Clinical studies are underway which are examining the utility of the LCI in obstructive respiratory disease (cystic fibrosis and asthma). However, the majority of studies have examined asthmatics with ongoing evidence of reversible disease on spirometry. There is a very limited body of research comparing LCI values in well-controlled asthmatics to healthy controls. Furthermore, the type of inflammation occurring in asthma may have a different site of action, we will prospectively study whether there is a difference in LCI between eosinophilic and neutrophilic inflammation to give us an indication of whether the site of non-eosinophilic inflammation is primarily in the small airways as well.