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MMCTS (December 17, 2007). doi:10.1510/mmcts.2006.002121
Copyright © 2007 European Association for Cardio-thoracic Surgery

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Procedure


Bronchoscopic lung volume reduction{star}

Federico Venuta*, Erino A. Rendina, Tiziano De Giacomo and Giorgio F. Coloni

Department of Thoracic Surgery, University of Rome ‘La Sapienza’, Rome, Italy

* Corresponding author: * UniversitÀ di Roma ‘La Sapienza’, Cattedra di Chirurgia Toracica, Policlinico Umberto I, V.le del Policlinico 00100 Rome, Italy. Tel.: +39-06-4461971; fax: +39-06-49970735. sofed{at}libero.it


   Summary
Top
 Summary
Introduction
 Airway bypass
 Bronchoscopic lung volume...
 Results
 References
 
Emphysema is a debilitating lung disease continuing to be a major source of morbidity and mortality in the developed countries. Medical treatment is the mainstay of therapy and consists of smoking cessation, pulmonary rehabilitation, administration of bronchodilators and, when indicated, steroids and supplemental oxygen. Various surgical procedures have been promoted in the past to relieve dyspnoea and improve quality of life in patients with advanced emphysema; whilst early results were often encouraging, a sustained objective functional improvement was rarely achieved and most of those procedures were progressively abandoned. Despite controversies, LVRS has been shown to be beneficial to selected patients with end-stage emphysema when medical therapy has failed. There is no doubt that LVRS allows a significative functional improvement in a selected group of patients; however, it still carries a substantial morbidity, even if mortality is low at the centers with the larger experience. Patients with a most advanced functional deterioration show a higher surgical mortality and less impressive functional results, suggesting that LVRS should be considered more carefully in these situations. Bronchoscopic alternatives to the surgical approach have been recently proposed and some of them may play an important role in the future; in particular, the airway bypass and bronchoscopic lung volume reduction with one-way valves are certainly one step beyond on their way to clinical application. We hereby report the initial experimental and clinical experience with these new treatment options.

Key Words: Bronchoscopy • Emphysema • Lung volume reduction


   Introduction
Top
 Summary
 Introduction
Airway bypass
 Bronchoscopic lung volume...
 Results
 References
 
Emphysema is characterized by a permanent and anatomically irreversible enlargement of air spaces distal to the terminal bronchiole, accompanied by destruction of their walls, and without obvious fibrosis [1]. Medical treatment is the mainstay of therapy and consists of smoking cessation, pulmonary rehabilitation, administration of bronchodilators and, when indicated, steroids and supplemental oxygen.

Over the past 50 years many investigators have attempted to determine which factors influence survival of patients with COPD: when the FEV1 is lower than 30% of the predicted value, <50% of patients will survive for 3 years [2, 3] notwithstanding optimal medical therapy; thus, medical treatment certainly shows some limitations in the most advanced phases of the disease.

For this reason, various surgical procedures have been promoted in the past to relieve dyspnoea and improve quality of life in patients with advanced emphysema [4]; whilst early results were often encouraging, a sustained objective functional improvement was rarely achieved and most of those procedures were abandoned. Bullectomy is the only operation that has stood the test of time. Lung transplantation and lung volume reduction surgery (LVRS) are now established treatment modalities in selected patients.

Despite some controversies, LVRS has been shown to be beneficial to selected patients with end-stage emphysema [5, 6, 7]. The basic principle of this procedure is that removal of the most diseased parts of the hyperinflated lungs helps to restore the chest wall and diaphragmatic mechanics during respiration. There is no doubt that LVRS allows a significative functional improvement in a selected group of patients; however, it still carries a substantial morbidity, even if mortality is low at the centers with the larger experience [8, 9]. In particular, patients with very low FEV1 and either homogeneous emphysema or a very low DLCO are at high risk of death; recent data have also indicated that patients with non-upper lobe disease have a higher operative mortality [8, 9].

