Endoscopic retrograde cholangiopancreatography (ERCP) is an imaging procedure that visualizes the drainage ducts of the pancreas, gallbladder, and liver through the use of a duodenoscope and contrast media. By endoscopically identifying the ampulla of Vater, the common bile duct is cannulated. ERCP is also frequently utilized for therapeutic interventions, such as endoscopic sphincterotomy, bile duct stone extraction, stent placement in malignant and benign biliary strictures, and biopsy collection, thus playing a critical role in both the diagnosis and treatment of pancreatobiliary disorders.

ERCP, being more invasive than routine upper endoscopies or colonoscopies, typically necessitates deeper levels of sedation. The procedure is performed in the prone, modified prone, or lateral decubitus position, which increases the risk of hypoxemia and hypoventilation due to upper airway obstruction. Furthermore, endoscopic instruments inserted through the oral cavity limit anesthesiologists' access to the patient's airway, thereby restricting ventilation support during gastrointestinal endoscopy. Ensuring airway stability during sedation is paramount for patient safety and procedural efficacy. Currently, a range of devices, including traditional nasal cannulas, high-flow oxygen masks, and procedural oxygen masks, are routinely employed to provide oxygen support throughout the procedure.

The existing literature includes randomized controlled trials and systematic reviews aimed at preventing hypoxemia during ERCP. Through this study, investigators aim to make a novel contribution to the literature by assessing the effectiveness of a recently introduced procedural oxygen mask.

This study aims to compare the efficacy of different oxygen delivery methods (Nasal Cannula [NC] and Procedural Oxygen Mask [POM]) in preventing the incidence of hypoxemia during Endoscopic Retrograde Cholangiopancreatography (ERCP). Designed as a randomized controlled prospective study, participants were assigned into two groups, Group N (NC) and Group P (POM), at a 1:1 ratio through randomization. The randomization was performed using computer-assisted random allocation; however, due to the visual differences in the oxygen delivery devices, neither healthcare providers nor patients could be blinded to the randomization results. A power analysis conducted to establish a statistical power of 80% and an alpha level of 0.05 indicated that a total of 140 patients, with 70 patients in each group, should be included in the study. Considering potential dropouts, 150 patients will be included in the study This evaluation ensures that an adequate sample size is obtained to detect a significant difference in the incidence of hypoxemia.

Throughout the ERCP procedure, all patients will be monitored using pulse oximetry, electrocardiography (ECG), and non-invasive blood pressure monitoring. Capnography will be applied in both groups, and necessary interventions will be carried out by anesthesia specialists if a patient's oxygen saturation falls below 90%. All interventions and events will be meticulously documented. Following the procedure, patients will be monitored in the post-anesthesia care unit (PACU), and those with a Post-Anesthesia Discharge Scoring System (PADSS) score of 9 or higher will be discharged.

Anesthesia Management The oxygen flow rate will be maintained constant throughout the procedure. Initially, patients will receive midazolam at a dose of 0.02 mg/kg, followed by 0.3 mg/kg of ketamine. To ensure sedation, propofol will be administered as an initial bolus dose of 0.5-1.0 mg/kg; further bolus doses of 0.25-0.5 mg/kg will be given every 1-3 minutes to maintain the desired sedation level. The target sedation level will be aimed at 3-4 on the Ramsay Sedation Scale (RSS), and these target values will be preserved during the procedure. Upon completion of the procedure, patients will be awakened using verbal and tactile stimuli; once the RSS reaches 2, they will be transferred to the PACU. In the PACU, patients will be discharged if they achieve a PADSS score of 9 or above.

Oxygen Reserve Index (ORi) measurement will performed on all patients. The ORi value will measured and recorded at the plateau level during the preoxygenation stage (as the baseline), immediately after the start of the procedure, at the end of the procedure, and the highest ORi value measured throughout the procedure

Vital signs, procedure durations, and dosages of medications used for each patient will be meticulously recorded. All anesthesia-related decisions during the procedure will be made by the supervising anesthesia specialist.

Inclusion Criteria:

• Aged 18-75 years
• American Society of Anesthesiologists (ASA) classification of 1-2-3
• Patients scheduled for ERCP at Kocaeli City Hospital Endoscopy Unit

Exclusion Criteria:

• Patients who refuse to participate in the study
• Patients with allergies to ketamine, propofol, or midazolam
• Patients diagnosed with psychiatric disorders
• Patients with a body mass index (BMI) >30 kg/m²
• Patients with cognitive impairment, dementia, or communication issues
• Pregnant patients or those in the postpartum period
• Patients diagnosed with sleep apnea syndrome
• History of intubation within the last 3 months
• History of lower respiratory tract infection within the last 3 months
• History of intensive care unit admission within the last 3 months
• Patients with a tracheostomy
• Patients with a history of tracheostomy
• Patients who are oxygen-dependent due to a medical condition
• Patients with lung cancer or who have undergone surgery on their lungs
• Patients with asthma, COPD, or interstitial lung diseases
• Patients with uncontrolled hypertension (BP >180/110)
• Patients receiving home care

Personal data and study data will not be shared.