Study objective: High inspired oxygen concentrations (FiO2) are claimed to cause resorption atelectasis increasing the risk for perioperative hypoxemia and postoperative pulmonary complications. Pediatric physicians are still reluctant to accomplish low FiO2 strategies in children. We investigated the association between lung ultrasound score (LUS) and arterial oxygenation (PaO2/FiO2 ratio)in anesthetized mechanically ventilated children undergoing non-abdominal surgery using different FiO2 fractions.

Study design: Observational cohort.

Study settings: Operative rooms and post-anesthesia care unit.

Patients: Thirty-three patients aged (3–12 years) of both sexes.

Intervention: Patients were anesthetized while receiving high FIO2 protocol (preoxygenation 1.0, induction and recovery 0.8, maintenance 0.6, post-extubation 1.0 and 0.21 for 2h postoperative).

Measure: ments: LUS was performed after intubation and initiation of mechanical ventilation, after the end of surgery, and 2h postoperatively. Arterial blood gas analysis was performed at the same time points and respiratory mechanics were recorded intraoperatively. LUS scores were tested for probability of bivariate correlation with PaO2/FiO2 ratio (primary endpoint), age, weight, operation time, PaO2, and dynamic compliance.

Main results: After intubation, the median LUS score was 2 (Range: 0–14) which significantly decreased after surgery to 1 (0–8), (P = 0.010). At 2- hours postoperatively, it was 0 (0–6) which was significantly lower than both after intubation (P = 0.001) and after surgery (P = 0.007). No significant Correlation was found between the LUS score and any investigated parameters. Conclusions: Even though we found no significant correlation between LUS and PaO2, or PaO2/FiO2 ratio, the high values of LUS after intubation necessitate caution when administering high FiO2 levels in pediatrics.