(269b) An a Priori Estimate of Oxygen Delivery at the Capillary and Skeletal Muscle Interface


Oxygen delivery to skeletal muscle has been modeled in a Krogh Tissue Cylinder Model with a mixture of human red blood cells and hemoglobin based oxygen carriers. The model geometry consists of three distinct subdomains representing the capillary, the membrane wall of the capillary, and the skeletal muscle tissue space. Oxygen transport in each of these subdomains is represented by a nonlinear partial differential equation. These PDEs were solved using the finite element method in Comsol Multiphysics 3.2. The oxygen dissociation curves were represented by the four parameter Adair equation, which more accurately models the data at high and low pO2s. The following parameters were studied in detail: the oxygen affinities of hemoglobin based oxygen carriers (P50s) ranging from 5-55 mmHg; tissue oxygen consumption rates (Vmax) ranging from 5-150 μM/s; human red blood cell hematocrits ranging from 0.1-0.5; and capillary inlet pO2s ranging from 5-115 mmHg.

Our results show that at low inlet pO2s, high affinity O2 carriers most effectively deliver O2 to tissues compared to the low affinity O2 carriers. Additionally, low affinity O2 carriers delivered similar amounts of O2 to the skeletal muscle at normoxic inlet pO2s compared to human red blood cells and high affinity O2 carriers. However, the pO2 tensions in each subdomain were higher for the the oxygen transport simulations conducted with low affinity O2 carriers. This increased oxygen tension can be the cause of the autoregulatory induced vasoconstriction effect seen in clinical HBOC studies.