Measurement of acoustic transients during pulsed holmium : YAG laser ablation of cadaveric human temporal bone

Pulsed infrared (IR) and ultraviolet (UV) lasers have been suggested for us e in middle ear surgery due to potential fiberoptic delivery, decreased the rmal trauma and precise ablation characteristics. Although attention has be en focused on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies which evaluate the ac oustic energy generated from these devices from an audiological standpoint. In this study, the mastoid cavities of cadaveric human temporal bones were irradiated with a holmium: yttrium aluminium garnet (Ho:YAG) laser (lambda =2.12 mu m) using the following parameters: 5, 10, and 15 Hz pulse repetiti on rate and 1, 2, 4, 6, 8, and 10 W average power. During ablation, acousti c measurements were made using a sound level meter positioned 5 cm away fro m the target site. With each set of laser parameters, the sound intensity e xceeded 85 dB (dBA scale). Peak intensities of 125 dB were measured, and a saturation effect noted above 4 W or 500 mJ/pulse. The clinical significanc e of these findings is discussed and the acoustical aspects of middle ear f unction and noise trauma are reviewed.