Its use in intensive care for spontaneously breathing patients is well established and novel uses are emerging in anaesthesia. High flow nasal oxygen (HFNO) is delivered through specialised nasal cannula and can achieve a flow rate of up to 70 L/min and FiO2 near 100% (1). The patient therefore entrains room air with inspiration and does not get the desired oxygen concentration (1,2). These conventional oxygen delivery devices fail to supply oxygen at high enough flow rates to match a patient’s peak inspiratory flow rate. Typically they deliver a low flow of nonhumidified oxygen at up to 15 L/min, often without a defined fraction of inspired oxygen (FiO2) concentration. The delivery of oxygen to patients is conventionally via face masks or nasal cannula.

High flow oxygen has a role in hypoxaemic respiratory failure in intensive care management of patients.

Apnoeic time can be safely extended using high flow nasal oxygen (HFNO) for 22 minutes.

Carbon dioxide rise during apnoea is less with high flows (40-70L/min) than with conventional oxygenation duringapnoea.

Positive airway pressure is achieved through the high flow rates with approximately 1cmH2O increase for each 10L/min flow rate above 30L/min.

High flow oxygen delivers oxygen at flow rates at or above peak inspiratory flow rates in patients, typically 40-70L/min.

Tracheostomy physiological dead space