Introduction
Chronic obstructive pulmonary disease (COPD) causes considerable morbidity, mortality, and health care expenditure both in the United States and globally. For COPD patients with burdensome symptoms despite standard medical therapy, historically, few treatment options have been available. In the last 20 years, a variety of bronchoscopic interventions have expanded therapeutic options for emphysema patients with hyperinflation. Several techniques are now recognized by the Global Initiative for Chronic Obstructive Lung Disease (GOLD), and two devices have gained FDA approval. With increasing treatment options for patients with emphysema, practical knowledge of available technologies, proper patient evaluation and selection, and preparedness for procedures and for procedure-related complications will be integral to optimized care for these vulnerable patients.
Definition
Bronchoscopic lung volume reduction (BLVR) interventions are performed with a standard bronchoscope for the treatment of emphysema. The goal of these treatment methods is to deflate or promote physical changes of the severely emphysematous lung in order to improve respiratory mechanics and physiology. BLVR treatments were developed as alternatives to lung volume reduction surgery (LVRS). They include one-way valves, coils, thermal vapor ablation, and biological lung volume reduction. Stents placed for airway bypass were developed in the past; however, they failed in clinical trials and their use has been abandoned. Of the aforementioned interventions, one-way valves are currently the most widely accepted and recommended devices, whereas the others remain largely investigational. As of 2020, one-way valves are the only BLVR intervention approved in the United States; other treatments have approval in other countries.
Preprocedural Preparation
Patient Selection and Initial Patient Evaluation
Appropriate patients for BLVR include patients with advanced emphysema and hyperinflation who have significant dyspnea despite standard-of-care noninvasive management strategies, including smoking cessation, maintenance medications such as inhaled bronchodilators and corticosteroids, and pulmonary rehabilitation. Evaluation of BLVR candidates is ideally made by a multidisciplinary team, with consideration of surgical interventions including lung transplantation, LVRS, and bullectomy when appropriate. Emerging evidence may also assist in proper patient profiling; the relative benefit of surgical versus BLVR is currently under investigation.
Upon initial work up for BLVR, a general medical and pulmonary evaluation should be performed, including basic laboratory analysis, blood gas, electrocardiogram (ECG), echocardiogram, and pulmonary function tests including spirometry, lung volumes, diffusion capacity for carbon monoxide (D lco ), and 6-min walk test (6MWT). Pulmonary function tests should reveal severe obstruction (forced expiratory volume in 1 s, FEV 1 , of 15%–45%), hyperinflation (total lung capacity, TLC ≥100%), and air trapping with residual volume (RV) ≥150%. 6MWT should demonstrate diminished exercise capacity (100–500 m). Patients should lack significant comorbidities that may compromise short-term survival and performance status. Severe hypercapnia (Pa co 2 >55 mmHg) or hypoxia (Pa o 2 <45 mmHg) (measured on room air), severely decreased D lco (<20%), and pulmonary hypertension (right ventricular systolic pressure [RVSP] ≥50) are generally contraindications as well. If echocardiogram demonstrates concern for pulmonary hypertension, further evaluation with right heart catheterization may be needed.
A noncontrast, thin-cut computed tomography (CT) chest (≤1.5-mm slice thickness) is also part of the initial evaluation. The CT is useful to examine the extent and distribution of emphysema and the radiographic integrity of lobar fissures. The CT also functions to screen patients for other potential contraindications including severe bronchiectasis, concerning pulmonary nodules and masses, and interstitial lung disease. The amount of emphysema in individual lung lobes can be assessed by quantifying the proportion of lung voxels below an attenuation threshold such as −910 or −950 (this correlates with emphysema pathologically), which is accomplished by evaluating the chest CT via specialized software programs. This emphysema severity information is used for targeting sites for treatment and for quantifying the distribution of the disease (heterogeneous vs. homogeneous). Additionally, perfusion scintigraphy can be used to quantify relative perfusion. This can facilitate target lobe selection in patients with homogeneous and heterogeneous disease where there are two potential target lobes for treatment. It is important to avoid targeting lobes with high perfusion (compared to other lobes), as this can lead to imbalances in perfusion/ventilation matching and subsequent respiratory failure.