Bronchoscopic alternatives to the surgical approach have been proposed [10, 11, 12] and some of them may play an important role in the future; in particular, the airway bypass and bronchoscopic lung volume reduction with one-way valves are certainly one step beyond on their way to clinical application.


   Airway bypass
Top
 Summary
 Introduction
 Airway bypass
Bronchoscopic lung volume...
 Results
 References
 
This endoscopic procedure is based on the concept of ‘collateral ventilation’, first described by Van Allen and colleagues [13] in 1930. Collateral ventilation is defined as the ability of gas to move from one part of the lung to another through nonanatomical pathways (intraalveolar pores, bronchoalveolar connections, interbronchial channels). Collateral ventilation is present in normal lungs but in this physiologic setting it does not play an important role. In fact, in normal subjects the lower resistance of the normal airway (normal bronchial divisions) allows physiologic expiratory flows; in emphysematous lungs the destruction of alveolar septa creates a preferential low resistance route for collateral air flow through the newly opened windows; this is also possible because of the elevated airflow resistance in the bronchial tree related to COPD.

Macklem [14] suggested that creating extraanatomic pathways through the chest wall, between the surface of the lung and the skin, might alleviate hyperinflation and improve respiratory mechanics; in fact, ‘bypassing’ the small obstructed airways should allow trapped gas to exit from the hyperinflated emphysematous lung. The procedure proposed by Macklem was certainly a great idea; however, it could create some problems of acceptance and management in the clinical setting.

The concept of bypassing the small obstructed airways was recently rescued and simplified by the group of the Washington University in St. Louis [15]. They proposed that the creation of artificial communications between lung parenchyma and segmental bronchi would facilitate lung deflation and improve expiratory air flow and respiratory mechanics. In fact, on inspiration the regular airways can open, allowing air passage through normal channels; on expiration, the new passageways provide escape pathways bypassing the obstructed small airways.

The airway bypass procedure was initially performed by bronchoscopically puncturing the wall of segmental bronchi with a radiofrequency catheter and inserting a specially designed stent to keep open the internal bronchopulmonary communications. The potential benefit of this procedure was evaluated in the laboratories of the Washington University School of Medicine in St. Louis [15]. Lungs resected for lung transplantation were closed in a specially designed ventilation chamber and connected to a pneumotachygraph; the baseline FEV1 was measured and then flows were measured again after creation of stented passages. As a result of this study, the FEV1 increased from an average of 245±107 ml at baseline to 447±199 ml after the creation of three stented passages in each lung, and to 666±284 ml after six stented passages.

The second step has been designed to assess safety of the procedure and ability to avoid injury to the adjacent blood vessels. A specially designed Doppler probe (Bronchus Technologies Inc, Mountain View, CA, USA) was used to map the extrabronchial vessel distribution (Photo 1) [16]. This probe can be introduced through the operating channel of the flexible bronchoscope and used to scan from the inner surface of the bronchus the bronchial and pulmonary vessels located outside it. A preliminary safety study was performed in patients undergoing lobectomy for lung cancer and lung transplantation for emphysema. In this group of patients, after selecting the target site, the Doppler probe was withdrawn and a radiofrequency catheter was advanced to create a passage through the bronchial wall into the lung parenchyma (Video 1). No major complications were observed in that study [16]. Further laboratory observations and preliminary clinical work subsequently demonstrated that the new pathways progressively close within 2 to 3 weeks after the procedure, and that stents derived from intracoronary devices (Video 2) can prolong patency only for a limited period of time. The technique was subsequently simplified [17]. Once the appropriate site within the airway was identified, the Doppler probe is exchanged for a 22-gauge transbronchial needle that is advanced through the bronchial wall to create a small passage into the lung parenchyma. Aspiration through the needle is performed while slowly withdrawing it out of the bronchial wall. An angioplasty catheter with an expandable balloon diameter of 2.5 mm and a length of 30 mm is then inserted into the fenestration and dilated. A 3 mm-longx3 mm-wide balloon expandable stainless steel stent covered with a sleeve of silicone rubber is placed into the dilated passage. To avoid, or at least delay obstruction by granulation tissue, mitomycin C is delivered over the stent. This is an anti inflammatory and antifibrotic agent that has been reported to be useful in the treatment of airway stenosis [18]. Mitomycin C-treated stents showed a prolongation of patency, and the duration of stent patency is also associated with the number of weekly topical mitomycin applications, reaching 20 weeks for dogs treated for 9 weeks with topical application of the drug.


