Bronchoscopic Interventions in the Management of COPD
Purpose of review In the past few years, there have been exciting developments in bronchoscopic efforts at attaining lung volume reduction (LVR), given real and perceived risks of surgical LVR. The purpose of this review is to discuss these techniques, with special emphasis on what we have learnt in the past 1–2 years.
Recent findings Bronchoscopic techniques can be broadly classified as one-way valves, which allow air to exit but not enter, thus reducing air trapping; airway bypass stents, which create an extra-anatomical pathway for air to exit; biologic and polymeric substances, which seal the emphysematous lung, eventually collapsing it; bronchial thermal vapor ablation, which causes thermal damage and thus achieves LVR; and endobronchial elastic coils, which mechanically cause LVR. The specific role of these is being defined by recent publications. The central role of collateral ventilation in choosing amongst these procedures is now established, as it has become clear that in the presence of collateral ventilation, valves provide only modest benefit, if any at all. Thus it is of interest that the other modalities which are independent of collateral ventilation are being studied further.
Summary Though the preliminary results are quite encouraging, further trials need to be done before these procedures can be adopted in daily practice.
Emphysema is characterized by alveolar destruction leading to impaired gas exchange and loss of elastic recoil. This results in expiratory flow limitation and air-trapping, which have serious mechanical and sensory repercussions. By changing the length–tension characteristics of inspiratory muscles and by decreasing the inspiratory capacity, air trapping leads to increased dyspnea. In addition, there is increased disparity between effort and ventilatory output. Air trapping also impairs cardiac performance. During exercise, expiratory time decreases further and air trapping worsens. Exercise limitation is thus multifactorial in chronic obstructive pulmonary disease (COPD).
Therapeutic interventions that reduce operational lung volumes and air trapping during exercise may improve endurance and alleviate dyspnea. Reducing the volume of the most damaged lung segments gives more room to remaining less damaged tissues to expand. By eliminating areas with longest time constant, and reducing dead space, dynamic air trapping is reduced and V/Q matching improved. This is the physiologic basis for lung volume reduction (LVR).
Though surgical LVR has been around for a long time, it was studied rigorously only in the past decade. Salient points from the National Emphysema Treatment Trial (NETT) are: patients with forced expiratory volume in 1 s (FEV1) or diffusion capacity of carbon monoxide (DLCO) below 20%, or with homogenous emphysema had a high risk of 1 month mortality (16%); a subgroup with upper lobe predominant emphysema and decreased exercise tolerance derived the most benefit with improvement noted not only in functional status but more importantly even in survival; surgery is associated with high morbidity and mortality. For example, a 30% incidence of major pulmonary and 20% incidence of major cardiac morbidity is described. Overall mortality was 7.9% at 90 days (2.9% for the favorable subgroup). In general, surgical LVR is infrequently done due to real and perceived risks. This has been the incentive for development of bronchoscopic methods of LVR. The purpose of this article is to review these different techniques.
Abstract and Introduction
Abstract
Purpose of review In the past few years, there have been exciting developments in bronchoscopic efforts at attaining lung volume reduction (LVR), given real and perceived risks of surgical LVR. The purpose of this review is to discuss these techniques, with special emphasis on what we have learnt in the past 1–2 years.
Recent findings Bronchoscopic techniques can be broadly classified as one-way valves, which allow air to exit but not enter, thus reducing air trapping; airway bypass stents, which create an extra-anatomical pathway for air to exit; biologic and polymeric substances, which seal the emphysematous lung, eventually collapsing it; bronchial thermal vapor ablation, which causes thermal damage and thus achieves LVR; and endobronchial elastic coils, which mechanically cause LVR. The specific role of these is being defined by recent publications. The central role of collateral ventilation in choosing amongst these procedures is now established, as it has become clear that in the presence of collateral ventilation, valves provide only modest benefit, if any at all. Thus it is of interest that the other modalities which are independent of collateral ventilation are being studied further.
Summary Though the preliminary results are quite encouraging, further trials need to be done before these procedures can be adopted in daily practice.
Introduction
Emphysema is characterized by alveolar destruction leading to impaired gas exchange and loss of elastic recoil. This results in expiratory flow limitation and air-trapping, which have serious mechanical and sensory repercussions. By changing the length–tension characteristics of inspiratory muscles and by decreasing the inspiratory capacity, air trapping leads to increased dyspnea. In addition, there is increased disparity between effort and ventilatory output. Air trapping also impairs cardiac performance. During exercise, expiratory time decreases further and air trapping worsens. Exercise limitation is thus multifactorial in chronic obstructive pulmonary disease (COPD).
Therapeutic interventions that reduce operational lung volumes and air trapping during exercise may improve endurance and alleviate dyspnea. Reducing the volume of the most damaged lung segments gives more room to remaining less damaged tissues to expand. By eliminating areas with longest time constant, and reducing dead space, dynamic air trapping is reduced and V/Q matching improved. This is the physiologic basis for lung volume reduction (LVR).
Though surgical LVR has been around for a long time, it was studied rigorously only in the past decade. Salient points from the National Emphysema Treatment Trial (NETT) are: patients with forced expiratory volume in 1 s (FEV1) or diffusion capacity of carbon monoxide (DLCO) below 20%, or with homogenous emphysema had a high risk of 1 month mortality (16%); a subgroup with upper lobe predominant emphysema and decreased exercise tolerance derived the most benefit with improvement noted not only in functional status but more importantly even in survival; surgery is associated with high morbidity and mortality. For example, a 30% incidence of major pulmonary and 20% incidence of major cardiac morbidity is described. Overall mortality was 7.9% at 90 days (2.9% for the favorable subgroup). In general, surgical LVR is infrequently done due to real and perceived risks. This has been the incentive for development of bronchoscopic methods of LVR. The purpose of this article is to review these different techniques.
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