Real-time measurement of blood vessel occlusion during microsurgery.

Measurement and feedback of vascular properties during microsurgery is generally not available. We carried out real-time in vivo measurement and analysis of microsurgical occlusion of 1-2-mm diameter arteries and veins in rodents. A pair of forceps mounted with strain gauges was designed for applying and directly measuring the force on tissue. Forces between 0 and 450 mN were applied, with the device having a resolution of 0.5 mN. We performed in vivo experiments on the rat femoral (n = 5) and abdominal (n = 8) blood vessels to measure the elastic restoration force of the tissue in response to radial compression at different levels of force. On average, the minimum occlusion force was 57 mN for the rat artery. During steady application of force, the perturbations in the blood vessel due to heartbeat are visible in the force data. These force oscillations ranged between 1 and 3 mN around the mean steady-state force applied. It was determined that the magnitude of the Fourier spectral peak corresponding to heartbeat frequency can be used as a measure of the patency of the blood vessel, and can provide feedback to microsurgeons to avoid damage to the vessel by application of excess force.