Abstract 171: Understanding the Relationship Between Capillary Occlusion and Central Blood Pressures
Hypothesis: Early goal directed therapies for resuscitation include target blood pressures for the central venous and arterial vessels. While a pressure drop is required to achieve perfusion it is not sufficient to guarantee perfusion, and successful pressure stabilization does not correlate with outcomes. We hypothesize that arterial and venous pressure values are not very sensitive to changes in capillary perfusion density.
Methods: Using the Matlab software package, we developed a physiologically motivated numerical model of the vasculature of an organ. The model is developed recursively using fractal geometry. The advantages of this methodology are the ability to rapidly define different vessel network allowing for variations in branch symmetry and number of branches per node. Each vessel was modeled using resistor, capacitor, inductor (RLC) elements. Flow resistances that arise due to branching and active vasodilatation and constriction mechanisms were ignored. Relevant physiological parameters were pulled from the literature. Using this model we investigated the role of branch symmetry, branch number, number of capillaries blocked, and elasticity of capillaries on central pressure and flow values.
Results: The figure shows the pressure and flow at each node as a function of percentage of blocked capillaries. This data set is for two branches per node, where the branches are slightly asymmetric. The pressure and flow for the central vessels are the rightmost data points. This data makes it clear that almost 50% of the capillaries need to be blocked for there to be significant changes in the flowrate and pressure in the central vessels.
Conclusions: Based on these data we conclude that central pressure and flow measurements are not sensitive to the flow states of the capillaries. This data brings the limitations of current hemodynamic measurements during the treatment of shock into sharp focus.
- © 2010 by American Heart Association, Inc.