In vivo pO2 measurements in hamster skinfold by recessed pO2 microelectrodes and phosphorescence quenching are in agreement

Objective: Phosphorescence quenching has been used successfully to optically measure in vivo blood pO(2) in the microvasculature. Optical measurements have also been made in some tissues, but it is not clear whether these results accurately reflect tissue pO(2). Methods: Recessed pO(2) microelectrodes and the phosphorescence quenching technique were used simultaneously to measure in vivo tissue pO(2) in hamster skinfold. The optical window for phosphorescence quenching was focused around the tips of microelectrodes that were positioned in tissue regions at least 100 mu m from large microvessels. Results: Mean tissue pO(2) measured by recessed pO(2) microelectrodes was 18.4 +/- 1.7 (SE) Torr, and mean tissue pO(2) determined from the time course of phosphorescence decay was 18.8 +/- 2.0 Torr (no significant difference). The two tissue pO(2) measurements agreed over a wide range, from 2 to 46 Torr (r = 0.93, 39 paired measurements from six sites in 3 animals). There nas no systematic change in the microelectrode tissue pO(2) during the period of light excitation used for the optical method. Conclusions: Under the conditions of our study, sufficient amounts of porphyrin dye leaked from the vasculature and diffused into tissue, allowing accurate measurements of tissue pO(2) by the phosphorescence quenching technique. Furthermore, the optical method did not deplete significant amounts of O(2) from tissue during light excitation.