Upper gastrointestinal endoscopy is a commonly performed diagnostic and, when necessary, therapeutic procedure in pediatric patients for the evaluation of the esophagus, stomach, and duodenum. Additional interventions such as biopsy, foreign body removal, or polypectomy can also be performed during the same session. Sedation is generally required during the procedure, and the depth of sedation is often greater than that used for routine examinations. Because of anatomical and physiological differences in children-such as smaller airway diameter, higher oxygen consumption, and lower functional residual capacity-the risks of upper airway obstruction, hypoxemia, and hypoventilation are higher than in adults. The passage of the endoscope through the mouth, combined with the respiratory depressant effects of sedatives and the smaller airway diameter, increases the likelihood of hypoxemia and limits the anesthesia team's access to the airway. Therefore, maintaining airway stability and optimizing oxygenation during sedation are particularly critical in pediatric patients. Currently, several oxygen delivery methods are used during upper gastrointestinal endoscopy, including conventional nasal cannulas, high-flow nasal oxygen systems, and procedural oxygen masks. The Procedural Oxygen Mask (POM™) is a specially designed device that delivers oxygen through both the mouth and nose while allowing endoscope passage and continuous capnography monitoring. Previous studies in adults have shown that the use of POM™ or high-flow nasal oxygen reduces the incidence of hypoxemia during endoscopy. However, in children, there is a lack of randomized controlled trials directly comparing POM™ with nasal cannula use. This single-center prospective randomized controlled trial aims to compare the effectiveness of the Procedural Oxygen Mask (POM™) and nasal cannula in preventing hypoxemia during pediatric upper gastrointestinal endoscopy under sedation. The findings are expected to contribute to safer sedation practices and improved airway management strategies in pediatric endoscopic procedures.