Oxygen delivery systems used in acute oxygen therapy

Choice of oxygen delivery system depends on the desired fraction of inspired oxygen (FiO₂). Approximate FiO₂ values delivered by different delivery systems are:

• standard nasal cannulae: FiO₂ 0.24 to 0.35 at an oxygen flow of 1 to 4 litres per minute
• Venturi masks: FiO₂ 0.24 to 0.60
• simple face mask: FiO₂ 0.35 to 0.60 at an oxygen flow of 5 to 10 litres per minute
• 100% non-rebreather reservoir mask: FiO₂ greater than 0.60 at 15 litres per minute
• high-flow nasal cannulae: FiO₂ 0.21 to 0.80.

High-flow nasal cannula oxygen therapy provides heated and humidified oxygen blends through loose fitting nasal prongs. FiO₂ can be titrated independently of the overall flow rate. The overall flow rate generates continuous positive airway pressure (CPAP) in the range of 2 to 3 cm H₂O (producing a CPAP–like effect). First used in neonatal care, its use in bronchiolitis is becoming more widely accepted. Evidence-based recommendations for other conditions in children and for adults are yet to be established. Some centres recommend therapy be used only in the emergency department, high-dependency unit or intensive care unit. Different flow rates are used in children compared to adults, and high-flow nasal cannula oxygen therapy in children should be used in centres with expertise in its use, or in consultation with a specialist centre. For more information on high-flow nasal cannula oxygen therapy in children, see The Royal Children’s Hospital (Melbourne) guidelines.