Predicting burst pressure of radiofrequency-induced colorectal anastomosis by bio-impedance measurement

The present study investigates the relationship between bio-impedance and burst pressure of colorectal anastomosis created by radiofrequency (RF)-induced tissue fusion. Colorectal anastomosis were created with ex-vivo porcine colorectal segments, during which 5 levels of compression pressure were applied by a custom-made bipolar prototype, with 5 replicate experiments at each compression pressure. Instant anastomotic tensile strength was assessed by burst pressure. Bio-impedance of fused tissue was measured by Impedance Analyzer across frequency that 100Hz to 3MHz. Statistical analysis shows only a weak correlation between bioimpedance modulus and burst pressures at frequency of 445 kHz (ρs= -0.426, P=0.099>0.05). In contrast, results demonstrated a highly significant negative correlation between reactance modulus and burst pressures (ρs= -0.812, P=0.000<0.05). The decrease in mean reactance modulus with increasing burst pressures was highly significant (p=0.019<0.05). The observed strong negative correlation between reactance modulus and burst pressures at frequency of 445 kHz indicates that reactance is likely to be a good index for tensile strength of RF-induced colorectal anastomosis, and should be considered for inclusion in a feedback loops in devices design.