minimally invasive techniques New and Emerging Minimally Invasive Techniques for Lung Volume Reduction*

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1 minimally invasive techniques New and Emerging Minimally Invasive Techniques for Lung Volume Reduction* Roger A. Maxfield, MD, FCCP Lung volume reduction surgery (LVRS) has been shown to improve pulmonary function, exercise capacity, quality of life, and survival in selected patients with heterogeneous emphysema. However, LVRS is a major surgical procedure with potential morbidity and mortality. Minimally invasive techniques are emerging to achieve lung volume reduction without open thoracotomy. Devices and techniques under study include one-way bronchial valves inserted via fiberoptic bronchoscopy to promote atelectasis in emphysematous lung, promotion of focal atelectasis and fibrosis by bronchoscopic injection of polymers into emphysematous regions of lung, bronchopulmonary fenestrations to enhance expiratory flow, and thoracoscopic plication or compression of emphysematous lung. The goal of all of these procedures is to replicate the benefit of LVRS without the trauma, risks, and extended recovery of open LVRS. Refinement and application of these techniques will allow patients with emphysema and their physicians and surgeons to choose from a number of viable options for lung volume reduction. (CHEST 2004; 125: ) Key words: bronchoscopy; COPD; emphysema; endobronchial valve; interventional bronchoscopy; lung volume reduction; lung volume reduction surgery; minimally invasive; thoracoscopy Abbreviations: Dlco diffusing capacity of the lung for carbon monoxide; EWS endoscopic Watanabe spigot; FRC functional residual capacity; LVRS lung volume reduction surgery; NETT National Emphysema Treatment Trial; RV residual volume; TLC total lung capacity; VALR vacuum-assisted lung reduction; V /Q ventilation/perfusion *From the Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Columbia University College of Physicians & Surgeons, New York, NY. Dr. Maxfield will be an investigator in the Endobronchial Valve for Emphysema Palliation Trial (pending institutional review board approval) sponsored by Emphasys Medical, Inc., Redwood City, CA. Manuscript received May 30, 2003; revision accepted August 6, Reproduction of this article is prohibited without written permission from the American College of Chest Physicians ( permissions@chestnet.org). Correspondence to: Roger A. Maxfield, MD, FCCP, Columbia Presbyterian Eastside, 16 East 60th St, Suite 320, New York, NY ; ram7@columbia.edu Emphysema is characterized by destruction of alveolar walls distal to the terminal bronchioles. 1 This process leads to enlargement of distal air spaces with development of emphysematous blebs, cysts, and bullae. Because capillary-rich alveolar walls are also destroyed in areas of emphysema, these enlarged air spaces have very high ventilation/perfusion (V /Q ) ratios creating physiologic dead space. Increased dead space ventilation reduces efficiency of breathing, resulting in increased work and impaired gas exchange. 2 The destruction of alveolar walls also leads to decreased alveolar elastic recoil and decreased traction support of small airway lumens, leading to impaired exhalation. Reduced elastic recoil combined with expiratory airway collapse causes hyperinflation and air trapping in overly compliant emphysematous areas of lung. 2 This hyperinflation can compress areas of more normal lung, leading to reduced ventilation in areas of lung that are well perfused. The resulting low V /Q ratios in areas of compressed lung further impair gas exchange, leading to hypoxemia. 3 Lung volume reduction surgery (LVRS) with surgical removal of hyperinflated poorly perfused areas of lung has been shown in numerous uncontrolled 4 6 and controlled 7 10 studies to benefit patients with emphysema. Functional, physiologic, and quality-oflife benefits have been demonstrated. These positive results have been validated by the recently reported CHEST / 125 / 2/ FEBRUARY,

