Background: Endoscopic retrograde cholangiopancreatography (ERCP) is one of the most invasive procedures of upper gastrointestinal endoscopy routinely performed under intravenous sedation and local anesthesia. We lack knowledge on incidence and nature of disordered breathings during sedation for the endoscopic procedures, while sedatives and local anesthetics to upper airway may significantly depress respiratory control and arousal responses. Nasal cannula pressure measurement may be clinically useful for detecting abnormal breathings during sedation as is in sleep medicine. The aims of this study are 1) to test a hypothesis that nasal pressure measurement alone reflects breathing even during insertion of an endoscope through the mouth, and 2) to describe breathing during ERCP procedure in elderlies.
Methods: With Institutional Ethics Review Board approval, we conducted an exploratory observational study in elderlies undergoing ERCP under sedation. In addition to routine cardiorespiratory monitoring, close respiratory monitoring was performed by measurements of nasal cannula pressure and oral airflow with a thermistor. Four liter/min oxygen was administered via nasal prong throughout the sedation. Percutaneous carbon dioxide monitoring was also performed in some patients. Ramsey Sedation Score 5 and 6 were achieved and maintained by doses of midazolam 0.5-2mg, fentanyl 50 to 200 mcg, and continuous infusion of dexmedetomidine 0.7mcg/kg/hr. 
Result: Twenty-one elderly patients, aged 77±15 years old (mean±SD) and BMI 23.2±3.0 kg/m2, were recruited and completed the study protocol. Disordered breathings were common in all cases during sedation and apnea- hypopnea index (AHI) with and without insertion of endoscopy were 16.1±12.0 and 10.8±11.4 hour-1. Central apnea and hypopneas were less common and specifically limited immediately after injection of the sedatives and narcotics. Insertion of the endoscopy shifted predominant breathing route from the nasal (78.3±34.8% of the study time) to the oro-nasal (86.8±28.7%), and the nasal pressure signals were significantly weakened, but assessable 90% of time of the sedation. Flatten nasal pressure signals were helpful to determine the obstructive nature of the breathing abnormalities.
Conclusions: Our results indicate clinical effectiveness of the nasal pressure monitoring to diagnose disordered breathings during endoscopic procedure under sedation.

07 / Breathing pattern and route of breathing during endoscopic retrograde cholangiopancreatography (ERCP) under sedation in elderlies