The Effect of Bolus Characteristics and Endoscope Position on the Whiteout During Fiberoptic Endoscopic Evaluation of Swallowing

Abstract

Background: During fiberoptic endoscopic evaluation of swallowing (FEES), the whiteout (WO) phenomenon arises when pharyngeal structures obscure the endoscopic view by contacting the tip of the endoscope during the pharyngeal phase of swallowing. The objective of this study was to investigate the influence of endoscope positioning, bolus volume, and bolus opacity on the duration and intensity of the WO observed with thin liquid boluses during FEES.

Methods: Thirty healthy volunteers undergoing nasoendoscopy performed 3 empty swallows with the endoscope positioned in the nasopharynx (NP), oropharynx (OP), and hypopharynx (HP). Bolus trials consisting of 5 mL and 10 mL portions of green-dyed 3% milk and water were administered in a randomized order. Whiteout duration (WOd) and WO intensity (WOi) were measured for all 11 swallowing trials. The WOd was calculated by a manual frame count and WOi was scored with a 5 point ordinal scale.

Results: Endoscope position significantly affected WOi, but not WOd. Mean WOi was 3.07 ± 1.2 for the NP, 3.3 ± 0.95 for the HP, and 3.67 ± 0.66 for the OP (P = .039, Friedman’s test). The WOd was significantly longer for milk boluses than for water boluses (0.52 ± 0.13 seconds for water vs. 0.59 ± 0.17 seconds for milk, P = .019). The WOi was significantly weaker for milk boluses compared to water boluses (3.49 ± 0.43 for water compared to 3.32 ± 0.49 for milk, P = .022). No significant differences in either WOd or WOi were detected between 5 and 10 mL boluses.

Conclusion: The intensity and duration of the WO observed with thin liquid boluses are significantly influenced by both the bolus opacity and the endoscope’s position, while the bolus volume has no significant effect.

Cite this article as: Betito HR, Yaka R, Lahav Y, Galitz YS. The effect of bolus characteristics and endoscope position on the whiteout during fiberoptic endoscopic evaluation of swallowing. Balkan ORL-HNS. 2026, 3, 0070, 10.5152/bohns.2026.25070.