Impact of Holmium Laser Settings and Fiber Diameter on Stone Fragmentation and Endoscope Deflection*

Holmium:YAG Lithotripsy: Optimal Power Settings

“…Optical energy would be absorbed by water so that less stone irradiation and fragmentation would ensue unless the optical fiber were moved synchronously with the retropulsed stone.13 In a lithotripsy experiment using stone phantoms, lithotripsy efficiency decreased as pulse energy exceeded 1.0 J for the 365-/xm optical fiber, an effect attributed by the authors at least in part to retropulsion. 16 We have observed clinically that retropulsion increases as the stone is debulked to a small fragment when using a constant pulse energy. Momentum is defined as mass X velocity.…”

Pneumatic Lithotripsy versus Laser Lithotripsy in the Endoscopic Treatment of Ureteral Calculi

“…The tip of the fiber is placed in direct contact with the stone edge, and a cavity is created on the surface, which is then enlarged using an up-and-down motion. 7 We describe the manner as "worm biting." Otherwise, with the tip aimed at the center of the stone constantly, the stone would be fragmented into several parts, some of which still need fragmentation but might drain out of sight or be flushed back into the caliceal system.…”

Improved Functional Deflection with a Dual-Deflection Flexible Ureteroscope

“…Because of this limitation, stones that can initially be accessed cannot be reached when laser fibers or stone baskets are inserted to fragment or retrieve the stone. Two studies 12,13 have demonstrated that instruments with increasing diameters in the working channels of these ureteroscopes create a progressive degradation in their deflection capabilities. Our study produced similar results, as the maximum deflection obtained by both the single-and the dual-deflection ureteroscopes decreased as the diameter of the laser fibers in the working channel was progressively increased from 200 to 550 mm.…”