M-tip electro-ablation of pneumo-cysts for treatment of spontaneous pneumothorax as a secondary method to stapling: a confirmation study
http://www.100md.com
《血管的通路杂志》
M-tip electro-ablation of pneumo-cysts for treatment of spontaneous pneumothorax as a secondary method to stapling: a confirmation study
Noriyoshi Sawabata, Shin-Ichi Takeda, Masayoshi Inoue, Masaru Koma, Toshiteru Tokunaga and Hajime Maeda
Division of Surgery, Toneyama National Hospital, 5-1-1, Toneyama, Toyonaka, Osaka 560-8552, Japan. Department of Surgery (E1), Osaka University Graduate School of Medicine, Osaka Japan
Abstract
Background: We recently established new guidelines for our electro-ablation technique, which has been shown to be a ubiquitous, easy, and cost effective method secondary to stapled resection of pneumo-cysts for the treatment of pneumothorax. The present study was conducted as a confirmation of the effectiveness of this technique. Patients and methods: Between July 1998 and June 2003, 164 consecutive patients with spontaneous pneumothorax underwent surgery. Dependent lesions were resected using staplers. If found, residual lesions were ablated using M-tip electro-ablation (Group M). When the ablated pneumo-cysts were greater than 2 cm in diameter, pleural treatment was carried out by covering the surface with absorbable mesh sheets (Group L). Results: There were 7 cases (4.2%) of relapse of spontaneous pneumothorax and each underwent another operation due to the relapse. None of the lesions in the relapse cases received electro-ablation in the first operation. Relapse-free cases were 97/103 (94%) in Group N (no ablation group), 48/49 (98%) in Group M, and 12/12 (100%) in Group L (P=0.4). Comments: Our results demonstrated the safety and efficacy of our M-tip electro-ablation technique for pneumo-cysts as a secondary method to stapling. We considered that it was feasible for the treatment of spontaneous pneumothorax.
Key Words: Spontaneous pneumothorax; Ablation; Stapler; Electro-surgical unit
1. Introduction
Several methods are available to treat pneumo-cysts, of which surgical resection is the most commonly performed. The stapling method is also frequently used, because it is very easy to carry out [1–8], though it may have anatomic and quantitative limitations.
Ablation is considered a safe technique for the resection of pneumo-cysts [9–13], with the use of an electro-surgical unit the most ubiquitous and cost effective, while a laser technique is also often employed. We developed a new tip (M-tip) for use on an electro-surgical unit and previously conducted a prospective study to assess its clinical efficacy for electro-ablation of pneumo-cysts [11]. In cases with tiny lesions that remained after stapled resection of pneumo-cysts, there were no instances of pneumothorax relapse in patients who underwent the M-tip technique. However, relapse occurred in approximately 30% of cases with large pneumo-cysts that were ablated with the M-tip and without any pleural treatment.
Based on the results of that study, our group established guidelines for electro-ablation using the M-tip following stapled resection of pneumo-cysts during the treatment of spontaneous pneumothorax. The present report shows the results of treatment of spontaneous pneumothorax using those guidelines.
2. Patients and methods
2.1. Patient backgrounds
From July 1998 to June 2003, 164 consecutive patients (148 males, 16 females; age range 14–78 years, median age 35 years) with spontaneous pneumothorax underwent surgery at Toneyama National Hospital and their results were analyzed. The reasons for surgery were persistent air leakage for more than 7 days despite chest drainage in 41 cases, repeated spontaneous pneumothorax in 110 cases, persistent air leakage and repeat relapse in 6 case, and postoperative relapse in 6 cases. The involved side was right in 79 cases, left in 80 cases, and both in 5 cases. The method of access to inside of the thoracic cage used was thoracoscopic surgery in 145 cases and axillar thoracotomy in 19 cases.
2.2. Surgical techniques
Dependent lesions (ruptured pneumo-cyst or apical) were first resected using a stapler and all residual pneumo-cysts were ablated using an electro-surgical unit equipped with a ball-shaped tip, 8 mm in diameter and made of stainless steel, which can be used with any electro-surgical unit (M-tip, Senko Ika, Tokyo, Japan) [14]. The power level was set at 20 W using a Bovie X U (Hokusan, Tokyo, Japan) and 10 W using an MS-BM2 U (Senko Ika, Tokyo, Japan), with both units set to spray coagulation mode. The pneumo-cysts were first soaked with normal saline solution and then rubbed with the tip of an electro-coagulator to obtain adequate shrinkage (Fig. 1). Treatment ceased when white coloration and shrinking occurred. When the ablated pneumo-cysts were large (2 cm or more in diameter), pleural treatment was carried out by wrapping the surface with oxycellulose mesh seals (Surgicall, Ethicon, Tokyo, Japan). This technique is different from that of our previous report published in 2002 [11]. Pleurodesis was not carried out in any of the cases.
The patients were divided into 3 groups. Group N (n=103) included patients who underwent only stapled resection of pneumo-cysts and had no residual lesions, Group M (n=49) included those who underwent stapled resection of pneumo-cysts and then electro-ablation of tiny pneumo-cysts (less than 2 cm in diameter) with the M-tip, and Group L (n=12) patients underwent both stapled resection of large pneumo-cysts and electro-ablation of large pneumo-cysts (more than 2 cm in diameter) with the M-tip, after which the treated lesion surface area was covered with an oxycellulose mesh seal. Group N and group M were conducted with cases of primary spontaneous pneumo- thorax, while group L contented cases of secondary pnoeumothorax.
2.3. Patient follow-up
Data regarding the status of relapse were obtained by reviewing hospital records, or by contacting the patients or their families. All patients were followed-up by July 2003. The follow-up period was from 367–1760 days, with a median of 1275 days.
2.4. Statistical analysis
Statistical analyses of the data were performed using a factorial analysis of variance with a commercially available software package (StatView, version 5.0; Institute Inc. Tokyo, Japan). Statistical significance was calculated using Fisher's exact test, a 2-test, a t-test, and ANOVA as appropriate. Significance was assumed when the calculated P value was less than 0.05.
3. Results
3.1. Patient characteristics and indication of M-tip
The prevalence of gender, age, side of disease, and indication of operation are shown in Table 1. There were no statistically significant differences for gender or side of disease, however, Group L patients were older and had a significantly higher rate of persistent air leakage prior to surgery.
3.2. Surgery
There were no complications experienced by any of the patients during surgery. The average duration of the operation was 56±13 min in Group N, 63±14 min in Group M, and 118±22 min in Group L. The difference was not statistically significant between Group N and Group M (P=0.3). The thoracotomy methods used were VATS in 75 patients and axillar thoracotomy in 8 in Group N, VATS in 40 and axillar thoracotomy in 2 in Group M, and VATS in 4 and axillar thoracotomy in 5 in Group L.
Postoperative complications occurred in 4 (3.8%) Group N patients (n=103), of whom 3 had persistent air leakage for more than 7 days and 1 had postoperative bleeding that required a second operation. There was only 1 (2%) postoperative complication in Group M (n=49), which was persistent air leakage for more than 7 days. There was no statistically significant difference between Group N and Group M (P=0.7). In Group L patients (n=12), there were 5 cases (42%) of persistent air leakage, of whom 2 had a reoperation. The ratio of postoperative complications in Group L was significantly greater than in the other 2 groups (P<0.01).
3.3. Relapse of spontaneous pneumothorax
There were 7 cases of relapse of spontaneous pneumothorax after surgery and all underwent another operation thereafter, however, none of the relapse lesions had electro-ablation performed on them during the first operation. The leaking area was found in 4 of 7 cases. Three lesions were at the stapled line and the others were newly developed cysts which were different from ablated lesions. Adhesion was observed in all 7 cases but the grade was trivial. In addition, there was no adhesion at the region of electro-ablation. The relapse-free ratio (Fig. 2) was 97/103 (94%) in Group N (no ablation group), 48/49 (98%) in Group M, and 12/12 (100%) in Group L (Fig. 2), which were not significantly different (P=0.4).
4. Comments
Electro-ablation of pneumo-cysts as a secondary procedure to stapled resection was found to be safe in the present series of patients. Further, the ratio of relapse-free patients who underwent both stapled resection and electro-ablation with the M-tip was very high, and was similar to that of patients who received only a stapled resection of pneumo-cysts. In addition, the ruptured lesion in the lung of a patient who had received both stapled resection and electro-ablation was not in the area where electro-ablation had been carried out.
The two ablation techniques commonly used for pneumo-cysts are electro-ablation and laser ablation. Electro-ablation was first used in the late 1980s, during which the results were found to be acceptable, however, the rate of postoperative recurrence was approximately 10% [9], which was slightly higher than that of patients who underwent an operation without the ablation technique [1–8]. On the other hand, laser ablation methods have produced slightly better results in surgical cases of spontaneous pneumothorax [10,12,13], which are similar to our results in patients who underwent electro-ablation for tiny lesions with the use of the M-tip. Therefore, we consider that both electro-ablation using the M-tip and laser ablation are acceptable treatments for tiny pneumo-cysts.
Use of the M-tip for ablation of large pneumo-cysts is controversial, however, we believe it can be effective when combined with the covering technique used in the present Group L. Although our previous study showed that the rate of relapse was approximately 30% [11], no postoperative relapse of spontaneous pneumothorax was seen in any patients when the ablated lesion was covered using an absorbable mesh sheet.
The present results show that the M-tip technique for electro-ablation is a highly successful secondary method to stapling. We suggest that this ubiquitous, easy, and cost effective method is feasible for the treatment of spontaneous pneumothorax.
References
Inderbitzi RG, Leiser A, Furrer M, Althaus U. Three year's experience in video-assisted thoracic surgery (VATS) for spontaneous pneumothorax. J Thoracic Cardiovasc Surg 1994;107:1410–1415.
Naunheim KS, Mack MJ, Hazelrigg SR, Ferguson MK, Ferson PF, Boley TM, Landreneau RJ. Safety and efficacy of video-assisted thoracic surgical techniques for the treatment of spontaneous pneumothorax. J Thorac Cardiovasc Surg 1995;109:1198–1204.
Bertrand PC, Regnard JF, Spaggiari L, Levi JF, Magdeleinat P, Guibert L, Levasseur P. Immediate and long-term results after surgical treatment of primary spontaneous pneumothorax by VATS. Ann Thorac Surg 1996;61:1641–1645.
Mouroux J, Elkaim D, Padovani B, Myx A, Perrin C, Rotomondo C, Chavaillon JM, Blaive B, Richelme H. Video-assisted thoracoscopic treatment of spontaneous pneumothorax: technique and results of one hundred cases. J Thorac Cardiovasc Surg 1996;112:385–391.
Passlick B, Born C, Haussingger K, Thetter O. Efficiency of video-assisted thoracic surgery for primary and secondary spontaneous pneumothorax. Ann Thorac Surg 1998;65:324–327.
Hatz RA, Kaps MF, Meimarakis G, Loehe F, Muller C, Furst H. Long-term results after video-assisted thoracoscopic surgery for first-time and recurrent spontaneous pneumothorax. Ann Thorac Surg 2000;70:253–257.
Korner H, Andersen KS, Stangekand L, Ellingsen I, Engedal H. Surgical treatment of spontaneous pneumothorax by wedge resection without pleurodesis or pleurectomy. Eur J Cardiothorac Surg 1996;10:656–659.
75:Lazdunski LL, Chapuis O, Bonnet PM, Pons F, Jancovici R. Videothoracoscopic bleb excision and pleural abrasion for the treatment of primay spontaneous pneumothorax: long-term results. Ann Thorac Surg 2003;960–965.
Wakabayashi A. Thoracoscopic ablation of blebs in the treatment of recurrent or persistent spontaneous pneumothorax. Ann Thorac Surg 1989;48:651–653.
Sharpe DA, Dixon C, Moghissi K. Thoracoscopic use of laser in intractable pneumothorax. Eur J Cardiothorac Surg 1994;8:34–36.
Sawabata N, Ikeda M, Matsumura A, Maeda H, Miyoshi S, Matsuda H. New electroablation technique following the first-line stapling method for thoracoscopic treatment of primary spontaneous pneumothorax. Chest 2002;121:251–255.
Hazama K, Akashi A, Shigemura N, Nakagiri T. Less invasive needle thoracoscopic laser ablation of small bullae for primary spontaneous pneumothorax. Eur J Cardiothoracic Surg 2003;24:139–144.
Wakabayashi A, Brenner M, Wilson AF, Tadir Y, Berns M. Thoracoscopic treatment of spontaneous pneumothorax using carbon dioxide laser. Ann Thorac Surg 1990;50:786–789.
