Sensory-Mechanical Responses to Eucapneic Voluntary Hyperventilation and Mannitol

This study is looking at how the airways respond to two different breathing challenges — one involving fast breathing (hyperventilation) and one involving inhaling a powder called mannitol — in people with a condition called cough variant asthma (CVA) and in healthy people. The goal is to better understand what triggers coughing and airway sensitivity. **You may be eligible if...** - You are between 18 and 65 years old - You have been diagnosed with cough variant asthma (CVA): you have had a chronic cough for 8+ weeks as your main symptom, your airways showed sensitivity to a methacholine test, and your cough improved with asthma medications - OR you have a chronic cough for 8+ weeks but a normal methacholine test result - OR you are a healthy person with no history of asthma or chronic cough **You may NOT be eligible if...** - Your condition worsened in the last 4 weeks, requiring a change in medication, an ER visit, or hospitalization - You are unable to perform acceptable breathing (spirometry) tests - You have a medical reason why you cannot do a methacholine challenge test - You have smoked heavily (more than 10 pack-years) Talk to your doctor to see if this trial is right for you.