Grant: Master's Award: Canada Graduate Scholarships

Cough is a common, disruptive and at times disabling symptom which often prompts patients to seek medical attention. Determining the cause(s) of chronic cough can be challenging, and costly. Asthma and other airway disorders are among the most common causes of chronic cough. In addition, cough can be the only symptom of asthma. Little is known about why some patients with asthma primarily cough and do not develop the other symptoms of asthma such as shortness of breath or wheeze. Improved understanding of the reasons for these different manifestations may lead to new and more effective treatment strategies. The purpose of this research is to better understand the mechanisms of cough in asthma and cough variant asthma, and to try to identify a fundamental difference in the mechanism between these two related conditions. This will be done by controlled testing in the laboratory of individuals with asthma and cough variant asthma. Study subjects will undergo two inhalation challenge tests on separate days (using mannitol and methacholine). These agents cause the airways to temporarily constrict (narrow) and simulate an asthma attack. We will record the type and severity of symptoms (shortness of breath and cough) and record pressures in their chest (using a special balloon catheter) and their lung function. In this way, we will be able to determine if their symptoms, particularly cough, relate to specific changes in lung function (such as air trapping). This will be the first study to research the relationship between lung mechanics and pressure recordings and cough in asthma and cough variant asthma. We have noted that some individuals without regular asthma but with chronic cough trap air in their lungs similar to regular asthma, and this may be the stimulus for cough. Whether or not a deep breath can reverse the bronchoconstriction and relieve air trapping may be the main difference between asthma and cough variant asthma, which has not been reported previously.