Air leak after lung resection: pathophysiology and patients' implications

Outcomes of chest drain management using only air leak (without fluid) criteria for removal after general thoracic surgery-a drainology study

Background

Chest drain management is a variable aspect of postoperative care in thoracic surgery, with different opinion for air and drain volume output. We aim to study if acceptable safety was maintained using air leak criteria alone.

Methods

A 9-year retrospective analysis of protocolised chest drain management using digital drain air leak cut off less than 20 mL/min for more than 6 h for drain removal in patients undergoing general thoracic surgery. We excluded patients if a chest drain was not required nor removed during admission or if patients underwent volume reduction or pneumonectomy. Withdrawal criteria were suspected bleeding or chylothorax. Postoperative films were reviewed to document post-drain removal pneumothorax, pleural effusion, and reintervention (drain re-insertion).

Results

Between 2012 and 2021, 1,187 patients had thoracic surgery under a single surgeon. Following exclusion and withdrawal criteria, 797 patients were left for analysis. The mean age [standard deviation (SD)] was 61 [16] years and 383 (48%) were male. Median [interquartile range (IQR)] duration of drain insertion was 1 [1-2] day with a median length of hospital stay of 4 [2-6] days. Post-drain removal pneumothorax was observed in 141 (17.7%), post-drain removal pleural effusion was observed in 75 (9.4%) and re-intervention (reinsertion of chest drain) required in 17 (2.1%).

Conclusions

Our results demonstrate acceptable levels of safety using digital assessment of air leak as the sole criteria for drain removal in selected patients after general thoracic surgery.

Risk factors, complications and costs of prolonged air leak after video-assisted thoracoscopic surgery for primary lung cancer

Background

Prolonged air leak (PAL) represents a common complication after lung resection. This study aims to analyze the risk factors for the development of a PAL, its impact on the postoperative outcome and to estimate additional treatment costs.

Methods

A single center database was queried for all patients scheduled for video-assisted thoracoscopic surgery for primary lung cancer. In total, 957 patients between 2009 and 2021 were analyzed. Exclusion criteria was pneumonectomy. Collected data included demographics and perioperative data (e.g., duration of surgery, postoperative infections, air leak duration etc.). PAL was defined as an air leak lasting for 5 days or longer. The PAL cohort included 103 patients, the non-PAL included 854 patients. Univariate analysis and binomial logistic regression were performed. Cost calculation was performed using available data from prior publications to estimate treatment costs.

Results

Male sex, chronic obstructive pulmonary disease (COPD) and low body mass index (BMI) showed to be risk factors for the development of postoperative PAL (P<0.001). Using these risk factors, a risk prediction score for PAL has been established. A subgroup analysis showed a significantly higher rate of sarcopenia in patients with PAL (P<0.001). The mean duration until removal of chest drains and length of stay (LOS) was significantly longer in the PAL cohort (14.2 vs. 4.4 days, P<0.001; 19.8 vs. 9.3 days, P<0.001). Also, the duration of the operation was longer in PAL patients (179.1 vs. 161.2 minutes, P=0.001). Patients with PAL had an elevated risk for postoperative infections [odds ratio (OR) 3.211, 31.1% vs. 12.3%, P<0.001]. As a result of a prolonged LOS, estimated treatment costs were significantly higher for PAL, ranging from 2,888.2 to 12,342.8 € depending on available cost bases compared to the non-PAL cohort, which ranged from 1,370.5 to 5,856.8 € (P<0.001).

Conclusions

PAL is a frequent complication that prolongs the LOS after thoracic surgery and, according to the literature, results in elevated readmission rates, leading to excess health care costs. Risk factors for PAL are well established. Preoperative treatment of sarcopenia and dismal nutritional status might alter the risk. As measures to prevent PAL are otherwise limited, guidelines for effective management of PAL need to be established.

Outcomes of patients discharged home with a chest tube after lung resection: a multicentre cohort study

Background:

Prolonged air leaks are increasingly treated in the outpatient setting, with patients discharged with chest tubes in place. We evaluated the incidence and risk factors associated with readmission, empyema development and further interventions in this patient population.

Methods:

We undertook a retrospective cohort analysis of all patients from 4 tertiary academic centres (January 2014 to December 2017) who were discharged home with a chest tube after lung resection for a postoperative air leak lasting more than 5 days. We analyzed demographics, patient factors, surgical details, hospital readmission, reintervention, antibiotics at discharge, empyema and death.

