Rest and peak exercise flow volume (FV) responses in a healthy, average fit adult plotted within a maximal FV curve

Comparison of maximal and tidal flow-volume loops in a healthy subject and a patient with COPD, at rest and at a standardized exercise level (oxygen consumption 30% predicted max). Volume compartments of the VC are also depicted at rest and at a standardized exercise level. In normal subjects, minimal expiratory flow limitation is evident during exercise, there is no ventilatory limitation, and IC increases during exercise. By contrast, expiratory flow limitation is evident at rest in COPD, end-expiratory lung volume increases with exercise due to dynamic lung hyperinflation as evidenced by the reduced IC.