Upper airway dysfunction detected by respiratory flow oscillations.

In 3 patients with chronic respiratory symptoms, we identified rapid flow oscillations on flow-time and flow-volume recordings, corresponding to fluttering of lax but otherwise normal-appearing upper airway structures at cinefluoroscopy and fiberoptic endoscopy. This entity of upper airway dysfunction was responsible for, or at least contributed to, the respiratory symptoms as evidenced by dramatic relief of dyspnea following tracheostomy in one patient, and significant improvement of flow rates following helium breathing in the other 2 patients. We suggest that identification of flow oscillations on flow recordings, in particular flow-volume loops, should lead to investigation of the upper airway. When fluttering is the only abnormality observed, it should not be disregarded, but rather considered as possibly contributing to airflow limitation.