Arterial elastic modulus for fixed and varied wall volume.

It is commonly assumed that a blood vessel maintains a constant wall volume over a wide range of intraluminal pressures. We have found that vessel wall volume decreases under increasing load. To determine the effect of decreasing wall volume on values of Elastic modulus (Em), two computer models were used. The first model held volume constant with measured values of rabbit carotid artery length and width while thickness was calculated. In the second model wall volume was allowed to vary with measured length, width and thickness. Em increased with increasing load in both models with higher values in the nonconstant volume model. Up to 30% loading, the difference was 11% or less; above 30% loading, the difference increased to over 100%.