Endoscopic One-Way Valve Implantation in Patients With Prolonged Air Leak and the Use of Digital Air Leak Monitoring

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1 Endoscopic One-Way Valve Implantation in Patients With Prolonged Air Leak and the Use of Digital Air Leak Monitoring Irene Firlinger, MD, Elisabeth Stubenberger, MD, Michael Rolf Müller, MD, Otto C. Burghuber, MD, and Arschang Valipour, MD Department of Respiratory and Critical Care Medicine, Ludwig-Boltzmann-Institute for COPD and Respiratory Epidemiology, Otto Wagner Hospital, and Department of Thoracic Surgery, Otto Wagner Hospital, Vienna, Austria Background. Prolonged alveolar-pleural air leaks are associated with increased morbidity and mortality. Endoscopic valve therapy has been recently introduced as a potential less invasive treatment option. We aimed at quantifying the effects of valve therapy on air leak flow and clinical outcomes in patients with prolonged air leaks. Methods. We report on a series of 16 patients with high comorbidity and evidence of continuous air leak flow in whom chest tubes remained in place for at least 7 days. After identification of the source of the air leak by use of the balloon occlusion technique, endobronchial one-way valves were implanted. Digital chest tube monitoring was used to assess air leak flow before, during, and after valve implantation until chest tube removal. Results. The source of the air leak was endoscopically identified in 13 patients (81%). After valve implantation, air leak flow decreased significantly from ml/min to ml/min immediately after the intervention (p < 0.001). The mean duration of chest tube drainage was 18 8 days before and 9 6 days after the intervention (p < 0.01). Ten patients were considered responders, and 3 patients were nonresponders. Responders demonstrated consistent air leak flow levels below 100 ml/min until chest tube removal. Long-term follow-up was available for 9 patients. No adverse events related to the valve implants were reported at follow-up. Seven patients underwent valve removal without any further complications. Conclusions. Endoscopic implantation of one-way valves leads to a significant reduction in air leakage flow and may thus be a valuable treatment option in patients with prolonged air leakage. (Ann Thorac Surg 2013;95: ) 2013 by The Society of Thoracic Surgeons Prolonged pulmonary air leaks are abnormal communications between the bronchial tree and the pleural space that persist for more than 7 days despite continuous drainage of the thoracic cavity [1]. The presence of an air leak is associated with high morbidity and mortality, prolonged hospital stay, and increased use of health care [2]. Patients with underlying pulmonary disease and comorbidities are at a particularly increased risk for prolonged air leaks. Surgical procedures are considered the standard care to treat prolonged air leaks. An increasing number of patients, however, are high-risk surgical candidates who have underlying respiratory comorbidities or are in poor general condition. Thus, there is an urgent need for minimally invasive treatment options. Endoscopic techniques to treat (peripheral) air leaks aim at selectively blocking airways that are connected with the injured pleural surface. The instillation of sclerosing agents, however, has shown little efficacy and variable patient tolerance [2]. Watanabe and coworkers [3] reported on 63 patients who received silicone-made bronchial fillers (Watanabe Spigots, Novatech, France) to treat patients with intractable pneumothorax and pulmonary fistula. Although the air leak in the majority of patients in that study was either reduced or stopped with these implants, only 57% of patients treated were liberated from their chest tubes. Furthermore, a recent study suggests a moderate risk of respiratory complications associated with the implantation of spigots [4]. More recently, the implantation of endobronchial one-way valves has been studied in the management of prolonged pulmonary air leaks [5 7]. The decision to target airways for valve treatment in these studies, however, was based on visual assessment of the chest tube connected to water seal systems. Furthermore, there has been no systematic long-term follow-up as far as we are aware. The present study used a digital chest tube monitoring device both as an adjunct during endoscopic air leak identification and to quantify the effects of valve implantation in a clinical case series of prolonged air leaks. Accepted for publication Dec 7, Address correspondence to Dr Valipour, Department of Respiratory and Critical Care Medicine, Ludwig-Boltzmann-Institute for COPD and Respiratory Epidemiology, Otto-Wagner-Hospital, Vienna, 1140, Austria; arschang.valipour@wienkav.at. Dr Valipour discloses financial relationships with Pulmonx and Spiration by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc

2 1244 FIRLINGER ET AL Ann Thorac Surg ENDOSCOPIC TREATMENT OF AIR LEAKS 2013;95: Patients and Methods Patients Nineteen consecutive patients were evaluated between May 2010 and May Patients included in the study had to demonstrate persistent continuous air leak, defined as intrathoracic chest tube duration for more than 7 days despite conservative therapy, surgical therapy, or both, with an air leak flow of at least 100 ml/min. Patients referred for evaluation of endoscopic treatment were considered not to be good surgical candidates because of high comorbidities or previous failed surgical treatment of the air leak. Patients were excluded in the presence of intermittent or low-flow air leak [8] or if they were unwilling to undergo the procedure. Bronchoscopy and Valve Placement Flexible bronchoscopy with a 2.8-mm working channel videobronchoscope (Olympus Europa Holding GmbH, Olympus Europe) was performed with the patients under general anesthesia by use of a rigid bronchoscope for mechanical ventilation. Rigid bronchoscopy was used as part of the standard procedure for endoscopic interventions at our institution. Mechanical ventilation was performed by use of superimposed high frequency jet ventilation (TwinStream, Carl Reiner Medizintechnik, Austria). Air leak flow levels before, during, and after the intervention were recorded with a digital chest tube monitoring device (Thopaz-System, Medela AG, Baar, Switzerland). Before bronchoscopy the suction level was standardized at 10 cm H 2 O in all patients. Identification of the source of the air leak was performed by the endoscopic balloon occlusion technique. In a first step, a balloon catheter passed through the working channel of the bronchoscope was inflated in the suspected lobar bronchus. Balloon occlusion of the targeted lobar bronchus was continued for at least 2 minutes to ensure sufficient time for the Thopaz system to respond to a reduction in air flow. In the case of a reduction of at least 50% in air leak flow during continuous observation of the digital chest tube monitor, the balloon catheter was deflated and the searching process was extended to segmental and then subsegmental bronchi. The process was repeated to identify airways that, when occluded, offered the greatest reduction in air leak rate. Only those airways with a reduction of at least 50% in air leak flow levels, air leak flow below 100 ml/min during balloon occlusion, or both were targeted for valve placement. The cutoff point of 100 ml/min has not been investigated systematically before; however, according to Cerfolio and Bryant [9] that point has been considered a small air leak and has proved to be useful in our clinical setting. If several affected bronchi were apparent, the segmental bronchus where the blockade by balloon catheter was most effective in reducing air leakage was occluded first, followed by valve treatment in other bronchi that fulfilled the already mentioned criteria for air leakage flow reduction. However, when the goal of air leak reduction was achieved by occlusion of the first segmental bronchus, no further valves were implanted. After the procedure, suction on the digital monitoring device was kept at 10 cm H 2 O until chest tube removal. If the source of the air leak could not be allocated to a segmental or subsegmental bronchus. Endobronchial valve treatment was not performed. Two different endobronchial valve systems were used: the IBV Valve System (Spiration, Inc) and the Zephyr Endobronchial Valve (Pulmonx Co.). These valves have received European Conformity certificates and thus can be used in clinical practice for both air leak and emphysema treatment in Austria. The IBV Valve System consists of a nitinol frame and a polymer membrane and has the shape of an umbrella. The frame has five flexible anchors that secure to the mucosal wall at a controlled depth. The Zephyr Endobronchial Valve is made of a silicone-based one-way valve in a self-expanding nitinol retainer. Both valves are designed to block air entry but to allow the escape of air and secretions during expiration or coughing. The decision to choose either valve was based on the bronchial anatomy during endoscopy. These valves were delivered to the target airway by use of a flexible catheter. The valves were compressed into the distal tip of the delivery catheter by a valve loading system supplied with the system. The delivery catheter was then passed through the working channel of the bronchoscope and guided to the target airway. After valve implantation, patients were allowed to recover from anesthesia according to standard practice. Their vital signs were closely monitored and a chest roentgenogram was used to assess valve placements and target lung inflation status. Air leak flow levels were recorded twice daily during the morning and evening rounds until chest tube removal. Owing to the lack of generally accepted recommendations with respect to chest tube management in patients with prolonged air leakage, the final decision about chest tube removal in this case series was left to the discretion of the treating physician and thus was based on individual clinical experience. Patients were considered responders if chest tube removal was successful without the need for further interventions. Patients were considered nonresponders if air leak persisted or recurred despite valve implantation with the need of further interventions or long-term chest tube placement. The decision about alternative treatment was left to the treating physician. Patients who were successfully treated with valves (responders) made a follow-up visit after 3 months for optional valve removal; thereafter, the clinical follow-up time was extended to 6 months. The following data were collected for each patient: demographic information; the cause of the air leak; Charlson Comorbidity Index score [10]; American Society of Anesthesiologists score [11]; pulmonary function test results; duration of chest tube drainage; average air leak flow before, during, and twice daily after the intervention until chest tube removal (the average of two measurements is reported); the need for other interventions to treat the air leak; length of hospital stay; and mortality.

