Objective: Inhaled mannitol increases mucus clearance in patients with bronchiectasis by an unclear mechanism. The effect of mannitol on lung function, health status and sputum properties was investigated.
Methodology: Nine patients with bronchiectasis inhaled 400 mg of mannitol once daily for 12 days. Health status was assessed using the St George's Respiratory Questionnaire (SGRQ). Sputum was analysed for viscosity, elasticity, spinnability, surface tension, contact angle, solids, mucociliary transportability (MCTR) on a frog palate, and cough transportability (CTR) on a simulated cough machine.
Results: Lung function was unchanged with treatment (baseline FEV1 82.0 +/- 16.2%) apart from an improvement in FEF from 85.4 +/- 13% (baseline) to 90.7 +/- 14.4% (P < 0.05; 12th treatment; visit 7). The total SGRQ score (mean +/- SD) of 49.3 +/- 13.8 at baseline, decreased by 12.4 +/- 10.2 (P < 0.01; visit 7) and 10.1 +/- 9.4 units (P < 0.02) 6-10 days after treatment cessation. The baseline subscores for symptoms (72.9 +/- 11.8), activity (44.7 +/- 20.9) and impact (44.4 +/- 14.3) were reduced by 0.8 +/- 9.1 (P > 0.7), 8.4 +/- 16.0 (P > 0.1) and 19.2 +/- 13.7 (P < 0.005) units, respectively (visit 7). Mannitol reduced the baseline (mean +/- SE) surface tension from 94.5 +/- 1.4 to 84.7 +/- 2.1 mN/m (P < 0.0001), contact angle from 51.1 +/- 2.8 to 33.2 +/- 2.4 degrees (P < 0.0001), spinnability from 11.6 +/- 0.4 to 10.0 +/- 0.2 mm (P < 0.005), and solids from 5.7 +/- 0.4 to 4.3 +/- 0.7% (P < 0.02), acutely (visit 7). Viscosity, elasticity and MCTR did not change significantly, while CTR was increased from 25.8 +/- 1.0 to 34.1 +/- 2.7 mm (P < 0.003).
Conclusion: Mannitol significantly improved the health status over 12 days and this improvement was maintained for 6-10 days after cessation of treatment. In addition, mannitol reduced the tenacity, increased the hydration of mucus acutely and improved cough clearability in patients with bronchiectasis.