Measuring the effects of bronchial thermoplasty using oscillometry

Bronchial Thermoplasty Improves Ventilation Heterogeneity Measured by Functional Respiratory Imaging in Severe Asthma

Purpose

Bronchial thermoplasty (BT) is a bronchoscopic intervention for the treatment of severe asthma. Despite demonstrated symptomatic benefit, the underlying mechanisms by which this is achieved remain uncertain. We hypothesize that the effects of BT are driven by improvements in ventilation heterogeneity as assessed using functional respiratory imaging (FRI).

Patient and Methods

Eighteen consecutive patients with severe asthma who underwent clinically indicated BT were recruited. Patients were assessed at baseline, 4-week after treatment of the left lung, and 12-month after treatment of the right lung. Data collected included short-acting beta-agonist (SABA) and oral prednisolone (OCS) use, asthma control questionnaire (ACQ-5) and exacerbation history. Patients also underwent lung function tests and chest computed tomography. Ventilation parameters including interquartile distance (IQD; measure of ventilation heterogeneity) were derived using FRI.

Results

12 months after BT, significant improvements were seen in SABA and OCS use, ACQ-5, and number of OCS-requiring exacerbations. Apart from pre-bronchodilator FEV1, no other significant changes were observed in lung function. Ventilation heterogeneity significantly improved after treatment of the left lung (0.18 ± 0.04 vs 0.20 ± 0.04, p=0.045), with treatment effect persisting up to 12 months later (0.18 ± 0.05 vs 0.20 ± 0.04, p=0.028). Ventilation heterogeneity also improved after treatment of the right lung, although this did not reach statistical significance (0.18 ± 0.05 vs 0.19 ± 0.04, p=0.06).

Conclusion

Clinical benefits after BT are accompanied by improvements in ventilation heterogeneity, advancing our understanding of its mechanism of action. Beyond BT, FRI has the potential to be expanded into other clinical applications.

Bronchial thermoplasty attenuates bronchodilator responsiveness

INTRODUCTION

Bronchial thermoplasty is an effective intervention to improve respiratory symptoms and to reduce the rate of exacerbations in uncontrolled severe asthma. A reduction in airway smooth muscle is arguably the most widely discussed mechanisms accounting for these clinical benefits. Yet, this smooth muscle reduction should also translate into an impaired response to bronchodilator drugs. This study was designed to address this question.

METHODS

Eight patients with clinical indication for thermoplasty were studied. They were uncontrolled severe asthmatics despite optimal environmental control, treatment of comorbidities, and the use of high-dose inhaled corticosteroids and long-acting β2-agonists. Lung function measured by spirometry and respiratory mechanics measured by oscillometry were examined pre- and post-bronchodilator (salbutamol, 400 μg), both before and at least 1 year after thermoplasty.

RESULTS

Consistent with previous studies, thermoplasty yielded no benefits in terms of baseline lung function and respiratory mechanics, despite improving symptoms based on two asthma questionnaires (ACQ-5 and ACT-5). The response to salbutamol was also not affected by thermoplasty based on spirometric readouts, including forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio. However, a significant interaction was observed between thermoplasty and salbutamol for two oscillometric readouts, namely reactance at 5 Hz (Xrs5) and reactance area (Ax), showing an attenuated response to salbutamol after thermoplasty.

CONCLUSIONS

Thermoplasty attenuates the response to a bronchodilator. We argue that this result is a physiological proof of therapeutic efficacy, consistent with the well-described effect of thermoplasty in reducing the amount of airway smooth muscle.

Bronchial smooth muscle cell in asthma: where does it fit?