3 Ann Thorac Surg FIRLINGER ET AL 2013;95: ENDOSCOPIC TREATMENT OF AIR LEAKS Fig 1. Patient selection algorithm. (BPF bronchopleural fistula.) 1245 Digital Air Leak Monitoring: Mode of Action Through the double-lumen tubing and the two integrated pressure sensors, Thopaz continually measures and compares the pressure at the patient s chest with the set negative pressure. In case of a persistent air leak, Thopaz will run to maintain the prescribed vacuum; in the event of too high negative pressure within the pleural cavity, Thopaz will automatically reduce the pressure back to the set level. The integrated sensor technology of the Thopaz further allows the detection of fluid and clots in the double-lumen tubing, whereby clots will always be cleared first if possible. When occlusions cannot be cleared, a message will occur on the display followed by an audible notification. These Thopaz functions allow for active regulation of the pressure at the prescribed level at the patient s chest (eg, set at 20 cm H 2 O). In case of no air leak and when the vacuum level is set below the patient s own intrapleural pressure (eg, set at 5 cm H 2 O), Thopaz is in a monitoring mode, starting to regulate only in case of a recurring air leak. All procedures were performed under compassionate use regulatory provisions, and each patient signed a written informed consent. The ethics committee of the Vienna City Council approved data collection for this case series. Simple descriptive statistics were conducted to determine statistical significance and frequency distributions. Results Three patients with intermittent air leak were excluded, leaving 16 patients with evidence of continuous air leakage flow (Fig 1). Table 1 illustrates the patient characteristics, including results of lung function tests. The majority of patients were smokers, with a high prevalence of comorbid disease. Table 2 provides information on the underlying causes of the prolonged air leaks, prior interventions, average duration of chest tube placement before and after bronchoscopy, and target sites of valve placement in these patients. All procedures were performed by the same team were uneventful, showed no evidence of anesthesiologic complications, and were followed by a stable postinterventional course. The source of the air leak was not identifiable by balloon occlusion technique in three patients (ie, despite repeated attempts at balloon occlusion on various lobar levels, there was no reduction in air leak flow during the procedure, suggesting that the air leak was dispersed into different lobes). These patients had the chest tube in place for days after the index date. Thus, 13 patients (81%) received endobronchial valve treatment within one session. The mean duration of chest tube drainage before the intervention in this group was 18 8 days (median, 17 days, including interquartile range 11 to 23 days). The suction levels at the time of inclusion varied between 8 and 20 cm H 2 0. The mean air leakage flow recorded at a standardized suction level of 10 cm H 2 O before bronchoscopy was ml/min. Overall, a mean standard deviation of valves were implanted. The mean procedure time was 30 5 minutes from the beginning to the end of bron- Table 1. Patient Characteristics Characteristics Values Age, y Female 16% Smoking history 53% (29 20 pack years) BMI, kg/m Spirometry FEV1, L (% predicted) (74 16) FVC, L (% predicted) (82 14) FEV1/FVC Comorbidities COPD n 9 (47%) Arterial hypertension n 9 (47%) Diabetes mellitus n 4 (21%) Cancer n 7 (37%) Alcohol abuse n 3 (16%) Cardiac insufficiency n 3 (16%) Systemic rheumatic disease n 2 (11%) Charlson Comorbidity Index score ASA physical status The data is presented as means SD, % study population, and/or absolute values. ASA American Society of Anesthesiologists; BMI body mass index; COPD chronic obstructive pulmonary disease; FEV1 forced expiratory volume in 1 second; FVC forced vital capacity.

