End-Tidal CO2 Instability Predicts Hypoxia and Optimizes Sedation Safety During Endoscopic Submucosal Dissection

Objectives: Endoscopic submucosal dissection (ESD) requires deeper and more prolonged sedation than standard endoscopic procedures, increasing the risk of ventilation-related complications. We aimed to evaluate the utility of capnographic monitoring during ESD, specifically its capacity to detect early respiratory compromise compared with conventional pulse oximetry, and to assess the efficacy of nasal high-flow oxygenation (NHFO) in managing hypoxia.Methods: In this prospective observational study, we enrolled 98 consecutive patients who underwent ESD with both capnographic and conventional monitoring. End-tidal carbon dioxide (EtCO<sub>2</sub>) was recorded at one-minute intervals. Patients were stratified into hypoxic and nonhypoxic groups based on the occurrence of intraprocedural oxygen desaturation. We compared demographic and procedural factors between groups and analyzed the therapeutic efficacy of NHFO in patients developing hypoxia. Multivariate logistic regression was performed to identify independent predictors of hypoxia.Results: EtCO<sub>2</sub> instability was independently associated with intraprocedural hypoxia (odds ratio, 2.427; <i>p</i>=0.002). Predictors of EtCO<sub>2</sub> instability included a higher Mallampati score, a tendency toward oral breathing, and lower baseline oxygenation. NHFO substantially improved peripheral oxygen saturation and sedation quality in patients with hypoxia.Conclusions: EtCO<sub>2</sub> instability serves as an early indicator of hypoxia during ESD. Continuous EtCO<sub>2</sub> monitoring facilitates the early detection of respiratory compromise, enabling timely intervention. Furthermore, NHFO reduces the need for awakening patients or adjusting sedation, thereby improving safety and procedural stability. Combining capnography with NHFO enhances patient safety and procedural efficiency during ESD.