Intraoperative techniques to prevent air leaks

A novel system applying artificial intelligence in the identification of air leak sites

Objective

Prolonged air leak is the most common complication of thoracic surgery. Intraoperative leak site detection is the first step in decreasing the risk of leak-related postoperative complications.

Methods

We retrospectively reviewed the surgical videos of patients who underwent lung resection at our institution. In the training phase, deep learning-based air leak detection software was developed using leak-positive endoscopic images. In the testing phase, a different data set was used to evaluate our proposed application for each predicted box.

Results

A total of 110 originally captured and labeled images obtained from 70 surgeries were preprocessed for the training data set. The testing data set contained 64 leak-positive and 45 leak-negative sites. The testing data set was obtained from 93 operations, including 58 patients in whom an air leak was present and 35 patients in whom an air leak was absent. In the testing phase, our software detected leak sites with a sensitivity and specificity of 81.3% and 68.9%, respectively.

Conclusions

We have successfully developed a deep learning-based leak site detection application, which can be used in deflated lungs. Although the current version is still a prototype with a limited training data set, it is a novel concept of leak detection based entirely on visual information.

Management of Complications After Lung Resection: Prolonged Air Leak and Bronchopleural Fistula

Prolonged air leak or alveolar-pleural fistula is common after lung resection and can usually be managed with continued pleural drainage until resolution. Further management options include blood patch administration, chemical pleurodesis, and 1-way endobronchial valve placement. Bronchopleural fistula is rare but is associated with high mortality, often caused by development of concomitant empyema. Bronchopleural fistula should be confirmed with bronchoscopy, which may allow bronchoscopic intervention; however, transthoracic stump revision or window thoracostomy may be required.

Off-the-Shelf Cell Sheets as a Pleural Substitute for Closing Visceral Pleural Injuries

During pulmonary resections, removal of visceral pleura is frequently required, resulting in lung air leakage (LAL) and bleeding. Especially persistent LAL after pulmonary surgery has negative consequences. Current surgical procedures are ineffective in closing these visceral pleural injuries. Previously, the authors' laboratory has developed a novel and effective LAL sealant using tissue-engineered cell sheets harvested from temperature-responsive culture dishes. The clinical application of fresh fibroblast sheets (FSs) is limited by several problems related to the cell culture period, mass production, preservation, and transportation. Therefore, cryopreservation of FSs and feasibility of off-the-shelf FSs for repairing visceral pleural defects were investigated. Over 3 to 6 months, harvested skin-derived FSs in Dulbecco's modified Eagle's medium supplemented with 10% dimethyl sulfoxide were stored in an atmosphere of liquid nitrogen. The amounts of cytokines (basic fibroblast growth factor [bFGF] and vascular endothelial growth factor) released from frozen-thawed FSs were determined. bFGF levels were significantly elevated in frozen-thawed FSs compared with fresh FSs. After a visceral pleural injury model was created, a frozen-thawed skin-derived FS was transplanted directly to the defect. One month after transplantation, the frozen-thawed FS remained on the pleural surface, resulting in permanent closure, suggesting that cells in the off-the-shelf FS had the ability to proliferate and release various cytokines. Frozen-thawed FSs were useful for closing LALs during pulmonary surgery as an off-the-shelf technique and would be used as a pleural substitute.

[Establishment of A Clinical Prediction Model of Prolonged Air Leak after Anatomic Lung Resection]

背景与目的

解剖性肺切除术后持续漏气（prolonged air leak, PAL）是胸外科常见并发症，重在准确预测及时预防，但目前国内尚缺少有效的预测模型，本研究旨在建立解剖性肺切除术后PAL临床预测模型。

方法

回顾分析2016年1月-2016年10月安徽医科大学附属省立医院胸外科解剖性肺切除术患者的临床资料和术后漏气情况，其中A组病例359例，通过对患者的年龄（岁）、性别、身体质量指数（body mass index, BMI）、吸烟史、肺功能指数、手术方式（开放或腔镜，肺段、肺叶或其他，如支气管袖式或血管袖式）、手术切除肺叶位置、肺部病灶性质和胸腔粘连情况进行单因素及多因素分析，寻找解剖性肺切除术后PAL的独立预测因子，并建立临床预测模型。随后利用不同时期、不同治疗组完成的112例解剖肺切除患者作为B组，用于验证本模型的诊断效能，并绘制受试者工作特征（receiver operating characteristic curve, ROC）曲线。

结果

多因素Logistic回归分析筛选出BMI、性别、吸烟史、第一秒用力肺活量占用力肺活量的百分比（forced expiratory volume in one second, FEV₁%）、胸腔粘连及是否上叶切除为解剖性肺切除患者术后PAL的独立预测因子。利用筛选出的预测因子建立的诊断模型ROC曲线下面积为0.886（95%CI: 0.835-0.937），最佳临界值P=0.299，对应的诊断敏感性为78.5%，特异性为93.2%。

结论

本研究建立的预测模型能较准确的预测解剖性肺切除术后PAL的发生，对及时有效预防PAL发生有指导作用。

Intraoperative ventilatory leak predicts prolonged air leak after lung resection: A retrospective observational study

Prolonged air leak (PAL), defined as air leak more than 5 days after lung resection, has been associated with various adverse outcomes. However, studies on intraoperative risk factors for PAL are not sufficient. We investigated whether the intraoperative ventilatory leak (VL) can predict PAL. A retrospective study of 1060 patients with chest tubes after lung resection was conducted. Tidal volume data were retrieved from the electronic anesthesia records. Ventilatory leak (%) was calculated as [(inspiratory tidal volume-expiratory tidal volume)/ inspiratory tidal volume × 100] and was measured after restart of two-lung ventilation. Cox proportional hazards regression analysis was performed using VL as a predictor, and PAL as the dependent outcome. The odds ratio of the VL was then adjusted by adding possible risk factors including patient characteristics, pulmonary function and surgical factors. The incidence of PAL was 18.7%. VL >9.5% was a significant predictor of PAL in univariable analysis. VL remained significant as a predictor of PAL (1.59, 95% CI, 1.37-1.85, P <0.001) after adjusting for 7 additional risk factors including male gender, age >60 years, body mass index <21.5 kg/m2, forced expiratory volume in 1 sec <80%, thoracotomy, major lung resection, and one-lung ventilation time >2.1 hours. C-statistic of the prediction model was 0.80 (95% CI, 0.77-0.82). In conclusion, VL was a quantitative measure of intraoperative air leakage and an independent predictor of postoperative PAL. Monitoring VL during lung resection may be uselful in recommending additional surgical repair or use of adjuncts and thus, help reduce postoperative PAL.

[Analysis of Postoperative Complications and Risk Factors of Patients with Lung Cancer through Clavien-Dindo Classification]

背景与目的

术后并发症是肺切除术后患者死亡的重要原因。在本研究中，我们应用Clavien-Dindo并发症分级系统对肺癌术后并发症按照严重程度进行分级，并分析术后并发症的发生率，探讨不同分级术后并发症的危险因素。

方法

回顾性分析2013年6月-2014年12月四川大学华西医院胸外科966例行肺叶切除术的肺癌患者，依据术后30 d内是否发生并发症将此966例患者分为并发症组与无并发症组；同时根据Clavien-Dindo分级系统将并发症分为4级，并针对不同分级的并发症进行危险因素分析。

结果

966例患者中，并发症组占15.0%（145/966），发生总数380次；依据Clavien-Dindo分级系统将此380次并发症进行分级，其中Ⅰ级、Ⅱ级、Ⅲ级、Ⅳ级及以上分别占6.8%、75.3%、15.0%和2.9%。Logistic回归分析结果显示术前第1秒用力呼气容积（forded expiratory volume in one second, FEV₁）、肺一氧化碳弥散量（diffusion capacity for carbon monoxide of the lung single breath, DLco SB）及术前合并慢性阻塞性肺疾病（chronic obstructive pulmonary disease, COPD）是术后并发症的独立危险因素；其中术前FEV₁是Ⅰ级、Ⅱ级、Ⅲ级及以上并发症的独立危险因素。

结论

在Clavien-Dindo分级系统下，Ⅱ级并发症在术后30天内最常见；FEV₁与术后并发症的发生密切相关，可作为评估术后并发症发生风险的可靠指标之一。

In Vitro Evaluation for Potential Calcification of Biomaterials Used for Staple Line Reinforcement in Lung Surgery