4 Table 2. Causes of Prolonged Air Leakage, Chest Tube Management, and Treatment Sites in Patients Treated With Endobronchial Valves No. Cause of BPF Prior Interventions Duration of Drainage Before Valve (d) Treated Lobe Segments Valve Type No. of Valves Duration of Drainage after Valve (d) Responders 1 Empyema Chest tube 27 LLL LB 9, LB 10 Spiration Pulmonary metastasis Thoracotomy, 23 LLL LB 6 Spiration 1 5 lobectomy 3 Empyema VATS: 31 RLL RB 8 Spiration 1 15 decortication 4 Pleural mesothelioma Thoracotomy, 20 LUL LB 3 Spiration 1 1 radical pleurectomy 5 Pleural mesothelioma Thoracotomy, 11 RUL Stem bronchus Pulmonx 1 5 radical pleurectomy 6 Pleural mesothelioma Thoracotomy, 8 RUL RB 1, RB 2, RB 3 Spiration 3 9 radical pleurectomy 7 Empyema Chest tube 14 LLL LB 10 Pulmonx Pneumothorax Thoracotomy 3: 30 RUL RB 2, RB 3, RB 5 Pulmonx 3 18 muscle flap, thoracic patch, pleurodesis 9 Empyema Thoracotomy: 14 LLL LB 9 Spiration 1 4 decortication 10 Lung cancer with malignant Chest tube 10 RUL Stem bronchus Pulmonx 1 6 fluidopneumothorax Nonresponders 11 Bronchial carcinoma Thoracotomy, 17 RUL RB 2, RB 3 Spiration 2 12 lobectomy 12 Bronchiectasis Thoracotomy, 8 RLL Stem bronchus Spiration 1 10 lobectomy 13 Pneumothorax Chest tube 19 LUL LB 3 Spiration 1 21 BPF bronchopleural fistula; LB left bronchus; LLL left lower lobe; LUL left upper lobe; RB right bronchus; RLL right lower lobe; RUL right upper lobe; VATS video-assisted thoracic surgery FIRLINGER ET AL Ann Thorac Surg ENDOSCOPIC TREATMENT OF AIR LEAKS 2013;95:

5 Ann Thorac Surg FIRLINGER ET AL 2013;95: ENDOSCOPIC TREATMENT OF AIR LEAKS 1247 Fig 2. Mean air leakage flow before, immediately after, and within 10 days of endoscopic one-way valve implantation in responders and nonresponders. choscopy. Air leak flow in treated patients decreased significantly to ml/min immediately after valve implantation (p 0.01 compared with baseline). Ten patients were considered responders and 3 patients were considered nonresponders according to the predefined criteria. Figure 2 demonstrates the air leak flow trend over time in responders and nonresponders. All nonresponders experienced a recurrence of air leak flow within 24 hours after valve implantation. By contrast, responders consistently had air leak flow levels below 100 ml/ min after the procedure (p 0.01 responders vs nonresponders for all time points after valve implantation). The average chest tube duration in the total group of patients receiving valves was 9 6 days (median, 8 days; interquartile range, 5 to 12 days; p 0.01 before vs after valve treatment). Responders had the chest tube removed at days after the intervention. Digital air leak flow monitoring demonstrated zero flow in these patients at the time of chest tube removal. The 3 nonresponders had the chest tube in place for 14 6 days after the treatment date, with evidence of persistently elevated air leak flow. Of these, 1 patient died of progression of lung cancer 12 days after valve implantation, and 2 patients underwent surgical interventions, including one anatomic resection (10 days after valve placement) and one surgical closure with a thoracic patch (21 days after valve placement). The latter patient required postoperative intensive care unit monitoring for 14 days before attending a step-down unit and final discharge. There was no difference in clinical outcomes with the two different types of valves used or with the different sizes of valves. Follow-Up Long-term follow-up was available for 9 patients at an average of months. No adverse events related to the valve implants were reported at follow-up. Seven patients underwent valve removal by use of flexible bronchoscopy and grasping forceps under sedation and spontaneous breathing without any further complications. At bronchoscopy there was no evidence of valve migration and only minor granulation tissue in 3 patients, without need of further intervention. Valves were not removed in 2 patients. One patient had persistent signs of bronchopleural fistula on computed tomographic scan, and 1 patient refused to undergo valve explantation. There were no valve-related complications in the patients in whom the valves were not removed. Comment Treatment of prolonged air leaks with endobronchial one-way valves is feasible, is safe, and resulted in successful treatment and reduction of air leakage flow in the majority of patients included in this report. Patients with prolonged air leaks are at an increased risk of morbidity and mortality in as high as 70% [2]. A variety of risk factors may contribute to prolonged air leaks, including preexisting lung disease, steroid use, prior radiochemotherapy, malnutrition, diabetes, or a combination of any of these conditions [2]. In fact, the patients reported here all had significant comorbidities and an elevated average American Society of Anesthesiologists score [11], which limited the safe application of surgical interventions and necessitated the use of less invasive therapy. Various endoscopic techniques have previously been reported for the treatment of prolonged air leaks, including lead shots [12], instillation of ethanol [13], fibrin glue [14 19], antibiotics [20], or albumin glutaraldehyde tissue adhesive [21]. Unfortunately, the instillation of these substances is frequently associated with irreversible obstruction of selected airways, marked foreign body reaction, or both. Alternatively, commercially available Watanabe spigots have been used to treat prolonged air leaks [3]. They act as airway or bronchial blockers; however, according to a recent report they are associated with the risk of spigot migration and considerable pulmonary morbidity, including atelectasis, lung abscess, and pneumonia [4].

