Investigation of Flexible High-Speed Video Nasolaryngoscopy

Objective: High-speed videolaryngoscopy is widely used in voice practices as a complement to videostroboscopy, especially when it is desired to visualize asymmetric and nonperiodic vocal fold vibration or voice onset and offset. Because of the requirement for greater illumination at higher frame rates, the high-speed exam is usually performed with a rigid transoral laryngoscope. Although it is possible to obtain color high-speed video images with a flexible fiberoptic nasoendoscope, the results are often disappointing because of the inability to provide adequate lighting inside the larynx. This paper will present the results of a systematic exploration of tools and techniques to optimize the image brightness of flexible color high-speed videolaryngoscopy exams using the KayPENTAX Model 9710 Color High-Speed Video (CHSV) System. Methods: The KayPENTAX CHSV System was used with three PENTAX flexible fiberoptic nasolaryngoscopes and a new supplemental light fiber bundle to perform high-speed examinations of healthy vocal folds. Variables of the investigation included camera frame rate, camera sensitivity (color head versus black-and-white head), optics (camera lens focal length), light coupling, nasoendoscope outer diameter, and endoscopy technique (visually perceived distance of the distal tip of scope from the glottal plane). Results and Conclusions: The manipulation of camera gain, the proper selection of lens coupler focal length, and the adjustment of scope distal tip distance from the glottal plane were found to be most effective for optimizing image brightness, whereas the supplemental light fiber bundle provided minimal benefits. Other factors considered include patient comfort, practicality, and ease of use by the clinician.