PURPOSE: This study compares displacement of simulated mucus aliquot in a tracheal model during controlled coughs with superimposed oscillations generated by three commercially available mechanical oscillators differing in their frequencies and amplitudes.
METHODS: Three external oscillators were compared: Flutter(r) (Axcan Scandipharm Inc, Birmingham, AL), Acapella(r) (Smiths Medicals Inc, Rockland, MA) and Quake(r) (Thayer Medical, Tucson, AZ). Displacement of 0.3ml aliquot of simulated mucus placed inside an inverted “D” shaped, horizontally oriented, Plexiglas model trachea (cross-sectional area of 2.44cm^2) was measured during controlled coughs. Mucus simulants were prepared using 0.01molar locust bean gum solution (Sigma, St Louis, MO) cross-linked with 3ml or 12ml solutions of sodium tetra-borate (0.02 molar). The resulting simulants had rheological properties similar to fluid-like, healthy or more gel-like respiratory secretions typical of Chronic Obstructive Pulmonary Disease (COPD) patients (CHEST, 2010, 137:355-361). Cough transients of 300ms at iso-velocity of 14m/s (representative of the low cough velocity of a typical adult COPD patient) were generated using a computer controlled solenoid valve. Oscillations were superimposed by the devices in line at the outlet of the tracheal model.
RESULTS: The gel-like mucus (as found in COPD patients) moved significantly larger distances (p=0.003, ANCOVA) with all three oscillators compared to the fluid-like mucus found in healthy individuals. Quake(r) (frequencies and amplitudes of 27Hz and 9.5m/s) resulted in the largest mucus displacement, followed by Acapella(r) (55Hz and 4.2m/s) while Flutter(r) (27Hz and 3.2m/s) showed the smallest displacement of the three devices, only slightly larger than that of coughs without oscillations. (p=0.01, ANCOVA), all at average cough velocity of 14m/s.
CONCLUSION: Distance travelled by simulated mucus aliquot during controlled coughs increased significantly with the amplitude of superimposed oscillations. Gel-like, mucus is better cleared with and without oscillations compared to thinner fluid-like mucus found in healthy individuals.
CLINICAL IMPLICATIONS: Results suggest that oscillators which generate larger amplitude waves may significantly enhance secretion clearance. Our bench-test data may predict the clinical utility of these types of devices in aiding cough effectiveness in patients with mucus hypersecretion.
DISCLOSURE: Peter Krumpe, Grant monies (from industry related sources) ; Consultant fee, speaker bureau, advisory committee, etc. Dr Krumpe has been paid as a consultant during the past year by the Philips-Respironics Corporation regarding applications of the Cough-Assist device (a commercial product that they manufacture).; No Product/Research Disclosure Information