6 1248 FIRLINGER ET AL Ann Thorac Surg ENDOSCOPIC TREATMENT OF AIR LEAKS 2013;95: The valves used in the present study are usually placed in the segmental or subsegmental airways leading to the air leak. The air is prevented from entering the pleural space, thereby enabling the lung to possibly reexpand and heal spontaneously. In contrast to other blocking devices, however, these valves allow for expiration and clearance of bronchial secretions, therefore reducing the risk of postobstructive pneumonia. In an experimental study using a sheep model, Fann and associates [5] were the first to demonstrate the usefulness of endobronchial valves to treat surgically created air leaks by eliminating antegrade flow. In addition to several case reports, two clinical multicenter case series have demonstrated the applicability and efficacy of valve treatment for air leaks. Gillespie and colleagues [6] studied 9 patients with prolonged air leaks who received IBV valves. The air leak persisted for many weeks in these patients before valve treatment (range, 18 days to 5 months). Similarly to our results, the authors were not able to identify the source of air leak in 2 patients. All 7 patients who received valve treatment were considered responders, and the chest tube was removed between 10 and 36 days after the intervention. A median of 3.5 valves (range, 2 to 10 valves) were used, and no valve expectorations were reported. That report did not include a systematic long term follow-up of the patients. Bronchial valves were removed in 5 of the 7 patients at a mean of 37 days (range, 14 to 55 days). In another recent case series of 40 patients with prolonged air leak, Travaline and colleagues [7] reported on the outcomes of Zephyr valve implantations after endobronchial identification of the airway source. The median duration of air leak before valve implantation was 20 days. Of those patients, 48% had a complete resolution of air leak, and 45% had a reduction of the air leak. The mean time from valve placement to chest tube removal for the 28 patients with complete information was 21 days. Furthermore, 6 patients in that report experienced adverse events, such as valve expectoration, oxygen desaturation, malpositioning of the valve, and pneumonia. The current study confirms and extends these earlier findings. First, we opted for the use of a digital chest tube monitoring device as guidance for identifying the source of air leakage. In most cases, air leaks are monitored with chest tubes connected to water trap systems, which may not be adequate to quantify the severity and provide trends on air leaks. Real-time quantification of the impact of balloon occlusion during the bronchoscopic procedure enabled objective assessment and targeting of the responsible airways. Using this approach, we were unsuccessful at localizing the source of the air leak in 3 patients. The latter observation can be explained either by multiple sources of air leak or by underlying collateral ventilation from adjacent lobes. Second, we aimed at identifying and treating the source of the air leak on a segmental or subsegmental level rather than on a lobar level in most cases. Thus, the number of valves inserted was reduced to a minimum; therefore, ventilation was preserved in untreated areas of the lung, and hypoxemia as previously reported was not observed [6]. Furthermore, the decision to use either of the commercially available valves based on the individual patient s anatomy appeared to be useful because we did not observe valve migration or malpositioning, as has been reported [6]. Third, our analysis suggests that responders can be discriminated from nonresponders within 24 hours of treatment, with evidence of recurrence of a large air leak in the latter group. Finally, the number of days with chest tube after endoscopic valve treatment reported here appeared to be fewer than in both previously reported clinical trials [6, 7], confirming the usefulness of digital chest tube monitoring in quicker chest tube removal in comparison with the conventional water-seal system [22]. Because the timing of chest tube removal was left to the treating physician rather than being guided by predefined criteria, however, some patients in this case series had the chest tube in place for more days despite zero air leak flow levels. Thus, although digital air leak flow monitoring was well used to remove the chest tube as early as possible in some patients, it was not well used in other patients. We believe that the lack of generally accepted recommendations for chest tube management in prolonged air leak may have contributed to this variable decision making. This scientific limitation, however, may have rather resulted in underestimation of the clinical benefits of valve implantation in our