Exertional dyspnea and cough as preludes to acute attacks of bronchial asthma.

Although wheezing is believed to be a cardinal manifestation of asthma, some patients with this disorder may not present with wheezing, but rather with either exertional dyspnea or cough. In 14 such patients with dyspnea, there was peripheral airway dysfunction with markedly elevated residual volumes, frequency dependence of dynamic compliance and depressed flow rates in the middle-vital-capacity range, whereas specific conductance and one-second forced expiratory volumes were normal. Circumstantial evidence suggests that mucosal edema or mucous secretions may have been responsible. In seven patients with cough, studies revealed a more severe obstructive pattern that appeared to be the result of increased large-airway resistance, and the patients' response to isoproterenol indicated that contraction of bronchial smooth muscle may have been principally responsible. Thus, intermittent episodes of cough or breathlessness may represent variant aspects of asthmatic attacks.