Background: Decannulation failure is usually due to tracheal obstruction. Prior to decannulation, inspection by the invasive procedure of bronchoscopy that permits morphological evaluation of a tracheal stenosis is standard practice. A non-invasive method enabling the quantification of the airway obstruction that requires little cooperation is measurement of the airway resistance by the forced oscillation technique. Objectives: The aim of the present study was to define oscillatory impedance thresholds which predict successful decannulation. Methods: A total of 131 patients were investigated prospectively. Step 1: Following probatory decannulation, measurement of the oscillatory impedance. Step 2: Blinded to the results of the impedance measurement, bronchoscopy-assisted decannulation attempt. The criteria for renewed cannulation were high-grade laryngeal or tracheal obstruction, dyspnea or stridor, or a drop in SaO2 <90% under O2 insufflation. Statistics: Determination of the ratio tracheal tube remains/tracheal tube removed (TT+/TT–) for every measured value of the oscillatory resistance at 5 Hz (Ros 5 Hz). Determination of specificity and positive predictive value for determined threshold values with respect to TT–. Results: The data of 126 patients were evaluated. TT+ n = 26, TT– n = 100. Decannulation on the basis of bronchoscopy criteria: Specificity and positive predictive value found out for Ros 5 Hz <0.35 kPa/l/s (n = 44) were 1.00 and 1.00, respectively, and for Ros 5 Hz <0.47 kPa/l/s (n = 71) 0.88 and 0.96, respectively. Conclusions: Measurement of the oscillatory airway resistance represents a practicable method prior to decannulation. Below a value of Ros 5 Hz <0.35 kPa/l/s, bronchoscopy would appear not to be necessary.

Keywords:
Long-term mechanical ventilation, Oscillatory impedance, Tracheal obstruction, Tracheostomy decannulation, Weaning failure
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2010
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