Oxygen, high-flow and non-invasive respiratory support

A six-month-old infant arrives with bronchiolitis, grunting and retracting, saturating 89 per cent in room air. You start oxygen — but which oxygen? A simple nasal cannula might be enough, or it might be too little. High-flow might rescue the child and avoid intubation, or it might delay it dangerously if the child is already tiring. CPAP could splint collapsing alveoli, or BiPAP might be needed if the carbon dioxide is climbing. The decision turns on three questions: what does the gas exchange problem look like, what can each device actually do about it, and how do you know when it is working or failing? This page teaches the whole ladder. ^{[1] [7]}

This hub owns the device logic for paediatric oxygen and non-invasive support. Sister pages carry the disease algorithms: respiratory distress and failure for the assessment framework, bronchiolitis for the commonest indication, acute severe asthma for a disease where the approach differs, and paediatric acute respiratory distress syndrome for the severe end. ^[9]

Overview & Definition

Think of respiratory support not as a list of gadgets but as a toolkit that addresses two separate problems. The first is hypoxaemia — the blood is not getting enough oxygen because gas exchange is failing. The second is ventilatory failure — the lungs are not moving enough air to clear carbon dioxide. Every device on the ladder addresses one or both, and matching the device to the problem is the central skill. ^[6]

Standard oxygen therapy delivers oxygen-enriched gas through low-flow devices — nasal cannula or a simple face mask. It raises the fraction of inspired oxygen (FiO2) above the 21 per cent of room air, and in a child with normal ventilation this corrects mild hypoxaemia. But it delivers no pressure: it cannot splint collapsed alveoli, and it cannot reduce the work a tiring child expends with each breath. The FiO2 is also imprecise and varies with the child's inspiratory flow, mouth-breathing and leak. ^[10]

High-flow nasal cannula (HFNC) is the first step that does more than add oxygen. A specialised system delivers gas that is blended to a precise FiO2, heated to near body temperature (about 37 degrees), and fully humidified, at flows high enough to match or exceed a young child's own inspiratory demand — classically 2 L/kg/min, capped at about 60 L/min in older children. At those flows the device does four things at once: it washes CO2-rich gas out of the upper-airway dead space so each breath draws fresh gas, it meets inspiratory demand so the child's muscles do less work, it generates a modest positive end-expiratory pressure (PEEP) that splints the airways, and it delivers optimally conditioned gas that preserves mucociliary clearance. ^{[5] [6]}

Continuous positive airway pressure (CPAP) delivers a single, set positive pressure throughout the respiratory cycle via a sealed interface — a nasal mask, nasal prongs or a full face mask. Unlike HFNC, where PEEP is an incidental and variable by-product of flow, CPAP delivers a controlled, reliable distending pressure, typically 5 to 7 cmH2O in children. Its job is recruitment: it stents open alveoli that would otherwise collapse at end-expiration, raises functional residual capacity, reduces intrapulmonary shunt and so improves oxygenation. It is the tool of choice for hypoxaemic failure from recruitable lung disease. ^[9]

Bilevel positive airway pressure (BiPAP, or NIV) is CPAP plus a pressure boost. It cycles between a higher inspiratory positive airway pressure (IPAP) and a lower expiratory positive airway pressure (EPAP). The difference between them — the pressure support — actively augments each breath, increasing tidal volume and so improving ventilation and CO2 clearance. BiPAP is therefore the right tool when the problem is ventilatory: neuromuscular weakness, central hypoventilation, chest-wall deformity, or a child in hypercapnic failure who is tiring. ^[9]

References10ShowHide

1. [1]Franklin D A Randomized Trial of High-Flow Oxygen Therapy in Infants with Bronchiolitis. N Engl J Med, 2018.PMID 29562151
2. [2]Kepreotes E High-flow warm humidified oxygen versus standard low-flow nasal cannula oxygen for moderate bronchiolitis (HFWHO RCT): an open, phase 4, randomised controlled trial. Lancet, 2017.PMID 28161016
3. [3]Milési C High flow nasal cannula (HFNC) versus nasal continuous positive airway pressure (nCPAP) for the initial respiratory management of acute viral bronchiolitis in young infants: a multicenter randomized controlled trial (TRAMONTANE study). Intensive Care Med, 2017.PMID 28124736
4. [4]Ramnarayan P Effect of High-Flow Nasal Cannula Therapy vs Continuous Positive Airway Pressure Therapy on Liberation From Respiratory Support in Acutely Ill Children Admitted to Pediatric Critical Care Units: A Randomized Clinical Trial. JAMA, 2022.PMID 35707984
5. [5]Spentzas T Children with respiratory distress treated with high-flow nasal cannula. J Intensive Care Med, 2009.PMID 19703816
6. [6]Haq I The evidence for high flow nasal cannula devices in infants. Paediatr Respir Rev, 2014.PMID 24472697
7. [7]Milési C Clinical practice guidelines: management of severe bronchiolitis in infants under 12 months old admitted to a pediatric critical care unit. Intensive Care Med, 2023.PMID 36592200
8. [8]Memar EHE Efficacy and safety of high-flow nasal cannula versus continuous positive airway pressure and conventional oxygen therapies in pediatric acute respiratory failure: a systematic review and meta-analysis. BMC Pediatr, 2026.PMID 42387462
9. [9]Emeriaud G Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2). Pediatr Crit Care Med, 2023.PMID 36661420
10. [10]Coghill M Accuracy of a novel system for oxygen delivery to small children. Pediatrics, 2011.PMID 21727103