Clinical evaluation of 70 degrees and 90 degrees laryngeal telescopes

Rigid telescopy is widely used in otorhinolaryngology for endolaryngeal visualization. Laryngeal telescopes are made with several angles, including 70 degrees and 90 degrees. In this study, the performances of 70 degrees and 90 degrees telescopes are compared and evaluated on the basis of ability to visualize specific regions of the larynx.

Each subject (N = 121) received evaluation with both 70 degrees and 90 degrees telescopes. The investigator used the telescopes to attempt to visualize 4 key regions: (1) the subglottic area, (2) the pyriform fossae, (3) the anterior commissure, and (4) the laryngeal surface of the epiglottis. The telescopes were connected to a video camera and videotape recordings were made. The percentage of attempted visualizations that were successful was calculated for both the 70 degrees and the 90 degrees telescopes.

The 70 degrees telescope provided successful visualization of the subglottic area in 111 patients (91.7%), of the pyriform fossae in 115 (95.0%), of the anterior commissure in 112 (92.6%), and of the laryngeal surface of the epiglottis in 114 (94.2%). The 90 degrees telescope provided successful visualization of the subglottic area in 103 patients (85.1%), of the pyriform fossae in 112 (92.6%), of the anterior commissure in 100 (82.6%), and of the laryngeal surface of the epiglottis in 102 (84.3%). Differences in rates of visualization were significant for the posterior surface of the epiglottis, the anterior commissure, and the subglottic area.

The 70 degrees telescope provided a significantly higher rate of successful visualization for 3 of the 4 regions studied. This result contributes information that may help the clinical examiner select an instrument of choice.