The present study has the following objectives:
to evaluate the relationship between BHR and mid-expiratory flow, to assess the diagnostic accuracy of fractional exhaled nitric oxide，impulse oscillometry and mid-expiratory flow in CVA with special regard to its discriminating value between CVA and other causes of a chronic cough, to estimate prognostic value of BHR and fractional exhaled nitric oxide (FeNO) count in predicting response to asthma treatment.
