Monitoring of the oxygen pressure in the blood of live animals using the oxygen dependent quenching of phosphorescence.

Oxygen dependent quenching of phosphorescence is a powerful new method for measuring oxygen pressure in biological systems (see Vanderkooi et al, J. Biol. Chem. 262 (1987) 5476; Wilson et al, J. Biol. Chem. 263 (1988) 2712). This technology has now been extended to include measurements of the phosphorescent of oxygen probes dissolved in the blood as a complex with albumin. In this communication, we report on a new microcomputer controlled phosphorimeter in which the tissue is illuminated by a flash lamp and the phosphorescence observed through flexible light guides designed to make measurements in regions down to approximately 1 mm in diameter. Measurements of the phosphorescence lifetimes of these probes in regions of tissue necessarily report a distribution of oxygen pressures due to the presence of blood in veins and arteriols as well as that present in the capillaries. Thus the phosphorescence decay is the sum of a continuum of exponentials with different decay constants and initial intensities. The complete phosphorescence decay curve is digitized using a 12 bit, 1 MHz A/D board and deconvoluted using numerical methods to yield a distribution of exponentials contributing to the total decay curve.