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

Abstract

Study design: A case report. Objectives: To demonstrate forced oscillation technique's (FOT) utility in a tetraplegic patient with tracheostenosis. Setting: A Rehabilitation Hospital, BrasõÂ lia, 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 ®xed 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 con®rmed 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¯ow-volume data problematic. Spinal Cord (2000) 38, 445 ± 447

Forced Oscillation Technique to Evaluate Tracheostenosis in Patients With Neurologic Injury

“…This capability was demonstrated in our index case reported earlier. 6 The relationship of respiratory resistance to tracheal stenotic diameter is most marked at low frequencies. As frequency rises, the measured resistance falls.…”

“…Our present study of the usefulness of forced oscillation technique (FOT) in tracheostenosis was suggested by our experience with a previously reported patient. 6 Other authors have suggested another technique performed at quiet breathing during bronchoscopy for preoperative assessment of tracheal stenotic lesions. 7 Our objective was to assess FOT as a potential screening and follow-up method, with a view to reducing the dangers of stenotic tracheal lesions at the time of diagnosis, while reducing the need for costly invasive and radiologic exams.…”

Forced oscillation technique and impulse oscillometry

“…Changes in central airway calibre correlate more strongly with resistive parameters and are less well represented in the inertive spectral range. Finally, it should be noted that oscillometric reactance occasionally demonstrates a low-to-mid frequency plateau in the Xrs (f) tracing, which is suggestive of possible upper airway obstruction [47][48][49][50].…”

Vocal Cord Dysfunction as Demonstrated by Impulse Oscillometry

“…IOS has been applied in a number of clinical situations including detection of fixed airway obstruction, upper airway resistance in obstructive sleep apnea, tracheal stenosis, and significant inhalational exposures. 17–19 …”