Ann Thorac Surg 2006;82:1880-1883
© 2006 The Society of Thoracic Surgeons
New Technology
Functional Comparison of Staple Line Reinforcements in Lung Resection
Douglas M. Downey, MDa,*,
Joseph G. Harre, DVMb,
Jerry W. Pratt, MDa
a Department of Surgery, Keesler Medical Center, Keesler Air Force Base, Mississippi
b Clinical Research Laboratory, Keesler Medical Center, Keesler Air Force Base, Mississippi
Accepted for publication February 22, 2006.
* Address correspondence to Dr Downey, Suite 7000, Miami Valley Hospital, One Wyoming St, Dayton, OH 45409. (Email: douglasdowney{at}hotmail.com).
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Abstract
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PURPOSE: Staple line reinforcement with bovine pericardium and expanded polytetrafluoroethylene during lung resections has shown reduction in air leak incidence and duration. Small intestinal submucosa and polyglycolic acid–trimethylene carbonate, have been introduced as new reinforcements for nonpulmonary staple lines. We hypothesize that reinforcement of staple lines in lungs with commercially available materials will decrease staple line leak at increased pressures.
DESCRIPTION: We evaluated 8 staple lines per reinforcement material (4 groups) and a control group (n = 40) in healthy living pigs. After resections (up to four per animal), the lungs were tested sequentially using hand ventilation to increasing pressures (5–75 cm H2O). The occurrence of pressure at which leaks was recorded.
EVALUATION: All reinforced staple lines exhibited higher mean leak threshold when compared with the controls; however only small intestinal submucosa achieved significance when compared with the controls.
CONCLUSIONS: Commercially available reinforcements allow pulmonary staple lines to tolerate higher intrabronchial pressures without demonstrating air leak. In addition, reinforcement with small intestinal submucosa imparts a significant advantage to the other reinforcements in terms of pulmonary staple line leak rate.
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Introduction
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In nonanatomic lung resection, gastrointestinal anastomotic stapling devices are often responsible for tearing small holes in the lung parenchyma that may lead to air leaks [1]. In addition, the lungs may be stretched and torn by the staples during reexpansion. The incidence of persistent air leak is approximately 15% for all patients undergoing thoracic procedures. Interventions to reduce air leaks have included buttressing the staple line with polydioxanone ribbon or glutaraldehyde-treated bovine pericardial strips, oversewing the staple margins with mattress sutures, using excised pleura as reinforcement, and using autologous blood by injecting it beneath the staple line [1]. In current clinical practice, the two most used reinforcements are bovine pericardium (Peri-Strips Dry TM [Biovascular, Inc, Saint Paul, MN]) and expanded polytetrafluoroethylene (ePTFE) (Seamguard [W.L. Gore & Associates, Inc, Flagstaff, AZ]).
Previous studies have shown that bovine pericardium and ePTFE impart an advantage to staple lines in terms of leak-threshold pressures in cadaveric lungs and isolated canine lungs and reduce the leaks experienced by patients undergoing thoracic procedures [1, 2]. Furthermore, Murray and colleagues [1] postulated that the optimal staple line reinforcement is one that would combine: (1) ease of use, (2) biocompatibility, (3) flexibility and strength, (4) air tightness, and (5) cost effectiveness [1]. A potential drawback to these materials is that neither is resorbable in pulmonary tissue [3]. A newer material composed of polyglycolic acid–trimethylene carbonate named Bioabsorbable Seamguard (W.L. Gore & Associates, Inc, Flagstaff, AZ) has the purported advantage of being completely resorbable [4]. Porcine small intestinal submucosa (SIS), another absorbable tissue matrix, has also recently been introduced as nonpulmonary reinforcement for stapler devices [5].
Our goal was to provide an objective comparison between four commercially available staple line reinforcements in a living model. By exposing the staple lines to incrementally increasing intrabronchial pressures, our experimental study assessed immediate postresection strength of reinforcement materials as well as unreinforced staple lines.
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Technology
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All procedures were approved by the Keesler Medical Center Institutional Animal Care and Use Committee and conducted within fully-accredited facilities (ie, Association for the Assessment and Accreditation of Laboratory Animal Care, International). The animals were housed and cared for in accordance with the guidelines of the "Institute of Laboratory Animal Resources' Guide for the Care and Use of Laboratory Animals" and applicable federal, Department of Defense, state, and local regulations.
