In Vitro Comparison of Holmium Lasers: Evidence for Shorter Fragmentation Time and Decreased Retropulsion Using a Modern Variable Pulse Laser

Abstract Objective To compare the performance of variable and fixed pulse lasers on stone phantoms in vitro. Methods Seven millimeter stone phantoms were made to simulate calcium oxalate monohydrate stones using BegoStone Plus. The in vitro setting was created with a clear PVC tube. For each trial, a stone phantom was placed at the open end of the tubing. The Cook Rhapsody H-30 variable pulse laser was tested on both long and short pulse settings and compared to the Dornier H-20 fixed pulse laser, five trials were conducted for each trial arm. Fragmentation was accomplished with the use of a flexible ureteroscope and a 273 micron holmium laser fiber using settings of 1Jx12 Hz. Treatment time (min) for complete fragmentation was recorded as was the total retropulsion distance (cm) during treatment. Laser fibers were standardized for all repetitions. Results Treatment time was significantly shorter with the H-30 vs the H-20 laser (14.3±2.5 vs 33.1±8.9 min, P=0.008). There was no difference between the treatment times using the long vs short pulse widths of the H-30 laser (14.4±3.4 vs 14.3±1.7 min, P=0.93). Retropulsion differed by laser type and pulse width, H-30 long pulse (15.8±5.7cm), H-30 short pulse (54.8±7.1cm) and H-20 (33.2±12.5 cm) (P