High intrathoracic airway obstruction
This patient received radiotherapy because of a central bronchial carcinoma. The forced expiratory pattern is definitely abnormal, exhibiting a ‘shoulder’ in the flow-volume curve due to variable obstruction in large intrathoracic airways. The by and large normal inspiratory pattern rules out fixed airway obstruction. Also shown are the flow-volume curve during resting ventilation, and (interrupted line) the curve predicted for age, gender and standing height.
Poor cooperation does not lead to reproducible flow-volume curves. Therefore, if it appears that a patient is co-operating well, take a reproducibly abnormal pattern of the flow-volume curve seriously, and check carefully for the presence of an inspiratory or expiratory stridor.
See also: Tidal flow-volume loop