The 24-h effect of mannitol on the clearance of mucus in patients with bronchiectasis

Study objective: To investigate the acute effect of mannitol on the clearance of mucus, and (1) the 24-h mucus retention, and (2) the mucus clearance rate and lung function 24 h after inhalation of a single dose of mannitol. Design: Clearance of mucus was measured on 3 consecutive days using Tc-99m-sulfur colloid radioaerosol and a gamma camera. Interventions: Mannitol, 330 +/- 68 mg (mean +/- SD), was inhaled using a dry powder inhaler only on day 2. Patients: Eight patients with bronchiectasis (age range, 29 to 70 years). Measurements and results: On each day, lung images were collected over 2 h and at 24 h. Key findings of the study are as follows: (1) the 24-h retention of mucus was reduced the day after mannitol had been inhaled, compared to the day without mannitol (day 1) in the whole light lung (57.6 +/- 6.2% vs 68.1 +/- 5.9%), central (47.5 +/- 6.7% vs 56.9 +/- 6.5%), intermediate (61.1 +/- 5.6% vs 73.8 +/- 5.5%), and peripheral regions (70.9 +/- 4.3% vs 86.6 +/- 4.6%)(p < 0.02); and (2) mannitol helped patients clear mucus within 2 h that might otherwise take up to 24 h, from the whole right lung and defined regions. However, clearance over 60 min measured 24 h after mannitol inhalation was not significantly different to baseline clearance without mannitol (8.7 +/- 1.9% on day 1 vs 9.7 +/- 3.7% 24 h after mannitol; p > 0.8). The patients maintained the same lung function the day before and after mannitol had been inhaled: FEV1 (percent predicted), 79 +/- 5 on day 1 vs 80 +/- 5 on dav 3; and forced expiratory flow, midexpiratory phase (percent predicted), 50 +/- 6 on day 1 vs 51 +/- 6 on day 3; p > 0.6). Conclusions: Mannitol inhalation acutely increases clearance of mucus, and this effect extends beyond the acute study period, resulting in decreased mucus retention at 24 h.