Fourteen Yorkshire-cross pigs were used. The animals were anesthetized, endotracheally intubated, and maintained on isoflurane gas anesthesia. A median sternotomy was used to gain access to both lungs. We chose to evaluate 8 staple lines per reinforcement, in addition to an unreinforced control group of 8 (total, n = 40). The reinforcements we used were donated for this study: (1) porcine SIS (Surgisis [Cook-Biotech, Inc, Bloomingdale, IN]), (2) polyglycolic acid–trimethylene carbonate (Bioabsorbable Seamguard [W.L. Gore & Associates, Inc]) (3) bovine pericardium (Peri-Strips Dry TM [Biovascular, Inc]), and (4) ePTFE (Seamguard [W.L. Gore & Associates, Inc]). Approximately one third of each lobe was removed with a gastrointestinal anastomotic stapling device (60 mm–4.8; Auto Suture gastrointestinal anastomotic [United States Surgical, Norwalk, CT]). All pigs received bilateral lung resections on separate lobes, and the side and lobe were randomized. All animals received at least two resections, but no more than four. There were a total of 32 reinforced staple lines tested for integrity.
The staple lines were next assessed for durability. The chest cavity was filled with saline so that leaks would be identified by visualization of bubbles from the staple lines. Positive intrabronchial pressures were generated using hand-ventilation on an anesthesia machine (Ohmeda Modulus, GE Healthcare, Buckinghamshire, England) to hold incrementally increasing pressures of 5, 10, 20, 30, 40, 50, and 75 cm H2O for 60-second intervals. Pressures were not randomized to avoid unnecessary barotrauma to the lung parenchyma during measurements. Regardless of the pressure achieved, subsequent measurements were aborted once all staple lines exhibited leak. For this reason, not all staple lines were inflated to 75 cm H2O. All animals were euthanized at the conclusion of the experiment per protocol.
Analysis of variance was used to determine whether the location of the lobe resected influenced the leak rate (upper vs lower and right vs left). The log-rank test of the Kaplan-Meier survival was used to determine whether there was an advantage to reinforcement of the staple lines with the materials compared with the controls. In addition, we used analysis of variance of the Kaplan-Meier survival curves of all five groups to determine whether differences existed among the groups. Finally, the Breslow statistical analysis of the Kaplan-Meier survival was used to compare each of the experimental groups with one another. A p value of less than 0.05 was set as significant.
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Clinical Description
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Our data show a direct relationship between increased airway pressure and development of staple line leaks (Fig 1;
Table 1). We demonstrated a mean leak pressure of 44 cm H2O in unreinforced staple lines. No leaks were observed in either reinforced or unreinforced tissues that were less than 20 cm H2O. Comparisons made using analysis of variance among the burst pressures of the upper and lower lobes as well as the right and left lungs revealed that location of the resection did not influence the leak rate.
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Fig 1. Graph demonstrating the percent of staple lines that are leak free as a function of pressure (cm H2O). The leak rate was significantly improved with reinforcement of the staple lines with small intestinal submucosa (SIS). (BASG = bioabsorbable Seamguard [W.L. Gore & Associates, Inc, Flagstaff, AZ]; BP = bovine pericardium; ePTFE = expanded polytetrafluoroethylene.)
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Table 1. The Number of Staple Lines that Exhibited an Air Leak by Bubble Test at Nonrandomized Sequential Airway Pressure Challenges
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Staple lines reinforced with SIS had the highest mean leak pressure of 75 cm H2O (Table 2). When each of the experimental groups is compared with the control group using log rank analysis of the Kaplan Meier survival function, only SIS demonstrated a statistically significant difference (p < 0.04).
The analysis of variance had a p value of less than 0.001 for the five group comparison, demonstrating differences in survival between the five groups. The Breslow statistical analysis of the Kaplan-Meier survival function was used to compare each of the experimental groups with one another. When we used a p value of less than 0.05 as a threshold of significance, we determined SIS reinforced staple lines tolerated significantly higher pressures than the other three experimental groups without demonstrating leaks, despite the small number of reinforcements tested: SIS versus ePTFE (p = 0.005); SIS versus bovine pericardium (p = 0.019); and SIS vs Bioabsorbable Seamguard (p = 0.012).
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Comment
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Pulmonary staple line reinforcement with buttress materials has been shown to significantly decrease the duration of postoperative air leaks and duration of patient hospital stay in clinical trials. Unfortunately a cost benefit has not been demonstrated secondary to the cost of added materials [2].
Bovine pericardium and ePTFE have established predictable tissue response and biocompatibility in human pulmonary tissues. Small intestinal submucosa and Bioabsorbable Seamguard have established biocompatibility in nonpulmonary tissues [6–8]. Small intestinal submucosa is an acellular xenograft made up of mostly type I porcine collagen and has many applications in other areas as an absorbable matrix that may give a similar advantage in terms of staple line durability [8].
Murray and colleagues [1] compared air leak rates in reinforced staple lines as a function of pressure in a previously frozen, thawed human cadaveric model. The comparison of ePTFE, bovine pericardium, and unreinforced staple lines showed a clear benefit for reinforcement in the cadaveric lung [1]. The primary goal of our study was to assess efficacy of the reinforcements over an unreinforced staple line in a living model. In our study, only SIS showed a statistically significant advantage for lung reinforcement in terms of the intrabronchial pressures that the staple lines may tolerate without an air leak.
