title: The relative influence of hematocrit and red blood cell velocity on oxygen transport from capillaries to tissue.
abstract: Oxygen transport to parenchymal cells occurs mainly at the microvascular level and depends on convective RBC flux, which is proportional in an individual capillary to the product of capillary hematocrit and RBC velocity. This study investigates the relative influence of these two factors on tissue PO2.
  
  
  
  A simple analytical model is used to quantify the respective influences of hematocrit, RBC velocity, and RBC flow on tissue oxygenation around capillaries. Predicted tissue PO2levels are compared with a detailed computational model.
  
  
  
  Hematocrit is shown to have a larger influence on tissue PO2than RBC velocity. The effect of RBC velocity increases with distance from the arterioles. Good agreement between analytical and numerical results is obtained, and the discrepancies are explained. Significant dependence of MTCs on RBC velocity at low hematocrit is demonstrated.
  
  
  
  For a given RBC flux in a capillary, the PO2in the surrounding tissue increases with increasing hematocrit, as a consequence of decreasing IVR to diffusive oxygen transport from RBCs to tissue. These results contribute to understanding the effects of blood flow changes on oxygen transport, such as those that occur in functional hyperemia in the brain.
authors.affiliation: Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland.
authors.forename: Adrien
authors.initials: A
authors.lastname: Lücker
authors.affiliation: Department of Physiology, University of Arizona, Tucson, AZ, USA.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Secomb
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
authors.forename: Bruno
authors.initials: B
authors.lastname: Weber
authors.affiliation: Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Jenny
mesh_terms: D000818:Animals; D001692:Biological Transport; D001783:Blood Flow Velocity; D002196:Capillaries / Q000378:metabolism; D004912:Erythrocytes / Q000502:physiology*; D006400:Hematocrit; D006801:Humans; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
chemical_list: D010100:Oxygen
keywords: blood flow; mathematical modeling; tissue oxygenation