Simulated Repetitive Coughing at Vertical Tracheal Angles Significantly Improve Clearance of Simulated Gel‐like Mucus found in Patients with Respiratory Diseases

Abstract

Interactive role of repetitive simulated coughing and vertical angles of trachea on clearance of gel‐like mucus produced by patients with respiratory diseases is analyzed in this study. Repetitive coughs (3 coughs of 0.1 sec. and 4 coughs of 0.075 sec. duration) were generated in a model trachea slightly larger in dimensions than average adult trachea placed at 4 vertical angles (0o, 15o, 30o, 45o), using a simulated cough machine. Mucus simulants with varying apparent viscosities (0.1 Pascal sec. (PaS) to 3 PaS) at relatively large storage modulus (13±1.0 Pa) were prepared to represent tracheal mucus of patients with various respiratory diseases. Rheological properties (storage mucudus (G') and apparent viscosity (η')) and displacement of leading and trailing edges of 0.3 ml simulant aliquots during coughs were measured. Repetition of coughs induced increased simulant clearance (p<0.05) compared to single coughs (0.3 sec duration) of the same velocity. The percentage increase in clearance was significantly larger at increased angles of the tracheal model (p<0.05). Significant negative correlations (−0.54) existed between percentage increase of clearance and η'. Results suggest that repetitive cough may increase the clearance efficiency of mucus with shear dependent properties compared to single cough of the same velocity and duration.