Abstract/Details

Microviscometric analysis of microvascular hemodynamics in vivo


2004 2004

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Abstract (summary)

Studies of blood flow in the microcirculation have been conducted for over a hundred years. Other than in 5–8 μm-diameter capillaries, where red cells travel in single-file flow, no method has been developed for either quantitatively predicting or accurately measuring the salient dynamic, kinematic, and rheological properties of blood flow in intact microvessels in vivo. A new microviscometric approach is presented, which we have validated through glass-tube studies in vitro (30–80 μm in diameter) and through isovolemic hemodilution studies in vivo, that provides estimates of hemorheological and fluid dynamical distributions over the cross section of microvessels greater than ∼20 μm in diameter with an accuracy and detail unprecedented in microvascular research. Microviscometry depends only upon knowledge of the velocity profile over the cross section of a microvessel, which can readily be extracted using fluorescent micro-particle image velocimetry (μ-PIV) from distributions in the translational speed and radial position of systemically injected sub-micron spheres within the microvessel. Microviscometric analysis solves the equation for conservation of momentum for a general incompressible non-Newtonian fluid, subject to the velocity profile extracted from the μ-PIV data, to provide viscosity, shear-rate, and shear-stress profiles as well as the axial pressure gradient, volume flow, local and apparent blood viscosities, and the tube and discharge hematocrit in intact microvessels in vivo. Using microviscometry, together with a detailed three-dimensional analysis of the local fluid dynamics in the vicinity of the vessel wall, we have been able to infer important hydrodynamic properties associated with the vascular endothelium. In recent years, the interface between blood and the vascular endothelium in microvessels has drawn considerable attention as evidence is uncovered that a macromolecular endothelial surface layer (ESL), strategically located at this interface, may play several important functional roles in microvascular physiology. First visualized in vivo using dye-exclusion methods in capillaries, our microviscometric analysis shows that the ESL exerts a significant effect on near-wall microfluidics in post-capillary venules, and provides the first direct estimate of the hydrodynamically relevant thickness of the layer in vivo. Results from our analysis have implications for broad areas of cardiovascular research including hemodynamics, inflammation, endothelial-cell mechanotransduction, angiogenesis, and tissue engineering.

Indexing (details)


Subject
Biomedical research;
Biophysics
Classification
0541: Biomedical research
0786: Biophysics
Identifier / keyword
Applied sciences; Biological sciences; Endothelial surfaces; Hemodynamics; Microvascular; Microviscometric; Rheology
Title
Microviscometric analysis of microvascular hemodynamics in vivo
Author
Long, David Scott
Number of pages
215
Publication year
2004
Degree date
2004
School code
0090
Source
DAI-B 65/11, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
0496139444, 9780496139446
Advisor
Damiano, Edward R.
University/institution
University of Illinois at Urbana-Champaign
University location
United States -- Illinois
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3153368
ProQuest document ID
305200055
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305200055
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