Dyspnea and Bronchospasm from Inappropriate Postexercise Hyperventilation

A group of 10 patients who complained of exertional dyspnea largely after exercise and who had normal physical examination and chest roentgenograms is described. Chronic obstructive lung disease, pulmonary vascular disease, and interstitial pneumonitis were excluded because mechanics of breathing and respiratory gas exchange were normal. Comparison with normal volunteers and with patients with diffuse lung disease showed that their symptoms were the result of inappropriate postexercise hyperventilation. Three minutes after completion of the exercise their PCO2 averaged 23 mm Hg compared with 37 mm Hg for normals and 31 mm Hg for patients with diffuse lung disease. The decreased PCO2 in the airways produced bronchospasm that could be reversed by adding carbon dioxide to the inspired gas. Dyspnea appeared to result from increased work of breathing, in part from hyperventilation and in part from increased resistance to air flow. In some, the postexercise hyperventilation could be related to anxiety over previous chest disease that had been slight and from which they had recovered. Therapy consisting of reassurance and physical training was effective. It is suggested that exerciseinduced asthma is part of the hyperventilation syndrome.