High-Flow nasal cannula therapy is the administration of heated, humidified and blended air/oxygen via nasal cannula at rates of at least 2 L/kg bodyweight /min. This high-flow nasal cannula therapy was developed in neonatal intensive care unit for preterm babies with respiratory pauses as an alternative to continuous pressure support (CPAP). Due to its ease of use and safety to apply to a wide range of indication, this oxygen delivery therapy is increasingly gaining interest for providing respiratory support in paediatric and adult patients with respiratory failure in the ICU. High-flow nasal cannula therapy is applied in preterm infant with respiratory distress syndrome, apnoea of prematurity or a respiratory support after extubation. In the adult population the use of HFNCT focuses on hypoxemic respiratory failure and improvement reduction of hypoxemia during intubation in the anesthesia environment. A new application for high-flow nasal cannula therapy in adults is the extension of apnoea time in patients with difficult airways who are undergoing general anesthesia. In this environment a new term for this kind of oxygen therapy was created: THRIVE transnasal humidified rapid-insufflation ventilatory exchange. To distinguish this kind of high-flow nasal cannula therapy in apnoeic patients from the one in the paediatric ICU or ward the investigators use the term i-THRIVE for infant transnasal humidified rapid insufflation ventilation exchange.

Due to the increased oxygen consumption and the reduced functional residual capacity, neonates, infants, and small children have a reduced apnoea tolerance compared to adults. Furthermore infants and small children have a greater closing capacity, which increases the airway collapse under general anesthesia and muscle paralysis. A direct consequence is that hypoxemia is very likely to occur after cessation of spontaneous or assisted ventilation during induction of anesthesia. Apnoea without supplemental oxygen leads to hypoxemia in a 1-year-old infant without preoxygenation within seconds. All paediatric (and adult) patients undergoing general anesthesia have at least a brief period of apnoea during intubation between the time the face-mask is removed from the patient and the tube is placed in the trachea. Therefore, at least short phases of deoxygenation may occur.

However if anesthesia needs to be provided in emergency situations or in the presence of a difficult airway, the rate of complication increases rapidly. In these circumstances methods that reduce desaturation incidents during prolonged difficult intubation are desirable. Due to oxygen toxicity in neonates or small children, prevention of hypoxemia with oxygen concentration below 60% would be favourable in this setting. Despite promising pilot results with high-flow nasal cannula therapy, it is unknown whether this technique is superior to low-flow oxygenation with high concentration and whether it is necessary to apply high-flow nasal cannula therapy with high (80-100%) versus low (30-50%) concentration oxygen.

This study investigates under controlled circumstances the concept of i-THRIVE to prolong the apnoea time without deoxygenation and to improve safety of airway management in paediatric patients. Furthermore, this study enables to quantify the effects of different oxygen concentrations with high-flow nasal cannula therapy and distinguishes it better from conventional low-flow apnoeic oxygenation methods.