Figure 1
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  		Photo 1 Specially designed Doppler probe (See text).

 

Figure 1
Click on image to view video		 Video 1 After scanning the inner surface of the bronchus a target site is chosen, the cautery probe is introduced through the working channel of the fiberoptic bronchoscope and the bronchial wall is easily breached.
 

Figure 2
Click on image to view video		 Video 2 Specially designed stents are placed after creating holes.
 
A combined needle-and-balloon device has subsequently been developed to overcome the disadvantages encountered with the separate needle and balloon devices used in that study. To further improve patency avoiding multiple drug instillations within the airway a drug eluting stent has been proposed and experimented in an animal model. One hundred and seven controlled release Paclitaxel stents have been implanted in dogs and compared with 50 control stents with no impregnation; the follow-up at 12 weeks demonstrated that 65% of the Paclitaxel stents were patent while no control stent was patent (footnote 1). However, no long-term follow-up is available.


   Bronchoscopic lung volume reduction (BLVR) with one-way valves
Top
 Summary
 Introduction
 Airway bypass
 Bronchoscopic lung volume...
Results
 References
 
The airway bypass is not the only endoscopic procedure proposed to improve symptoms and quality of life in patients with emphysema. Other procedures have been described both experimentally and in selected clinical settings with the use of occlusive stents, synthetic sealants and unidirectional valves (footnote 2, [19, 20, 21, 22, 23]). These procedures were all designed to reduce hyperinflation and obtain atelectasis of the most destroyed functionless parts of the emphysematous lungs (heterogeneous emphysema).

It has been postulated that blocking an airway supplying the most overinflated emphysematous parts of the lung could cause atelectasis of these regions and contribute to alleviate symptoms. This has been experimentally demonstrated by Ingenito and colleagues [22] using sealants. Instead of sealants, other authors have used endobronchial devices working as one-way valves. These devices allow air to exit from the lung parenchyma but not to enter and should also allow a sufficient clearance of bronchial secretions.

There are basically two devices under clinical evaluation: the Spiration umbrella (Photo 2) [25] and the Emphasis one-way valve [25] (Photo 3). These devices are placed in the lobar, segmental or subsegmental bronchi to obtain lobar exclusion. The goal of the procedure is deflation of the target area in patients with heterogeneous emphysema, mimicking surgical lung volume reduction.


Figure 2
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  		Photo 2 The Spiration umbrella (see text). Courtesy of Dr. DE Wood, Seattle, Washington, USA.

 

Figure 3
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  		Photo 3 Zephyr new generation endobronchial valve.

 
The Umbrella implantable intrabronchial valve (IBV®) (Spiration Inc, Redmond, WA, USA) is a one-way valve designed for placement in the bronchi via flexible bronchoscopy. The valve is made of nitinol framework with five anchors that seat distally, engaging the airway without perforation, and providing stability. The proximal portion is made up of six support stents that expand radially. These struts are covered by a synthetic polymer forming an umbrella shape that conforms to the airway wall. The flexible membrane and struts allow conformation to the airways to improve sealing with minimal pressure on the mucosa. The valve is designed to limit airflow distally, but the membrane and support stents allow mucociliary clearance, air and mucous to flow proximally past the valve in order to allow decompression of collateral ventilation and to reduce the hazards of mucous impaction and obstruction pneumonia. The valve design includes a proximal center rod that allows repositioning or removal if required. This device has recently been evaluated in a North American multicenter trial with encouraging short-term results [24].