2 National Emphysema Treatment Trial (NETT), 11 which also demonstrated a survival benefit following LVRS for patients with upper-lobe heterogeneous emphysema and limited exercise capacity. The encouraging results from the NETT 11 confirm the value of removing hyperinflated, nonfunctioning areas of lung in patients with emphysema. Although the surgical morbidity and mortality data in the NETT study 11 are acceptable, LVRS remains a major surgical procedure requiring general anesthesia and postoperative intensive care. LVRS is associated with potential complications including prolonged air leak, which can lead to lengthy hospitalization. 12,13 The NETT study also identified a group of patients with very severe emphysema (FEV 1 20% and either diffusing capacity of the lung for carbon monoxide [Dlco] 20% or homogeneous emphysema) who had unacceptably high 30-day mortality (16%) from LVRS. 14 The demonstrated benefits of LVRS and the rigors of surgical lung volume reduction have led investigators and medical equipment manufacturers to develop minimally invasive techniques to achieve lung volume reduction without open thoracotomy. Devices and techniques under study include bronchial occlusion devices inserted via fiberoptic bronchoscopy, promotion of focal atelectasis and fibrosis by bronchoscopic injection of polymers into emphysematous regions of lung, bronchopulmonary fenestrations to enhance expiratory flow, and thoracoscopic plication or compression of emphysematous lung. The goal of all of these procedures is to replicate the benefit of LVRS without the trauma, risks, and extended recovery of open LVRS. Furthermore, the one-way valve should inhibit dynamic hyperinflation of overly compliant emphysematous lung during exercise. The Emphasys Endobronchial Valve consists of a silicone duckbill, one-way valve attached to a nitinol self-expanding stent retainer with silicone seals to occlude the bronchus around the valve (Fig 1). The valve is inserted into the intended segmental or subsegmental bronchus via a delivery housing device over a guidewire placed via a fiberoptic bronchoscope in a manner similar to stent insertion (Fig 2, 3). The bronchoscope should be reinserted to confirm proper positioning before deployment of the valve from the delivery device. Position adjustments or removal (if necessary) can be accomplished with a biopsy forceps. Animal studies were performed on sheep with the Emphasys Endobronchial Valve, 15 in which 35 valves were inserted in eight sheep. At sacrifice, gross collapse distal to the valves was seen in 83% of the segments with valves inserted. A phase I human study 16 of valve placement in 10 patients with emphysema has been reported. Mean FEV 1 was L (range, 0.37 to 1.02 L; 19 to 46% Bronchoscopic Methods A one-way endobronchial valve system has been developed (Emphasys Endobronchial Valve; Emphasys Medical; Redwood City, CA) for the treatment of emphysema. The valve is designed for insertion into bronchi leading to emphysematous regions of lung. The intent is to promote atelectasis in emphysematous regions by preventing airflow into the bronchus while allowing outflow of air. The resulting atelectasis could reduce hyperinflation and dead space and allow expansion of previously compressed normal regions of lung, improving gas exchange. Emphysematous regions of lung may not always collapse following valve insertion due to collateral ventilation and/or severely reduced recoil in the lung distal to the valve. Even without atelectasis, the valve is intended to improve V /Q ratio by shifting ventilation away from emphysematous regions of dead space to better perfused areas of lung. Figure 1. Emphasys Endobronchial Valve consisting of a silicone duckbill, one-way valve attached to a nitinol self-expanding stent retainer with silicone seals to occlude the bronchus around the valve. 778 Minimally Invasive Techniques

3 Figure 2. Emphasys Endobronchial Valve compressed in housing device and advanced over guidewire. predicted), with a 6-min walk of 340 m (range, 245 to 425 m). Four to 11 valves were inserted per patient under general anesthesia. Symptomatic improvement was noted in four patients. Spirometry and 6-min walk distances were unchanged, but Dlco increased significantly ( to ml/ min/mm Hg at 1 month; 11% increase). Inpatient stay ranged from 1 to 8 days. Minor complications included exacerbations of COPD (three patients), hemoptysis, pneumothorax, and left lower lobe pneumonia (one each). This initial study established that the valve could be safely placed in patients with emphysema. A subsequent pilot study 17 with a second-generation Emphasys Endobronchial Valve has been recently published. Eight patients had severe emphysema that was heterogeneous on CT and V /Q scan with severe dyspnea on exertion despite pulmonary Figure 3. Emphasys Endobronchial Valve deployed by retracting housing and releasing the