Direct measurement of clamping forces in cardiovascular surgery.

Equipment for measuring the direct tip force of a clamp arm on the vessel wall is designed as an adjustable surgical clamp with strain gauges applied and connected via an amplifier to a computer-based data acquisition system. A mechanical model that incorporates the resistance of tissue against momentary deformations is developed to analyse and justify measured results. In in vivo experiments on rat thoracic aorta, the minimum occlusion force, stationary clamping force and the momentary peak clamping force are measured and observed as an important cause of damages in the endothelial layer of vascular walls.