Hemodynamics

Abstract

A review is presented of the physical principles governing the distribution of blood flow and blood pressure in the vascular system. The main factors involved are the pulsatile driving pressure generated by the heart, the flow characteristics of blood, and the geometric structure and mechanical properties of the vessels. The relationship between driving pressure and flow in a given vessel can be understood by considering the viscous and inertial forces acting on the blood. Depending on the vessel diameter and other physical parameters, a wide variety of flow phenomena can occur. In large arteries, the propagation of the pressure pulse depends on the elastic properties of the artery walls. In the microcirculation, the fact that blood is a suspension of cells strongly influences its flow properties and leads to a non-uniform distribution of hematocrit among microvessels. The forces acting on vessel walls include shear stress resulting from blood flow and circumferential stress resulting from blood pressure. Biological responses to these forces are important in the control of blood flow and the structural remodeling of vessels, and also play a role in major disease processes including hypertension and atherosclerosis. Consideration of hemodynamics is essential for a comprehensive understanding of the functioning of the circulatory system.

Computational Fluid Dynamics and Additive Manufacturing to Diagnose and Treat Cardiovascular Disease

“…Functional differences between vascular beds are attributable to both the structural properties of the vessels (i.e., vessel diameter, length, tortuosity, and stiffness) and the effects of hemodynamic forces on vascular phenotype. Blood vessels are continuously exposed to hemodynamic forces resulting from pulsatile pressure generated by cardiac contraction, the flow characteristics of circulating blood, and modifications to these forces locally by the geometry and mechanical properties of the blood vessels themselves [3]. …”

Blood flow rate and wall shear stress in seven major cephalic arteries of humans

“…The normal ‘set‐point’ is considered a regulated value of wall shear stress (WSS; dyn cm −2 ). WSS can be evaluated from haemodynamic theory (Secomb, ). The famous haemodynamic paradigm that relates laminar flow rate to vessel size is the Poiseuille‐Hagen (P‐H) equation, which is a solution to one of the incompressible Navier‐Stokes equations:where Δ P is the pressure difference required to achieve a rate of laminar flow () of a fluid of given viscosity (η) in a straight, horizontal tube of length ( L ) and inner radius ( r i ).…”

“…The normal 'set-point' is considered a regulated value of wall shear stress (WSS; dyn cm À2 ). WSS can be evaluated from haemodynamic theory (Secomb, 2016). The famous haemodynamic paradigm that relates laminar flow rate to vessel size is the Poiseuille-Hagen (P-H) equation, which is a solution to one of the incompressible Navier-Stokes equations:…”

Resistive Factors of the Blood Flow and Energy Distribution in the Body

“…Blood vessels and cells are viscoelastic, so classical hydrodynamics and fluids mechanics based on the use of classical viscometers cannot explain hemodynamics. Herewith, it is crucial to take into account a nonNewtonian feature of the blood, which is best studied in rheology and not hydrodynamics [1].…”