valve. rehabilitation. Baseline median FEV 1 was 0.79 L (23% predicted; range, 18.4 to 35.7% predicted), residual volume (RV) was 6.82 L (272.8% predicted; range, 219 to 321% predicted), and Dlco was 35.6% predicted (range, 24.8 to 51.4% predicted). Twentyfive endobronchial valves were inserted over a guidewire placed bronchoscopically under general IV anesthesia with pressure-limited ventilation. Valves were inserted unilaterally in all segmental bronchi leading to the upper lobe most affected by emphysema in each patient. Median procedure time was 1 h (range 0.5 to 2.5 h). All patients were extubated immediately following the procedure. Four of eight patients showed radiographic signs of volume reduction. These four patients showed the greatest improvement in pulmonary function test results. However, improvements in FEV 1 and Dlco capacity were seen in some patients without collapse, suggesting improved V /Q ratios following valve insertion. For the entire group, significant improvements in median FEV 1 (0.79 to 1.06 L; p 0.025) and median Dlco (3.05 to 3.92 ml/min/mm Hg; p 0.017) were seen at 4 weeks. There were no significant changes in RV, shuttle distance, or quality-of-life scores. Ipsilateral pneumothoraces developed in two patients at 2 days and 4 weeks after the procedure, respectively. Three patients had exacerbations of COPD (two patients at 7 days and one patient at 30 days). A randomized controlled study of the Emphasys Endobronchial Valve in the United States recently obtained US Food and Drug Administration approval. Another endobronchial valve for lung volume reduction has been developed, the Spiration Intra- Bronchial Valve (Spiration; Redmond, WA). The Spiration Intra-Bronchial Valve is an umbrellashaped device consisting of a polyurethane membrane on a nitinol frame (Fig 4). The valve is placed in the bronchus via a delivery catheter inserted directly through the working channel of a fiberoptic bronchoscope (Fig 5). The valves are produced in various sizes. In an animal study, 21 valves were inserted into the upper lobes of five healthy swine. After 4 to 6 days, bronchoscopy and fluoroscopy confirmed proper positioning of the valves. 18 One valve in each of the four swine was easily removed and replaced bronchoscopically. 19 No complications were observed. At thoracotomy 4 to 6 days after valve insertion, visual confirmation of volume reduction was observed The umbrella-shaped valve with the convex side distally is designed to allow mucus and air to escape from the targeted bronchus while preventing air from entering the bronchus. The intent is to limit ventilation to emphysematous regions of lung, allowing better CHEST / 125 / 2/ FEBRUARY,

4 Figure 4. Spiration Intra-Bronchial Valve consisting of an umbrella-shaped polyurethane membrane on a nitinol frame. ventilation of healthier regions, while allowing mucus to escape from the treated region to avoid postobstructive pneumonia. Human trials are pending. Bronchoscopic occlusion of bronchi to treat bronchopleural fistulae has been reported. Twenty-three patients with emphysema and bronchopleural fistula were treated with endoscopic Watanabe spigots (EWSs; Fig 6) [Novatech; Plan degrasse, France] during 2000 and Ninety-one spigots were inserted in 23 patients. Upper-lobe collapse was seen in two patients who had their whole upper lobe occluded. Complications reported were pneumonia (n 2) and dyspnea (n 1). A patient with emphysema and giant bullae was treated with the EWS. 21 The bullae became larger following insertion of the EWS, presumably due to collateral ventilation with impaired exhalation from the occluded bronchus. One-way valve devices described previously avoid this complication. Based on the favorable results from LVRS, Ingenito et al 22 theorized that collapse of emphysematous regions of lung via fiberoptic methods consisting of surfactant washout and fibrin-based glue instillation could achieve results similar to LVRS. This hypothesis was tested on 12 sheep with emphysema induced by four weekly papain inhalations. The nebulized papain produced histologically confirmed emphysema. Total lung capacity (TLC), RV, and RV/TLC increased in all animals. Lung compliance increased as well. After intubation and ventilation with 100% oxygen, selected lung subsegments were Figure 5. Spiration Intra-Bronchial Valve and delivery system shown folded (top) allowing passage through the working channel of a bronchoscope and deployed (bottom). Figure 6. EWS consisting of 5 mm, 6 mm, and 7 mm in diameter silicon plugs. 780 Minimally Invasive Techniques

