Objective: The constraints imposed by the minimal access surgical approach have driven the need for enabling technologies for vessel occlusion and tissue welding. The objective of this study is to determine the values of, and interaction between, temperature, apposition force and clamp time for optimum tissue welding.
Methods: A dedicated experimental step up including a specially constructed parallel occluding conductive heating (POCH) device was used for the ex vivo experiments which were carried out on harvested sheep carotid vessels. Weld strength was measured by bursting pressure. The experimental set up allowed control and individual variation of temperature (60, 70, 80 and 90°C), apposition force (20, 40, 60 and 80N) and clamp time (5, 10, 15s). The experiment was filmed using an infra-red to verify thermal spread and the welded vessel were examined histologically to determine the margin of cellular disruption.
Results: The best seal quality was obtained by a temperature of 90°C (p = 0.03), an apposition force of between 60 and 80 N (p = 0.03) and clamp time of 10 s (p = 0.058).
On statistical evaluation of the data, the individual effects of temperature, apposition force and clamp time were all significant at p-values less than 0.001. Individually, these factors had a large size effect having partial Eta2 values of 0.63, 0.64 and 0.18 respectively. Although all three were considered to have large effects, clamp time had a smaller effect, relative to temperature and apposition force.
Histologic evidence of tissue injury revealed a direct association between temperature and the distance of tissue injury from the POCH jaws and correlated well with the infra red thermograph of heat distribution during the experiment.
Conclusions: Temperature, apposition force and clamp time influence the quality of thermal welding but the interaction between temperature and apposition force appears to be more dominant. Thermal cellular damage is localised.
Program Number: P084