Application of the Optode to Measurements of Surface Po₂ And Pco₂ of the Isolated Guinea-Pig Heart

Abstract

We described in previous papers that the so-called optode (LÜBBERS and OPITZ, 1975 and 1976) was especially well suited for the quantitative determination of Po₂ and Pco₂. For the measurement of Po₂, the flourescence quenching of the indicator pyrene butyric acid by oxygen (VAUGHAN and WEBER, 1970; KNOPP and LONGMUIR, 1972) and for Pco₂, the change of the fluorescence indicator β-methylumbelliferone with pH was used (OPITZ and LÜBBERS, 1975). In summary, the characteristical details of this optode-device are:

• 1. A few microns thick indicator layer is separated from the medium to be measured by a gas-permeable membrane which prevents possible toxic influences and spectral distortions by interactions of the indicator molecules with molecules of the substance.

• 2. The indicator film is tightly held between a quartz window (on the excitation side) and the membrane so that no changes in the indicator concentration can occur.

• 3. The optode is located in front of the biological object so that the filter effect of the tissue is avoided.