Forced oscillation technique to detect and monitor tracheal stenosis in a tetraplegic patient

Study design: A case report. Objectives: To demonstrate forced oscillation technique's (FOT) utility in a tetraplegic patient with tracheostenosis. Setting: A Rehabilitation Hospital, Brasilia, Brazil. Methods: Serial evaluations of spirometry, bronchoscopy and forced oscillation assessment. Results: A 16-year-old male with C7 spinal cord injury, initially required mechanical ventilation and subsequent tracheostomy over a period of 4 weeks. Five months after the accident the onset of tracheostenosis was diagnosed. Flow-volume data were compatible with a fixed tracheal stenosis. FOT showed an obstructed pattern, manifested by high levels of resonance frequency and impedance. The FOT pattern returned to normal after dilatation. The FOT abnormalities recurred with two subsequent broncoscopicaly confirmed episodes of tracheal restenosis without parallel changes in spirometric parameters. Conclusion: This case suggests a role for FOT in the non invasive detection and follow up of tracheal stenosis. FOT may be particularly useful in tetraplegic patients, in whom the restriction from muscle weakness may make interpretation of forced expiratory flow-volume data problematic.