This study aims to investigate the optimal oxygen flow rate needed during tracheal intubation with the C-MAC video laryngoscope (Karl Storz, Tuttlingen, Germany) using Miller-blade or Macintosh-blade size No. 0 or No. 1 in the operating room or intensive care unit. The investigators hypothesize that the difference between low-flow and high-flow supplemental oxygen is negligible.

Eligible children will be prepared for intubation according to the local SOPs of the pediatric anesthesia departments. Mandatory monitoring will consist of: SpO2, HR, NIBP.

Induction of anesthesia: If feasible, all children included in this protocol will be pre-oxygenated before induction of anesthesia for one minute through face-mask with FiO2 1.0 and flow rates of 6-10L/min. The induction of anesthesia for tracheal intubation will be performed using a combination of sedative/hypnotic drugs, opioids and non-depolarizing muscle relaxant.

The following medications will be mandatory as per protocol:

• A neuromuscular blocking agent (NMBA): Rocuronium 0.5-1 mg/kg, Cis-Atracurium 0.2-0.5 mg/kg, Atracurium 0,5 mg/kg, Vecuronium 0.1 mg/kg, Mivacurium 0.2 - 0.3 mg/kg or Succinylcholine 2 mg/kg.
• One or more of the following hypnotic agents (Thiopentone 4-7 mg/kg, Ketamine 0.5-2 mg/kg, Propofol 1-4 mg/kg, Midazolam 0.5-1 mg/kg, Sevoflurane up to 8%).
• An opioid drug and anticholinergic can be chosen and administered at the discretion of the anesthetist in charge.

Before intubation: After induction of anesthesia and the administration of a NMBA, bag-mask ventilation with FiO2 1.0 (flow rates of 6-10 L/min) will be performed for 60 seconds until apnea sets in. After induction all patients will be paralyzed to facilitate airway management. Full neuromuscular blockade will be assessed by train-of-four (TOF) monitoring. Thereafter oxygen administration, laryngoscopy and tracheal intubation are performed.

During intubation: The administration of oxygen during intubation is mandatory for every study participant and is randomized as follows:

Low-flow Oxygen Group: For orally intubated children, the administration of low-flow oxygen (0.2 L/kg/min FiO2 1.0) takes place via conventional nasal cannula (Intersurgical, Wokingham, UK). For nasally intubated children, the administration of low-flow oxygen (0.2 L/kg/min FiO2 1.0) takes place via a nasal oxygen sponge cannula (Vygon, Ecouen, France) adapted to the dimension of nare. After administration of low-flow oxygen laryngoscopy and tracheal intubation are performed.

High-Flow Oxygen Group (control-group): For all orally intubated children, the administration of high-flow oxygen (2 L/kg/min FiO2 1.0) takes place via nasal cannula with the Optiflow (Fisher & Paykel Healthcare, Auckland, New Zealand). For nasally intubated children, the administration of low-flow oxygen (2 L/kg/min FiO2 1.0) takes place via the anaesthesia circuit through the tracheal tube placed in the nose. After administration of high-flow oxygen laryngoscopy and tracheal intubation are performed.

For a premature neonate < 1kg an uncuffed tube ID 2.5 will be used. For premature babies and newborn between 1kg and 3.0 kg an uncuffed tube ID 3.0 will be used. For babies > 3.0 kg - 8 months a cuffed tube ID 3.0 or an uncuffed tube 3.5 will be used. For infants 8 months - 12 months a cuffed tube ID 3.5 or an uncuffed tube 4.0 will be used. Based on the group of randomization, the child will receive supplemental oxygen low-flow via a conventional nasal cannula vs high-flow with the Optiflow (Fisher & Paykel Healthcare, Auckland, New Zealand).

Miller-blade or Macintosh-blade size No. 0 will be used for children < 1 kg. In cases of unexpected difficult intubation, the difficult airway algorithm (18) will be followed. After the first unsuccessful intubation attempt with the randomized flowrate, the investigators encourage to perform a second attempt with the same rate but based on the clinical judgment the intubating physician can proceed to an attempt with the same technique, or change the flow rate, blade size or the type of laryngoscope. A maximum of 4 intubation attempts in total will be performed. The last intubation attempt must be performed by the most experienced physician in the room. Additional devices like stylet, bougie, etc., can be used at any stage of the intubation process. If the intubation remains unsuccessful the difficult airway algorithm will be followed (Appendix) and a supraglottic airway - SGA will be inserted.

Inclusion Criteria:

• Pediatric patients requiring oral or nasal tracheal intubation for elective, semi-elective, or urgent surgical and non-surgical indications.
• Neonates and infants up to 52 weeks postconceptual age, with legal guardians providing written informed consent before the intervention

Exclusion Criteria:

• Prediction of difficult intubation upon physical examination or previous history of difficult intubation, mandating a technique different than direct laryngoscopy to secure the airway;
• Congenital heart disease demanding FiO2 < 1.0
• Cardiopulmonary collapse requiring advanced life support
• Intubation for emergency surgical and non-surgical indications.