Functional location of airway inflammation in eosinophilic asthma

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Asthma is a prevalent, complex and highly heterogeneous chronic airways disease, whose treatment is guided by its classification according to levels of type 2 inflammation, namely into 'TH-2 high' and 'TH-2 low' subtypes (commonly called endotypes), with TH-2 high asthma being responsive to treatment with inhaled corticosteroids, while TH-2 low asthma is not. Despite the success of endotyping, there remains the important issue that while TH-2 high asthma is generally responsive to treatment with inhaled corticosteroids, a substantial subgroup of patients with this endotype have persistent symptoms and uncontrolled asthma despite such treatment. There may be several reasons for this failure to respond, one of which is if the location of the inflammation within the airway tree renders it inaccessible to inhaled therapy, i.e. is the inflammation in the proximal or distal airways. This proposal seeks to address this outstanding question in the treatment of TH-2 high asthma by developing a world-leading instrument capable of functionally locating airways inflammation. The instrument will combine highly time-resolved measurements of the fraction of exhaled nitric oxide, FeNO, with highly precise measurements of respiratory gas exchange to assess functional inhomogeneity in the lung, and thereby help ascertain which TH-2 patients, which constitute more than 50% of all asthmatics, are most likely to be unresponsive to inhaled steroid therapy. A key feature of asthma is the variability of symptoms over time - between attacks patients may display apparently normal lung function and, when attacks occur, a number of treatments may be used to reverse airway inflammation. Measurement of FeNO is already a reliable NICE approved method of detecting the presence of eosinophilic airway inflammation, however current methods provide a single FeNO value from sustained expiration at constant flow. This is an important limitation as it is not possible to determine the site of NO production and hence the location of the inflammation within the airways. Furthermore, even if a time-resolved FeNO measurement were obtained, there is no recognition of the fact that the asthmatic lung is highly inhomogeneous and therefore any such time-resolved FeNO can only be interpreted in terms of the person-specific lung inhomogeneity. This research will provide a sea-change in the location and quantification of inflammation by linking for the first time, quantitative and individualised measures of lung inhomogeneity and structure with time-resolved measurements of FeNO.