Capillary Red Cell Residence as a Measure of Tissue Oxygen Delivery
Experimental measurements of changes in the fluorescence intensity of endogenous and exogenous indicators of tissue oxygen tension must be corrected for changes in red cell mass in the observed volume of tissue. In our presentation last year (Longmuir et al. 1984) we assumed that localized increased oxygen consumption in the sensory cortex on peripheral stimulation would result in increases only in red cell mass. Thus any observed increases in fluorescence of pyrenebutyric acid would be equal to or less than the actual change in fluorescence quenching by oxygen: that there was a real fall in local tissue oxygen tension. However, subsequent studies have shown that following sensory stimulation, some areas of the cortex show reduced red cell mass. These reductions in microregional blood flow do not appear to be a direct consequence of sensory stimulation, but are part of the normal pattern of fluctuations in the distribution of red cells which occur continuously in the brain, giving rise to the oscillations in local PO2 described by Manil et al. (1984). When large areas of cortex are studied, these fluctuations average out and the problem of correction is simplified.
KeywordsSensory Stimulation Light Reflection Tissue Oxygen Tension Peripheral Stimulation Television System
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