Development of a reflected optical fiber system for measuring oxygen saturation in an integrated artificial heart-lung system.

The purpose of this study was to develop a blood oxygen saturation (OS) monitoring system for use with an integrated artificial heart-lung system (IAHLS). The OS monitoring system consists of two paired optical fiber probes (OFPs) and a measurement system. To investigate the effect of the OFP configuration and incident light wavelength on the relationship between OS and the reflectance ratio for wavelengths of 810 and 645 nm, we performed theoretical analyses of the relationship between OS and R810/R645 using a diffusion equation. The prototype OFP located on the blood outlet port of our IAHLS housing was evaluated using an in vitro test. An OS range of 65-100% was adjusted to supply oxygen and nitrogen gas to the IAHLS. The blood flow rate was maintained at 3 L/min by the rotational speed of an impeller in the IAHLS. The OS-corrected blood from the IAHLS was measured using a commercial gas analyzer. The correlation coefficients (r(2)) between the theoretical ratio of R810/R645 and OS, and between measured OS and the reflectance ratio of R810/R645 were 0.97 and 0.78, respectively. In conclusion, we confirmed that the development of this oximetry system is applicable for IAHLS.