Endobronchial-Valve Therapy for Emphysema

Chronic obstructive pulmonary disease (COPD) is characterized by progressive limitation of air flow that results in air trapping and hyperinflation. Some of the patients with COPD exhibit irreversible pulmonary emphysema that develops from destruction of alveolar septa in the lung. These patients present with breathlessness that limits their activity and impairs the quality of their life.

Hyperinflation is the characteristic abnormality in emphysema. However, it is associated with inefficient contraction of respiratory muscles both at rest and during exertion. Therapeutic interventions to reduce lung volumes that have been thought will be beneficial.

Therapy with bronchodilators (tiotropium) has shown some improvement in resting inspiratory capacity and hyperinflation in COPD patients with increased static lung volumes.¹ Even the corticosteroids (fluticasone) with or without salmeterol have been able to reduce lung hyperinflation and exercise endurance in COPD patients.²

For as much as relief from medical therapy is not spectacular, surgical treatment in the form of lung volume reduction surgery (LVRS) has been in vogue to reduce hyperinflation and improve respiratory muscle function. In a randomized trial comparing LVRS and medical treatment in severe emphysema, it has been shown that LVRS improves exercise capacity in a subgroup of patients having upper lobe distribution of emphysema and low-exercise capacity.³ This surgical procedure is not widely practiced as the long-term benefits are not sustained and in fact has become a vanishing operation.

However, bronchoscopic approach was employed experimentally to lung volume reduction using a valve device.⁴ A pilot study undertaken in the year 2003 showed the potential for insertion of prosthesis in the form of valves through a bronchoscope to bring about lung volume reduction.⁵ Subsequently, such studies using different endobronchial-valve (EBV) devices have shown benefit by decreasing the lung hyperinflation and improving exercise capacity. In these studies, unidirectional valves were placed in the selected bronchial passages to block regional inflation while allowing exhalation.^6-9. The one-way valve allows the air to come out from the isolated lung segment during exhalation and prevent entry of air. The hyperinflated emphysematous lung areas undergo deflation even producing atelectasis and reduce the symptoms. The procedure was associated with distal pneumonia or pneumothorax as complications.

A polymer duckbill valve that is mounted inside a stainless-steel cylinder is designed to control and redirect airflow. This EBV is available in three sizes to target the different bronchial lumen sizes allow both air and mucus to come out. The inner/outer diameter of these valves is 4/5.5 mm, 5/7 mm, and 6.5/8.5 mm with length of 10 mm. Such valves attached to nitinol self-expanding retainer are placed in targeted lobe to cause atelectasis. The second-generation valves allow better expiratory flow due to their larger size. They come with two sizes 4.0 (for bronchial lumen diameters of 4-7 mm) and 5.5 (for bronchial lumen diameters of 5.5-8 mm). The valve has a handle of deployment system.

Endobronchial unidirectional valves placed in selected lung airways leading to a pulmonary lobe, blocks the regional inflation while allowing exhalation. Proper positioning of these valves brings about complete lobar isolation. Thus, it can bring about a reduction in lung volume leading to improvement in lung function and exercise capacity in patients with pulmonary hyperinflation related to severe emphysema.

The study carried out by Wang et al in nine centres in seven countries on 98 patients had a heterogeneous disease and persistent dyspnea despite medical therapy.¹⁰ They found the valves targeting one lobe or valves placed unilaterally achieved better results. There was a 10.7% improvement in forced expiratory volume in one second (FEV1) and 23% in exercise capacity, 90 days post-operatively. There were serious complications in eight patients such as death, pneumothorax, and prolonged air-leak. Five patients had pneumonia and 17 patients showed exacerbation of COPD.

In a recent study, the Endobronchial Valve for Emphysema Palliation Trial (VENT) group compared the safety and efficacy of endobronchial-valve therapy in patients with heterogeneous emphysema vs the standard medical care.¹¹ The procedure brought about modest improvements in lung function, exercise performance, and symptoms. However, it was associated with more frequent exacerbations of COPD, pneumonia in the target lobe distal to the valves, and hemoptysis following implantation. The valves had been placed in selected sub-segmental bronchi of hyperinflated lung lobes while allowing air to escape from them. At the end of 6-months there was an increase of 1.0 percentage point FEV1 in the percent of the predicted value, as compared with the control group that showed a decrease of 0.9 percentage point in the percent of the predicted value.

Bronchoscopic lung volume reduction may be associated with complications, such as pneumothorax, bronchospasm, atelectasis, infections, and persistent bronchial hypersecretion.¹⁰

The procedure requires proper selection of patients and targeting lobes to minimize collateral ventilation. The patients should be aged 40-70 years exhibiting predominantly upper lobe emphysema with severe dyspnea. The valve should be positioned properly to isolate the lobe. The valves are to be placed in the segmental bronchi. This will definitely bring about improvement in the clinical response to EBV therapy. The selection of patients with greater heterogeneous emphysema between lobes and intact interlobar fissures are likely to show clinical improvement. These patients must have received full course of treatment with medical regimen before undergoing surgical intervention. The functional improvement following EBV therapy needs to be substantiated by well-designed clinical trials. This therapy needs more studies before it is routinely recommended in selected patients with advanced hyperinflated emphysema.