Sensory-Mechanical Responses to Eucapneic Voluntary Hyperventilation and Mannitol

Inclusion Criteria: * Individuals aged 18-65 years of age with CVA and individuals with methacholine-induced cough but normal airway sensitivity. The following definitions will be used: 1. CVA: chronic cough (≥8 weeks) is the sole or predominant symptom and positive methacholine challenge (PC20 ≤ 16 mg/mL) and history of cough responding to specific asthma treatment (such as inhaled steroid or 1 week trial of bronchodilator); 2. Methacholine-induced cough but normal airway sensitivity: chronic cough (≥8 weeks) is the sole or predominant symptom and negative methacholine challenges (PC20 \> 16 mg/mL). * Individuals aged 18-65 years of age with no history of asthma or chronic cough. Exclusion Criteria: * an exacerbation necessitating a change in medication, emergency department visit or hospitalizations within the previous 4 weeks * inability to perform acceptable spirometry * medical contraindications to methacholine challenge testing * smoking history in excess of 10 pack years Note: Previous treatment with inhaled or systemic corticosteroids is not an exclusion criterion; medication use will be recorded and examined in the analysis.