Study objectives: To determine the utility of forced
oscillation technique (FOT) for measuring pulmonary resistance and
reactance in patients with central nervous system injuries, for
detection and follow-up of posttracheostomy tracheal stenosis.
Design: Case series.
rehabilitation hospital, Brasilia, Distrito Federal, Brazil.
Patients: Ten consecutive neurologically impaired patients,
who had previously undergone tracheostomies, with tracheostenosis
without current tracheostomy or other tracheal lesion.
Interventions and measurements: FOT evaluations were
compared to tracheal diameter before and after bronchoscopic
tracheostenosis dilatation procedures. Forced spirometry examinations
were also obtained and compared.
stenotic lesions were characterized by marked increase in resistance
and reduction in reactance at low frequency and a marked increase in
resonance frequency (Rf). Consistent reversal of this
pattern with large reductions in total impedance of the respiratory
system (Zresp) Rf and resistance at 5 Hz (R 5 Hz) were
noted in all patients after each successful dilatation. Diameter of the
stenosis was strongly correlated with Rf, Zresp, and R 5
Hz. The change in diameter before and after dilatation was similarly
correlated with the changes in FOT values of Rf and
Zresp. Spirometry values did not correlate well with the diameter of
the tracheal stenosis.
Conclusion: The strong
correlation of Rf, Zresp, and R 5 Hz to diameter of
tracheostenosis suggests a previously unappreciated role for FOT in the
noninvasive detection and follow-up of airway stenosis. This may be
especially useful for patients with concomitant neurologic disabilities
who are at risk of airway stenosis.