Thermal effects of endoscopy in a human temporal bone model: implications for endoscopic ear surgery.

OBJECTIVES/HYPOTHESIS: Although the theoretical risk of elevated temperatures during endoscopic ear surgery has been reported previously, neither temperature change nor heat distribution associated with the endoscope has been quantified. In this study, we measure temperature changes during rigid middle ear endoscopy in a human temporal bone model and investigate whether suction can act as a significant cooling mechanism.

STUDY

DESIGN

Human temporal bone model of endoscopic middle ear surgery.

METHODS

Fresh human temporal bones were maintained at body temperature (∼ 36°C). Temperature fluctuations were measured as a function of 1) distance between the tip of a 3-mm 0° Hopkins rod and round window membrane, and 2) intensity of the light source. Infrared imaging determined the thermal gradient. For suction, a 20-Fr suction catheter was utilized.

RESULTS

We found: 1) an endoscope maximally powered by a xenon or light-emitting diode light source resulted in a rapid temperature elevation up to 46°C within 0.5 to 1 mm from the tip of the endoscope within 30 to 124 seconds, 2) elevated temperatures occurred up to 8 mm from the endoscope tip; and 3) temperature decreased rapidly within 20 to 88 seconds of turning off the light source or applying suction.

CONCLUSIONS

Our findings have direct implications for avoiding excessive temperature elevation in endoscopic ear surgery. We recommend: 1) using submaximal light intensity, 2) frequent repositioning of the endoscope, and 3) removing the endoscope to allow tissue cooling. Use of suction provides rapid cooling of the middle ear space and may be incorporated in the design of new instrumentation for prolonged dissection.