Asthma is a frequent respiratory condition whose pathophysiology relies on altered interactions between bronchial epithelium, smooth muscle cells (SMC) and immune responses. Those leads to classical hallmarks of asthma: airway hyper-responsiveness, bronchial remodelling and chronic inflammation. Airway smooth muscle biology and pathophysiological implication in asthma are now better understood. Precise deciphering of intracellular signalling pathways regulating smooth muscle contraction highlighted the critical roles played by small GTPases of Rho superfamily. Beyond contractile considerations, active involvement of airway smooth muscle in bronchial remodelling mechanisms is now established. Not only cytokines and growth factors, such as fibroblats growth factor or transforming growth factor-β, but also extracellular matrix composition have been demonstrated as potent phenotype modifiers for airway SMC. Although basic science knowledge has grown significantly, little of it has translated into improvement in asthma clinical practice. Evaluation of airway smooth muscle function is still limited to its contractile activity. Moreover, it relies on tools, such as spirometry, that give only an overall assessment and not a specific one. Interesting technics such as forced oscillometry or specific imagery (CT and MRI) give new perspectives to evaluate other aspects of airway muscle such as bronchial remodelling. Finally, except for the refinement of conventional bronchodilators, no new drug therapy directly targeting airway smooth muscle proved its efficacy. Bronchial thermoplasty is an innovative and efficient therapeutic strategy but is only restricted to a small proportion of severe asthmatic patients. New diagnostic and therapeutic strategies specifically oriented toward airway smooth muscle are needed to improve global asthma care.

Plethysmography Derived Gas Trapping Lacks Utility in Predicting Response to Bronchial Thermoplasty

There is a paucity of literature on measurable baseline parameters predicting response and guiding selection for bronchial thermoplasty. This study examines whether baseline gas trapping, as assessed by plethysmography, is associated with a response to bronchial thermoplasty at 12 months.

43 consecutive patients with severe asthma (mean±sd age 57.6±13.3 years) were evaluated at baseline and 12 months post bronchial thermoplasty. Data collected at both time points included spirometry, body plethysmography and four clinical outcome measures, namely Asthma Control Questionnaire (ACQ) score, annual exacerbation frequency, maintenance oral corticosteroid requirement and short-acting β-agonist use.

At baseline, participants had severe airflow obstruction (forced expiratory volume in 1 s 49.1±15.8%) with marked gas trapping (residual volume (RV) 150.3±40.8%, RV/total lung capacity (TLC) 51.3±10.5%), poor symptom control (ACQ 3.3±1.0) and frequent exacerbations (median 4, interquartile range 8). 12 months after bronchial thermoplasty, significant improvements were observed in all four clinical outcome measures. However, baseline RV and RV/TLC were not significantly associated with changes in ACQ nor any other clinical outcome measure, and changes in RV and RV/TLC did not significantly correlate with a change in any clinical outcome measure.

Plethysmography-derived gas trapping does not demonstrate utility in predicting response and guiding selection for bronchial thermoplasty. An improvement in gas trapping was not associated with positive clinical outcomes, suggesting that this may not be the dominant mode of action of bronchial thermoplasty in generating clinical improvement.

This study examined whether measuring gas trapping by plethysmography could be used to predict response to bronchial thermoplasty; no association was foundhttps://bit.ly/3tJN1X8

Effect of Bronchial Thermoplasty on Air Trapping Assessed by Xenon Ventilation Computed Tomography

Objective Bronchial thermoplasty (BT) is a bronchoscopic procedure for patients with severe asthma. Although it has been suggested that BT works by reducing airway smooth muscle, the detailed mechanism underlying its effects is still unknown. Methods We performed xenon ventilation computed tomography (Xe-CT) before each BT procedure and six weeks after the third treatment to assess the improvement in lung ventilation at each separate lung region. The air trapping index in each lobe was defined as the mean trapping value (0: none, 1: mild, 2: moderate, and 3: severe) of the included segments. Patients and Materials Four patients were included. Results Asthma symptoms were improved after BT. The comparison of the scores at baseline with those after the third treatment showed that the air trapping index was improved in both the treated and untreated regions. However, neither the pulmonary function nor the exhaled nitric oxide was improved. Conclusion Using Xe-CT, we successfully evaluated the air trapping in patients who underwent BT. The improvement in asthma symptoms by BT may be related to the amelioration of peripheral lung ventilation in both the treated and untreated regions.

Bronchoscopic treatments for early-stage peripheral lung cancer: Are we ready for prime time?

