Physiology of Cough in Asthma: Comparison of Sensory-Mechanical Responses to Mannitol and Methacholine Challenge Tests
Physiology of Cough in Asthma: Comparison of Sensory-Mechanical Responses to Mannitol and Methacholine Challenge Tests
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;
 and cough can be the sole 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. We have notices differences in
 pressure measurements inside the chest in patients who mostly cough during induced
 bronchoconstriction, which might be part of the explanation for varying symptoms. This study
 will compare lung mechanical responses during methacholine and mannitol-induced induced
 airway narrowing between typical asthma, cough variant asthma (CVA) and an airway
 inflammatory disorder that is not asthma.The purpose of this research is to explore the
 pathophysiology and sensory-mechanics of cough in individuals with asthma, CVA and
 methacholine-induced cough but normal airway sensitivity using mannitol and high-dose
 methacholine bronchoprovocation testing.
Inclusion Criteria:

 1. Subjects with asthma or suspected CVA who have previously participated in or who have
 expressed interest in participating in studies will be invited to participate in the
 study. Previous treatment with inhaled or systemic corticosteroids is not an exclusion
 criterion, but medication use will be recorded and examined in the analysis.

 Exclusion Criteria:

 1. An exacerbation necessitating any alteration in medication, emergency department visit
 or hospitalizations within the previous 4 weeks;

 2. Inability to perform acceptable quality spirometry;

 3. Medical contraindications to methacholine challenge testing 35, including:

 1. Severe airflow limitation (FEV1 <50% predicted or <1.0 L);

 2. Heart attack or stroke in last 3 months;

 3. Uncontrolled hypertension, systolic BP > 200 or diastolic BP > 100;

 4. Known aortic aneurysm;

 5. Moderate airflow limitation < 60% predicted or <1.5 L);

 6. Inability to perform acceptable quality spirometry;

 7. Current use of cholinesterase inhibitor medication (for myasthenia gravis); and

 8. Pregnant or nursing mothers.

 4. Smoking history in excess of 10 pack years;

 5. Medical contraindications to mannitol challenge testing, including:

 1. Aortic or cerebral aneurysm;

 2. Uncontrolled hypertension; and

 3. Myocardial infarction or a cerebral vascular accident in the previous six
 months).

 6. Women who are pregnant or breastfeeding because the effects of a possible
 hyperresponsiveness reaction to mannitol in mothers and/or fetuses are unknown and
 many compounds are excreted in human milk therefore caution should be taken.