Effect of increasing doses of mannitol on mucus clearance in patients with bronchiectasis

Bronchiectasis is characterised by hypersecretion and impaired clearance of mucus. A 400-mg dose of inhaled mannitol improves mucus clearance however, the effect of other doses is unknown. A total of 14 patients, aged 63.3 +/- 5.7 yrs, were studied on five visits. Mucus clearance at baseline and with mannitol (160, 320 and 480 mg) was measured using technetium-99m-sulphur colloid and imaging with a gamma camera over 45 min, followed by a further 30 min involving 100 voluntary coughs. A control study assessed the effect of cough provoked by mannitol during the intervention. Whole right lung clearance over 45 min was 4.7 +/- 1.2 and 10.6 +/- 2.6% on baseline and control days, respectively, and increased to 16.7 +/- 4.2, 22.8 +/- 4.2 and 31 +/- 4.7% with 160, 320 and 480 mg mannitol, respectively. Clearance over 45 min with 480 mg mannitol was greater than clearance with 320 and 160 mg. Total clearance over 75 min, after mannitol administration and voluntary coughs, was 36.1 +/- 5.5, 40.9 +/- 5.6 and 46.0 +/- 5.2% with 160, 320 and 480 mg mannitol, respectively, all significantly different from baseline (24.1 +/- 6.0%) and control (13.1 +/- 3.0%). Total clearance over 75 min with 480 mg mannitol was greater compared with 160 mg. In conclusion, mucus clearance increases with increasing doses of mannitol and can be further increased by cough in patients with bronchiectasis.