Oxygen Reserve Index in Predicting Hypoxemia in Morbidly Obese Patients 

BACKGROUND: This study evaluated whether the oxygen reserve index(ORi) decreases earlier than percutaneous oxygen saturation(SpO 2 ) and provides added warning time in morbidly obese patients. METHODS: After obtaining the approval of the Hospital Ethics Committee, this prospective, observational study included written informed consent from 51 patients with 1940m/kg2 undergoing an elective surgical requiring endotracheal intubation.In addition to standard monitors, an ORi sensor was placed and baseline values were recorded.The patients were preoxygenated until end tidal expiratory oxygen concentration is reached to 90%.After anesthesia induction and endotracheal intubation, the breathing circuit was not connected endotracheal tube until the SpO 2 decreased to 95%.Times of tolerable apnea,ORi warning,SpO 2 warning and added warning were also recorded at the end of preoxygenation, beginning of intubation,beginning of the ORi alarm,when SpO 2 reached 95%,when ORi reaches a plateau. RESULTS: In both groups,ORi warning time was longer than the SpO 2 warning time.While ORi warning time was observed as 32seconds in morbidly obese patients and 94seconds in patients with normal body mass index(BMI),SpO 2 warning time was determined as 15seconds and 36seconds in these patients, respectively.It is observed that tolerable apnea, ORi,SpO 2 and added warning times are longer in those with normal BMI compared to those with morbidly obese. CONCLUSIONS: As a result, ORi can provide an early warning to prevent unexpected hypoxia before saturation begins to decrease.In particular, it allows faster intervention in airway management and protection of patient safety by calling for help earlier in high-risk patients such as morbidly obese with reduced pulmonary reserve.