First report of the real-time observation of mucociliary clearance using high-definition bronchoscopy.

The airways are naturally equipped with mucociliary escalators, a primary defense mechanism for removing foreign substances. Mucociliary clearance velocity has traditionally been assessed using radiolabeled aerosols; however, real-time dynamic observations have yet to be described. A high-definition bronchoscope was used to observe foamy secretions on the tracheal mucus layer. These secretions moved slowly in a counterclockwise direction at 2.26 cm/min, as measured using distance analysis software. In contrast, movement was noticeably slower in a young adult with recurrent pneumonia. This real-time observation has the potential to offer a minimally invasive method for quantifying mucociliary clearance by tracking the movement of mucus on the epithelial surface. These findings may contribute to understanding individual and pathological variations in airway epithelial mucus dynamics.