Results:

Overall, 253 of 2794 patients were analyzed (9.0% of all resections), including 30 of 759 from centre 1 (4.0%), 67 of 857 from centre 2 (7.8%), 9 of 247 from centre 3 (3.6%) and 147 of 931 from centre 4 (15.8%) (p < 0.001). Our cohort consisted of 56.5% men, and had a median age of 69 (range 19–88) years. Despite similar initial lengths of stay (p = 0.588), 49 patients (19.4%) were readmitted (21%, 0%, 23% and 11% from centres 1 to 4, respectively, p = 0.029), with 18 (36.7%) developing empyema, 11 (22.4%) requiring surgery and 3 (6.1%) dying. Only chest tube duration was a significant predictor of readmission (p < 0.001) and empyema development (p = 0.003), with a nearly threefold increased odds of developing empyema when the chest tube remained in situ for more than 20 days.

Conclusion:

Discharge with chest tube after lung resection is associated with serious adverse events. Given the high risk of empyema development, removal of chest tubes should be considered, when appropriate, within 20 days of surgery. Our data suggest a potential need for proactive postdischarge outpatient management programs to diminish risk of morbidity and death.

Functional Adhesion of Pectin Biopolymers to the Lung Visceral Pleura

Pleural injuries and the associated "air leak" are the most common complications after pulmonary surgery. Air leaks are the primary reason for prolonged chest tube use and increased hospital length of stay. Pectin, a plant-derived heteropolysaccharide, has been shown to be an air-tight sealant of pulmonary air leaks. Here, we investigate the morphologic and mechanical properties of pectin adhesion to the visceral pleural surface of the lung. After the application of high-methoxyl citrus pectin films to the murine lung, we used scanning electron microscopy to demonstrate intimate binding to the lung surface. To quantitatively assess pectin adhesion to the pleural surface, we used a custom adhesion test with force, distance, and time recordings. These assays demonstrated that pectin-glycocalyceal tensile adhesive strength was greater than nanocellulose fiber films or pressure-sensitive adhesives (p < 0.001). Simultaneous videomicroscopy recordings demonstrated that pectin-glycocalyceal adhesion was also stronger than the submesothelial connective tissue as avulsed surface remnants were visualized on the separated pectin films. Finally, pleural abrasion and hyaluronidase enzyme digestion confirmed that pectin binding was dependent on the pleural glycocalyx (p < 0.001). The results indicate that high methoxyl citrus pectin is a promising sealant for the treatment of pleural lung injuries.

Local lung coagulation post resection: an ex-vivo porcine model

Following non-anatomical resection of lung parenchyma with a Nd:YAG laser, a coagulated surface remains. As ventilation starts, air leakage may occur in this area. The aim of the present study was to investigate, whether additional coagulation either before or after ventilation has an additional sealing effect. Freshly slaughtered porcine heart-lung blocks were prepared. The trachea was connected to a ventilator. Using a Nd:YAG laser (wavelength: 1320 nm, power: 60 W), round lesions (1.5 cm in diameter) with a depth of 1.5 cm were applied to the lung using an 800-μm laser fiber (5 s per lesion). Group 1 (n = 12) was control. Additional coagulation was performed in group 2 (n = 12) without and in group 3 (n = 12) with ventilation restarted. Air leakage (ml) from the lesions was measured. The thickness of each coagulation layer was determined on histological slices. Differences between individual groups were analyzed by one-way ANOVA (significance p < 0.05). After resection, 26.2 ± 2.7 ml of air emerged from the lesions per single respiration in group 1. Air loss in group 2 was 24.6 ± 2.5 ml (p = 0.07) and in group 3 23.7 ± 1.8 ml (p = 0.0098). In comparison to groups 1 and 2 thickness of the coagulation layers in group 3 was significantly increased. After non-anatomical porcine lung resection with a Nd:YAG laser, additional coagulation of the ventilated resection area can reduce air leakage.

A review of the outcomes of rigid medical thoracoscopy in a large UK district general hospital

Objectives

Local anesthetic medical thoracoscopy (LAT) is a well-established diagnostic, therapeutic, and preventative intervention in undiagnosed pleural effusions with a high diagnostic sensitivity and low complication rates. There is a large variability in practice. We describe a nine-year experience in a large district general hospital in England.

Methods

Two hundred seventy-five patients had LAT between January 2010 and December 2018. Data on outcomes and complications were obtained from the patients’ notes, electronic records, laboratory, and radiographic findings.

