Subject(s)
Diphosphoglyceric Acids/physiology , Oxygen/blood , 2,3-Diphosphoglycerate , Biological Transport , Blood Transfusion , Carbon Dioxide/metabolism , Diphosphoglyceric Acids/blood , Erythrocytes/metabolism , Hemoglobins/metabolism , Humans , Hydrogen-Ion Concentration , Oxygen Consumption , Oxyhemoglobins/metabolismSubject(s)
Carbon Dioxide , Hemoglobins , Bicarbonates , Carbon Dioxide/blood , Diffusion , Electrophysiology , Hemoglobins/metabolism , Hydrogen-Ion Concentration , Ions , Models, Biological , SodiumABSTRACT
The model of the respiratory function of blood as outlined here is judged to be a powerful tool for the evaluation of the potential effects of changes in blood as well as tissue parameters upon the supply of oxygen to tissue. The erythrocyte-plasma disequilibria in lung and systemic capillaries which is a consequence of the slowness of plasma CO2 hydrolysis are not significant in terms of the delivery of oxygen to tissue, but result in slightly lower unloading of CO2 in the lungs compared to that which might occur at full equilibration. However, the effects might be of greater interest when relating pH values measured by in vivo sampling to actual values prevailing within the capillaries. The physiological importances of hyperventilation and elevated DPG levels in anemia cannot as yet be clarified. If anything, it appears that increased DPG is a compensatory mechanism to restore proper O2-Hb affinity in alkalosis, while the purpose for an alkalosis is not obvious.
Subject(s)
Anemia/blood , Carbon Dioxide/metabolism , Models, Biological , Oxygen Consumption , Oxygen/blood , Oxyhemoglobins/metabolism , Respiration , Bicarbonates/blood , Blood Flow Velocity , Carbon Dioxide/blood , Chlorides/blood , Diphosphoglyceric Acids/blood , Hydrogen-Ion Concentration , Kinetics , Muscles/metabolismABSTRACT
A theoretical model of the process of respiratory gas exchange between capillary and tissue is described, with special reference to the importance of variations in blood properties. The volume of tissue supplied with oxygen from a single vessel, as a function of the blood flowrate (u), hematocrit (h), and 2,3 diphosphoglycerate concentration (DPG), is calculated from a solution to the set of equations governing species distributions in the blood and tissue. The results, which are presented in the form of crossplots of the three blood parameters (u, h, and DPG) at a constant oxygen supply rate, show the possible significance of in vivo variations in the oxygen affinity of hemoglobin as a compensatory mechanism. Of further physiological interest is the sharp increase in venous erythrocyte pH in response to decreases in hematocrit, once the hematocrit is below a certain level. These results, and those relating DPG to hematocrit at constant O2 supply, are consistent with experimental observations of elevated DPG and pH levels in anemic individualts, and the dependence of erythrocyte DPG concentration upon pH.
