During mechanical ventilation (MV) hypoxemic or hyperoxemic events should be carefully monitored and a quick response should be provided by the caregiver at the bedside. Pediatric mechanical ventilation consensus conference (PEMVECC) guidelines suggest to measure SpO2 in all ventilated children and furthermore to measure partial arterial oxygen pressure (PaO2) in moderate-to-severe disease. There were no predefined upper and lower limits for oxygenation in pediatric guidelines, however, Pediatric acute lung injury consensus conference PALICC guidelines proposed SpO2 between 92 - 97% when positive end-expiratory pressure (PEEP) is smaller than 10 cm H2O and SpO2 of 88 - 92% when PEEP is bigger or equal to 10 cm H2O. For healthy lung, PEMVECC proposed the SpO2>95% when breathing a FiO2 of 21%. As a rule of thumb, the minimum fraction of inspired O2 (FiO2) to reach these targets should be used. A recent Meta-analyze showed that automated FiO2 adjustment provides a significant improvement of time in target saturations, reduces periods of hyperoxia, and severe hypoxia in preterm infants on positive pressure respiratory support. This study aims to compare the closed-loop FiO2 controller with conventional control of FiO2 during mechanical ventilation of pediatric patients

Inclusion Criteria:

• Pediatric patients older than 1 month and younger than18 years of age; hospitalized at the PICU with the intention of treatment with IMV at least for the upcoming 5 hours
• Requiring FiO2 ≥ 25% to keep SpO2 in the target ranges defined by the clinician
• Written informed consent signed and dated by the patient or one relative in case that the patient is unable to consent, after full explanation of the study by the investigator and prior to study participation

Exclusion Criteria:

• Patient with indication for immediate noninvasive ventilation (NIMV), High flow oxygen therapy (HFOT)
• Hemodynamic instability defined as a need of continuous infusion of epinephrine or norepinephrine > 1 mg/h
• Low quality on the SpO2 measurement using finger and ear sensor (quality index below 60% on the SpO2 sensor, which is displayed by a red or orange colour bar)
• Severe acidosis (pH ≤ 7.25)
• Pregnant woman
• Patients deemed at high risk for the need of non-invasive mechanical ventilation within the next 5 hours
• Patients deemed at high risk for the need of transportation from PICU to another ward, diagnostic unit or any other hospital
• Diseases or conditions which may affect transcutaneous SpO2 measurement such as chronic or acute dyshemoglobinemia: methemoglobinemia, carbon monoxide (CO) poisoning, sickle cell disease
• Formalized ethical decision to withhold or withdraw life support
• Patient included in another interventional research study under consent
• Patient already enrolled in the present study in a previous episode of acute respiratory failure