Results

The main diagnoses were malignant pleural mesothelioma (MPM) (n=110, 40%), chronic inflammation/fibrinous pleuritis (77, 28%), lung cancer (26, 9.5%), and breast cancer (16, 6%). LAT failed to diagnose cancer in 7/275 patients (false-negative rate 2.5%, diagnostic sensitivity 97.5%). Out of the 105 patients with chronic inflammation/fibrinous pleuritis or atypical proliferative processes, 21 (20%) were subsequently diagnosed with malignancy. Talcum pleurodesis was performed in 146 patients, and was successful in 86%. Seventy eight (28%) patients had trapped lung; 27 of those had a repeat procedure. The median length of stay was 3.96 days. There was one hospital death (0.3% mortality). Complications of LAT included pleural (3, 1%) and wound infections (4, 1.4%), persistent air leaks (9, 3.2%), subcutaneous emphysema (10, 3.6%), and tumor extension to the access port (1, 0.3%).

Conclusions

In this cohort, LAT was safe, effective, and enabled high diagnostic sensitivity. Further areas of study include optimal sedation and anesthetic pathways and combining LAT with indwelling pleural catheters (IPC).

Autologous Blood Patching to Mitigate Persistent Air Leaks Following Pulmonary Resection: A Novel Approach

Background

Autologous blood patch (ABP) utilized as a visceral pleural sealant for air leak post lung resection has been well documented in medical literature.

Purpose

To present our experience of a novel approach, we employed to instill autologous blood into the pleural space to mitigate persistent air leaks following pulmonary resection.

Methods

From January 2007 to September 2011, 19 patients were submitted to autologous blood patching for persistent air leaks following surgery. Demographic and surgical characteristics were collected at baseline. Blood patching measures were recorded at the time of the event. Continuous variables were summarized with median and range while categorical measures were summarized with frequency and percent. Due to the small sample size and descriptive nature of this study, no hypothesis tests were performed. All analyses were conducted using R Statistical Software.

 Results

The median age of patients who required a blood patch for a persistent air leak was 67.9 (Range: 50.3-78.7) years and 11 (57.9%) were males and 8 (42.1%) were females. The majority (78.9%) of the patients’ first surgery was mass resection and 4 (21.1%) had a lung volume reduction. Seven (36.7%) required a re-do surgery, and almost all (89.5%) had 28 mm chest tubes used during surgery. The majority or 63.2% (N=12) of the patient's air leaks were classified as moderate, 21.1% (N=4) as severe, 15.8% as mild (N=3); twelve (63.2%) required one attempt for a successful blood patch, 6 (31.6%) required two attempts, and one (5.3%) required three which were all unsuccessful. The median number of days from detecting air leaks to blood patch for the air leak that required two attempts was 9 (Range: 8, 23) days for lung volume reduction patients and 16 (Range: 6, 26 ) days for mass resection patients.

Conclusion

Blood patching remains an effective bedside strategy that can be carried out with minimal risk. We believe opportunities exist to further advance the method of delivering blood as an autologous sealant to mitigate persistent air leaks (PAL).

The benefits of digital drainage system versus traditional drainage system after robotic-assisted pulmonary lobectomy

Background

Postoperative air leaks are the most common complication after a pulmonary resection. There is no data in the literature comparing the traditional and digital chest drainage system after a robotic-assisted pulmonary lobectomy.

Methods

This was a retrospective, correlational study. Medical records from 182 eligible robotic-assisted lobectomy patients were evaluated to determine the association between digital and traditional chest tube drainage systems (CTDS) with postoperative chest tube days, hospital LOS, chest tube reinsertion during hospitalization, and 30-day readmission for pneumothorax. Multiple regression was used to determine the association between CTDS while controlling for confounding variables.

Results

No differences were noted between groups for age, gender, BMI, smoking, adhesions or neoadjuvant therapy. Patients with digital drainage systems had significantly shorter chest tube duration than those with traditional drainage systems (2.07 vs. 2.73 days, P=0.003). After controlling for age and BMI, CTDS was not found to be a significant predictor of CT duration. Digital drainage system were also associated with significantly shorter hospital LOS (4.02 vs. 5.06 days, P=0.01) After controlling for age, BMI, and presence of post-op a-fib, use of a digital CTDS was significantly associated with 1 day shorter hospital LOS. Chest tube reinsertion occurred four times more frequently with traditional drainage systems, but the difference did not achieve the level of statistical significance (P=0.059). The frequency of readmission due to pneumothorax was very low (1 patient per group), which prevented comparative statistical analysis.

