Real time monitoring of oxygen saturation in extracorporeal circulation using an optical reflectance transducer.

A novel optical reflectance transducer for continuous and real time monitoring of oxygen saturation (So2) in extracorporeal tubings during cardiopulmonary bypass (CPB) is described. The optical transducer integrates 2 light-emitting diodes and a photodiode. The transducer is attached to the extracorporeal tubing by a transparent flow through a 3/8 x 3/8 inch connector/cuvette. Four transducers were built and evaluated in vitro in a mock extracorporeal system at a controlled So2. The correlation index (r2) between the So2 measured by the transducers and values determined by a commercial blood gas analyzer was 0.998 with an absolute difference < 0.5%. The performance of the transducer was also evaluated during 16 CPB surgeries in patients with an r2 of 0.873 and an absolute difference < 3.5%. The results obtained demonstrate the applicability of the optical reflectance transducer for monitoring So2 in the tubings of the CPB circuit.