Reference Ranges for the Cough Responsiveness to Inhaled Mannitol

Inclusion Criteria: * age 18 years or older * capable to understand the purpose of the study * female/male ratio approximately 50%/50% in both of the following age groups: * 50% aged 18- 50 yrs, and 50 % aged 51 - 90 years Exclusion Criteria: * Current daily smoking * Ex-smoking with a greater than 10 pack years' daily smoking history or with stopping of daily smoking less than one year ago * Pregnancy and breastfeeding * A doctor's diagnosis of any respiratory diseases, including both upper and lower airway diseases, lung parenchymal diseases and the sleep apnoea syndrome * A doctor's diagnosis of gastro-oesophageal reflux disease or symptoms suggestive of it * Current use of angiotensin-converting enzyme inhibitors * Upper respiratory tract infection ('flu') within 4 weeks * Any current (within 4 weeks) cough 8 * Chronic (over 2 months' duration) cough during the last 12 months * Wheezing during the last 12 months * Attacks of shortness of breath or cough at night during the last 12 months * Symptoms of rhinitis in a prolonged fashion during the last 12 months * Heartburn or regurgitation once a week or more often during the last 3 months * Abnormal anatomy of the respiratory organs, which may affect the deposition of the mannitol powder * Any previous operations to the respiratory organs that can affect the deposition of the mannitol powder * Unable to provide written informed consent to participate in the study