Conclusions

In the digital drainage system there are shorter chest tube days and hospital length of stay after a robotic-assisted lobectomy. The decision to remove chest tubes in the traditional drainage system is burdened with uncertainty. The digital drainage system reduces intraobserver variability allowing for improved decision making in chest tube removal. Both CT duration and hospital LOS were shorter using unadjusted analyses. Type of CTDS was not significantly associated with CT duration after controlling for age and BMI. However, after controlling for age, BMI, and post-op atrial fibrillation, use of the digital CTDS was associated with a 1 day reduction in hospital LOS.

Association of tumor location with economic outcomes and air leak complications in thoracic lobectomies: results from a national hospital billing dataset

Purpose: To assess whether tumor location during thoracic lobectomies affects economic outcomes or air leak complications.

Patients and methods: Retrospective, observational study using Premier Healthcare Database. The study included patients aged ≥18 years who underwent elective inpatient thoracic lobectomy for lung cancer between 2012 and 2014 (first qualifying=index admission). Three mutually exclusive tumor location groups were formed: upper lobe, middle lobe, and lower lobe. Primary outcomes were index admission’s length of stay (LOS), total hospital costs, and operating room time; in-hospital air leak complications (composite of air leak/pneumothorax) served as an exploratory outcome. Multivariable models were used to examine the association between tumor location and the study outcomes, accounting for covariates and hospital-level clustering.

Results: 8,750 thoracic lobectomies were identified: upper lobe (n=5,284), middle lobe (n=512), and lower lobe (n=2,954). Compared with the upper lobe, the middle and lower lobe groups had statistically significant (p<0.05): shorter adjusted LOS (7.0 days upper vs 5.8 days middle, 6.6 days lower), lower adjusted mean total hospital costs ($26,177 upper vs $23,109 middle, $24,557 lower), and lower adjusted odds of air leak complications (odds ratio middle vs upper=0.81, 95% CI=0.74–0.89; odds ratio lower vs upper=0.60, 95% CI=0.46–0.78). Findings were similar but varied in statistical significance when stratified by open and video-assisted thoracoscopic surgery approach.

Conclusion: Among patients undergoing elective thoracic lobectomy for lung cancer in real-world clinical practice, upper lobe tumors were significantly associated with increased in-hospital resource use and air leak complications as compared with lower or middle lobe tumors.

Structural heteropolysaccharides as air-tight sealants of the human pleura

Pulmonary "air leaks," typically the result of pleural injury caused by lung surgery or chest trauma, result in the accumulation of air in the pleural space (pneumothorax). Air leaks are a major source of morbidity and prolonged hospitalization after pulmonary surgery. Previous work has demonstrated structural heteropolysaccharide (pectin) binding to the mouse pleural glycocalyx. The similar lectin-binding characteristics and ultrastructural features of the human and mouse pleural glycocalyx suggested the potential application of these polymers in humans. To investigate the utility of pectin-based polymers, we developed a simulacrum using freshly obtained human pleura. Pressure-decay leak testing was performed with an inflation maneuver that involved a 3 s ramp to a 3 s plateau pressure; the inflation was completely abrogated after needle perforation of the pleura. Using nonbiologic materials, pressure-decay leak testing demonstrated an exponential decay with a plateau phase in materials with a Young's modulus less than 5. In human pleural testing, the simulacrum was used to test the sealant function of four mixtures of pectin-based polymers. A 50% high-methoxyl pectin and 50% carboxymethylcellulose mixture demonstrated no sealant failures at transpleural pressures of 60 cmH2 O. In contrast, pectin mixtures containing 50% low-methoxyl pectin, 50% amidated low-methoxyl pectins, or 100% carboxymethylcellulose demonstrated frequent sealant failures at transpleural pressures of 40-50 cmH2 O (p < 0.001). Inhibition of sealant adhesion with enzyme treatment, dessication and 4°C cooling suggested an adhesion mechanism dependent upon polysaccharide interpenetration. We conclude that pectin-based heteropolysaccharides are a promising air-tight sealant of human pleural injuries. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 799-806, 2019.

Forecasting pulmonary air leak duration following lung surgery using transpleural airflow data from a digital pleural drainage device

Background

Prolonged air leak (PAL) is often the limiting factor for hospital discharge after lung surgery. Our goal was to develop a statistical model that reliably predicts pulmonary air leak resolution by applying statistical time series modeling and forecasting techniques to digital drainage data.

