Bronchial Thermoplasty (BT) improves symptom control and reduces exacerbations in patients with refractory asthma. The precise mechanism remains unclear, but consistent improvement in spirometry has not been recorded. We postulate that assessment of lung function during tidal breathing with oscillometry to measure respiratory impedance may better reflect the clinical improvements reported.
Patients with refractory asthma (GINA Step 5) had the Asthma Control Questionnaire (ACQS), spirometry, resistance at 5 Hz (R5) and reactance at 5 Hz (X5) recorded before and 6 weeks after completing BT. One centre measured impedance with the forced oscillation technique (FOT) (TremoFlo C-100, Thorasys Medical Systems, Canada) and the other with impulse oscillometry (105) (Sensormedics).
The average age was 60.8 (1.4) years in the FOT group and 61.2 (11.4 years in the lOS group. ACQS scores improved in both groups. In the FOT group, there were significant improvements in spirometry and X5; and the change in X5 correlated