Asthmatics with overproduction of mucus that is viscous and sticky have impaired mucociliary clearance (MCC) leading to mucus plugs, and airway obstruction. Inhaled mannitol improves mucus clearance in other hypersecretory diseases. This study investigated the effect of mannitol and cough in asthmatics with mucociliary dysfunction. Seven stable asthmatics, age 52 ± 20 yr, lifelong non-smokers, without the diagnosis of bronchiectasis, with chronic cough and sputum production, treated with inhaled corticosteroids participated in the study. MCC and cough clearance (CC) was measured on 4 visits: at baseline (no cough or mannitol), with mannitol (240 and 480 mg) and cough control (no mannitol) over total 90 min using a radioaerosol technique and imaging with a gamma camera. Cough clearance was assessed after MCC by asking subjects to cough 100 times over 30 min. Premedication with eformoterol (12 μg) on all visits protected all subjects from bronchoconstriction (fall in FEV(1) > 15%) in response to mannitol. Mean (±SD) clearance over 60 min increased from 5.5 ± 5.6% at baseline and 7.3 ± 6.6% with cough control to 19.5 ± 14.6% and 26.4 ± 11.5% with 240 mg (p < 0.003) and 480 mg (p < 0.0001) of mannitol respectively. Total clearance (MCC + CC) over 90 min increased from 6.9 ± 6.5% (baseline) and 12.6 ± 8.3% without mannitol (cough control) to 34.6 ± 13.5 and 36.6 ± 10.4% with 240 and 480 mg mannitol respectively (p < 0.0001). Clearance over 90 min at baseline was not significantly different to cough control (p > 0.05). Mannitol improved clearance in all lung regions (p < 0.005). In conclusion, mannitol improved both mucociliary and cough clearance in asthmatics with mucociliary dysfunction and ineffective cough clearance. Clinical Trial registered with www.anzctr.org.au; Number ACTRN 12609001066279.aspx.
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