HYPOTHESIS: During anesthetic pre-oxygenation with high FiO2, pulmonary atelectasis occur, especially in patients \< 6 years old, where FRC and pulmonary closing volume may overlap. New borns and children \<1 year old are especially vulnerable. OBJECTIVES: 1. Validate "air test" as a individualized and non-invasive diagnostic method of clinically significant atelectasis in pediatrics. 2. Determine what other factors contribute to atelectasis development in pediatrics METHODS: 30 pediatric patients will be studied with ages ranged between 45 postconceptional weeks and16 years old. Baseline SpO2 and lung ultrasound will be performed for each patient upon arrival at the operating theatre before preoxygenation with FiO2 of 1.0 SpO2 will be measured 15 min after intubation during a 5 min long "air test" trial (FiO2 0.25). lung collapse will be verified by lung ultrasound at the end of the 15 min trial. Lung collapse will be eventually granted upon lung US verification by a blind researcher.
Patients will breathe 0.21 \< FiO2 \< 0.25 during 5 min and have a lung ultrasound perfomed at the end of the 5 min trial.
Córdoba, Argentina