For one-way valve placement, subgroup analysis from initial multicenter studies demonstrated that clinical benefit with placement of these devices is dependent on lack of collateral ventilation (CV) due to intact fissures. Quantification of fissure integrity can be accomplished by analyzing the patient’s high-resolution computed tomography (HRCT) chest with dedicated software. Fissure completeness less than 80% is considered incomplete and not amenable to one-way valve placement. A fissure integrity of ≥95% is considered complete and amenable to endobronchial valve (EBV) therapy. Fissure integrity of 80%–94% can be further assessed with a proprietary balloon occlusion-based system (Chartis) during bronchoscopy to evaluate for CV. The balloon is typically inserted via the bronchoscope and inflated in the target lobe. The tip of the catheter distal to the balloon remains open and can measure the flow returning from the obstructed target lobe. If CV exists, then air flow from the obstructed lobe will continue. If CV is absent, then air flow from the obstructed lobe will gradually decrease until it ceases. In contrast to one-way valves, lack of CV is not a prerequisite for other BLVR techniques.
Equipment and Procedural Techniques
One-Way Valves
One-way valve devices cause target lung region collapse by preventing air entry during inspiration while allowing air to exit during exhalation. The valves are placed within all the segments of the most emphysematous lobe target in order to elicit a lobar atelectasis. There are two commercially available valves, both of which received US Food and Drug Administration (FDA) approval: an EBV (Zephyr, Pulmonx Corporation, Redwood City, CA, USA) and an intrabronchial valve (IBV) (Spiration Valve System [SVS], Spiration Inc./Olympus Respiratory America, Redmond, WA, USA). Both valve devices can be placed under general anesthesia or moderate sedation.
Zephyr Endobronchial Valve
Recent landmark trials that studied the Zephyr EBV used the Chartis Pulmonary Assessment System (Pulmonx Corporation) for bronchoscopic evaluation for the presence or absence of CV as part of the inclusion/exclusion criteria. The Chartis system uses a single-use balloon catheter with a central channel that can measure pressure and flow during balloon occlusion of a lung segment in order to quantify CV. Chartis assessment is generally performed during the same procedure as EBV placement, as part of final evaluation of eligibility for valve placement. Targets for treatment can also be modified based on Chartis evaluation: if the right upper lobe (RUL) is the primary target, but CV is found at the RUL, the integrity of the major fissure can then be assessed by placing the Chartis balloon in the right lower lobe (RLL). If there is no CV at the RLL, there is the option of treating both the RUL and right middle lobe (RML).
The Zephyr valve is a silicone, “duckbill”-shaped valve device mounted within a self-expanding nitinol silicone covered stent-like retainer structure ( Fig. 13.1 ). The valve comes in four sizes: 4.0, 4.0 low-profile (LP), 5.5, and 5.5 LP. The 4.0-size valves can be deployed for airways between 4 and 7 mm, whereas the 5.5 valve can be deployed for airways between 5.5 and 8.5 mm. The LP valve has a shorter proximal to distal length, allowing placement in shorter bronchial segments. Zephyr valve delivery catheters have delivery gauges for selecting proper valve size. The valves are intended for segmental and/or subsegmental airway placement with no defined limit to the number of valves placed within a lobe. The propeller-like sizing catheters should verify that the target airway is appropriate for the selected valve size ( Fig. 13.1 ). There are also depth markers for choosing between LP and standard-length valves. Once a valve size is selected, the endobronchial loader system is used to load the valve into the delivery catheter. Within the bronchoscope (either in a central airway or outside the patient), the delivery catheter is advanced until the tip of the catheter can be viewed with the bronchoscope camera. The bronchoscope is then navigated to the target airway orifice and the delivery catheter is advanced into the airway until the diameter gauge is flush with the airway orifice. Valve deployment is initiated by partially advancing the actuator of the delivery catheter handle; as the valve begins deployment, the position of the distal end should be verified as against the carina distal to the valve target, after which the actuator can be advanced to complete valve deployment. The main body of the stent-like retainer portion of the valve should fully interface with the target airway and should not protrude outside of the airway orifice. If the valve is malpositioned and/or concluded to be the wrong size, it can be removed using rat tooth forceps with grasping of the retainer portion of the valve device and subsequent removal en bloc.
