Comparison of temperature rise curve and steady state temperature during thulium and holmium laser lithotripsy / 中华泌尿外科杂志

ABSTRACT

Objective:To compare the temperature rise curve and steady-state temperature of thulium and holmium laser in lithotripsy.Methods:This study was conducted from November to December 2021. Firstly, we designed an experimental water tank(10 cm×10 cm×10 cm) that can carry out constant temperature water bath, with a 8ml simulated renal pelvis, and can carry out constant velocity perfusion in the simulated renal pelvis. A 1 cm×1 cm×1 cm cubic artificial stone was placed in the simulated renal pelvis to perform 36.5℃-37.5 ℃ water bath. The simulated renal pelvis was closed with an oak plug, the temperature measuring probe and flexible ureteroscope were placed through the hole on the oak plug and entered into the simulated renal pelvis. Flexible ureteroscope was carried out by urologists. The lithotripsy lasted a total of 180 seconds for thulium and holmium laser respectively under different parameter settings (10 Hz×1.0 J, 10 Hz×2.0 J, 10 Hz×3.0 J, 20 Hz×0.5 J, 20 Hz×1.0 J, 20 Hz×1.5 J, the corresponding gravel power is 10 W, 20 W and 30 W respectively), the constant speed water pump flow rate was separate as the high flow rate group (35 ml/min) and low flow rate group (15ml/min), and leave a temperature probe 5mm around the optical fiber. Water temperature change during the lithotripsy was recorded by probes, the average of 10 temperature values of two probes measured every 5 seconds was taken as the water temperature value of this period, with a total of 216 time points in 6 parameter settings. Under the same parameter settings, the temperature of two lasers at each time point was plotted and compared to form the corresponding temperature rise curve. The average temperature in the last 30 seconds during lithotripsy in the record was used as the steady-state temperature, which of thulium and holmium laser lithotripsy was compared under the same parameter setting and the same water flow velocity. Finally, 43℃ was taken as the safety threshold temperature to evaluate whether the temperature of the two lasers during lithotripsy exceeds the safety threshold.Results:According to the temperature rise curve, the water temperature of thulium laser during lithotripsy was higher than that of holmium laser at 77.7% (168/216)of time points. At the flow rate of 15 ml/min, thulium laser was significantly higher than that of holmium laser at 10 Hz×1.0 J[(32.43±2.19℃)vs. (30.99±0.90)℃, P<0.01], 10 Hz×2.0 J[(41.21±3.30℃) vs. (38.13±1.26)℃, P<0.01], 10 Hz×3.0 J[(49.54±2.44)℃vs. (44.91±0.65)℃, P<0.01], 20 Hz×0.5 J[(32.75±1.41)℃vs. (30.84±1.16)℃, P<0.01], 20 Hz×1.0 J[(41.67±1.76)℃vs. (37.51±1.25)℃, P<0.01], 20 Hz×1.5 J [(47.54 ± 3.48)℃vs. (46.12±1.04)℃, P<0.01]. At the flow rate of 35 ml/min, the thulium laser was significantly higher than that of holmium laser at 10 Hz×1.0 J[(28.01±0.57)℃ vs. (26.84±0.97)℃, P<0.01], 10 Hz×2.0 J[(31.31±1.07)℃vs.(30.41±1.39)℃, P<0.01], 10 Hz×3.0 J[(33.29±0.70)℃vs.(32.25±2.55)℃, P<0.01], 20 Hz×0.5 J[(28.36±0.99)℃vs.(26.22±0.66)℃, P<0.01], 20 Hz×1.0 J [(30.80±2.06)℃vs.(30.08±0.78)℃, P=0.012], and the steady-state temperature was not significant different between two laser at 20 Hz×1.5 J [(34.54±3.08)℃ and(33.93±1.49)℃, P=0.163]. In the low flow rate group, thulium laser at 10 Hz×1.0 J, 10 Hz×2.0 J, 20 Hz×0.5 J and 20 Hz×1.0 J does not exceed the safety threshold temperature, while in the high flow rate group, any combination of laser parameters of the two lasers does not exceed the safety threshold temperature. Conclusion:Under the same laser parameter setting and flow rate, the thermal eff of thulium laser is more obvious. When using thulium laser for lithotripsy, the flow rate in the process of lithotripsy being faster than that of holmium laser with the same laser setting should be ensured to avoid tissue damage.