An unusual example of exercise-induced asthma.

A patient with exercise-induced asthma is described in whom the post-exercise fall in F.E.V.1 was not prevented by the inhalation of isoprenaline immediately before exercise but was almost completely prevented by subcutaneous atropine given 40 minutes before exercise. A large fall in F.E.V.1 similar to the fall after exercise occurred after carbon dioxide-induced hyperventilation and voluntary hyperventilation performed at rest. Only a slight fall in F.E.V.1 occurred when atropine was given before voluntary hyperventilation was performed. It is postulated that the post-exercise fall in F.E.V.1 in this patient is due to hyperventilation reflexly causing bronchial constriction.