Purpose: To assess the effects of color, coating, and opacity on the detection of aspiration, penetration, and residue during flexible endoscopic evaluations of swallowing (FEES).

Methods: Thirty dysphagic adults underwent FEES while swallowing five 5 mL thin liquid boluses (1x each, randomized): white water, blue water, white milk, blue milk, and barium water. To assess the effects of color,
blue milk was compared to white milk. To assess the effects of coating, barium, white water, and white milk were compared to each other. To assess the effects of opacity, blue milk was compared to blue water. Videos
were blindly analyzed and judged for the presence of pharyngeal residue, penetration, and aspiration. Repeated measures analyses were used to assess differences in the frequency of detection across bolus types.

Results: Pharyngeal residue was detected more frequently for liquids that were blue, had a coating effect, or were opaque (p < .05) when compared to liquids that were white, did not have a coating effect, or were
translucent, respectively. Penetration and aspiration were detected more frequently for liquids that had a coating effect (p < .05), but not for liquids that were colored blue or opaque (p > .05).

Conclusion: Coating appears to be the most important factor detecting thin liquid residue, penetration, and aspiration during FEES. Given these findings, standardized use of boluses that possess a coating effect (e.g., white dyed water or barium) is highly recommended to enhance the sensitivity of identifying impairments in swallowing safety and efficiency during FEES.