Aerosol deposition in the airway model with excessive mucus secretions

Aerosol deposition in the airways with excessive mucus secretions was investigated utilizing an in vitro airway model lined with various mucus simulants of differing rheological properties. The airway model was made with a straight glass tube (1.0 cm ID and 20 cm in length) and positioned vertically. The mucus simulants were supplied into the tube at a constant rate and made to move upward through the tube as a thin layer (0.6-1.7 mm) undergoing a random wave motion by means of upward airflow. Aerosols (3.0 and 5.0-micron diam) were passed through the mucus-lined tube at flow rates of 0.33-1.17 l/s, and the deposition of the aerosols in the tube was determined by sampling the aerosols at the inlet and the outlet of the tube on filters. During the sampling, pressure drop across the tube model was also measured. Deposition efficiency in the 20-cm-long mucus-lined tube ranged from 13 to 92% with 3.0-micron-diam particles and from 66 to 98% with 5.0-micron-diam particles. This deposition was 25-300 times higher than that in the dry tube. The deposition was higher with increasing viscosity of mucus but was lower with increasing elasticity of mucus. Pressure drop across the mucus-lined tube was much higher than that in the dry tube, and the increase was more prominent with mucous layers with higher viscosity but lower elasticity values. Therefore, aerosol deposition showed a good positive relationship with pressure drop. However, percent increase of aerosol deposition in the mucus-lined tube was 2-5 times higher than that of pressure drop.(ABSTRACT TRUNCATED AT 250 WORDS)