Asthma inhale use. Animation showing a bronchodilator drug (green), dispensed by an asthma inhaler, being delivered to the lungs. Asthma is a condition in which the small airways (bronchioles) in the lungs constrict, making it difficult to breathe. Bronchodilator drugs widen the airways allowing oxygen to reach the alveoli (purple) the site of gaseous exchange.HD master is flattened onto a black background, as seen in this preview. The original file has a transparent alpha channel and is available as the HD master of clip K003 3792.