Inhaled isotonic alkaline versus saline solution and radioaerosol clearance in chronic cough

The aim of the present study was to test the influence of inhaled isotonic Ems salt (brine from the spa of Bad Ems, Germany) compared to isotonic saline on radioaerosol clearance (RC) in patients with chronic cough. Ems salt is an alkaline solution (pH 8.0-9.0) containing largely bicarbonate ions rather than the chloride ions present in isotonic saline (pH 6.4). RC was assessed with a radioaerosol technique using technetium-99m albumin in supine patients. After a 30-min baseline measurement of RC according to a single blind and randomized design, patients inhaled Ems salt (n=22, 20-77 yrs) or isotonic saline (n=21, 34-72 yrs) via a jet nebulizer (Pari Boy) for 10 min and were scanned for an additional 30 min. There was no difference between the two groups before intervention in terms of deposition pattern, lung function and baseline RC rate. After inhalation of Ems salt, the RC rate (1/tau) improved significantly from 0.15+/-0.14 (mean+/-SD) to 0.53+/-0.70 L.h(-1) (p<0.005); no change was found after isotonic saline (0.13+/-0.13 to 0.08+/-0.09 L.h(-1), NS). Voluntary coughs performed after 60 min had no effect on the RC rate. However, in the Ems salt group, significantly more patients reported an inhalation induced cough. Compared to the Ems salt patients, who did not cough during and after inhalation, the RC rate in the cough group was enhanced significantly (0.10+/-0.12 versus 0.73+/-0.83, p=0.017), this effect being seen more frequently in females (p=0.003). It is concluded that Ems salt improves radioaerosol clearance significantly in patients with chronic cough. The underlying mechanism, regarding whether induced cough, increased water content in the mucus or enhanced ciliary beat frequency is the leading cause of Ems salt action, remains unclear.