5 lavaged with antisurfactant solution via a multichannel, balloon-tipped catheter inserted through a fiberoptic bronchoscope. Following suction, a fibrinbased sealant was injected into the selected subsegment with bronchoscopic confirmation of effective sealing. Animals treated with this method of bronchoscopic volume reduction had significant reductions in TLC (64% return to baseline) and RV (72% return to baseline), with decreased compliance. Visual atelectasis was apparent at autopsy. These results were similar to those in a group of sheep treated with surgical lung volume reduction. Sterile lung abscesses developed in two of four of the sheep treated with bronchoscopic volume reduction. Only 11 of 20 subsegments treated exhibited sustained collapse. A newer technique of bronchoscopic lung volume reduction has been recently reported by Ingenito et al. 23 Six sheep in this study had papain-induced emphysema that produced increases in TLC, functional residual capacity (FRC), RV, and airway resistance with reduction in elastic recoil and Dlco. Six lung segments in each sheep had fiberoptic bronchoscopy with instillation of an enzymatic solution of trypsin to remove epithelial cells in the targeted region. This was followed by instillation of fibrin hydrogel and thrombin through a bronchoscopically placed catheter to promote fibroblast attachment and collagen synthesis. The intent was to remodel hyperinflated emphysematous lung segments into contracted scar tissue. The bronchoscopic lung volume reduction procedure was well tolerated without hypoxemia or bronchospasm. Three weeks after bronchoscopic volume reduction, there were significant reductions in TLC (3.63 to 3.01 L, p 0.02), FRC (2.04 to 1.66 L, p 0.05), and RV (1.43 to 0.63 L, p 0.002). Recoil pressure increased. These improvements in lung function were maintained at 9 weeks. Dlco improved following bronchoscopic volume reduction, but not back to levels measured before papain installation. Serial CT scans and autopsy at 9 weeks after bronchoscopic lung volume reduction confirmed volume reduction and fibroblastic scar formation with collagen deposition in the treated areas. There were no lung abscesses with this method. Lausberg et al 24 recently reported a method of radiofrequency-induced fenestrations in segmental bronchi to enhance expiratory airflow in emphysematous lungs. Twelve explanted emphysematous lungs removed during lung transplantation were studied in a ventilation chamber ex vivo. Three to five fenestrations were made in segmental or subsegmental bronchi adjacent to lung parenchyma with a radiofrequency catheter (Exhale RF Probe; Bronchus Technologies; Mountain View, CA) inserted via a fiberoptic bronchoscope. Patency of the bronchopulmonary fenestrations was maintained with uncovered coronary stents (3 mm in diameter, 15 mm in length). Mean FEV 1 measured in the experimental pressurized ventilation chamber increased from 245 to 447 ml (83% increase, p 0.001) following creation of the stented fenestration. In vivo animal studies of this procedure are underway. Thoracoscopic Techniques Prolonged air leaks remain a common complication following LVRS. 12,13,25,26 Most surgeons use bovine pericardial strips to buttress the staple line during LVRS. 12,26,27 Another method reported to minimize postoperative air leaks involved thoracoscopic lung plication rather than standard resection for LVRS. Swanson et al 28 reported a method of plication involving grasping the involved portion of lung with a ring forceps, folding the tissue with a plication clamp, followed by stapling across the folded lung through four layers of visceral pleura. Thirty-two patients with emphysema (mean FEV 1, 0.68 L; 22% predicted) were operated on in 50 procedures (14 unilateral and 18 bilateral). Two procedures (4%) were converted to open thoracotomy for air leak. Four other procedures (9%) were associated with prolonged air leaks ( 7 days). FEV 1 increased by a mean of 29%, with 78% of patients showing an increase in FEV 1. Iwasaki et al 29 described another method of thoracoscopic plication involving stapling across the apex of the lung, folding the lung at the staple line, and then restapling across the fold, holding the lung in a folded position. Twenty patients with emphysema had unilateral thoracoscopic lung reduction by this method of fold plication. Postoperative air leak lasted 0 to 5 days (1.7 days). FEV 1 increased from 24.2 to 42.4% predicted with improvement in dyspnea in all patients. One patient had a spontaneous pneumothorax on day 7. Air leaks have not been eliminated following LVRS with either bovine pericardium 12,13,25 27 or lung plication. 