patients. Whether or not suction may have an impact on outcomes after valve treatment in prolonged air leak remains unanswered. According to earlier reports, suction might increase the flow through the fistula and thus prevent natural healing of parenchymal defects [23]. More recent data, however, suggest a potential advantage of higher suction levels, which were associated with earlier postoperative air leak closure [24]. To prevent confounding by different suction levels, we opted for a standardized suction level, which was applied immediately before the intervention and then kept for the remainder of the study. We similarly have to acknowledge other potential limitations in our study, including the absence of a control group, the relatively small sample size, and the heterogeneity of the underlying causes of air leak. Unlike conditions in the United States, where the use of one-way valves is restricted to air leakage after lung resection, both valves used in the present report have received European Conformity certification and thus can be used for the treatment of emphysema and air leak in Austria without specific restrictions. Thus, it needs to be acknowledged that the indications for valve treatment presented here may not be applicable to other countries; however, our findings suggest that the use of these devices is safe and effective in the majority of patients included. Notably, we did not observe any difference in the efficacy of the different type of valves used. Furthermore, endoscopic air leak identification by the use of digital chest tube monitoring was obtained during a single mode of ventilation (jet ventilation). Thus, the current observation should be repeated under other

7 Ann Thorac Surg FIRLINGER ET AL 2013;95: ENDOSCOPIC TREATMENT OF AIR LEAKS circumstances, such as spontaneous breathing or positive pressure ventilation. In conclusion, the implantation of bronchial one-way valves may be a valuable, less invasive treatment option in the management of prolonged air leakage. Air leakage flow monitoring is a useful adjunct in the diagnosis and treatment of prolonged air leakage. On the basis of the current data, prospectively conducted, randomized, controlled clinical trials are needed in which valve treatment is compared with other bronchoscopic techniques, surgical procedures, or both. References 1. Brunelli A, Monteverdi M, Borri A, Salati M, Marasco RD, Fianchini A. Predictors of prolonged air leak after pulmonary lobectomy. Ann Thorac Surg 2004;77: Lois M, Noppen M. Bronchopleural fistulas: an overview of the problem with special focus on endoscopic management. Chest 2005;128: Watanabe Y, Matsuo K, Tamaoki A, Komoto R, Hiraki S. 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Postoperative chest tube management: snapshot of German diversity. Interact Cardiovasc Thorac Surg 2012;15: INVITED COMMENTARY This article from Firlinger and colleagues [1] looks at a series of 13 patients with a prolonged air leak for longer than 7 days with air flow greater than 100 ml/min with use of a digital monitoring device (Thopaz, Medela, AG Baar, Switzerland), who underwent endobronchial valve (EBV) placement to treat the air leak with either the IBV-Valve system or the Zephyr Endobronchial Valve. Ten patients had their air leak significantly reduced after EBV placement, with chest tube removal days after the intervention. In 3 patients the air leak did not diminish, and their chest tubes were in situ twice as long after EBV placement; 2 patients required surgical intervention. These results provide additional data to suggest that EBVs have a role in the management of air leak. However, there are three important issues to highlight. First, the approved indications for EBV placement vary by region. In the United States, the Food and Drug Administration allows compassionate use of these valves through a humanitarian device exemption for postoperative air leaks after lobectomy, segmentectomy, or lung volume reduction. In Europe, the use of EBVs was cleared by CE Mark for the treatment of emphysematous patients and for damaged lung resulting in air leaks [2]. Second, although the results are promising, this trial and others have appropriately cautioned that randomized controlled data are required to truly evaluate which subset of patients may benefit from EBV placement in the setting of prolonged air leak. Third, patient selection and operator expertise remain critical in the decision to use EBV because the presence of collateral ventilation, valve misplacement, or failure to occlude are significant contributors to EBV failure. In comparison with previously published experiences, one of the unique features of this series is the use of a digital monitoring device to evaluate and 2013 by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc