Holmium:YAG Lithotripsy: Optimal Power Settings
Spore S, Teichman J, Corbin N, Champion P, Williamson E, Glickman R

INTRODUCTION AND OBJECTIVES: We test the hypothesis that holmium:YAG lithotripsy speed is best maximized using low pulse energy at high pulse frequency.

METHODS (A) To show that optical fiber damage increases with pulse energy and irradiation, the 365 �m optical fiber irradiated calcium phosphate dihydrate (CP), calcium oxalate monohydrate (COM), cystine, magnesium ammonium phosphate hexohydrate (MAPH), and uric acid calculi at pulse energies 0.5 - 2.0 J. Optical energy output was measured with an energy detector. (B) To show that lithotripsy efficiency varies with power, fragmentation was measured at varying power settings with the 365 and 272 �m optical fibers. (C) To show that low pulse energy produces smaller fragments versus high pulse energy, fragment size was characterized using the 272 - 940 �m optical fibers at 0.5 - 1.5 J pulse energies.

RESULTS: (A) Damage to the 365 �m optical fiber was greatest for irradiation of CP, followed by MAPH, and COM, p<0.001. There was no significant optical fiber damage after cystine or uric acid lithotripsy. (B) For the 365 �m optical fiber, fragmentation was not statistically different either at constant irradiation when power varied, or at constant power and irradiation when pulse energy varied (1.0 J vs. 2.0 J). However, calculated lithotripsy speed was greatest at high power settings, p<0.001. For the 272 �m optical fiber, CP fragmentation was greatest for the 1.0 J pulse energy, p=0.05. (C) Mean fragment size and relative quantity of fragments = 2 mm both increased as pulse energy increased, p<0.01.

CONCLUSIONS: Holmium:YAG lithotripsy speed is maximized with increased power. Since low pulse energy may be safer (less fiber damage) and yields smaller fragments than high pulse energy, holmium:YAG lithotripsy speed is best increased by using pulse energies = 1.0 J at high repetition rate.

Journal of Endourology, Vol. 13 Supplement 1, A22, Sep 1999

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