In vivoTissue pO₂Measurements in Hamster Skinfold by Recessed pO₂Microelectrodes and Phosphorescence Quenching Are in Agreement

Abstract

Objective:Phosphorescence quenching has been used successfully to optically measure in vivoblood pO₂in the microvasculature. Optical measurements have also been made in some tissues, but it is not clear whether these results accurately reflect tissue pO₂. Methods:Recessed pO₂microelectrodes and the phosphorescence quenching technique were used simultaneously to measure in vivotissue pO₂in hamster skinfold. The optical window for phosphorescence quenching was focused around the tips of microelectrodes that were positioned in tissue regions at least 100 µm from large microvessels. Results:Mean tissue pO₂measured by recessed pO₂microelectrodes was 18.4 ± 1.7 (SE) Torr, and mean tissue pO₂determined from the time course of phosphorescence decay was 18.8 ± 2.0 Torr (no significant difference). The two tissue pO₂measurements agreed over a wide range, from 2 to 46 Torr (r = 0.93, 39 paired measurements from six sites in 3 animals). There was no systematic change in the microelectrode tissue pO₂during 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 pO₂by the phosphorescence quenching technique. Furthermore, the optical method did not deplete significant amounts of O₂from tissue during light excitation.

• O₂transport
• phosphorescence quenching
• photochemical depletion
• recessed pO₂microelectrode
• tissue pO₂
• microvascular pO₂.