Comparative model study of mechanical resistance of intestinal and stomach walls to the pressure in the device prototype for circular anastomosis
Background. The vital margins of the gut wall squeezing, which is observed in cases of functional distension, negative pressure wound therapy or magnetic anastomosis device placing, ranged from 0.005 to 0.4 N/m2. The desirable short-time formation of structural connection in anastomotic line due to radio frequency electric influence, obviously, requires not vital, but a tight compression of the intestine wall on the verge of its structural deformation. C. Holmer et al. established the optimal value of electrode pressure onto the porcine intestine close to 1,125 mN/mm2.
In our experiments, compression range of 2–6 · 104 N/m2 was found as more favorable for the radio frequency electric welding connection in anastomosis of the hollow organs. The purpose was to study the mechanical resistance of gut and stomach walls for comparative projection on its structural changes under strong pressure at the anastomosis model conditions. Materials and methods. The porcine intestine and stomach were delivered from the farm to laboratory during 6 hours in 4 оС and then heated in 0.9% NaCl up to 26–32 оС . Two organ walls were placed inside the prototype device for human circular anastomosis, and then pressed for 60 seconds before radio frequency welding. The 117 probes were made in several combinations investigating pressure values 2.1, 3.0, 3.9 and 6.0 N/mm2 (or · 104 N/m2) effect for organ wall by connected micrometer device. Results. The wall thinning time, which is inversely proportional to resistance, visually divided into two phases: the fast (1–5 s) and significant thinning of the tissue after initial pressure application, then slow and low-amplitude thinning. The small intestine wall resistance was higher than the stomach one as well as the combination of the stomach and intestinal under all values of initial pressure. Conclusions. The first compression phase is unique according to the thinned organ. Some thinning rate decrease occurred at the second phase under the pressure 3.0–3.9 N/mm2 comparing to 2.1 N/mm2 up to 60 seconds, determines the limit of mechanical resistance of the wall muscle layer as well as overall gut and stomach integrity up to such pressure level. Obtained data helps to project the structural changes inside intestinal and/or stomach walls compressed into circular anastomotic device, which is important for the planning of further effects.
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