Bovine pericardium (BPC) and polytetrafluoroethylene (PTFE) have been widely used to reinforce staple lines in lung resection. Since limited Information regarding the calcification of these biomaterials is available, we undertook an In vitro study to evaluate their calcification potential. Commercially available BPC and PTFE biomaterials were evaluated and compared with custom-prepared BPC tissue. In vitro calcification was performed via submersion in supersaturated solution In a double-walled glass reactor at 37.0°C ± 0.1°C, pH 7.4 ± 0.1, mimicking most ion concentrations of human blood plasma. In processing of calcification, the pH decrease of the solution simulated the addition of consumed H+, Ca2+, and PO43– ions from titrant solutions, the concentrations of which were based on the stolchiometry of octacalcium phosphate. The molar ion addition with time was recorded, and the initial slope of the curve was computed for each experiment. The rate of calcification developed (molar calcium phosphate ion addition rate per time and total surface area) (R) was computed after that with respect to the relative supersaturation (σ) used in each experiment. R for custom-prepared BPC tissues was found to be in the range of 0.19 ± 0.08 to 0.52 ± 0.19 (n = 17) in σ range of 0.72 to 1.42. Commercial BPC was found to be 0.016 to 0.052 (n = 4), and PTFE was 0.005 to 0.05 (n = 8) in the same σ range. Both clinically applied biomaterials, BPC and PTFE, seemed to be calcified with rates of at least one order of magnitude lower than the custom-prepared BPC tissue. This data suggested that BPC and PTFE biomaterials showed a similar, relatively very low tendency for calcification compared with custom-prepared BPC tissue. Although further studies are necessary, staple line reinforcement by these two biomaterials should be considered safe from the calcification point of view.

Natural air leak test without submergence for spontaneous pneumothorax

Background

Postoperative air leaks are frequent complications after surgery for a spontaneous pneumothorax (SP). We herein describe a new method to test for air leaks by using a transparent film and thoracic tube in a closed system.

Method

Between 2005 and 2010, 35 patients underwent a novel method for evaluating air leaks without submergence, and their clinical records were retrospectively reviewed. The data on patient characteristics, surgical details, and perioperative outcomes were analyzed.

Results

The differences in the clinical background and intraoperative factors did not reach a statistically significant level between the new and classical methods. The incidence of recurrence was also equivalent to the standard method. However, the length of the operation and drainage periods were significantly shorter in patients evaluated using the new method than the conventional method. Further, no postoperative complications were observed in patients evaluated using the new method.

Conclusions

This simple technique is satisfactorily effective and does not result in any complications.

Special situations: air leak after lung volume reduction surgery and in ventilated patients

Patients undergoing lung volume reduction surgery and those supported by mechanical ventilation are among our most vulnerable patients. Prolonged air leak in these fragile patients can have dire, even fatal, consequences. This article describes the incidence of prolonged air leak in these populations, the causes ascribed to their development, and strategies that may be applied to their prevention and treatment.

Comparison of different bronchial closure techniques following pneumonectomy in dogs

The comparison of the histologic healing and bronchopleural fistula (BPF) complications encountered with three different BS closure techniques (manual suture, stapler and manual suture plus tissue flab) after pneumonectomy in dogs was investigated for a one-month period. The dogs were separated into two groups: group I (GI) (n = 9) and group II (GII) (n = 9). Right and left pneumonectomies were performed on the animals in GI and GII, respectively. Each group was further divided into three subgroups according to BS closure technique: subgroup I (SGI) (n = 3), manual suture; subgroup II (SGII) (n = 3), stapler; and subgroup III (SGIII) (n = 3), manual suture plus tissue flab. The dogs were sacrificed after one month of observation, and the bronchial stumps were removed for histological examination. The complications observed during a one-month period following pneumonectomy in nine dogs (n = 9) were: BPF (n = 5), peri-operative cardiac arrest (n = 1), post-operative respiratory arrest (n = 1), post-operative cardiac failure (n = 1) and cardio-pulmonary failure (n = 1). Histological healing was classified as complete or incomplete healing. Histological healing and BPF complications in the subgroups were analyzed statistically. There was no significant difference in histological healing between SGI and SGIII (p = 1.00; p > 0.05), nor between SGII and SGIII (p = 1.00; p > 0.05). Similarly, no significant difference was observed between the subgroups in terms of BPF (p = 0.945; p > 0.05). The results of the statistical analysis indicated that manual suture, stapler or manual suture plus tissue flab could be alternative methods for BS closure following pneumonectomy in dogs.

Dynamic sealing of lung air leaks by the transplantation of tissue engineered cell sheets

Current methods including the use of various biological and synthetic sealants are ineffective in the closure of intraoperative air leaks that often occur during cardiothoracic surgeries, resulting in a decreased quality of life for patients. We present the development of a novel lung air leak sealant using tissue engineered cell sheets. In contrast to previous materials such as fibrin glue, these bioengineered cell sheets immediately and permanently seal air leaks in a dynamic fashion that allows for the extensive tissue contraction and expansion involved in respiration, without any postoperative recurrences. Additionally, we demonstrate that mesothelial cells migrate to cover the transplanted cells sheets, thereby confirming excellent biocompatibility and integration with the host tissues. Finally, we present the use of skin fibroblasts as an effective and readily available autologous cell source that can be easily applied. This study shows for the first time, the development of an immediate and permanent lung air leak sealant, suitable for future clinical applications.

