PURPOSE: It has been suggested that the predominant sign ( cough vs wheezing ) during attacks may represent heterogeneity in the underlying pathophysiology of asthma. To better understand the significance of this observation, we performed methacholine challenges in known asthmatics to study the occurrence, timing and frequency of coughing and/or wheezing.
METHODS: We performed methacholine challenges on 10 subjects with asthma. In selected patients, repeat challenges were performed after bronchodilator use. Cough and wheezing were monitored with the Wholter ( Karmelsonix™ ) during the entire duration of the methacholine challenges.
RESULTS: 11 subjects underwent baseline methacholine challenges. 5 of these subjects underwent additional postbronchodilator challenges ( total of 8 ) on a separate day. 10 subjects had positive while 1 had a negative baseline challenge. All postbronchodilator were positive. In total, 18 positive challenges and 1 negative challenge were analyzed. Of the 18 positive challenges, 5 were associated with cough and wheezing, 9 were associated with cough alone and no wheezing, 4 were associated with no cough or wheeze. The subject with negative challenge had no cough or wheeze. There was no difference in the pattern of cough and/or wheeze during the baseline challenge and the postbronchodilator challenges in the same patients. We observed that there was an increase in cough close to the challenge endpoint in several subjects.
CONCLUSIONS: The majority of subjects had coughing during the methacholine challenges. Wheezing was observed less frequently. Cough had a significant correlation with a positive methacholine challenge ( 14 out of 18) while wheezing did not. Many factors could have affected the occurrence of cough and wheezing including the spirometry effort itself.
CLINICAL IMPLICATIONS: The predominant sign observed during bronchial constriction ( cough vs wheezing) may reflect the underlying pathophysiology of patients with asthma. We suggest that cough may signify hyper-irritability while wheezing reflects hyper-reactivity. This supports the view of asthma as a heterogeneous disease.
DISCLOSURE: The following authors have nothing to disclose: Sheldon Spector, Ricardo Tan, Randy Lee
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