure (Control).

Main outcome measures: The primary clinical outcome was time to liberation from respiratory support. The primary cost-effectiveness outcome was 180-day incremental net monetary benefit. Secondary outcomes included mortality at paediatric intensive care unit/high-dependency unit discharge, day 60 and day 180; (re)intubation rate at 48 hours; duration of paediatric intensive care unit/high-dependency unit and hospital stay; patient comfort; sedation use; parental stress; and health-related quality of life at 180 days.

Results: In the step-up randomised controlled trial, out of 600 children randomised, 573 were included in the primary analysis (median age 9 months). Median time to liberation was 52.9 hours for high-flow nasal cannula (95% confidence interval 46.0 to 60.9 hours) and 47.9 hours (95% confidence interval 40.5 to 55.7 hours) for continuous positive airway pressure (adjusted hazard ratio 1.03, one-sided 97.5% confidence interval 0.86 to ∞). The high-flow nasal cannula group had lower use of sedation (27.7% vs. 37%) and mean duration of acute hospital stay (13.8 days vs. 19.5 days). In the step-down randomised controlled trial, of the 600 children randomised, 553 were included in the primary analysis (median age 3 months). Median time to liberation for high-flow nasal cannula was 50.5 hours (95% confidence interval, 43.0 to 67.9) versus 42.9 hours (95% confidence interval 30.5 to 48.2) for continuous positive airway pressure (adjusted hazard ratio 0.83, one-sided 97.5% confidence interval 0.70 to ∞). Mortality at day 180 was significantly higher for high-flow nasal cannula [5.6% vs. 2.4% for continuous positive airway pressure, adjusted odds ratio, 3.07 (95% confidence interval, 1.1 to 8.8)].

Limitations: The interventions were unblinded. A heterogeneous cohort of children with a range of diagnoses and severity of illness were included.

Conclusions: Among acutely ill children requiring non-invasive respiratory support, high-flow nasal cannula met the criterion for non-inferiority compared with continuous positive airway pressure for time to liberation from respiratory support whereas in critically ill children requiring non-invasive respiratory support following extubation, the non-inferiority of high-flow nasal cannula could not be demonstrated.

Future work: (1) Identify risk factors for treatment failure. (2) Compare protocolised approaches to post-extubation non-invasive respiratory support, with standard care. (3) Explore alternative approaches for evaluating heterogeneity of treatment effect. (4) Explore reasons for increased mortality in high-flow nasal cannula group within step-down randomised controlled trial.

Study registration: Current Controlled Trials ISRCTN60048867.

Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 17/94/28) and is published in full in Health Technology Assessment; Vol. 29, No. 9. See the NIHR Funding and Awards website for further award information.