Optimization of laser, irrigation and suction settings for automated ureteroscopic lithotripsy in impacted stones ex vivo study part II

This study aims to optimize laser, irrigation, and suction settings for automated laser lithotripsy in impacted ureteral stones by analyzing intra-ureteral temperature (IUT) and pressure (IUP). A novel Laser: Stop ratio (LS ratio) was introduced to balance laser activation and resting times. An ex-vivo porcine kidney was used to evaluate the settings [Thulium fiber laser (TFL) and Holmium: Yttrium-aluminum-garnet (Ho: YAG) at 1.0 J/10Hz, 0.5 J/20Hz], pump-based irrigation of 30mmHg (P30) and 50 mmHg (P50), LS ratios (2s:2s, 2s:4s, 2s:6s) and the use of a flexible and navigable suction ureteral access sheath (FANS-UAS). With FANS-UAS, a Laser: Active suction: Rest ratio of 2s:2s:2s was applied at 200mmHg suction. IUT and IUP were recorded every 30 s for 5 min with dangerous thresholds at > 50 °C for over 1 min or > 56 °C at any time. Under P30 with an LS ratio of 2s:6s, pop-dusting was observed to be limited, with 15 and 30 s for TFL and Ho: YAG, respectively. At 0.5 J/20Hz, the pop-dusting was extended to 3 and 5 min, respectively. Under P50, continuous pop-dusting was achievable across all settings when an LS ratio of 2s:2s, 2s:4s, and 2s:6s were employed. The FANS-UAS enabled continuous pop-dusting under P30 at 0.5 J/20Hz, although it was restricted at 1.0 J/10Hz. Under P50, continuous pop-dusting was achievable across all settings, with the lowest recorded IUT. The IUP remained within safety thresholds under both P30 and P50. When defined with fixed activation and rest times, the LS ratio may serve as a practical reference for balancing safety and efficiency in automated laser lithotripsy.