Gas Trapping Improved With Bronchial Thermoplasty in Severe Asthma

The use of bronchial thermoplasty (BT) reduced gas trapping in individuals with asthma, with the greatest  effect occurring in patients who were the most severely obstructed, according to the results of a prospective cohort study published in BMC Pulmonary Medicine.

Investigators sought to assess changes in measures of gas trapping by body plethysmography. They evaluated a cohort of 32 consecutive patients at 2 Australian university hospitals with severe asthma who were scheduled for BT at 3 different time points: baseline, 6 weeks after completion of all procedures, and 6 months following completion of all procedures. At each assessment, symptom scores (Asthma Control Questionnaire [ACQ-5]), medication use, and exacerbation history were obtained. In addition, lung function was assessed by spirometry, gas diffusion (ie, gas transfer per lung unit [KCO]), and static lung volumes by body plethysmography.

Significant improvements in ACQ-5 were reported, from a mean of 3.0±0.8 at baseline to 1.5±0.9 at 6 months (P <.001). Moreover, significant improvements in daily salbutamol use were noted, from 8.3±5.6 puffs per day to 3.5±4.3 puffs per day (P <.001). Exacerbations that necessitated the use of oral corticosteroids also decreased significantly, from 2.5±2.0 in the 6 months prior to BT to 0.6±1.3 in the 6 months following BT (P <.001).

Regarding improvements in lung function, the mean forced expiratory volume in 1 second (FEV₁) was 57.8%±18.9% predicted, but no changes in any spirometric parameter were reported following BT.

Furthermore, KCO was unaltered with the use of BT. There was a significant reduction in gas trapping observed, with residual volume (RV) decreasing from 146%±37% predicted at baseline to 136%±29% predicted 6 months after BT (P <.005). Significant reductions in total lung capacity and functional residual capacity were also reported (P =.008 and P =.005, respectively). It should be noted that the change in RV was inversely correlated with baseline FEV₁ (P =.001).

The investigators concluded that the improvements in gas trapping with the use of BT in patients with severe asthma may be related to changes in the mechanical properties of small peripheral airways that are not measured with spirometry.

Reference

Langton D, Ing A, Bennetts K, et al. Bronchial thermoplasty reduces gas trapping in severe asthma. BMC Pulm Med. 2018;18(1):155.