Enhancing Mucus Clearance by Cough Through Repeated Pulses

Abstract

The aim of this study is to investigate the potential increase in the efficiency of the mucus clearance by repeated pulses of the same maximum speed and total air volume compared to single pulse simulated cough and to explore the effect of mucus simulant rheology and duration between repeated pulses on it. Experiments are conducted to study the behavior and clearance of a mucus simulant through a D-shaped rigid plexiglass horizontal tracheal model by approximately rectangular pulses. Mucus simulants with viscoelastic properties like mucus of patients with chronic obstructive pulmonary disease (COPD) or similar illnesses, a moderate increase in elastic modulus, and a sharp decrease in viscosity with increasing frequency were prepared by locust bean gum and borax-de-ionized water solutions (Ragavan, A. J., Evrensel, C. A., and Krumpe, P., 2010, “Interactions of Airflow Oscillation, Tracheal Inclination, and Mucus Elasticity Significantly Improve Simulated Cough Clearance,” Chest, 137(2), pp. 355–361). Displacement of 0.3 ml mucus simulant aliquot is measured during single or repeated airflow pulses with a total air volume of about 1.1 L and the same maximum velocity. The desired flow pattern is generated by a compressor set at 4.5 bar and a computer-controlled on–off valve. Displacement of the same volume of mucus aliquot increases with the increasing number of pulses with the same total volume of air and maximum velocity and increasing of elasticity of mucus simulants. The increased maximum airflow velocity of repeated pulses affects the displacement of mucus aliquot positively. Moreover, when the duration length between the repeated pulses increased up to 100 ms, the displacement of aliquot increased up to but after 100 ms to 150 ms started to decrease.