While inhaling the vocal cords
should open to let air into the lungs. With VCD the vocal cords
close together during inhalation. This makes it difficult for air to get into the lungs. A lot of the same things that trigger asthma can trigger VCD including upper respiratory infections, fumes, odors, cigarette smoke, singing, emotional upset, post-nasal drip and exercise. Sometimes the trigger is not known. Testing needs to be done while your son is having symptoms.