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Jacksonville, FL
Dr. Keller is Professor of Medicine, Mayo Clinic Jacksonville.
Correspondence to: Cesar A. Keller, MD, FCCP, Professor of Medicine, Medical Director, Lung Transplant Program, Mayo Clinic Jacksonville, 4205 Belfort Rd, Suite 1100, Jacksonville, FL 32216; e-mail: keller.cesar{at}mayo.edu
It has been over 12 years since Wakabayashi and colleagues1 reported preliminary beneficial results using laser-induced lung volume shrinkage via unilateral thoracoscopy while attempting to improve functional capacity in patients with severe emphysema, and over 8 years since Cooper and coworkers2 reported dramatic improvement in the lung function of such patients by surgically reducing lung volume bilaterally in emphysema patients with predominantly upper lobe disease, using stapling devices via sternotomy. This approach represented a modification of the original surgical concept by Brantigan and Mueller,3 who performed surgical lung volume reduction surgery (LVRS) via bilateral thoracotomies in emphysematous patients almost 50 years ago. Although most reported trials agree in the concept that well-selected patients with severe emphysema derive benefit from LVRS, producing improvement in pulmonary function,4 exercise capacity,5 6 and quality of life,7 there has been considerable debate throughout this time regarding the optimal surgical approach to achieve this end. In most reported surgical outcomes from patients undergoing LVRS, prolonged air leaks are the most common complication.
Several facts were learned about LVRS from various clinical trials. It was shown that surgical LVRS (by sternotomy or thoracoscopy), using stapling devices for the resection of diseased portions of the lung, was superior to laser therapy, having less incidence of air leaks and superior functional benefit.8 It was also shown that bilateral LVRS in one surgical stage was preferable to sequential unilateral LVRS through two separate surgical events.9 10 It also has been shown that the careful selection of patients is crucial to avoid disaster and to enhance favorable outcomes. Published results from the National Emphysema Treatment Trial (NETT) established several important points. Patients with very low FEV1 (ie, < 20% predicted), with very low carbon monoxide diffusion capacity (ie, < 20% predicted), and with evidence of homogeneously distributed emphysema by CT scanning have excessive 1-month and 6-month mortality rates (25% and 35%, respectively) when undergoing surgery.11 The health-related quality of life for these subjects either did not change, decreased, or ended in death in this subgroup of patients. Therefore, they should not undergo LVRS. In reported data derived from 1,218 patients with severe emphysema, randomized through the NETT study, 580 received surgery, 406 by median sternotomy and 174 via bilateral video-assisted thoracoscopy.12 The 90-day mortality rate was 7.9% in the surgical group. There was no advantage in survival comparing sternotomy to thoracoscopy. The same study defined a subgroup of these patients who had the best outcomes after undergoing surgery. Patients were characterized by a heterogeneous type of emphysema and by predominant disease in both upper lobes, with low baseline exercise capacity (defined as tolerance for < 10 W of workload in a bicycle ergometer for women, and < 40 W for men). These patients derived significantly better survival rates than medically treated subjects, and they showed significant improvement in exercise capacity and better quality-of-life scores compared to medically treated patients. The NETT study has thus defined which patients should avoid LVRS and which patients are most likely to benefit from such a procedure. The surgical approach (sternotomy vs thoracoscopy) probably should be decided by the preference and expertise of the surgeon.
For those patients undergoing LVRS, the morbidity derived from persistent air leaks following surgery continues to be the most common postoperative complication. Recently, Ciccone and collaborators13 reported the results of the long-term outcome of LVRS in 250 consecutive patients who were observed for up to 5 years. Prolonged air leaks were the most common surgical complication in their series, with 45% of patients (113 patients) having persistent air leaks for > 7 days, and 8 patients requiring surgical reexploration. Throughout the history of LVRS, multiple surgical manipulations have been reported to reduce the incidence or length of time of air leaks. Buttressing the staple line with bovine pericardium has been one of the most popular variations in surgical technique.14 15 16 Other authors have used talc poudrage,17 the application of various kinds of glues and sealants,18 19 and even the creation of pleural tents to cover the staple lines,20 all of which are reflections of the frustrating fact that it is hard to place air-tight sutures in lung tissue destroyed by emphysema. When air leaks are persistent, surgical reexploration can be attempted, although it is rarely successful, or patients are discharged home with Heimlich valve devices to allow the closure of air leaks after prolonged observation.21 Large air leaks can be further complicated by massive subcutaneous emphysema and, in some cases, by respiratory failure.