Sawabata N, Iuchi K, Ikeda M, Sueki H, Mori T. Safe pleural contraction employing a new tip for electrosurgical units. An ex vivo experiment. Jap J Thorac Cardiovasc Surg 1998;46:1221–1225.(Noriyoshi Sawabata, Shin-)
Noriyoshi Sawabata, Shin-Ichi Takeda, Masayoshi Inoue, Masaru Koma, Toshiteru Tokunaga and Hajime Maeda
Division of Surgery, Toneyama National Hospital, 5-1-1, Toneyama, Toyonaka, Osaka 560-8552, Japan. Department of Surgery (E1), Osaka University Graduate School of Medicine, Osaka Japan
Abstract
Background: We recently established new guidelines for our electro-ablation technique, which has been shown to be a ubiquitous, easy, and cost effective method secondary to stapled resection of pneumo-cysts for the treatment of pneumothorax. The present study was conducted as a confirmation of the effectiveness of this technique. Patients and methods: Between July 1998 and June 2003, 164 consecutive patients with spontaneous pneumothorax underwent surgery. Dependent lesions were resected using staplers. If found, residual lesions were ablated using M-tip electro-ablation (Group M). When the ablated pneumo-cysts were greater than 2 cm in diameter, pleural treatment was carried out by covering the surface with absorbable mesh sheets (Group L). Results: There were 7 cases (4.2%) of relapse of spontaneous pneumothorax and each underwent another operation due to the relapse. None of the lesions in the relapse cases received electro-ablation in the first operation. Relapse-free cases were 97/103 (94%) in Group N (no ablation group), 48/49 (98%) in Group M, and 12/12 (100%) in Group L (P=0.4). Comments: Our results demonstrated the safety and efficacy of our M-tip electro-ablation technique for pneumo-cysts as a secondary method to stapling. We considered that it was feasible for the treatment of spontaneous pneumothorax.
Key Words: Spontaneous pneumothorax; Ablation; Stapler; Electro-surgical unit
1. Introduction
Several methods are available to treat pneumo-cysts, of which surgical resection is the most commonly performed. The stapling method is also frequently used, because it is very easy to carry out [1–8], though it may have anatomic and quantitative limitations.
Ablation is considered a safe technique for the resection of pneumo-cysts [9–13], with the use of an electro-surgical unit the most ubiquitous and cost effective, while a laser technique is also often employed. We developed a new tip (M-tip) for use on an electro-surgical unit and previously conducted a prospective study to assess its clinical efficacy for electro-ablation of pneumo-cysts [11]. In cases with tiny lesions that remained after stapled resection of pneumo-cysts, there were no instances of pneumothorax relapse in patients who underwent the M-tip technique. However, relapse occurred in approximately 30% of cases with large pneumo-cysts that were ablated with the M-tip and without any pleural treatment.
Based on the results of that study, our group established guidelines for electro-ablation using the M-tip following stapled resection of pneumo-cysts during the treatment of spontaneous pneumothorax. The present report shows the results of treatment of spontaneous pneumothorax using those guidelines.
2. Patients and methods
2.1. Patient backgrounds
From July 1998 to June 2003, 164 consecutive patients (148 males, 16 females; age range 14–78 years, median age 35 years) with spontaneous pneumothorax underwent surgery at Toneyama National Hospital and their results were analyzed. The reasons for surgery were persistent air leakage for more than 7 days despite chest drainage in 41 cases, repeated spontaneous pneumothorax in 110 cases, persistent air leakage and repeat relapse in 6 case, and postoperative relapse in 6 cases. The involved side was right in 79 cases, left in 80 cases, and both in 5 cases. The method of access to inside of the thoracic cage used was thoracoscopic surgery in 145 cases and axillar thoracotomy in 19 cases.
2.2. Surgical techniques
Dependent lesions (ruptured pneumo-cyst or apical) were first resected using a stapler and all residual pneumo-cysts were ablated using an electro-surgical unit equipped with a ball-shaped tip, 8 mm in diameter and made of stainless steel, which can be used with any electro-surgical unit (M-tip, Senko Ika, Tokyo, Japan) [14]. The power level was set at 20 W using a Bovie X U (Hokusan, Tokyo, Japan) and 10 W using an MS-BM2 U (Senko Ika, Tokyo, Japan), with both units set to spray coagulation mode. The pneumo-cysts were first soaked with normal saline solution and then rubbed with the tip of an electro-coagulator to obtain adequate shrinkage (Fig. 1). Treatment ceased when white coloration and shrinking occurred. When the ablated pneumo-cysts were large (2 cm or more in diameter), pleural treatment was carried out by wrapping the surface with oxycellulose mesh seals (Surgicall, Ethicon, Tokyo, Japan). This technique is different from that of our previous report published in 2002 [11]. Pleurodesis was not carried out in any of the cases.
