PURPOSE: Cough clearance of mucus is fundamental to survival during airway inflammation. The aim of this study was to assess the effects of two factors believed to contribute to the displacement of mucus during cough. We measured displacement of mucus simulants with known viscoelsatic properties under conditions with and without airflow oscillations.
METHODS: Mucus simulants made from locust bean gum cross-linked with 3% or 12% borax (having high and low viscosity / elasticity ratios) were studied at measured cough velocities (Ù) with and without ∼60 Hz cough flow oscillations (Acapella™, Smiths Medical, Weston, MA). Studies were done in a dry, flat Plexiglas tracheal model. Mean mucus movement at Ù typical of COPD patients were compared using ANOVAR.
RESULTS: The correlation between cough mucus displacement and cough Ù were curvilinear under each experimental condition (R = .76, .77 without oscillations and R = .92, .76 with oscillations). Mean mucus displacements with oscillations for the 12% simulant (gel-like mucus)were 60 mm at Ù = 10 M/sec, but only 10 mm at Ù = 15 M/sec without oscillations. Data for 3% (syrupy) showed 12 mm displacement at Ù = 10 M/sec with oscillations and 10 mm displacement at Ù = 25 M/sec without oscillations. Both experimental factors were independent contributors to mucus displacement (P >.001 by ANOVAR).
CONCLUSION: This study illustrates that cough clearance is most effective with gel-like mucus under conditions of airflow oscillations.
CLINICAL IMPLICATIONS: COPD patients with thick mucus and noisy ronchi may be able to cough more effectively than those with syrupy mucus under noiseless cough conditions.
DISCLOSURE: Peter Krumpe, None.