The expiratory flow pattern is abnormal, exhibiting a ‘shoulder’ in the flow-volume curve due to a fixed obstruction in larger intrathoracic airways. The inspiratory pattern is normal, so that extrathoracic airway obstruction is unlikely. This patient received radiation therapy for a central tumor of the bronchus. Also shown is the flow-volume curve during normal tidal breathing, and the MEFV-curve (interrupted line) for a healthy person of the same age, standing height and gender.
Poor co-operation does not lead to reproducible curves. In general, therefore, if the patient appears to produce satisfactory efforts leading to a reproducible flow-volume curve with an abnormal pattern, take this seriously. Check carefully whether there is an inspiratory or expiratory stridor.
See also: Flow-volume curves during quiet tidal breathing