Functional mainstem bronchial obstruction

Maximal expiratory and inspiratory flow-volume loops before (inner dashed-line loop) and after (outer solid-line loop) surgery in a patient with mainstem bronchial obstruction. The diameter of the orifice at the site of maximal obstruction both before and after treatment is shown in relation to the corresponding flow-volume loop. Note the relatively parallel rightward shift of the descending limb of the maximal expiratory flow-volume curve after treatment.