Lung cancer is the leading cause of cancer-related death worldwide and surgical lobectomy remains the preferred therapy for patients with early-stage NSCLC. Medical comorbidities and advanced age preclude resection in many patients and minimally invasive ablative therapies are needed for treatment. Stereotactic ablative radiation is established as an effective modality in this patient group, although may be contraindicated in some patients with prior radiation exposure, comorbidities or centrally positioned tumours. Percutaneous ablative methods are available, although are frequently associated with significant complications. Numerous endoscopic ablative techniques are under evaluation. With a more favourable safety profile and the ability to provide diagnosis and staging information potentially within a single procedure, there is a strong rationale for development of bronchoscopic ablative modalities. In the following article, the authors aim to explore the role bronchoscopic ablation may play in treatment of peripheral lung tumours, and to describe a pathway to establishing these modalities as part of routine care. The current status of several bronchoscopic ablative options is discussed in detail.

Bronchial thermoplasty reduces airway resistance

BACKGROUND

The mechanism for symptomatic improvement after bronchial thermoplasty (BT) is unclear, since spirometry reveals little or no change. In this study, the effects of BT on airway resistance were examined using two independent techniques.

METHODS

Eighteen consecutive patients, with severe asthma (57.6 ± 14.2 years) were evaluated by spirometry and plethysmography at three time points: (i) baseline, (ii) left lung treated but right lung untreated and (iii) 6 weeks after both lungs were treated with BT. At each assessment, total and specific airway resistance (Raw, sRaw) were measured. High resolution CT scans were undertaken at the first two assessments, and measurements of lobar volume, airway volume and airway resistance were made. The Asthma Control Questionnaire (ACQ) was administered at each assessment.

RESULTS

The baseline ACQ score was 3.5 ± 0.9, and improved progressively to 1.8 ± 1.2 (p < 0.01). At baseline, severe airflow obstruction was observed, FEV1 44.8 ± 13.7% predicted, together with gas trapping, and elevated Raw at 342 ± 173%predicted. Following BT, significant improvements in Raw and sRaw were observed, as well as a reduction in Residual Volume, increase in Vital Capacity and no change in FEV1. The change in Raw correlated with the change in ACQ (r = 0.56, p < 0.05). CT scans demonstrated reduced airway volume at baseline, which correlated with the increased Raw determined by plethysmography (p = - 0.536, p = < 0.05). Following BT, the airway volume increased in the treated lung, and this was accompanied by a significant reduction in CT-determined local airway resistance.

CONCLUSION

Symptomatic improvement after BT is mediated by increased airway volume and reduced airway resistance.

Resistance of the respiratory system measured with forced oscillation technique (FOT) correlates with bronchial thermoplasty response

BACKGROUND

Bronchial Thermoplasty (BT) is an endoscopic treatment for severe asthma using radiofrequency energy to target airway remodeling including smooth muscle. The correlation of pulmonary function tests and BT response are largely unknown. Forced Oscillation Technique (FOT) is an effort-independent technique to assess respiratory resistance (Rrs) by using pressure oscillations including small airways.

AIM

To investigate the effect of BT on pulmonary function, assessed by spirometry, bodyplethysmography and FOT and explore associations between pulmonary function parameters and BT treatment response.

METHODS

Severe asthma patients recruited to the TASMA trial were analyzed in this observational cohort study. Spirometry, bodyplethysmography and FOT measurements were performed before and 6 months after BT. Asthma questionnaires (AQLQ/ACQ-6) were used to assess treatment response.

RESULTS

Twenty-four patients were analyzed. AQLQ and ACQ improved significantly 6 months after BT (AQLQ 4.15 (±0.96) to 4.90 (±1.14) and ACQ 2.64 (±0.60) to 2.11 (±1.04), p = 0.004 and p = 0.02 respectively). Pulmonary function parameters remained stable. Improvement in FEV₁ correlated with AQLQ change (r = 0.45 p = 0.03). Lower respiratory resistance (Rrs) at baseline (both 5 Hz and 19 Hz) significantly correlated to AQLQ improvement (r = - 0.52 and r = - 0.53 respectively, p = 0.01 (both)). Borderline significant correlations with ACQ improvement were found (r = 0.30 p = 0.16 for 5 Hz and r = 0.41 p = 0.05 for 19 Hz).

