Endoscopic Distance and its Impact on Quantified Age-related Vocal Fold Atrophy Measures.

ABSTRACT

INTRODUCTION: The bowing index (BI) and normalized glottal gap area (NGGA) are used to quantify vocal fold morphology in ARVA; however, the influence of the distance between the flexible laryngoscope lens and the target area is not known. The goal is to test whether the endoscopic distance impacts vocal fold morphology measurements in patients with ARVA during flexible video laryngostroboscopy (VLS). METHOD: Patients with ARVA who underwent VLS were included. Images were classified into near (close to the petiole of the epiglottis) and far (below nasopharynx, with tongue base and entire epiglottis visible) conditions. BI was calculated using a mobile application, and NGGA was measured using ImageJ. RESULTS: This study included 23 patients; the mean age was 77 ± 7 years. Mean BI measured at the near distance was higher than far distances with a mean difference of 1.94 (95% CI 0.92-2.96, p = 0.001). NGGA showed difference with changed distance -0.24 (95% CI -0.48 to 0.01, p < 0.05).When stratifying patients into two groups based on median BI measurement, there was a statistically significant difference between near and far conditions, with increased BI in the near condition for patients above the median (p < 0.05), but no difference between the near and far condition for patients with BI below the median. CONCLUSION: The BI and NGGA were impacted by the endoscopic distance during flexible VLS. BI was significantly higher in the near condition compared with the far condition. The difference in BI between the near and far conditions was more pronounced when the vocal fold bowing was greater. These findings call for heightened awareness of measurement discrepancies secondary to the endoscopic distance during flexible laryngostroboscopy. LEVEL OF EVIDENCE 2 Laryngoscope, 1344649-4655, 2024.