Abstract
The characterization of the dynamic process of veins walls is essential to understand venous functioning under normal and pathological conditions. However, little work has been done on dynamic venous properties.To characterize vein compliance (C), viscosity (eta), peak-strain (W St) and dissipated (W(D)) energy, damping (zeta), and their regional differences in order to evaluate their role in venous functioning during volume-pressure overloads.In a mock circulation, pressure (P) and diameter (D) of different veins (anterior cava, jugular and femoral; from 7 sheep), were registered during cyclical volume-pressure pulses. From the P-D relationship, C, W(St) and zeta (at low and high P-D levels), eta and W(D) were calculated.For each vein there were P-dependent differences in biomechanical, energetics, and damping capability. There were regional-differences in C, eta), W(St) and W(D) (p<0.05), but not in zeta.The regional-dependent differences in dynamics and energetics, and regional-similitude in damping could be important to ensure venous functioning during acute overloads. The lower C and higher W(St) and W(D) found in back-limb veins (femoral), commonly submitted to high volume-pressure loads (i.e. during walking), could be considered relevant to ensure adequate venous system functionality and venous wall protection simultaneously.
Highlights
The venous system is considered a low pressure and pulsate system, it can suddenly become a high pressure and/or pulsatility system, in which veins support acute cyclical volume and/or pressure overloads
C was lower at high P (p
Viscosity was higher in the peripheral segments, in the FV than in the anterior cava (ACV)
Summary
The venous system is considered a low pressure and pulsate system, it can suddenly become a high pressure and/or pulsatility system, in which veins support acute cyclical volume and/or pressure overloads. When one is standing, 0.4-0.5 liters of blood is shifted out of the thorax into the veins of the legs, causing an abrupt increase in their pressure from approximately 2.67 to 13.33 kPa (20 to 100 mmHg), and during running, pulsatility in leg veins is around 8.00-10.67 kPa (60-80 mmHg) (Holtz, 1996). Under these conditions, compensatory mechanisms are triggered to ensure adequate venous return and to minimize venous overload (Holtz, 1996).
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