Hemostasis and sealing of air leaks in the lung using high-intensity focused ultrasound

BACKGROUND

Operative management of parenchymal lung injury can be complicated by persistent hemorrhage and air leak, which might require resection. Techniques that preserve parenchyma are associated with improved survival. High-intensity focused ultrasound (HIFU) has been demonstrated as a useful method for hemostasis in experimental solid organ injuries. We wished to investigate whether this could be applied to lung injuries.

METHODS

An intraoperative HIFU device (frequency of 5.7 MHz, acoustic power of 65 W), equipped with a titanium coupler, was used. Incisions (average length of 2.5 cm, and depth of 5 mm) were made in the lungs of 11 pigs, which created both parenchymal hemorrhage and air leakage. In treatment experiments, 70 incisions were sealed with HIFU. The HIFU application started within 10 seconds of inducing the injury. Hemostasis was assessed by visual observation of sealed incisions. The possible air leakage was determined by submersing the sealed incision under the layer of water and observing for air bubble formation. In control experiments, five incisions were left untreated to monitor air leaks and bleeding for 2 minutes.

RESULTS

Hemostasis and pneumostasis (sealing of air leaks) of the treated incisions were achieved in 51 +/- 37 seconds (mean +/- SD) (range of 10-210 seconds) of HIFU application time. Over 95% of incisions were hemostatic within 2 minutes of HIFU application. The treatment time was not dependent on the incision length or depth. In control experiments, the air leaking and bleeding were still present at 2 minutes after the injury.

CONCLUSION

Intraoperative HIFU might provide an effective method of hemostasis and control of air leaks from lacerations caused by trauma.

Mechanical ventilation and air leaks after lung biopsy for acute respiratory distress syndrome

BACKGROUND

Open lung biopsy in acute respiratory distress syndrome (ARDS) may provide a specific etiology and change clinical management, yet concerns about complications remain. Persistent air leak is the most common postoperative complication. Risk factors in this setting are not known.

METHODS

We performed a retrospective analysis of 53 patients who underwent open lung biopsy for clinical ARDS (based on American European Consensus Conference criteria) between 1989 and 2000.

RESULTS

Sixteen patients (30.2%) developed an air leak lasting more than 7 days or died with an air leak. Univariate analyses showed no significant correlation with age, gender, sex, corticosteroid use, diabetes, immunocompromised status, or pathologic diagnosis. A lower risk of air leak was associated with lower peak airway pressure and tidal volume, use of pressure-cycled ventilation, and use of an endoscopic stapling device. In multivariate analyses, only peak airway pressure remained a significant predictor. The risk of prolonged air leak was reduced by 42% (95% confidence interval [CI: 17% to 60%]) for every 5 cm H2O reduction in peak airway pressure.

CONCLUSIONS

The use of a lung-protective ventilatory strategy that limits peak airway pressures is strongly associated with a reduced risk of postoperative air leak after open lung biopsy in ARDS. Using such a strategy may allow physicians to obtain information from open lung biopsy to make therapeutic decisions without undue harm to ARDS patients.

Characterization and Importance of Air Leak After Lobectomy

BACKGROUND

Air leak after pulmonary resection is a common occurrence that is incompletely characterized. Our objectives were to determine prevalence of air leak and identify its risk factors, characterize its duration and discover its correlates, and evaluate its clinical importance.

METHODS

Air leak was studied in 319 patients undergoing isolated anatomic lobectomy between January 1998 and July 2001. Risk factors for air leak were identified by logistic regression of patient characteristics, indications for lobectomy, lobe resected, and fissure management. Factors associated with air leak duration were sought by time-related analysis. Association of complications with air leak was evaluated by propensity-matched pairs analysis.

RESULTS

Prevalence: Air leak prevalence was 58% (186 patients). It occurred less frequently after left lower lobectomy (p < 0.0001) and later in the series (p = 0.008). It was surgeon dependent (p = 0.007) but not associated with forced expiratory volume in 1 second.

DURATION

The 10th, 50th, and 90th percentiles of air leak duration were 1.6, 3, and 7 days, respectively. No factors, including fissure management, were reliably associated with air leak duration.

IMPORTANCE

Air leak was associated with more complications (30% vs 18%, p = 0.07) and protracted hospital course (p = 0.02).

CONCLUSIONS

Postoperative air leak is a common occurrence after lobectomy, but fortunately it is self-limiting in most patients. Air leak is independently associated with longer hospital stay and other postoperative complications. Surgical technique is important and may be the only modifiable factor.