Influence Of Venous Pressure Research Articles

Investigation and comparative characteristic of factors determining human skin elasticity

The results of examining the variation in skin elasticity at its expansion are presented for different skin thickness, different content of collagen and intercellular and intracellular fluids, different venous pressure, and for tension and relaxation of the smooth muscle of skin vessels (vasomotion). Elasticity was determined using the acoustic method by the velocity of the surface shear acoustic wave, the self-resonance method by the frequency of mechanic skin resonance, and the vacuum method by the volume of the skin segment pulled into the aperture of a thin tube by air rarefaction. It is shown that the main factors determining the skin elasticity are its stretching, thickness, and collagen and fluid content. The influence of venous pressure and contractile activity of the vasculature on elasticity is insignificant. This gives grounds for using skin elasticity factors as indicators of systemic and local lesion of connective tissue.

Muscle blood flow response to contraction: influence of venous pressure.

The skeletal muscle pump is thought to be at least partially responsible for the immediate muscle hyperemia seen with exercise. We hypothesized that increases in venous pressure within the muscle would enhance the effectiveness of the muscle pump and yield greater postcontraction hyperemia. In nine anesthetized beagle dogs, arterial inflow and venous outflow of a single hindlimb were measured with ultrasonic transit-time flow probes in response to 1-s tetanic contractions evoked by electrical stimulation of the sciatic nerve. Venous pressure in the hindlimb was manipulated by tilting the upright dogs to a 30 degrees angle in the head-up or head-down positions. The volume of venous blood expelled during contractions was 2.2 +/- 0.2, 1.6 +/- 0.2, and 1.4 +/- 0.2 ml with the head-up, horizontal, and head-down positions, respectively. Although altering hindlimb venous pressure influenced venous expulsion during contraction, the increase in arterial inflow was similar regardless of position. Moreover, the volume of blood expelled was a small fraction of the cumulative arterial volume after the contraction. These results suggest that the muscle pump is not a major contributor to the hyperemic response to skeletal muscle contraction.

Influence of venous pressure on plasma-lymph transport in the dog's paw: Convective and dissipative mechanisms

Studies were carried out to evaluate convective and dissipative (diffusion and vesicular) components of blood-lymph transport of large molecules in the dog's paw. Steady-state lymph flow rates ( L) and lymph/plasma concentration ratios ( R) were measured for six plasma proteins and for exogenous Dextran (MW 110,000). Measurements were made under control conditions and at two to four elevated levels of venous pressure ( PV). Below 45 mm Hg, L increased linearly with PV, and R fell progressively, but less than in proportion to flow: the product LR (clearance) increased. Above 45 mm Hg, there was a time-dependent increase in R at constant or increasing L, which was greater for larger molecules and indicated an alteration of permeability. From values of L and R obtained for the normal permeability state, solvent drag coefficients ( σ f) and permeability surface area products ( PS) were calculated according to the principles of irreversible thermodynamics and hydrodynamics. Values obtained for σ f ranged from 0.82 for serum albumin to 0.95 for Dextran 110. At control levels of lymph flow, convection (solvent drag) accounted for about 30% of the total flux of albumin into lymph. With elevation of venous pressure, the contribution of convective flux increased.

The influence of venous pressure upon the heart‐rate

The influence of venous pressure upon the heart‐rate