Our current study strictly assessed immediate staple line strength in healthy porcine lung tissue at different intrabronchial pressures. Intrabronchial pressure measurements in patients with chronic obstructive pulmonary disease have been reported to exceed 80 cm H2O attributed to the amplified airflow resistance in the larger bronchi in patients with asthma and advanced emphysema [9]. These measurements are taken in closed-chest models and may not reflect the same open-chest stresses to which we have subjected the staple lines in our experiments. Nevertheless it was our goal to expose the staple lines to supra-physiologic stresses to induce failure of the staple line, and thus assess the true strength that each reinforcement imparts. Furthermore this study does not take into account possible healing properties with time nor does it characterize the tissue reaction to the reinforcements in pulmonary tissues. This study does not assess the efficacy of the staple line reinforcement in diseased tissues, and additional studies in such a model may prove useful to further characterize a suitable reinforcement for gastrointestinal anastomotic staplers. Potentially, SIS may prove to be a more suitable material for reinforcement in selected individuals requiring nonanatomic lung resection due to its bioabsorbable profile.
It may be concluded from our data that reinforcement with SIS imparts a significant advantage in terms of the leak rate as a function of pressure. Although the performance of SIS is encouraging, one of the main drawbacks with SIS is that its clinical performance in human thoracic staple line reinforcement is undocumented; however, these experiments certainly show merit for clinical research on this reinforcement.
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Disclosures and Freedom of Investigation
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The source of all funds used to perform this study was the Department of Defense, protocol no. FKE 20040021A. The staplers used for this study were donated by United States Surgical (Auto Suture gastrointestinal anastomotic, United States Surgical, a division of Tyco Healthcare, Norwalk, CT). The buttress material was donated by the respective companies: small intestinal submucosa (Surgisis [Cook-Biotech, Inc, Bloomingdale, IN]); bovine pericardium (Peri-Strips Dry [Biovascular, Inc, Saint Paul, MN]), expanded polytetrafluoroethylene (Seamguard [W.L. Gore & Associates, Inc, Flagstaff, AZ]), and polyglycolic acid–trimethylene carbonate Bioabsorbable Seamguard (W.L. Gore & Associates, Inc, Flagstaff, AZ). The authors had full control of the design of the study, methods used, outcome measurements, analysis of data, and production of the written report.
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Acknowledgments
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The opinions and assertions contained herein are the private views of the authors and are not to be construed as the official policy or position of the United States government, the Department of Defense, or the Department of the Air Force. We thank Heather J. Williams, Danny J. Duke, Cheryl L. Osiek-Comer, and Steven J. Twitchell for their animal care and protocol support, and Walter Brehm, biostatistician, for his statistical analysis.
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Footnotes
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Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
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References
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- Murray KD, Ho CH, Hsia JY, et al. The influence of pulmonary staple line reinforcement on air leaks Chest 2002;122:2146-2149.[Abstract/Free Full Text]
- Miller JI, Landreneau RJ, Wright CE, Santucci TS, Sammons BH. A comparative study of buttressed versus nonbuttressed staple line in pulmonary resections Ann Thorac Surg 2001;71(1):319-322discussion 323.[Abstract/Free Full Text]
- Vaughn CC, Vaughn PL, Vaughn 3rd CC, et al. Tissue response to biomaterials used for staple-line reinforcement in lung resection: a comparison between expanded polytetrafluoroethylene and bovine pericardium Eur J Cardiothorac Surg 1998;13(3):259-265.[Abstract/Free Full Text]
- Franklin ME, Berghoff KE, Arellano PP, Trevino JM, Abrego-Medina D. Safety and efficacy of the use of bioabsorbable seamguard in colorectal surgery at the Texas Endosurgery Institute Surg Laparosc Endosc Percutan Tech 2005;15(1):9-13.[Medline]
- Downey DM, Michel M, Harre JG, Pratt JW. Functional assessment of a new staple line reinforcement in lung resection J Surg Res 2005[Epub ahead of print].
- Edelman DS. Laparoscopic herniorrhaphy with porcine small intestinal submucosa: a preliminary study J Surg Laparosc Surg 2002;6:203-205.
- Oelschlager BK, Barreca M, Chang L, Pellegrini CA. The use of small intestine submucosa in the repair of paraesophageal hernias: initial observations of a new technique Am J Surg 2003;186:4-8.[Medline]
- Kini S, Gagner M, de Csepel J, Gentileschi P, Dakin G. A biodegradable membrane from porcine intestinal submucosa to reinforce the gastrojejunostomy in laparoscopic Roux-en-y gastric bypass: preliminary report Obes Surg 2001;11:469-473.[Medline]
- Dekker E, Defares JG, Heemstra H. Direct measurement of intrabronchial pressure; its application to the location of the check-valve mechanism J Appl Physiol 1958;13(1):35-41.[Abstract/Free Full Text]
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Abstract
Introduction