The Emphasys endobronchial valve (EBV) (Emphasys, Redwood City, CA, USA) is an endobronchial device designed to control and redirect airflow. The last generation of EBV is currently under evaluation in a multicenter prospective trial: the Zephyr endobronchial valve (Photo 3). This new valve is a device incorporating a one-way valve supported by a stent-like self-expanding retainer that secures the EBV in place during all physiological conditions, including coughing. The retainer is a self-expanding tubular mesh structure that is cut from nitinol (nickel–titanium) superelastic alloy tubing and processed to its final expanded dimensions. It is covered with silicone in order to create a seal between the implant and the bronchial wall; the silicone membrane is formed integrally with the struts of the self-expanding retainer component. When the EBV is delivered into the target bronchus, the retainer expands to contact the walls of the lumen. The valve vents during expiration and closes when flow is reversed during inhalation. The Zephyr EBV is provided in two sizes: the EBV 4.0 designed for bronchial lumens with diameters of 4.0–7.0 mm, and the Zephyr EBV 5.5, designed for bronchial lumens with diameters of 5.5–8.5 mm. The EBV can be easily seen at chest X-ray (Photo 4).


Figure 4
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  		Photo 4 Chest X-ray showing the Zephyr EBV in place in the right upper lobe.

 
These valves were initially placed in the operating room, with the patient intubated under intravenous anesthesia (Propofol infusion) and spontaneous assisted ventilation; however, the last generation devices can be deployed with the patient awake, spontaneously breathing under local anesthesia.

A flexible delivery catheter is used to place the valve in the targeted bronchial lumen. The catheter is constructed of a flexible stainless steel and polymer composite shaft. It has an actuation handle (Photo 5) on the proximal hand and a retractable polymer housing for containing the compressed Zephyr EBV on the distal end (Photo 6). A bronchial diameter measurement gauge made of flexible polymer is attached to the proximal end of the distal housing (Photo 6). This measurement gauge allows the user to visually (bronchoscopically) measure the diameter of the bronchial lumen prior to device deployment to verify that the size gauge of the valve is appropriate for the target lumen. The measurement gauge consists of two sets of flexible gauges. On the delivery catheter for the Zephyr EBV 4.0 the larger gauge spans a 7-mm diameter and the smaller gauge spans a 4-mm diameter, indicating the maximum and minimum treatable bronchial diameters, respectively, for this size of device. On the delivery catheter for the Zephyr EBV 5.5, the two gauges are sized to span diameters of 8.5  mm and 5.5 mm. The EBV is compressed into the retractable distal housing by the operator using a specifically designed EBV loader system. The loaded catheter is advanced to the target location through the operating channel of the fiberoptic bronchoscope and the valve is deployed by actuating the deployment handle, which retracts the distal housing and releases the EBV (Video 3). The delivery catheter is designed to be inserted through a 2.8-mm diameter working channel of a flexible bronchoscope.


Figure 5
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  		Photo 5 Actuation handle of the Zephyr EBV.

 

Figure 6
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  		Photo 6 Distal housing of the Zephyr EBV; flexible gauges are visible (blue wings).

 

Figure 3
Click on image to view video		 Video 3 EBV placement in a segment of the right upper lobe.
 

   Results
Top
 Summary
 Introduction
 Airway bypass
 Bronchoscopic lung volume...
 Results
References
 
