Temperature Changes Associated with Middle Ear Endoscopy in a Human Temporal Bone Model

Abstract

Objectives: Endoscopic ear surgery is rapidly gaining popularity as a minimally invasive approach to address chronic ear disease. However, little is known about the potentially damaging temperature increases associated with endoscopy in the middle ear. Specifically, neither temperature change nor heat distribution associated with the endoscope has been quantified. In this study, we aim to measure temperature changes throughout the middle ear during rigid endoscopy in a human temporal bone model. Methods: Fresh human temporal bones were maintained at physiologic temperature during middle ear endoscopy with a 3-mm 0° Hopkins rod. Temperature changes were measured as a function of the distance between the endoscope tip and the round window membrane. Thermal gradient was determined by infrared imaging. Control studies conducted at room temperature were also performed. Results: An endoscope with a xenon or light-emitting diode light source on maximal power induced a rapid temperature elevation up to 46°C within 0.5-1 mm of the tip of the endoscope within 30-124 seconds. Elevated temperatures occurred at distances up to 8mm from the endoscope tip. Temperatures rapidly returned to baseline within 20-88 seconds after turning off the light source. Conclusions: Our findings have direct implications for endoscopic ear surgery and affirm the importance of avoiding excessive temperature elevation. We recommend employing submaximal light intensity and repositioning the endoscope frequently to provide rapid cooling. Ongoing studies use an animal model to explore the in vivo effects of prolonged middle ear endoscopy and evaluate for potential threshold shifts in auditory brainstem responses.