Tissue-blood partition coefficient for xenon: temperature and hematocrit dependence

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Abstract
Ostwald''s solubility coefficients for 133Xe in plasma (Sp), red blood cells (Sc) and various tissue homogenates (St) obtained from the dogs were determined at 37, 27, 20 and 4.degree. C by counting the 133Xe activities of the air phase and the sample (liquid, cells or tissue) in the same tube following equilibration. For all tissues the solubility coefficient varies inversely with temperature. A linear relationship exists between Sp, Sc and St and the reciprocal of absolute temperature (Arrhenius plot). The values of red cell-plasma (.lambda.cp) and tissue-plasma (.lambda.tp) partition coefficients for xenon calculated from the measured Sp, Sc and St agree well with the predicted values obtained from the linear regressions of Arrhenius plots. With the use of .lambda.cp, .lambda.tp, and the hematocrit value, the tissue-blood partition coefficient (.lambda.tb) can be calculated. This type of approach yields more accurate .lambda.tb values and facilitates blood flow studies by Xe washout at abnormal body temperatures as well as in situations with a wide variation of hematocrit values. Because .lambda.cp increases and .lambda.tp for various tissues decreases at low temperature, .lambda.tb is lower in hypothermia. The temperature dependence of Xe solubility in various tissues is related to lipid content and amount of proteins.