The acute effects of bronchial thermoplasty on FEV₁

The most common adverse effect of bronchial thermoplasty (BT) is short-term aggravation of asthma immediately following the procedure. However, the magnitude and duration of this deterioration, and its predisposing factors are yet to be quantitated. This information will be particularly important as BT is extended to include more severely obstructed patients.

In this prospective, observational study of 20 consecutive patients with very severe asthma undergoing BT, post bronchodilator FEV₁ was measured in the 30 min prior to surgery, and then 24 h following the 60 procedures. In half the patients, further spirometry was conducted on day 3 and day 7 post procedure.

This study enrolled 12 males and 8 females, mean age 59.7 ± 12.8 years, with mean prebronchodilator FEV₁ of 52.3 ± 15.2% predicted, mean forced expiratory ratio of 51.4 ± 12.6%, and mean improvement in FEV₁ post salbutamol of 19.5 ± 15.3%. All patients were taking inhaled corticosteroids, mean beclomethasone equivalent dose 1950 ± 857 mcg, and 7 patients required maintenance oral corticosteroids for control of their asthma. Twenty four hours after BT, the mean deterioration in post bronchodilator FEV₁ was 166 ± 237 mls (CI 102-224, p < 0.001) or 9.1 ± 15.2% of baseline. This deterioration was significantly greater after upper lobe procedures (p < 0.01, ANOVA repeated measures), where a mean fall in FEV₁ of 17.1 ± 12.6% was observed. The change in FEV₁ post procedure was significantly correlated with the number of radiofrequency activations applied, r = -0.376, p < 0.005. By multivariate analysis, the only factor other than activations predictive of the change in FEV₁ was age, which was protective. When the lower lobes were treated, the postbronchodilator FEV₁ had returned to baseline values by day 3, but patients took 7 days to recover after upper lobe treatments. Despite the severity of asthma in these patients, and the measured deterioration post treatment, there was only one instance of readmission in the 60 procedures.

The deterioration in lung function after BT is transient and well tolerated, but is greatest after upper lobe treatment, and is significantly related to the number of radiofrequency activations applied.