Kinetic models of tissue fusion processes

Recent studies of tissue fusion (welding) processes have reported temperature ranges but have not carefully analyzed critical exposure time data. Electron microscopic (EM) studies suggest that the fusion process in blood vessels may be dominated by random re-entwinement of thermally dissociated adventitial collagen fibrils (Type I) during the end stage heating and early cooling phases. At the light microscopic level, this bonding process is reflected by the formation of an amorphous coagulum of thermally coagulated adventitial collagen at the anastomotic site. We have constructed a numerical model of the vessel welding process, assuming CO2 laser impingement, and used it to simulate quantitative histologic data obtained from successful welds of rat femoral and canine brachial arteries (unpublished data). The model estimates smooth muscle and collagen damage based on kinetic thermal damage analysis and water loss boundaries as a function of irradiation beam parameters and heating time. Both heating and cooling phases are simulated. The results illustrate the importance of the damage kinetics and local heat transfer phenomena to the weld characteristics realized.