Spiration Valve System
The Spiration valve system is composed of a nitinol frame and polyurethane membrane with an umbrella shape with anchors that hold it in place through superficial airway wall penetration ( Fig. 13.2 ). The struts of the umbrella expand and contract with the respiratory cycle so that the airway is occluded during inspiration, whereas air and mucus can exit during expiration. The valves come in four different sizes: 5, 6, 7, and 9 mm. The valves are placed in lobar, segmental, and/or subsegmental airways with no defined limitation to the number of valves placed, and with the goal of occluding the entire target lobe. Before placement of each valve, a calibrated balloon catheter is inserted in the working channel for sizing of the target airway (calibration of the balloon catheter system is a process that involves removing air from the catheter system with saline, precise saline volume measurement with a dedicated syringe, and sizing of the saline-filled balloon; this process takes approximately 5 min and is best done before the procedure begins).
Once the valve size is chosen, the valve is then loaded from a cartridge into the deployment catheter with a dedicated loading device ( Fig. 13.2 ). The deployment catheter is then inserted into the working channel with the bronchoscope within a central airway until the tip of the catheter and the tip of the removal rod and the yellow valve line are visible. The catheter tip should be retracted as needed to eliminate any gap between the stabilization wire and the tip of the removal rod. Once the bronchoscope is in position with the catheter within the target airway, the yellow valve line on the catheter should be aligned with the ostium of the target bronchial branch when deploying valve sizes 5, 6, and 7. On the other hand, when deploying the 9-mm valve size, it is recommended to align the yellow line 1 mm proximal to the ostium to correct for the fact that these valves can advance distally 1–2 mm over time following deployment. If valve removal is desired due to improper sizing or positioning, the valve can easily be removed with standard forceps. The center nitinol hub is a rod with a knob at the end that facilitates grasping the valve with forceps; once the valve is grasped, the bronchoscope and forceps can be withdrawn en bloc.
Coils
Endobronchial coil placement is a BLVR technique that targets one lobe of both lungs (each lung is treated in an individual procedure with the contralateral side treated 4–8 weeks after the initial procedure). These devices are nitinol wire with shape memory that are delivered into subsegmental airways in a straight conformation but transition into a predetermined angled shape after deployment ( Fig. 13.3 ). This change in shape allows the coils to apply traction on the airways, which leads to compression of the emphysematous lung tissue in the target lobe ( Fig. 13.3 ). Rather than atelectasis, the desired effect to the target lung territory is compression and improved elastic recoil. Given the physical compression mechanism, unlike one-way valves, coils do not rely on lack of CV for efficacy of lung volume reduction. Coils are generally thought of as permanent implants, though bronchoscopic removal, including late removal, has been reported. They can be placed under general anesthesia (preferred) or moderate sedation, under fluoroscopic guidance.
The coils are available in three different lengths (100, 125, and 150 mm). The coil delivery system consists of a guidewire, catheter, cartridge, and forceps that are inserted via the working channel of a standard bronchoscope. The guidewire guides the catheter to the target airway and is used for selecting the length of the coil. The cartridge is used to straighten and load the coil into the delivery catheter. The forceps are used to grasp the proximal end of the coil to deliver the coil through the catheter. The catheter and forceps can also be used to reposition the coil if needed. Once the bronchoscope is in position within a distal airway of the targeted treatment lobe, the catheter position is verified with fluoroscopy. The coils are deployed under fluoroscopic guidance ensuring there is a safe distance from the pleura. The coils are placed with an algorithm that facilitates anatomically dispersed placement; 8–12 coils are generally placed in the upper lobes and 10–14 in the lower lobes.
Thermal Vapor Ablation
Thermal vapor ablation uses heated water vapor to cause scarring of lung tissue as a lung volume reduction technique. This irreversible treatment modality was developed with the potential advantage of targeting severely emphysematous segments within a lobe rather than obligatory treatment of entire lobes as in one-way valves and coils. At present, published trials involving this technique have only been performed in patients with upper-lobe, heterogeneous emphysema. The equipment includes a catheter-based system with a multi-use vapor generator and a single-use catheter for proximal balloon occlusion of the targeted segment and delivery of the vapor distally over 3–10 s with a target dose of 8.5 calories per gram of lung tissue ( Fig. 13.4 ).