CONCLUSION

Pulmonary function remained stable after BT. Improvement in FEV₁ correlated with asthma questionnaires improvement including AQLQ. Lower FOT-measured respiratory resistance at baseline was associated with favorable BT response, which might reflect targeting of larger airways with BT.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02225392; Registered 26 August 2014.

Treatment for intractable asthma: bronchial thermoplasty

Bronchial Thermoplasty (BT) is an epoch-making treatment that reduces bronchial smooth muscle by using a bronchoscope to reach the basket catheter to the bronchus and directing high-frequency current directly into the bronchi. In GINA Guidelines 2019, BT is considered to be additional treatment at Step V (the most severe), and the evidence level is B. The Japanese guidelines (JGL) also added BT as a treatment for Step 4, but it is reserved because there are still unclear points regarding long-term efficacy and safety. In Japan, as of April 1, 2019, 672 treatments were performed at 123 institutions nationwide. The average age of patients was 54.1 years, but 84 cases were over 70 years old. The average value of %FEV1 was 78.2%, but there were 94 cases less than 60%. There were 32 cases that underwent BT treatment at our institution. Of them, 12 cases with progress up to one year later could be observed. The average age was 56.1 years old, and each of 6 men and women had a %FEV1 of 70.5%. One year later, AQLQ and %FEV1 improved, and the number of exacerbations decreased, but exhaled NO values increased. %FEV1 improvement might be due to poorer lung function (70.5% vs. 77.8%) and more BT activation (average 1.28 times AIR2) compared to the AIR2 trial. In terms of improvement in %FEV1, patients with moderate obstructive disorder from 50 to 80% responded well after BT treatment. In the near future, various new antibody preparations such as IL-4 / 13 antibody and anti-TSLP antibody are expected to be promoted. Therefore, we first consider whether these antibody preparations can be applied to patients with refractory asthma. We consider that BT is indicated only when there is no indication or no expected effect of antibody preparations. In other words, BT treatment is the last resort of intractable asthma, and it is the duty of medical professionals involved in BT treatment to be able to advocate when it is best to give BT to such patients.

Recent Developments In Bronchial Thermoplasty For Severe Asthma

PURPOSE

Bronchial thermoplasty is approved in many countries worldwide as a non-pharmacological treatment for severe asthma. This review summarizes recent publications on the selection of patients with severe asthma for bronchial thermoplasty, predictors of a beneficial response and developments in the procedure and discusses specific issues about bronchial thermoplasty including effectiveness in clinical practice, mechanism of action, cost-effectiveness, and place in management.

RESULTS

Bronchial thermoplasty is a treatment option for patients with severe asthma after assessment and management of causes of difficult-to-control asthma, such as nonadherence, poor inhaler technique, comorbidities, under treatment, and other behavioral factors. Patients treated with bronchial thermoplasty in clinical practice have worse baseline characteristics and comparable clinical outcomes to clinical trial data. Bronchial thermoplasty causes a reduction in airway smooth muscle mass although it is uncertain whether this effect explains its efficacy since other mechanisms of action may be relevant, such as alterations in airway epithelial, gland, and/or nerve function; improvements in small airway function; or a placebo effect. The cost-effectiveness of bronchial thermoplasty is greater in countries where the costs of hospitalization and emergency department are high. The place of bronchial thermoplasty in the management of severe asthma is not certain, although some experts propose that bronchial thermoplasty should be considered for patients with severe asthma associated with non-type 2 inflammation or who fail to respond favorably to biologic therapies targeting type 2 inflammation.

CONCLUSION

Bronchial thermoplasty is a modestly effective treatment for severe asthma after assessment and management of causes of difficult-to-control asthma. Asthma morbidity increases during and shortly after treatment. Follow-up studies provide reassurance on the long-term safety of the procedure. Uncertainties remain about predictors of response, mechanism(s) of action, and place in management of severe asthma.