Study objective: To investigate the acute effect of mannitol on the clearan
ce 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, 33
0 +/- 68 mg (mean +/- SD), was inhaled using a dry powder inhaler only on d
ay 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 retenti
on of mucus was reduced the day after mannitol had been inhaled, compared t
o the day without mannitol (day 1) in the whole light lung (57.6 +/- 6.2% v
s 68.1 +/- 5.9%), central (47.5 +/- 6.7% vs 56.9 +/- 6.5%), intermediate (6
1.1 +/- 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 de
fined regions. However, clearance over 60 min measured 24 h after mannitol
inhalation was not significantly different to baseline clearance without ma
nnitol (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 m
annitol had been inhaled: FEV1 (percent predicted), 79 +/- 5 on day 1 vs 80
+/- 5 on dav 3; and forced expiratory flow, midexpiratory phase (percent p
redicted), 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 m
ucus retention at 24 h.