The patients were divided into 3 groups. Group N (n=103) included patients who underwent only stapled resection of pneumo-cysts and had no residual lesions, Group M (n=49) included those who underwent stapled resection of pneumo-cysts and then electro-ablation of tiny pneumo-cysts (less than 2 cm in diameter) with the M-tip, and Group L (n=12) patients underwent both stapled resection of large pneumo-cysts and electro-ablation of large pneumo-cysts (more than 2 cm in diameter) with the M-tip, after which the treated lesion surface area was covered with an oxycellulose mesh seal. Group N and group M were conducted with cases of primary spontaneous pneumo- thorax, while group L contented cases of secondary pnoeumothorax.
2.3. Patient follow-up
Data regarding the status of relapse were obtained by reviewing hospital records, or by contacting the patients or their families. All patients were followed-up by July 2003. The follow-up period was from 367–1760 days, with a median of 1275 days.
2.4. Statistical analysis
Statistical analyses of the data were performed using a factorial analysis of variance with a commercially available software package (StatView, version 5.0; Institute Inc. Tokyo, Japan). Statistical significance was calculated using Fisher's exact test, a 2-test, a t-test, and ANOVA as appropriate. Significance was assumed when the calculated P value was less than 0.05.
3. Results
3.1. Patient characteristics and indication of M-tip
The prevalence of gender, age, side of disease, and indication of operation are shown in Table 1. There were no statistically significant differences for gender or side of disease, however, Group L patients were older and had a significantly higher rate of persistent air leakage prior to surgery.
3.2. Surgery
There were no complications experienced by any of the patients during surgery. The average duration of the operation was 56±13 min in Group N, 63±14 min in Group M, and 118±22 min in Group L. The difference was not statistically significant between Group N and Group M (P=0.3). The thoracotomy methods used were VATS in 75 patients and axillar thoracotomy in 8 in Group N, VATS in 40 and axillar thoracotomy in 2 in Group M, and VATS in 4 and axillar thoracotomy in 5 in Group L.
Postoperative complications occurred in 4 (3.8%) Group N patients (n=103), of whom 3 had persistent air leakage for more than 7 days and 1 had postoperative bleeding that required a second operation. There was only 1 (2%) postoperative complication in Group M (n=49), which was persistent air leakage for more than 7 days. There was no statistically significant difference between Group N and Group M (P=0.7). In Group L patients (n=12), there were 5 cases (42%) of persistent air leakage, of whom 2 had a reoperation. The ratio of postoperative complications in Group L was significantly greater than in the other 2 groups (P<0.01).
3.3. Relapse of spontaneous pneumothorax
There were 7 cases of relapse of spontaneous pneumothorax after surgery and all underwent another operation thereafter, however, none of the relapse lesions had electro-ablation performed on them during the first operation. The leaking area was found in 4 of 7 cases. Three lesions were at the stapled line and the others were newly developed cysts which were different from ablated lesions. Adhesion was observed in all 7 cases but the grade was trivial. In addition, there was no adhesion at the region of electro-ablation. The relapse-free ratio (Fig. 2) was 97/103 (94%) in Group N (no ablation group), 48/49 (98%) in Group M, and 12/12 (100%) in Group L (Fig. 2), which were not significantly different (P=0.4).
4. Comments
Electro-ablation of pneumo-cysts as a secondary procedure to stapled resection was found to be safe in the present series of patients. Further, the ratio of relapse-free patients who underwent both stapled resection and electro-ablation with the M-tip was very high, and was similar to that of patients who received only a stapled resection of pneumo-cysts. In addition, the ruptured lesion in the lung of a patient who had received both stapled resection and electro-ablation was not in the area where electro-ablation had been carried out.
