Pulse Modulation for Holmium Laser: Vapor Tunnel–Virtual Basket–Bubble Blast

Abstract

Introduction:

New pulse modulations for holmium laser (vapor tunnel, virtual basket, and bubble blast) have been introduced, seeking energy optimization and better efficiency for stone lithotripsy. We aim to assess vapor tunnel, virtual basket, and bubble blast effects for stone lithotripsy during ureteroscopy and retrograde intra-renal surgery.

Materials and Methods:

Seven patients (10 stones) were treated using a 100 W holmium laser generator (Cyber Ho; Quanta System). Three, 272, 372, and 550 μm, fibers were used. The settings used were 0.3–1.2 J/15–50 Hz, combined with short, medium, and long pulse length. Vapor tunnel, virtual basket, and bubble blast modulations were used during lithotripsy.

Results:

A smaller retropulsion and a more efficient ablation were observed with long pulse in combination with vapor tunnel and virtual basket effects, compared with regular mode fragmentation. No patient presented Clavien III/IV complications. The vapor tunnel technology consists in a long pulse, using the minimum peak power in accordance with selected output settings. The pulse creates a vapor tunnel, the remaining energy passes straight through the previously created tunnel, generating an elliptical shape bubble allowing less retropulsion. Virtual basket is composed of a double pulse emission. The time duration separating the two pulses is chosen so that the second pulse is emitted from the distal tip of the fiber when the bubble size, and the corresponding amount of displaced fluid, is at a maximum. The virtual basket emission mode combines a low retropulsion with a fragment suction effect. Bubble blast is a high-energy pulse resulting in the generation of a strong mechanical effect. The physical principle is that the first pulse generates a spherical bubble, the second pulse is emitted after the complete collapse of the first bubble generating a second bubble with bigger volume than the first pulse. This translates theoretically into a frontal and lateral increasing of the shock wave effects on the target.

Conclusion:

New pulse modulations vapor tunnel, virtual basket, bubble blast lead to retropulsion reduction, lithotripsy optimization, and theoretically to a shorter stone ablation time. Large clinical trials are needed to confirm their efficiency, advantages, and limitations.

No competing financial interests exist.

Runtime of video: 6 mins 33 secs