Measuring in situ central airway resistance in patients with laryngotracheal stenosis

Objectives: To evaluate a newly developed bronchoscopic technique for the assessment of intratracheal pressures. Study Design: In situ measurement of central airway resistance in 20 consecutive spontaneously breathing subjects. Thirteen patients had benign glottic or subglottic stenosis. Seven patients without central airway disease served as normal control subjects. Methods: A pressure catheter was introduced into the trachea via the working channel. The pressure swing was measured upstream and downstream of the stenosis. Central airflow was monitored simultaneously using a commercial pneumotachograph attached to a mouthpiece. Data acquisition frequency was 500 Hz. Prestenotic and poststenotic inspiratory and expiratory resistances could be calculated and displayed from the raw data off-line. Results: Inspiratory and expiratory resistances measured in mid-trachea or below the stenosis (subglottic) were 0.36 ± 0.13 and 0.35 ± 0.13 kPa·s/L for the control subjects (C), 1.11 ± 0.47 and 0.65 ± 0.26 kPa·s/L for patients who did not need to be operated on (NOOP), 7.11 ± 7.19 and 3.35 ± 2.25 kPa·s/L respectively for those who required surgical correction (OP). Supraglottic inspiratory and expiratory resistances for C were 0.22 ± 0.09 and 0.25 ± 0.06 kPa·s/L, for NOOP 0.15 ± 0.10 and 0.14 ± 0.11 kPa·s/L, and for OP 0.26 ± 0.13 and 0.24 ± 0.07 kPa·s/L respectively. The cut-off point for surgical correction was estimated to be >2.5 kPa·s/L of inspiratory resistance. Concurrent expiratory values showed a considerable overlap between OP and NOOP. No correlation could be established between local resistance values and dyspnea score. Conclusions: In situ subglottic flow-pressure tracing in spontaneously breathing patients who present with benign obstruction of the upper airways is well tolerated and may help to identify patients who need surgical correction.