Mucous gel transport in a simulated cough machine: effects of longitudinal grooves representing spacings between arrays of cilia.

Under some conditions, such as inhalation injury, an array of longitudinal channels without cilia may be formed on the epithelial surface, affecting mucus transport in the lung during coughing. Moreover, in certain cases of the diseased state of the lung, immotile cilia remain embedded in the serous fluid and may form channels in the direction of air motion during coughing, providing a resistance-free pathway for serous layer fluid and assist in mucus clearance. To understand this phenomenon, we have conducted experiments with mucous gel simulants (MGS) in a simulated cough machine (SCM) using soap solution as a serous layer simulant (SLS). The channel structure of the airway surface was modeled by introducing bottom plates with longitudinal grooves about 10 cm long having different depths, widths and number of grooves. It was shown that mucous gel transport increases as the cross-sectional area occupied by channel grooves increases. The effects of sinusoidal constriction and mucous gel filance were also investigated in this model system. It was found that mucous gel transport increases in the constricted case (minimum gap, 3 mm, and maximum gap, 9 mm) in comparison with that in the parallel case (constriction gap of 9 mm). The effect of increasing the mucous gel filance was to decrease the transport,, as reported in previous studies.