Inclusion Criteria:  patients undergoing ERCP 18 years and older capable of giving consent for the procedure  Exclusion Criteria:  Unwillingness or inability to consent for the study Age less than 18 years Standard contraindications to ERCP Acute pancreatitis within 72hrs prior to ERCP Chronic calcific pancreatitis Pancreatic divisum Pancreatic malignancy ICU patients Patients on home oxygen at baseline. Incarcerated patients.