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Modeling the hemodynamic response in capillaries to an altered tissue oxygen environment
Author(s) -
MacKie Meaghan,
Milkovich Stephanie,
Goldman Daniel,
Ellis Christopher G.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a480-c
Subject(s) - hematocrit , capillary action , microcirculation , chemistry , blood flow , hemodynamics , skeletal muscle , mechanics , biophysics , anatomy , biomedical engineering , medicine , thermodynamics , physics , biology , endocrinology
Regulation of the convective O 2 supply to capillary beds within organs is accomplished by coordinated changes in arteriolar diameter. To test the hypothesis that red blood cells (RBC) are a key component of this regulation system, in vivo experiments have been performed using a gas exchange chamber with computer‐controlled gas flowmeters to alter the O 2 environment at the surface of a rat skeletal muscle. The microvascular responses to sine oscillations in chamber O 2 levels were determined by measuring RBC velocity ( v ), hematocrit ( Hc ), and RBC supply rate ( SR ) in capillaries near the muscle surface. In approximately half the capillaries examined, the regulatory response resulted in changes in both v and Hc that were correlated to oscillations in chamber O 2 ; however, in other capillaries only one of these parameters was regulated. To explain the observed variability, we have developed a model describing the relative magnitude of blood flow and RBC distributions at arteriolar and capillary bifurcations deeper in the muscle that determine blood flow to the surface capillaries. This model utilizes empirical relations describing RBC distribution at diverging bifurcations (phase separation) and yields predictions of capillary velocity and hematocrit based on the baseline arteriolar geometry and the changes in vessel diameter resulting from the local regulation of O 2 supply.