Postoperative recurrent pneumothorax after bullectomy remains a clinical challenge, especially in young patients because they have a higher recurrence rate than in older patients [1]. The recurrence rate of bullectomy with no coverage in young patients is reported to be as high as 10.9–19.5% [6, 7, 9]. The etiology of postoperative recurrence of PSP is speculated to be rupture of the overlooked or regenerated bulla, which is formed at the staple line of the bullectomy. Therefore, we continued our research on appropriate covering materials for bullectomy staple lines; however, we could not find evidence of postoperative-recurrence suppression by ORC sheets. This finding was supported by our previous study [6].
This study demonstrated the superior effectiveness of the PGA sheet to that of the ORC sheet. The PGA sheet significantly decreased the recurrence rate of pneumothorax after bullectomy compared with the ORC sheet. PGA sheets have been reported to exhibit a limited effect on bulla regeneration [13]; nevertheless, recurrent cases in this study implied that the sheet was possibly more efficient in inducing pleural adhesion than the ORC sheet. We speculated that the pleural adhesion in the coverage area leads to reduced postoperative recurrence.
The PGA sheet is an absorbable reinforcement material for the pleura [11]. The sheet was pathologically proven to cause inflammatory cell infiltration with pleural fibrosis in this recurrent case. This indicated that the PGA sheet triggers inflammation in the visceral pleura, leading to the formation of strong and extensive pleural adhesions. Its use has not demonstrated an increase in surgical site infection [14]. PGA sheets on bulla have been reported to induce the formation of granulation tissue and reinforce the bulla wall 1 month after surgery in the case of secondary spontaneous pneumothorax [15]. In contrast, the ORC sheet just thickens the visceral pleura by fibrous hyperplasia and does not contribute to creating pleural adhesion or reducing postoperative recurrence as we previously reported [6].
Several previous reports, including the most recent meta-analysis, have demonstrated the effectiveness of PGA sheets in preventing postoperative recurrence compared with other methods [7,8,9,10]. However, these studies were retrospective, and none could use their data to establish the reason PGA sheets potentially suppress recurrence. Our study was conducted using a prospective cohort approach and provided precise radiological, intraoperative, and pathological information on recurrent cases. The methods of bulla resection, sheet coverage, and follow-up were the same in the prospective cohorts, and we included patients whose characteristics were similar in the fixed local region. Therefore, we were able to assess both groups equally.
We also reported that the ORC sheet only has a limited effect on suppressing the regenerating bulla on the staple line [6]. Thus, we expected a significant effect from a better covering material. The resected visceral pleura at the time of bullectomy is weakened by tensional force, which is responsible for bulla regeneration, even under the covering sheet [16]. Although the number of recurrent cases is limited, this study implied that PGA sheets have an equivalent suppressive effect on bulla regeneration to ORC sheets. PGA sheets reportedly do not prevent bulla regeneration, which is a risk factor for recurrence, even though it decreases the postoperative recurrence rate [16, 17]. Therefore, PGA sheets are believed to prevent postoperative recurrence by preventing bullae from rupturing.
Pleural adhesion may have an important influence on preventing air leakage from the staple line, and it is produced by various techniques. In European countries, thoracoscopic chemical pleurodesis using talc poudrage or mechanical pleurodesis (pleural abrasion and pleurectomy) is a common method because some studies have demonstrated its workability [2]. The recurrence rate may be low after VATS with talc poudrage; however, reoperation is difficult due to tight pleural adhesions at the time of reoperation [17]. Extensive and tight pleural adhesions are potential obstacles at the time of the second thoracic surgery, such as otitis lung injury, bleeding, and surgical time. Moreover, good pleurodesis reagents, such as talc, are not covered for PSP by the health insurance system in Japan. Therefore, pleurodesis for PSP often fails [1]. Mechanical pleurodesis is also known as a procedure to induce pleural adhesion, but its complications include postoperative chest pain, intra- and postoperative bleeding [4]. The severe adhesions can complicate the future surgery. Additionally, it was proven that mechanical pleurodesis does not have the significant effect to prevent recurrent pneumothorax. Although the local adhesion created by the PGA sheet may be disadvantageous and challenging, reoperation after PGA-sheet coverage seems easier than that of pleurodesis because of the limited adhesion area. Therefore, we consider that pleural adhesion is necessary; however, the adhesion area should be maintained at a minimum. A future clinical investigation comparing PGA sheet coverage with intraoperative pleurodesis is required.
Limitations
This study is limited by its single-center design. As in our previous study, most of the postoperative recurrence occurred within 2 years [6]. The observation period was limited to 3 years; nonetheless, it was a sufficient period for evaluating the presence of postoperative recurrence.
In previous studies on the recurrence of postoperative pneumothorax, follow-up by telephone or routine checkups might have been common. However, these methods fail to reveal the true recurrence rate because they cannot detect minor or asymptomatic recurrence. In this study, almost all patients visited our institution when they experienced any symptoms, such as dyspnea or chest pain, because our institution is the only medical center that can manage pneumothorax in the region. Therefore, follow-up through emergent visits, together with the observation of certain symptoms, was sufficient to compare treatment outcome in this study. This method was approved in our previous study [6].