THRIVE (Transnasal Humidified Rapid Insufflation Ventilatory Exchange) in Children at Different Flow Rates

Eligible, consented children will be prepared for general anaesthesia in the usual way. After start of anesthesia (="induction"), adequate face-mask ventilation will be established. The sealed envelope for randomisation will then be opened. Standard anesthesia will be continued, either using sevoflurane or propofol (anesthesia depth controlled by Narcotrend, to measure anesthesia depth using processed EEG waves). They will receive additional non-invasive monitoring for this study, such as transcutaneous measurement of tcCO2 and O2, NIRS, and thoracic electrical impedance tomography (EIT, PulmoVista® 500, Draeger, Luebeck, Germany) All patients will receive neuromuscular blockade medication of 2 x ED95 (standard intubation dose) to facilitate airway management and total intravenous anesthesia will be installed (continuous application of i.v. anesthesia medication). Up to two minutes of bag-mask ventilation with 100% oxygen and flow rates of 6-8L/min will be applied until an expired oxygen concentration of >90% is reached, as well as an SpO2 of 100% and an transcutaneous CO2 of 30-40mmHg.

For the study intervention, the bag-mask ventilation will be discontinued, and the child will be left apnoeic (the same happens always during intubation) until the saturation drops to 95%, which is still a low normal value. According randomization, any of the two study intervention s will be applied (THRIVE therapy with 100% O2 2l/kg/min, THRIVE therapy with 100% O2 4l/kg/min, all via nasal cannulas) while simultaneously guaranteeing an open airway by using Esmarch's procedure (jaw thrust) and an oral airway (Guedel tube). ECG, pulse-oximetry, blood pressure, Narcotrend, NIRS, thoracic EIT, PtcO2, PtcCO2 will be measured continuously over the study period. The time until desaturation from SpO2 100% to SpO2 95% will be also measured. A chest ultrasound at the end of the intervention will prove that no pneumothorax developed during the procedure. The study intervention will end at the time the saturation reaches SpO2 95% or when any other break-up criteria are reached. Bag mask ventilation will then be re-applied until SpO2 reaches again 100% and the patient will be treated according to the attending anaesthesiologist to ultimately establish a patent airway. Break-up criteria during apnoea are: SpO2 below 95%, transcutaneous CO2 above 70 mmHg, or time of apnoea >10 minutes. Drop of NIRS > 30% from baseline. A postmedication interview will be performed before PACU discharge.