Temporal heating profile influence on the immediate bond strength following laser tissue soldering

Background: Bonding of tissues by laser heating is considered as a future alternative to sutures and staples. Increasing the post-operative bond strength remains a challenging issue for laser tissue bonding, especially in organs that have to sustain considerable tension or pressure. In this study, we investigated the influence of different temporal heating profiles on the strength of soldered incisions. The thermal damage following each heating procedure was quantified, in order to assess the effect of each heating profile on the thermal damage. Materials and Methods: Incisions in porcine bowel tissue strips (1 cmx4 cm) were soldered, using a 44% liquid albumin mixed with indocyanine green and a temperature controlled laser (830 nm) tissue bonding system. Heating was done either with a linear or a step temporal heating profile. The incisions were bonded by soldering at three points, separated by 2mm. Set-point temperatures of T_set=60, 70, 80, 90, 100, 110, 150°C and dwell times of t _d=10, 20, 30, 40 seconds were investigated. The bond strength was measured immediately following each soldering by applying a gradually increased tension on the tissue edges until the bond break. Results: Bonds formed by linear heating were stronger than the ones formed by step heating: at T _set=80°C the bonds were 40% stronger and at T_set= 90°C the bonds strength was nearly doubled. The bond strength difference between the heating methods was larger as T_set increased. Conclusion: Linear heating produced stronger bonds than step heating. The difference in the bond strength was more pronounced at high set-point temperatures and short dwell times. The bond strength could be increased with either higher set-point temperature or a longer dwell time.