Tissue Bond Strength and Intraluminal Temperature
as a Function of Applied Fusion Pressure
Anderson, N.S., Kramer, E., Cezo, J., Ferguson, V.L., Rentschler, M.E.
In the clinical use of thermal tissue fusion, which uses heat and pressure to fuse arterial tissues, the input parameters of applied pressure, fusion temperature, and duration of energy input have largely been optimized through trial and error. The objective of this work is to experimentally elucidate the effect applied pressure has on bond strength and internal tissue temperature during fusion. The outcomes will aid in further characterization of the bond between thermally fused tissues which may direct the design of future thermal fusion devices.
The role of applied pressure was investigated by fusing porcine splenic arteries at applied loads ranging from 10-500 N. Pressure was applied to the arteries using a standard uniaxial tensile testing system to maintained a prescribed force (MTS Insight II). To achieve fusion, an input heat of 170° C was applied for 3.0 s via aluminum nitride heaters which were mounted to the MTS using custom fixtures. Fusion strength was then evaluated using burst pressure testing, which measures the intraluminal pressure at which a thermal bond fails. Intraluminal temperature was measured in a separate procedure with an array of five thermocouples inserted into the artery lumen during fusion . Finally, samples of fused arteries from each applied load were histologically assessed following Hematoxylin & Eosin staining.
The fused vessels exhibited a peak in burst pressure for an applied load of 35 N before falling to a near constant value at higher loads (Figure 1). The intraluminal temperature measurements largely increased with increasing applied pressure. Based on the histological images, the peak in fusion strength corresponds to fusions between the media layers of the vessel, while the fall and plateau occurs when the media ruptures out of the fusion region and bonds form between the adventitia layers. These results indicate that an applied load of approximately 35 N is optimal for thermal fusion, a previously undetermined value as most commercial fusion devices apply loads around 100 N. The results also suggest that media fusions are stronger than adventitia fusions; the particular compounds or ratio of compounds that allow media to form stronger fusions merits further investigation.
Cezo, J.D., Kramer, E., Taylor, K., Ferguson, V., Rentschler, M.E., "Temperature Measurement Methods during Direct Heat Arterial Tissue Fusion," IEEE Trans on Biomedical Engineering. 60(9):552-2558, 2013.