After a series of animal experiments, more than 100 patients have been treated so far in pilot studies performed at several centers worldwide, with selection criteria similar to those for LVRS (Table 1): heterogeneous emphysema, FEV1 <30%, DLCO higher than 20%, no pulmonary hypertension, no hypercapnia. Heterogeneous emphysema was chosen since this type of disease shows less collateral ventilation than the homogeneous type; thus, it should be easier to achieve volume reduction and even atelectasis. The first ten patients treated with a first generation type of EBV were reported by Snell and colleagues [26]. They demonstrated that that type of bronchoscopic prosthesis could be safely and reliably placed into the human bronchi; however, symptomatic improvement was observed only in four patients, with no major change in radiographic findings, lung function, or 6 min walk distance at one month, although gas transfer improved from 7.47±2.0 to 8.26±2.6 ml/min/mmHg and nuclear upper lobe perfusion fell from 32±10% to 27±9%. Toma and colleagues subsequently reported on eight patients [27] undergoing unilateral volume reduction with a second generation of EBV. Five patients had emphysema judged too severe for volume reduction surgery and three refused the operation. After valve placement there was a 34% increase in FEV1 and 29% difference in DLCO; CT scans showed a substantial reduction in regional volume in four of the eight patients. The same group also reported that in a subgroup of patients in whom invasive measurements were performed, improvement in exercise capacity was associated with a reduction of lung compliance and isotime esophageal pressure-time product [28]. Another two series of patients treated with EBV have been reported [29, 30] with encouraging functional results. Along with the functional improvement (Table 1) there was also a subjective improvement benefit reported by most of the patients, even if a dyspnoea score was not available in all the series. Between 3 and 5 valves were placed in the target lobe and most of them received unilateral treatment. It has been demonstrated that the procedure can be safely performed with encouraging short-term results. Up to now the data available for this technique are still extremely limited and the follow-up is too short to be compared with other therapies.


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  		Table 1 Worldwide experience with bronchoscopic lung volume reduction

 
In our experience [30] we have observed 1 contralateral and 2 bilateral pneumothorax out of 17 treatments (2 staged bilateral); this complication has been experienced also by other authors [29]. However, with the second generation of EBV valves (eight patients – unpublished data) we have not observed this complication any more. Three of our patients showed granulation tissue obstructing one or more of the valves; this complication occurred with the first generation valves 6 months after placement. One patient had pneumonia in the non-treated lobe; this complication was easily managed with the administration of broad spectrum antibiotics. The functional improvement was statistically significant; in particular FEV1 markedly improved and the residual volume decreased: at 3 months more than 50% of the patients still show at least a 30% functional improvement; most of them required less supplemental oxygen and 7 out of 15 were able to stop it. We were not able to observe a complete atelectasis of the lobe where valves were implanted, even if it has been described by other authors; however, in most of the patients, the shape of the chest was redesigned. Exercise tolerance was also improved and remained stable after 3 months of follow-up. Contralateral BLVR could be attempted to obtain a second functional improvement when pulmonary function tests start to deteriorate again, as it is done for LVRS [31]. A contralateral BLVR was performed in two of our patients, but neither was required for functional reasons: both patients had pneumothorax on the contralateral side and valves were placed with the aim of stopping the air leak; this result was easily obtained, along with further functional improvement. With more experience, simultaneous bilateral insertion of the valves could be attempted. One of the advantages of the endobronchial lung volume reduction is that the procedure can be reversed and other treatments tried if necessary.

The short-term results with BLVR are encouraging, but long-term follow-up is certainly required, as well as multicenter trials, to evaluate the therapeutic potential of this procedure. The correct selection of candidates is crucial and the evaluation of the presence of collateral ventilation could become one of the criteria for inclusion [32, 33, 34]. Also other techniques are coming to our attention and should be carefully evaluated [35].

Even if it is certainly too early to speculate about the potential clinical implications of these new techniques, we can postulate that airway bypass could be indicated for patients with homogeneous emphysema while BLVR with one-way valves should be indicated for patients with a heterogeneous distribution of the disease. However, it could be more likely that in the future both systems could be employed in each patient to optimize results in the different areas of the lung.



   Footnotes
 
{star} The text of this article is partly reproduced from Ref. 12 with the permission of Elsevier Inc. Back

1 Choong CK, Phan L, Massetti P, Haddad FJ, Roschak EJ, Cooper JD. Patency of airway bypass stents is prolonged with use of drug eluting stents. American Association for Thoracic Surgery 85th Annual Meeting; April 10–13, 2005, San Francisco, CA; Paper F20, page 160. Back

2 Snell GI, Smith GA, Silovers AJ. Bronchoscopic volume reduction: a pilot study. ACCP Meeting 2001; paper 25. Back


   References
Top
 Summary
 Introduction
 Airway bypass
 Bronchoscopic lung volume...
 Results
 References
 

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