Acute and durable effect of inhaled hypertonic saline on mucociliary clearance in adult asthma

BACKGROUND: Impaired mucus clearance and airway mucus plugging have been shown to occur in moderate–severe asthma, especially during acute exacerbations. In cystic fibrosis, where airway mucus is dehydrated, it has been shown that inhaled hypertonic saline (HS) produces both acute and sustained enhancement of mucociliary clearance (MCC). The current study was designed to assess the acute and sustained effect of inhaled 7% HS on MCC in adult asthma. METHODS: Well-controlled, moderate–severe female asthmatic patients (n=8) were screened with a single test dose of albuterol (four puffs by metered-dose inhaler) followed by HS (7% sodium chloride, 4 mL using PARI LC Star nebuliser). Spirometry was measured pre-treatment and 5 and 30 min post-treatment for safety. MCC was measured using γ-scintigraphy on three separate visits: at baseline, during inhalation and 4 h after a single dose of HS. RESULTS: MCC was acutely enhanced during HS treatment; mean±sd clearance over 60 min of dynamic imaging (Ave60Clr) was 8.9±7.9% (baseline) versus 23.4±7.6% (acute HS) (p<0.005). However, this enhancement was not maintained over a 4-h period where post-HS treatment Ave60Clr was 9.3±8.2%. In this small cohort we found no decrements in lung function up to 30 min post-treatment (forced expiratory volume in 1 s 97.4±10.0% predicted pre-treatment and 98.9±10.7% predicted 30 min post-treatment). CONCLUSION: While MCC was rapidly enhanced during 7% HS treatment there was no effect on MCC at 4 h post-treatment. While these findings may not support aerosolised HS use for maintenance therapy, they do suggest a benefit of treating acute exacerbations in patients with moderate–severe asthma.