This study compared the effect of inhaled hypertonic saline on 24 patients with cystic fibrosis over a 28 day period. Subjects were assigned to two groups receiving pretreatment with either amiloride or placebo before saline inhalation. One hour mucus clearance rates, lung function tests, and quality of life scores were used as outcome measures.

One hour mucus clearance rates were significantly increased compared with baseline levels in both groups. However, only the placebo pretreatment group showed a measurable increase over a sustained period of >8 hours (1 hour mucus clearance rate 14.0 (2.0)% in the placebo pretreatment group compared with 7.0 (1.5)% in the amiloride pretreatment group, p = 0.02). Lung function tests showed an improvement in forced vital capacity (FVC) between baseline and treatment in the placebo group (p = 0.05) but not in the amiloride pretreatment group (p = 0.83). Similar results were found for forced expiratory volume in 1 second (FEV₁), forced expiratory flow at 25–75% of FVC (FEF_25–75), and quality of life scores. In vitro experiments showed sustained hydration of airway surface liquid with hypertonic saline, a response inhibited by amiloride.

This study shows that inhalation of hypertonic saline produces a modest but sustainable increase in mucus clearance rates, lung function tests, and quality of life in patients with cystic fibrosis. This beneficial effect was negated by pretreatment with amiloride. Hydration of airway surface liquid may be an important underlying mechanism.