Wave transmission and input impedance of a model of skeletal muscle microvasculature

We analyzed wave transmission properties and input impedance of a microvascular network model. The model, derived from rat spinotrapezius muscle and previously described and validated by other investigators for steady pressure-flow relations, was expanded to include pulsatile phenomena. Microvessels...

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Bibliographic Details
Published in:Annals of biomedical engineering Vol. 22; no. 1; p. 45
Main Authors: Frasch, H F, Kresh, J Y, Noordergraaf, A
Format: Journal Article
Language:English
Published: United States 01.01.1994
Subjects:
Animals
Blood Pressure
Compliance
Elasticity
Linear Models
Microcirculation - anatomy & histology
Microcirculation - physiology
Models, Cardiovascular
Muscles - blood supply
Pulsatile Flow - physiology
Rats
Reproducibility of Results
Vascular Resistance - physiology
Viscosity
ISSN:0090-6964
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Summary:We analyzed wave transmission properties and input impedance of a microvascular network model. The model, derived from rat spinotrapezius muscle and previously described and validated by other investigators for steady pressure-flow relations, was expanded to include pulsatile phenomena. Microvessels are considered purely elastic, with compliances a function of vessel type; viscous dissipation follows Poiseuille's law. Linear and nonlinear results are presented. In the nonlinear case, shear rate-dependent viscosity of blood and transmural pressure-dependent vascular diameters were calculated and small signal perturbations were imposed around several working points. We investigated effects on input impedance of physiological variability of network parameters and structure: distribution of capillary diameters, capillary segment length, and presence or absence of cross-connecting capillaries. Results show that although wave transmission properties are complex, input impedance is simple. Apparent wave speeds differ substantially from phase velocities and change markedly from branch to branch; pressure and flow waves appear to travel at different speeds. These features result from the mesh-like structure of the network and the prominence of reflection at branchpoints. Input impedance displays a similar form under all conditions: Magnitude is a monotonically decreasing function of frequency, and phase decreases from 0 to approximately -45 degrees. Consideration of the characteristic impedance of a microvessel leads to modification of the three-element Windkessel as a reduced model of the observed input impedance.
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ISSN:0090-6964
DOI:10.1007/BF02368221