In this issue of CHEST (see page 633), a new approach is proposed by Steven Mink and coworkers. They describe an innovative surgical system that allows rapid resection of emphysematous tissue to produce effective surgical lung volume reduction, while avoiding the occurrence of air leaks.
The authors created an elegant emphysema model in 14 dogs undergoing multiple intrabronchial administration of papain, until the total lung capacity of these animals increased to 125% of baseline and functional residual capacity increased to 150% from baseline. The dogs developed marked decreases in flow rates. Seven of these dogs underwent LVRS via sternotomy, and seven were used as controls. To resect lung tissue, Mink et al used a prototype of a novel vacuum-assisted lung capture and reinforcement system (VALR Surgical System; Spiration Inc; Redmond, WA). This device consists of an implantable soft silicone cylindrical sleeve loaded inside a larger and rigid cylindrical introducer with an adapter to apply suction on its distal end. The vacuum is used to suction and drag the targeted lung tissue into the soft inner cylindrical sleeve. Once deployed, the radial traction of the silicone sleeve compresses lung tissue, producing volume reduction. Once the targeted lung is captured, the rigid cylinder is released and the soft compression sleeve with the lung tissue captured inside prevents the reexpansion of the lung tissue. The proximal section of this sleeve is sutured using U-stitches, and the sleeve is resected above the suture line. In most cases, they used one silicone sleeve to reduce the right upper lobe, and two sleeves to reduce the left upper lobe. They observed no air leaks in any of the surgically treated dogs. Chest tubes were removed within 4 h in all animals. Follow-up of pulmonary function revealed a significant reduction in total lung capacity, functional residual capacity, and residual volume among surgically treated dogs compared to controls. Likewise, significant improvements in pressure-volume curves and expiratory flows following lung reduction occurred at 1 and 6 months among surgically treated dogs compared with controls.
The animals were killed after the 6-month evaluation. In most animals that undergo surgery, the implanted devices were found in place covered by a thin fibrotic encapsulation limited to the silicone material, with the lung tissue inside the device appearing fibrotic and contracted within the device. Migration of the device was observed in two instances. Histologically, the tissue within the devices showed coagulative necrosis and chronic inflammation. Fibrotic encapsulation of the devices was described as being complete, with minimal extension to lung or pleura. In two of the seven animals operated on, there was histologic evidence of pyogranulomatous inflammation in the area associated with the devices, and cultures of such areas grew Pseudomonas aeruginosa, without evidence of infection in the surrounding nonreduced lung tissue.
The future of LVRS as a therapeutic alternative for emphysema patients in the United States is still undecided. Although the process of patient selection has been refined and the target population that may derive significant benefit from this technique has been clearly defined by the NETT trial, it remains to be seen whether this is a procedure that will be covered by Medicare and major insurance companies. If this procedure continues to be offered to selected emphysema patients, then the use of a device like the one proposed by Mink et al will likely find a place in the armamentarium of the thoracic surgeons performing these procedures. Larger animal studies will be required to define better the role of possible infection in the small portions of lung tissue captured within the piece of silicone cylinder that remains attached to the surgical site, and controlled randomized human trials will be required to show that this device or a variation of it can indeed be technically used in human lungs with advanced emphysema, which will pose new challenges. The anatomic characteristics of the human chest cage may pose limitations to the use of a large and rigid device that can be used more easily in the more flexible canine thorax. Likewise, human cases of emphysema frequently are associated with other complicating factors, such as pleural thickening and fibrosis, scarring, and presence of small nodules. These factors may pose a different resistance for this tissue to be captured within a silicone sleeve compared to the clean papain-created model.
Nevertheless, this is a novel idea to approach and resolve a frustrating problem that commonly complicates the outcomes of emphysema patients who undergo LVRS.
References
This article has been cited by other articles:
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  M. H. Cho, A. Malhotra, D. M. Donahue, J. C. Wain, R. S. Harris, D. Karmpaliotis, and S. R. Patel Mechanical ventilation and air leaks after lung biopsy for acute respiratory distress syndrome. Ann. Thorac. Surg., July 1, 2006; 82(1): 261 - 266. [Abstract] [Full Text] [PDF]
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