CO_2激光和Nd∶YAG激光照射豚鼠鼓膜对中耳和耳蜗结构的影响

Influence of CO_2 Laser and Nd∶YAG Laser Irradiation to Guinea Pig's Tympanic Membrane on the Structure of the Middle Ear and Cochlea

目的 探讨激光鼓膜造孔对听力的影响。方法 用不同功率密度的CO2激光或Nd∶YAG激光照射豚鼠鼓膜不同时间后,观察中耳和耳蜗结构的变化。结果 以功率密度153Wmm2的CO2激光照射豚鼠鼓膜2s,或以相同功率密度的Nd∶YAG激光照射豚鼠鼓膜10s,可引起鼓膜穿孔,听骨链和耳蜗凝固或点状炭化,凝固和炭化处柯蒂氏器官均明显破坏或变化。激光输出功率密度愈大,损伤听骨和耳蜗所需的照射时间愈短。中耳腔内注水可避免或明显减轻CO2激光对听骨和耳蜗的损伤,但对Nd∶YAG激光无效。结论 激光鼓膜造孔应严格控制激光功率密度和照射时间,以免损伤听力。用CO2激光造孔时,中耳腔内注水可避免或减轻激光对听骨和耳蜗的损伤。

Objective To study the influence of tympanic membrane perforation caused by CO 2 laser and Nd∶YAG laser on hearing. Methods The structure of the middle ear and cochlea was examined at various intervals after CO 2 laser or Nd∶YAG laser irradiation with different power densities to the guinea pig's tympanic membrane. Results The tympanic membrane irradiated for 2 seconds with CO 2 laser with a power density of 1 53 W/mm 2 or 10 seconds by Nd∶YAG laser with the same power density may become perforated, coagulated or carbonized in the ear bone and cochlea. The coagulated or carbonized structure in the Cortis organ was obviously damaged. The larger the output power density of laser, the shorter the irradiation time needed to impair the ear bone and cochlea. Water injection into the middle ear cavity may avoid or obviously alleviate the impairment caused by CO 2 laser but exert no effect on the impairment caused by Nd∶YAG laser. Conclusions To avoid impairment of hearing the laser power density and irradiation time should be strictly controlled in making the hole in tympanic membrene by laser. Water injection into the middle ear cavity may prevent or reduce the impairment of ear bone and cochlea when the tympanic membrane is perforated by CO 2 laser irradiation.