The chronicity of acute attacks of asthma--mechanical and therapeutic implications.

Defects in ventilatory function can persist for considerable periods of time following the amelicoration of the signs and symptoms of acute episodes of asthma. Serial spirographic and lung volume determinations in such patients demonstrate that the pattern of resolution of these abnormalities is such that their subtlest manifestations are depressed flow rates in the mid vital capacity range and/or elevations in residual volumes. These changes are believed to represent the effects of residual obstruction that is located in the airways in the periphery of the lung. Recent studies suggest that this residua is capable of influencing the lung's response to asthmogenic stimulis, and imply that it may be beneficial to place asthmatics on continuous therapy for as long as they have alterations in lung function.