Continuous measurement of blood oxygen pressure using a fiber optic sensor based on phosphorescence quenching

Measuring oxygen pressure within an artery is essential for providing information on blood perfusion. Optic-sensor is particularly well suited for oxygen pressure measurement because electrolytic or magnetic changes of the environment do not affect the measurement. We developed a fiber optical sensor based on phosphorescence quenching method. The probe, Pd-meso-tetra-(4-carboxyphenyl)porphyrin, was immobilized to the silicone resin membrane, which has high oxygen permeability, and attached to the tip of POF (outer diameter: 500 μm). The light source used for exciting the probe was a Nd:YAG-SH pulse laser (532 nm) and the phosphorescent emission was detected by a photomultiplier tube. The signal was fitted to a single exponential decay curve to acquire the time constant (life time), thereafter the oxygen pressure was calculated from Stern-Volmer relationship. The effectiveness of the sensor was obtained to measure the dissolved oxygen with high precision (correlation coefficient 0.999) and high response time (about 7 sec). In this study, measurement of oxygen pressure was also made in the femoral artery of the rat by using the developed sensor and it indicated that it was very useful to measure arterial oxygen pressure continuously.