Figure 1. Schematic diagram of 4-channel composite probe consisting of a laser Doppler component with separate emitting and receiving channels, a thermocouple, and a P_O2 probe.

The O₂ probe emits short pulses of blue LED light resulting in a fluorescent discharge of a dye on the probe surface. The fluorescence is quenched in proportion to O₂ concentration in the tissue. (Adapted from Oxford Optronix Ltd, Oxylite User's Manual.)