The two ablation techniques commonly used for pneumo-cysts are electro-ablation and laser ablation. Electro-ablation was first used in the late 1980s, during which the results were found to be acceptable, however, the rate of postoperative recurrence was approximately 10% [9], which was slightly higher than that of patients who underwent an operation without the ablation technique [1–8]. On the other hand, laser ablation methods have produced slightly better results in surgical cases of spontaneous pneumothorax [10,12,13], which are similar to our results in patients who underwent electro-ablation for tiny lesions with the use of the M-tip. Therefore, we consider that both electro-ablation using the M-tip and laser ablation are acceptable treatments for tiny pneumo-cysts.
Use of the M-tip for ablation of large pneumo-cysts is controversial, however, we believe it can be effective when combined with the covering technique used in the present Group L. Although our previous study showed that the rate of relapse was approximately 30% [11], no postoperative relapse of spontaneous pneumothorax was seen in any patients when the ablated lesion was covered using an absorbable mesh sheet.
The present results show that the M-tip technique for electro-ablation is a highly successful secondary method to stapling. We suggest that this ubiquitous, easy, and cost effective method is feasible for the treatment of spontaneous pneumothorax.
References
Inderbitzi RG, Leiser A, Furrer M, Althaus U. Three year's experience in video-assisted thoracic surgery (VATS) for spontaneous pneumothorax. J Thoracic Cardiovasc Surg 1994;107:1410–1415.
Naunheim KS, Mack MJ, Hazelrigg SR, Ferguson MK, Ferson PF, Boley TM, Landreneau RJ. Safety and efficacy of video-assisted thoracic surgical techniques for the treatment of spontaneous pneumothorax. J Thorac Cardiovasc Surg 1995;109:1198–1204.
Bertrand PC, Regnard JF, Spaggiari L, Levi JF, Magdeleinat P, Guibert L, Levasseur P. Immediate and long-term results after surgical treatment of primary spontaneous pneumothorax by VATS. Ann Thorac Surg 1996;61:1641–1645.
Mouroux J, Elkaim D, Padovani B, Myx A, Perrin C, Rotomondo C, Chavaillon JM, Blaive B, Richelme H. Video-assisted thoracoscopic treatment of spontaneous pneumothorax: technique and results of one hundred cases. J Thorac Cardiovasc Surg 1996;112:385–391.
Passlick B, Born C, Haussingger K, Thetter O. Efficiency of video-assisted thoracic surgery for primary and secondary spontaneous pneumothorax. Ann Thorac Surg 1998;65:324–327.
Hatz RA, Kaps MF, Meimarakis G, Loehe F, Muller C, Furst H. Long-term results after video-assisted thoracoscopic surgery for first-time and recurrent spontaneous pneumothorax. Ann Thorac Surg 2000;70:253–257.
Korner H, Andersen KS, Stangekand L, Ellingsen I, Engedal H. Surgical treatment of spontaneous pneumothorax by wedge resection without pleurodesis or pleurectomy. Eur J Cardiothorac Surg 1996;10:656–659.
75:Lazdunski LL, Chapuis O, Bonnet PM, Pons F, Jancovici R. Videothoracoscopic bleb excision and pleural abrasion for the treatment of primay spontaneous pneumothorax: long-term results. Ann Thorac Surg 2003;960–965.
Wakabayashi A. Thoracoscopic ablation of blebs in the treatment of recurrent or persistent spontaneous pneumothorax. Ann Thorac Surg 1989;48:651–653.
Sharpe DA, Dixon C, Moghissi K. Thoracoscopic use of laser in intractable pneumothorax. Eur J Cardiothorac Surg 1994;8:34–36.
Sawabata N, Ikeda M, Matsumura A, Maeda H, Miyoshi S, Matsuda H. New electroablation technique following the first-line stapling method for thoracoscopic treatment of primary spontaneous pneumothorax. Chest 2002;121:251–255.
Hazama K, Akashi A, Shigemura N, Nakagiri T. Less invasive needle thoracoscopic laser ablation of small bullae for primary spontaneous pneumothorax. Eur J Cardiothoracic Surg 2003;24:139–144.
Wakabayashi A, Brenner M, Wilson AF, Tadir Y, Berns M. Thoracoscopic treatment of spontaneous pneumothorax using carbon dioxide laser. Ann Thorac Surg 1990;50:786–789.
Sawabata N, Iuchi K, Ikeda M, Sueki H, Mori T. Safe pleural contraction employing a new tip for electrosurgical units. An ex vivo experiment. Jap J Thorac Cardiovasc Surg 1998;46:1221–1225.(Noriyoshi Sawabata, Shin-)