Severe upper airway obstruction caused by bullous pemphigoid: diagnostic usefulness of the flow-volume curve

The site and severity of upper airway obstruction accurately determined by analysis of the flow-volume curve obtained from a dyspneic patient with bullous pemphigoid. The limitation of maximum inspiratory flow to 0.5 L/s and of maximum expiratory flow to 0.7 L/s over most of the vital capacity suggested that the lumen of the extrathoracic trachea was narrowed to a diameter of 3 mm. The marked improvement in flow with the patient breathing a helium-oxygen mixture further confirmed that flow was limited in a large central airway. The predictions made from analysis of the flow-volume curve were confirmed by fiberoptic bronchoscopic examination and by computerized axial tomography, which revealed severe supraglottic obstruction. After a tracheostomy was performed, maximal inspiratory and expiratory flows were normal.