Significance of very-low-voltage coagulation plus coverage with polyglycolic acid sheet after bullectomy for primary spontaneous pneumothorax

Abstract

Background

The purpose of this study was to clarify the efficacy of the combination of low-voltage coagulation plus staple line coverage with a polyglycolic acid sheet after bullectomy for primary spontaneous pneumothorax to prevent a postoperative recurrence.

Methods

A total of 143 patients who underwent bullectomy for primary spontaneous pneumothorax between January 2014 and December 2019 were enrolled in this study. We classified the patients into two groups based on additional procedures after bullectomy, namely, low-voltage coagulation for the margin of the staple line plus coverage with a polyglycolic acid sheet (Group A) and staple line coverage with a polyglycolic acid sheet alone (Group B). We evaluated perioperative factors and recurrence-free survival after surgery in the two groups.

Results

Nine patients in Group B developed postoperative recurrences. In contrast, there was no postoperative recurrence in Group A. According to the Kaplan–Meier curves, the 2-year recurrence-free survival rates of the patients were 100% and 90.3%, in Group A and Group B, respectively. The log-rank test showed a significant difference between the two groups (p = 0.031).

Conclusion

Low-voltage coagulation for the margin of a staple line plus coverage with a polyglycolic acid sheet is a useful option as an additional technique after bullectomy for primary spontaneous pneumothorax to prevent a postoperative recurrence.

Keywords

Primary spontaneous pneumothorax low-voltage coagulation polyglycolic acid sheet bullectomy

Introduction

Primary spontaneous pneumothorax (PSP) is an abnormal accumulation of air in the pleural space due to the partial or complete collapse of a lung without underlying lung disease. Blebs or bullae in lung tissue that rupture cause PSP in many cases. PSP is not fatal but common, with an annual admission incidence of 70 per million among persons <50 years old in England.¹ Although conservative management, such as observation, simple aspiration, and chest tube drainage, is performed as the initial treatments for PSP, recurrence often occurs with a risk of ∼30%. The main option to prevent recurrence of PSP is surgical intervention, and video-assisted thoracic surgery (VATS) has gained popularity since the 1990s because of its minimal invasiveness.² There are various surgical techniques to treat PSP, such as bullectomy alone or in conjunction with additional techniques, including pleurectomy, parietal pleural abrasion, and staple line coverage.^3–5 However, a certain number of postoperative recurrences of PSP occur even though various additional techniques have been performed after bullectomy. In several randomized controlled trials, the incidence rate of postoperative recurrence was 3.8% to 13.6%.^6–9 The optimal additional techniques to prevent postoperative recurrence of PSP after bullectomy remain unknown.

Recently, a randomized controlled trial concluded that staple line coverage might potentially replace mechanical pleurodesis, which has potential disadvantages, such as disturbed pleural physiology.⁶ Another recent report demonstrated that the incidence of postoperative recurrent PSP in the staple line coverage with a polyglycolic acid (PGA) sheet group was significantly lower than that in the coverage with an oxidized regenerated cellulose mesh group.⁹

Low-voltage coagulation (LVC) of the margin of a staple line has been recently performed to reinforce the visceral pleura and prevent postoperative air leakage after pulmonary resection.¹⁰ Previous reports have shown that the formation of new bullae near a staple line caused postoperative recurrence after bullectomy for PSP.¹¹ Therefore, we hypothesized that LVC for the margin of a staple line, along with staple line coverage, may play an important role in preventing the formation of new bullae after bullectomy for PSP.

The purpose of this study was to evaluate whether the combination of LVC of the margin of a staple line and coverage with a PGA sheet after bullectomy prevents postoperative recurrence of PSP better than staple line coverage with a PGA sheet alone.

Material and methods

Study population

A total of 203 consecutive patients underwent surgery for pneumothorax at the Hachioji Medical Center of Tokyo, Medical University between January 2014 and December 2019. Patients >50 years old at the time of surgery (n = 49), having secondary primary pneumothorax (n = 10) and without bullectomy (n = 1), were excluded from this study (Figure 1). The remaining 143 patients formed the population of this study. The entire study population underwent bullectomy using surgical staplers and additional procedures after resection of PSP. The patients were classified into two groups based on additional procedures after bullectomy, namely, LVC for the margin of the staple line plus coverage with a PGA sheet (Group A) and staple line coverage with a PGA sheet alone (Group B). The patient allocation between the two groups was performed by attending surgeons at the time of surgery.

Surgical policy and procedures

Indications for surgical intervention for PSP were as follows: recurrent pneumothorax, prolonged air leakage over 5 days after chest drainage, bilateral pneumothorax, history of previous contralateral pneumothorax, and pneumothorax due to complete lung collapse. All patients underwent surgery under general anesthesia with a double-lumen endotracheal tube intubation. We performed bullectomy for PSP using a three-port thoracoscopic technique with an endoscopic stapling device (Endo GIATM Universal; Medtronic, Dublin, Ireland; Echelon; Ethicon, Cincinnati, OH, USA). Even when blebs or bullae were not found, bullectomy of the apex of the upper lobe or suspicious bullae was performed. After confirmation of no air leakage, for Group A, LVC (80 W) with a simple hand-activated 5 mm ball electrode, denoted as the SOFT COAG mode (Valleylab™ FT10; Medtronic, Dublin, Ireland), of the peripheral parenchyma of the staple line was performed. In both groups, the staple line was covered with an absorbable PGA sheet (Neoveil, 5 × 10 cm or 10 × 10 cm; Gunze Ltd, Kyoto, Japan) (Figure 2).

Postoperative care

A chest tube (18–20 Fr) was inserted into the intrapleural cavity for all patients, and suction (−10 to −20 cm H₂O) was applied immediately after surgery. The chest tube was disconnected if there was no evidence of air leakage on coughing or the Valsalva maneuver. In patients with air leakage, we removed the chest drainage on the day after confirmation of no air leakage.

Follow-up

All patients received outpatient follow-up care, including physical examination and chest radiography at 2 weeks and at 1 to 3 months after hospital discharge. Subsequently, patients were followed-up annually at the clinic or by telephone. Patients were examined in detail in our outpatient department if postoperative recurrence was suspected.

Data collection

Medical records of each patient were reviewed to collect clinical and pathological information. The clinical data included age, sex, body mass index (BMI), smoking history, laterality, history of pneumothorax, indication for surgery, operative findings, and postoperative information. The Tokyo Medical University Hospital Review Board approved the protocols for data collection and analyses and waived the need to obtain written informed consent from each patient (T2020-0236).

Statistical analysis

The primary outcome was recurrence-free survival (RFS). RFS was defined as the time from surgery to the date of postoperative recurrence or the last follow-up. Postoperative recurrence was defined as the development of lung collapse on the operated side on chest radiography or computed tomography after discharge, regardless of the necessity of treatment. RFS was assessed using the Kaplan–Meier method and differences in survival rates were determined by the log-rank test continuous variables were summarized as mean ± standard deviation and analyzed by Student's t-test when normally distributed and by Mann–Whitney U-test when non-normally distributed. Categorical variables were analyzed using the chi-square test. Univariable and multivariable analyses were performed using a backward stepwise selection method for the Cox proportional hazards model, including age, BMI, laterality, history of PSP, intraoperative bulla, and number of used staples. Sex, smoking history, and diameter of a chest tube were excluded from the univariable and multivariable analyses because these factors did not converge in the Cox proportional hazards model. All tests were two-sided and p-values <0.05 were considered to indicate a statistically significant difference between groups. All statistical calculations were performed using the SPSS statistical software package (version 26.0; SPSS, Inc., Chicago, IL, USA).

Results

Patient characteristics are summarized in Table 1. There were no statistically significant differences in preoperative factors between the two groups except for indication of prolonged air leakage for surgery (p = 0.048). The operative data are shown in Table 2. There were no statistically significant differences in operative findings, the diameter of a chest tube after surgery, and postoperative drainage duration between the two groups. In group A, the number of a complication of wound problems was statistically higher than that in Group B (p = 0.032). Seven and nine out of 93 patients in Group B experienced postoperative recurrence at 1 year and 2 years after surgery, respectively. Six of nine patients with postoperative recurrence developed the formation of bullae located on the margin of the staple line. The other three patients with postoperative recurrence had no imaging data of postoperative recurrence sites on chest computed tomography (CT). In contrast, there was no postoperative recurrence in Group A. The mean follow-up time was 21.7 ± 4.2 and 22.8 ± 5.4 months in Groups A and B, respectively (p = 0.238).

Table 1.

Patient characteristics.

Variable		Number of patients (%)
Variable		Group A (n = 50)	Group B (n = 93)	p-value
Age (years old)	Average	23.1 ± 9.1	21.6 ± 7.1	0.833
Sex	Male	45	87	0.448
Sex	Female	5	6
Smoking	Never	40	72	0.721
Smoking	Ever	10	21	0.721
BMI	Average	19.0 ± 2.4	18.9 ± 1.9	0.826
Laterality	Right	23	39	0.640
Laterality	Left	27	54	0.640
History of PSP before surgery	No	19	38	0.732
	Ipsilateral	24	46
	Contralateral	7	9
Indication	Recurrence	26	45	0.680
	Prolonged air leakage	8	30	0.048
	Post-contralateral	6	9	0.976
	Complete lung collapse	4	4	0.359
	bilateral	0	2	0.291

BMI: body mass index; PSP: primary spontaneous pneumothorax; n; number of sample size.

Table 2.

Operative outcomes.

Variable		Number of patients (%)
Variable		Group A (n = 50)	Group B (n = 93)	p-value
Operation time (min)	Average	79.1 ± 24.4	76.6 ± 30.5	0.618
Blood loss (ml)	Average	15.2 ± 30.8	9.8 ± 24.6	0.255
Intraoperative bulla	Suspected	2	5	0.654
	Simple	21	32
	Multiple	27	56
Number of used staples	1	9	14	0.647
	2	29	43	0.180
	3	8	22	0.389
	4	4	14	0.225
Diameter of a chest tube (Fr)	18	4	5	0.538
Diameter of a chest tube (Fr)	20	46	88
Postoperative drainage duration (days)	Average	2.4 ± 1.0	2.69 ± 1.8	0.752
Complication	No	42	80	0.745
	Air leakage >3 days	2	10	0.522
	Residual pain	2	2	0.165
	Wound problem	4	1	0.032
Postoperative recurrence (years)	≥1	0	7	0.047
Postoperative recurrence (years)	≥2	0	9	0.023
Follow-up time after hospital discharge (months)	Average	21.7 ± 4.2	22.8 ± 5.4	0.238

n: number of sample size.

According to the Kaplan–Meier curves, the 1-year and 2-year RFS rates of the patients in Group A were 100% and 100%, respectively, while those in Group B were 92.5% and 90.3%, respectively (Figure 3). The log-rank test showed a significant difference between the two groups (p = 0.031). The univariable and multivariable analyses showed that younger age (hazard ratio, 5.469; 95% confidence interval, 1.296–25.007; p = 0.028) was a significant risk factor for postoperative recurrence of PSP (Table 3).

Table 3.

Univariable and multivariable analyses for postoperative recurrence of PSP.

	Univariable			Multivariable
Variable	Hazard ratio	95% confidence interval	p-value	Hazard ratio	95% confidence interval	p-value
Age (<20 years old)	7.376	1.538–35.378	0.012	5.469	1.196–25.007	0.028
BMI	0.588	0.182–1.897	0.375
Laterality	0.319	0.092–1.110	0.073	0.350	0.105–1.164	0.087
History of PSP before surgery	0.995	0.288–3.437	0.993
Intraoperative bulla	2.154	0.549–8.455	0.271
Number of used staples	1.471	0.167–12.937	0.728

BMI: body mass index; PSP, primary spontaneous pneumothorax.

Discussion

This study aimed to compare two additional techniques for the prevention of PSP recurrence after bullectomy: LVC for staple line plus coverage with a PGA sheet and staple line coverage with a PGA sheet alone. The former group had significantly better RFS than the latter group and had no postoperative recurrence until 2 years in our study.

VATS for pneumothorax has been widely performed by many surgeons since the 1990s because of its merits, such as less operation time, shorter drainage duration, and lower complication rates than thoracotomy.² However, VATS for PSP occasionally presents more postoperative recurrence than thoracotomy.¹² Thus, many additional techniques after bullectomy have been performed in VATS for PSP.⁴

Mechanical pleurodesis, such as apical pleurectomy or parietal pleural abrasion, after bullectomy, has been widely performed to prevent postoperative recurrence of PSP.⁵ The British Thoracic Society guidelines indicate that pleurectomy may have slight advantages over pleural abrasion regarding postoperative recurrent pneumothorax.¹² However, Rena et al.⁸ reported that patients with PSP who underwent apical pleurectomy experienced significantly more frequent hemothorax, more operation time, and more residual pain than those who underwent parietal pleural abrasion and that there was no difference in postoperative recurrent rate between the two additional techniques.⁸ Park et al.³ concluded that pleural abrasion after bullectomy did not decrease recurrent pneumothorax compared with bullectomy alone. To date, there is little evidence that mechanical pleurodesis actually reduces postoperative recurrent PSP.

Staple line coverage after bullectomy for PSP has been recently performed in some studies.^5,13 Lee et al.⁶ indicated that staple line coverage after thoracoscopic bullectomy was not inferior to mechanical pleurodesis with regard to a postoperative recurrence rate in a randomized controlled trial. Staple line coverage has been performed mainly using an absorbable cellulose mesh or a PGA sheet to reinforce the visceral pleura. Ozawa et al.⁹ demonstrated that the postoperative recurrence rate of PSP treated with PGA sheets was lower than that with absorbable cellulose mesh. A PGA sheet has been reported to thicken the visceral pleura during absorption and to promote adhesion.⁵ Both PGA sheets and mechanical pleurodeses such as pleurectomy and pleural abrasion cause pleural adhesion, but PGA sheets may be safer because it does not damage normal pleura.

In our study, nine patients with PSP after bullectomy with a PGA sheet alone developed postoperative recurrences. Choi et al.¹⁴ demonstrated that 16 out of 21 patients (76%) had new bullae in the staple line with postoperative recurrence and concluded that new bullae in the staple line increased the risk of postoperative recurrence of PSP. In the present study, six out of the nine patients had the formation of bullae on the margin of the staple line, which did not exist on preoperative chest CT. The bullae were thought to be the cause of postoperative recurrence although it was difficult to evaluate whether the bullae were residual lesions or new formation of bullae after surgery because we did not take a chest CT just after surgery. Taking these into consideration, we think staple line coverage with a PGA sheet alone as the additional technique after bullectomy is insufficient to prevent postoperative recurrence of PSP.

Low-voltage coagulation (LVC) was recently used in thoracic surgery, especially for major pulmonary resection to decrease blood loss or prevent postoperative air leakage.¹⁴ Uchiyama et al.¹⁵ reported that the use of LVC with PGA sheets and fibrin glue after lobectomy for lung cancer efficiently prevented both intraoperative air leaks and prolonged air leaks after surgery. Takashi et al.¹⁶ pathologically demonstrated that LVC for pulmonary bullae thickened and degenerated the bulla wall without damaging lung parenchyma in pneumothorax surgery. However, Toyazaki et al.¹⁷ reported that occasionally LVC alone cannot control air leak completely, and considered it insufficient as a treatment to prevent air leak in pulmonary resection. We referred to these reports and started to perform LVC for the margin of a staple line after bullectomy, followed by coverage with a PGA sheet for PSP. LVC for the margin of a staple line reinforces the visceral pleura, and the PGA sheet causes adhesion to the parietal pleura. We believe that the combined activity prevents postoperative recurrence of PSP. Researchers have used various devices with coagulation. Ambrogi et al.¹⁸ coagulated bullae with the method called cold coagulation, which allowed irrigation with saline solution. We used the device with LVC which did not need a saline solution. However, cold coagulation and LVC have a common mechanism of coagulation without charring and burning.

Several researchers have reported risk factors for postoperative recurrence of PSP, such as younger age, a history of ipsilateral or contralateral pneumothorax, contralateral blebs or bullae on chest CT, and low BMI.^19,20 We also observed that age <20 years was a risk factor for postoperative recurrence of PSP in the current study. Onuki et al.¹¹ showed that 78% of younger patients with postoperative recurrence of PSP had neogenetic bullae around the staple line. In our study, the formation of new bullae around the staple line was found in 67% of patients with postoperative recurrence of PSP. Especially in younger patients, we suggest that LVC for the margin of a staple line plus coverage with a PGA sheet is more effective after bullectomy in preventing postoperative recurrence of PSP.

There were some limitations and biases in the present study. First, as this study was a retrospective analysis in a single institution, there may be patient selection bias. Second, several factors did not converge in the Cox proportional hazards model because the number of postoperative recurrence events was small. This limited the power of the statistical analysis. Third, it is unclear whether our surgical method was effective for the prevention of long-term postoperative outcome because the follow-up time was a short term with an average of 22.4 months after the initial surgery. Therefore, a multicenter randomized controlled trial with a larger sample size and a longer follow-up period will be required to reveal the clinical usefulness of LVC for the margin of a staple line plus coverage with a PGA sheet after bullectomy.

In conclusion, this study demonstrated that LVC for the margin of a staple line plus coverage with a PGA sheet is a useful option as an additional technique after bullectomy for PSP to prevent a postoperative recurrence.

Additional techniques after bullectomy for pneumothorax

Footnotes

Acknowledgements

The authors are indebted to the medical editors of the Department of International Medical Communications of Tokyo Medical University for editing the English manuscript. We also thank Mami Murakami for assistance with the statistical analysis of this work.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

The Tokyo Medical University Hospital Review Board approved the protocols for data collection and analyses and waived the need to obtain written informed consent from each patient (T2020-0236).

Informed consent

Not applicable.

ORCID iD

Shunsuke Shigefuku

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