Will is an 18-year-old track athlete in seemingly good health. Despite suffering from a slight cold, Will went jogging one morning with his running buddy, Al. After a few minutes of exercise, Will could hardly get enough air. Even though he stopped jogging, he continued to breathe rapidly and wheeze forcefully. Because his condition was not improving, Al took him to the emergency room of a nearby hospital. Using a stethoscope, the emergency room doctor discovered that air movement in Will’s lungs was poor. In addition, an arterial blood gas measurement revealed that Will had a PO2 of 60 mm Hg and a PCO2 of 30 mm Hg. Although Will had no previous history of asthma, the emergency room doctor was convinced he was having an asthma attack.

Asthma is a clinical condition characterized by airway inflammation that episodically results in shortness of breath, coughing, and wheezing due to bronchoconstriction. Bronchoconstriction decreases compliance, which makes expansion of the l