Interactions of Airflow Oscillation, Tracheal Inclination, and Mucus Elasticity Significantly Improve Simulated Cough Clearance

摘要

Background: Viscoelastic properties of simulated mucus, angle of tracheal inclination ( u ), and nhigh-frequency airfl ow oscillations on median displacement of simulated mucus during simulated ncough were investigated in this study. n Methods: Mucus simulants with viscoelastic properties similar to healthy individuals and patients nwith COPD were prepared using locust bean gum (LBG)-water solution (0.38 g LBG in 100 mL nwater) cross-linked with 3-mL and 12-mL borax-water solution (0.02 M), respectively. Aliquots of n0.3 mL of simulants were placed on a dry Plexiglas insert inside a D-shaped clear Plexiglas tra-ncheal model. Movement of aliquots of mucus simulants was measured during cough of 0.3 s duration. nCough velocities studied (5-30 m/s) are typical of patients with weak expiratory muscles and nairway obstruction. Studies were conducted with tracheal model placed horizontally (0°) and at nincreasing u (15°, 30°, and 45°), with and without superimposed airfl ow oscillations during coughs. nEffects of different parameters and their interactions on displacements of aliquots were com-npared using analysis of covariance (n 5 849). n Results: Signifi cant positive nonlinear associations existed between displacement and cough nvelocity for both 3-mL and 12-mL simulants ( P , .0001). Displacement was greatest for the cohe-nsive 12-mL simulant at all cough velocities. Displacement increased signifi cantly ( P , .0001) as u nwas increased for both types of simulants. Largest displacements at low cough velocities occurred nwith 12-mL simulant in the presence of oscillations at 45° angle. n Conclusions: Results support the use of airfl ow oscillations and sitting upright to facilitate mucus ndisplacement during cough, particularly with thick, elastic mucus found in patients with COPD n( P , .0001). CHEST 2010 ; 137(2):355–361