Preliminary study of a control algorithm for radio-frequency-induced intestinal tissue fusion

Purpose: A control algorithm for radio-frequency-induced intestinal tissue fusion was developed to explore the effects of different control parameters on intestinal tissue fusion.Materials and methods: Radio-frequency-induced fusion was performed on ex vivo small intestine tissue. The effect on the fusion was observed by changing the control parameters (power, interval time, and terminal impedance) in the algorithm. The quality of fusion was evaluated using the burst pressure and thermal damage measurement. Histological evaluation was used to assess the fusion quality indirectly.Results: A maximum burst pressure of 8.460 ± 0.2674 KPa was acquired when the power was set to 100 W, the interval time was set to 2000 ms, and the terminal impedance was set to 50 Ω. Moreover, the thermal damage range increased with an increase in power but decreased with an increase in the interval time and terminal impedance. Furthermore, the thermal damage range and temperature were presumably related.Conclusions: For an ex vivo small intestine tissue, the appropriate control parameters could be set when the power was approximately 100 W, the interval time was approximately 2000 ms, and the terminal impedance was approximately 50 Ω. This study could provide a basis for the selection of control parameters for intestinal tissue fusion.

Histological characteristics of collagen denaturation and injuries in bipolar radiofrequency-induced colonic anastomoses

Bipolar radiofrequency-induced thermo-fusion has been explored as an advanced surgical method for intestinal anastomoses; however, the histological characteristics of collagen denaturation and injuries arising from this process remain unclear. The aim of this study was to investigate the microcosmic changes and tissue damage of fusion regions with various parameters of injury. Ex vivo colons of pigs were fused serosa-serosa on two carrier rings, which were installed on a homemade anastomotic device. Five levels of compressive pressure from 171 to 313 kPa were applied for 5s to fuse the colons under radiofrequency power of 160 W, and then the collagen denaturation of the fused region was examined by transmission electron microscopy. Light microscopy was utilized to observe histological slices that were stained with picrosirius red in order to visualize the tissue injuries under two levels of radiofrequency power (120 vs. 140 W) and operation time (5 vs. 10s). Transmission electron micrographs showed that increased compressive pressure led to thicker denatured collagen fibrils and wider gaps between each collagen fibril. Serosa adhesion regions appeared abundant in collagen. No histological differences were observed when 120 W of power was applied for 5 and 10s. Significant muscle cracking occurred when colons were fused using 140 W for 5s. When the operation time was extended to 10s, 140 W led to tight fusion and less splitting on muscles. These results suggest that higher compressive pressure results in more severe collagen unfolding and also reduces collagen crosslinking in fused colons. Improved radiofrequency power along with operation time could avoid tissue injury upon radiofrequency-induced colonic anastomoses.