Modelos newtonianos y no newtonianos asociados al flujo sanguíneo: revisión

Abstract

El comportamiento y características de la sangre en el sistema circulatorio han generado diversos modelos que pueden ser aplicados para el análisis del flujo sanguíneo, entre los que se incluyen modelos newtonianos y no newtonianos. En esta revisión se presentan once modelos propuestos a partir de parámetros experimentales que incluyen estudios de viscosidad con diferentes velocidades de cizallamiento y densidad asociada a la dinámica de fluidos. Se caracterizaron de acuerdo con métodos, parámetros específicos y valores experimentales utilizados; además, se comparó la eficacia, certeza y precisión de los modelos utilizados.

The Physics of Fluid Dynamics Applied to Vascular Ulcers and Its Impact on Nursing Care

“…The blood reaches the vessels intermittently and, as it descends in level and reaches the arterioles, the flow becomes continuous and slow at the capillary level, from 400 mm/s in aorta to 0.1 mm/s in capillaries. This effect is essential for the tissue irrigation process, and to a greater extent in distal areas, because if the speed at which the blood circulates is faster than normal, the hydrostatic pressure ( P h ) would decrease until disappearing, implying no exchange, with the consequent ischemia of irrigated tissues by affected arterioles and its characteristic injury [ 21 ]. d = blood density; g = gravity; h = height …”

“…In the case of arterial ulcers, the capillaries lose their elasticity, which directly affects blood pressure ( P b ), understood as the force exerted by the passage of blood against the vascular walls per unit surface, measured in mmHg. This pressure is directly proportional to cardiac output ( CO ), and inversely proportional to the elasticity of the arterial walls ( e ), that determine peripheral resistance ( Rp ) [ 21 ]. …”

“…The veins also have the three layers mentioned above, but unlike the arteries, the pressure to be endured is much lower, so their walls are much thinner and with a lower proportion of muscle and elastic tissue. However, the cross-sectional diameter is elliptical and larger than its corresponding artery [ 21 ]. This return system has a high capacity to withstand large volumes with very low pressure, so the fluid dynamics is completely different from that of the arteries.…”

“…They usually measure 1 mm and have a diameter of approximately 5–10 microns, in many cases smaller than erythrocytes (8 microns). In an average body, the tissue exchange surface is around 700 m 2 , with no more than 20 microns distance between capillaries and cells [ 21 ].…”