28,29 Use of a novel, vacuum-assisted, implantable elastomer device for lung reduction has been reported in animals with emphysema. 30 Emphysema was induced in rabbits with nebulized elastase three times over 4 weeks. Development of emphysema was confirmed histologically and by increases in FRC and compliance. Twenty rabbits with emphysema had median sternotomy. Ten of the rabbits underwent lung reduction performed by applying suction to an elastomer sleeve in contact with the emphysematous lung. Lung tissue was CHEST / 125 / 2/ FEBRUARY,

6 drawn into the sleeve and held in place with a proximal purse string suture and distal sutures through the device and the reduced lung. There were no air leaks in any of the animals after the operation. FRC and compliance both decreased in the animals who underwent the lung reduction procedure, and did not change in the animals who underwent sternotomy without lung reduction. 30 Fluorescent microsphere injections in the treated rabbits demonstrated decreased blood flow to the reduced lung tissue as well. 31 Similar results with vacuum-assisted lung reduction were obtained in a study of dogs with papaininduced emphysema. Emphysema was confirmed by significant increases in TLC, FRC, and RV, with significant reduction in all three measurements at 1 month and 6 months following lung reduction. 32 There were no air leak complications. Extreme reduction in blood flow to the reduced areas of lung was demonstrated with fluorescent microsphere injections. 33 Spiration, Inc. (Redmond, WA) began a US Food and Drug Administration-approved clinical trial of vacuum-assisted lung reduction (VALR) in April The current elastomer sleeve under study is deployed with a button-activated introducer using gentle vacuum pressure to draw lung tissue into the sleeve (Fig 7). The sleeve applies radial compression via a band to the proximal lung tissue in the sleeve, sealing the compressed lung. Sutures are placed through the sleeve and the proximal compressed lung (Fig 8). The distal compressed lung and sleeve are removed, leaving a short cylinder of compressed lung on the surface. The VALR device was recently tested intraoperatively on six patients immediately prior to lobectomy for lung cancer. In each case, 20 to 30% of the Figure 8. Remaining short cylinder of compressed lung and proximal portion of Spiration VALR elastomer sleeve following removal of distal compressed lung and sleeve. affected lobe was compressed with a single device applied to a portion of the lobe not involved with cancer. Compressed lung inside the distal portion of the sleeve was resected after lobectomy. Lobe reinflation following resection showed no air leaks or tissue trauma. 35 Development of a thoracoscopic VALR system is underway (S. Springmeyer; personal communication; October 2003). Conclusion The value of LVRS in selected patients has been demonstrated in a large randomized controlled trial. 11 Efforts are underway to achieve similar beneficial results with minimally invasive techniques. Further study is needed to determine the optimal minimally invasive method for lung volume reduction and to compare the results of minimally invasive techniques directly with surgical lung volume reduction. Bronchoscopic lung volume reduction may permit lung reduction in patients with previous thoracotomy or pleural adhesions who would currently be excluded from surgical lung volume reduction. Bronchoscopic valve insertion may be used to predict outcomes of lung volume reduction before contemplating surgery. The preclinical and early clinical trials with minimally invasive lung reduction are promising. With further careful study, the risk/benefit profile of these procedures will be determined, allowing patients with emphysema and their physicians to choose among a number of viable options for lung volume reduction. Figure 7. Spiration VALR elastomer sleeve using gentle vacuum pressure to draw lung tissue into the sleeve. References 1 Snider G, Thurlbeck W, Bengali Z. The definition of emphysema: report of a National Heart, Lung, and Blood Institute 782 Minimally Invasive Techniques

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