Jovanovic S, Schönfeld U, Fischer R, Döring M, Prapavat V, Müller G, Scherer H
HNO-Klinik mit Polikliniken, Berlin.
HNO. 1996 Jan;44(1):6-13.
Apart from ablation properties at the stapes footplate, the degree of thermal stress of the inner ear is important when considering the suitability of pulsed lasers for stapedotomy. The aim of the present study was to compare the heating of cochlear structures with presently available pulsed laser systems during stapedotomy under reproducible conditions. Temperature increases and heat-exchange processes were examined in a physiologic model of the cochlea using various laser parameters effective for footplate perforations. With all systems, increases in energy density, number of pulses and resultant total energy led to higher temperatures. In the effective energy density range, the highest temperature increases achieved with the requisite number of pulses at a distance of 2 mm behind the footplate perforation were 30 degrees and 26 degrees C with the pulsed CO2 and Ho:YAG lasers, respectively. The lowest temperature recorded was 5.5 degrees C with the Er:YAG and <5 degrees C with the Er:YSGG laser. The excimer laser investigated at only one energy density showed maximum temperatures of 10 degrees C. With regard to possible inner ear damage from thermal stress during laser stapedotomy, the Er:YSGG laser can be used safely over a relatively broad energy density range. The Er:YAG laser investigated also appears suitable for stapedotomy when considering thermal effects. In contrast, application of the pulsed CO2 laser at parameters effective for stapedotomy leads to high temperatures and wide scattering to compromise its use. The Ho:YAG laser also appears to be unsuitable because of the higher energy density and pulse rate required for sufficient perforation and the resultant higher temperature increases in the perilymph. Although footplate perforations can be achieved with only slight temperature increases in the fluid of the cochlea model, the excimer laser does not seem to be appropriate for stapedotomy because of the long period of heat exposure required and the lower ablation rates at the stapes.
除了镫骨足板的消融特性外，在考虑脉冲激光用于镫骨切除术的适用性时，内耳的热应力程度也很重要。本研究的目的是在可重复的条件下，比较目前可用的脉冲激光系统在镫骨切除术中对耳蜗结构的加热情况。使用对足板穿孔有效的各种激光参数，在耳蜗的生理模型中检查温度升高和热交换过程。对于所有系统，能量密度、脉冲数和总能量的增加都会导致温度升高。在有效能量密度范围内，在足板穿孔后方2毫米处，使用所需脉冲数时，脉冲CO2激光和Ho:YAG激光分别使温度最高升高30摄氏度和26摄氏度。使用Er:YAG激光记录到的最低温度为5.5摄氏度，使用Er:YSGG激光记录到的最低温度低于5摄氏度。仅在一种能量密度下研究的准分子激光显示最高温度为10摄氏度。关于激光镫骨切除术期间热应力可能对内耳造成的损伤，Er:YSGG激光可以在相对较宽的能量密度范围内安全使用。考虑到热效应，所研究的Er:YAG激光似乎也适用于镫骨切除术。相比之下，以对镫骨切除术有效的参数应用脉冲CO2激光会导致高温和广泛的散射，从而影响其使用。Ho:YAG激光似乎也不合适，因为足够穿孔所需的能量密度和脉冲率较高，导致外淋巴中的温度升高更高。尽管在耳蜗模型的液体中仅轻微升高温度就能实现足板穿孔，但准分子激光由于所需的热暴露时间长且在镫骨处的消融率较低，似乎不适用于镫骨切除术。