Methods

Autoregressive Integrated Moving Average (ARIMA) modeling was used to forecast air leak flow from transplural air flow data. The results from ARIMA were retrospectively internally validated with a group of 100 patients who underwent lung resection between December 2012 and March 2017, for whom digital pleural drainage data was available for analysis and a persistent air leak was the limiting factor for chest tube removal.

Results

The ARIMA model correctly identified 82% (82/100) of patients as to whether or not the last chest tube removal was appropriate. The performance characteristics of the model in properly identifying patients whose air leak would resolve and who would therefore be candidates for safe chest tube removal were: sensitivity 80% (95% CI, 69-88%), specificity 88% (95% CI, 68-97%), positive predictive value 95% (95% CI, 86-99%), and negative predictive value 59% (95% CI, 42-79%). The false positive and false negative rate was 12% (95% CI, 12-31%) and 20% (95% CI, 12-31%).

Conclusions

We were able to validate a statistical model that that reliably predicted resolution of pulmonary air leak resolution over a 24-hour period. This information may improve the care of patients with chest tube by optimizing duration of pleural drainage.

Comparison study of computed tomography-guided radiofrequency and microwave ablation for pulmonary tumors: A retrospective, case-controlled observational study

BACKGROUND

The aim of this study was to compare the safety, efficacy, and prognostic value of radiofrequency ablation (RFA) and microwave ablation (MWA) for lung tumors.

METHODS

Between March 2012 and January 2018, 238 patients with lung cancer were treated with MWA (139, 58.4%) or RFA (99, 41.6%) in our center. Patient and tumor characteristics, complications, complete ablation (CA) rate, and prognosis were compared between the groups. Meta-analysis was used to systematically compare the outcomes of RFA and MWA for the treatment of lung tumors.

RESULTS

Ablation was successfully completed in all patients and no procedure-related death occurred. The total complication rates in the RFA and MWA groups were 24.2% (24/99) and 16.5% (23/139), respectively, and there was no statistically significant difference (P = 0.142). The initial and total CA rates were similar at P > 0.05 (RFA vs. MWA: initial CA, 97.0% vs. 96.4%; total CA, 99.0% vs. 98.6%, respectively). During follow-up, there was no significant difference in median progression-free (RFA vs. MWA: 12.5 months, 95% confidence interval [CI] 5.002-19.998 vs. 9.5 months, 95% CI 6.623-12.377; P = 0.673) or overall survival (RFA vs. MWA: 33 months, 95% CI 27.070-38.930 vs. 30 months, 95% CI, 18.482-41.518; P = 0.410) between the groups. Combined with the results of published comparison studies, meta-analysis further confirmed that the outcomes of these two treatments were similar.

CONCLUSION

Both RFA and MWA are safe and effective treatments with a survival benefit for selected patients with primary and metastatic lung tumors.

Management of residual pleural space after lung resection: fully controllable paralysis of the diaphragm through continuous phrenic nerve block

Background

Residual pleural space after lung resection associated with air leak is a challenging issue, potentially causing serious complications. We report a new, postoperative technique to reduce the pleural space, inducing a controlled and reversible paralysis of the diaphragm.

Methods

Ten patients were enrolled (7 lobectomies, 2 bilobectomy, 1 wedge resection). Inclusion criteria were: digitally detected air flow >200 mL/min at post-op day 3, presence of empty pleural space at chest x-ray, absence of restrictive lung disease, absence of known arrhythmias. A 22G nerve-block catheter was place under ultrasound guidance in proximity to the phrenic nerve, between the sternocleidomastoid muscle and the anterior scalene muscle at the level of 6^th cervical vertebra. Continuous infusion of ropivacaine 0.2% 3 mL/h was started. Fluoroscopy was used to confirm significant reduction in hemidiaphragm movements. Monitoring of vital signs and intense respiratory physiotherapy were enhanced. The infusion was stopped at air leak cessation and the catheter was removed along with the chest drain.

Results

No peri- and post-procedural complications occurred. In all patients, we observed an immediate reduction of the empty pleural space and resolution of the air leak within few days (3±1.16 days). After suspension of local anaesthetic, complete restoration of the hemidiaphragm function has been documented.

Conclusions

This is an effective and minimally invasive method to reduce the residual pleural space after lung resections. Narrowing of the pleural space facilitates the contact between the lung and the chest wall promoting the resolution of the air leak. Diaphragm paralysis is controlled and temporary with no residual disabilities.

Pathophysiological mechanism of post-lobectomy air leaks

Background

Air leak post-lobectomy continues to remain a significant clinical problem, with upper lobectomy associated with higher air leak rates. This paper investigated the pathophysiological role of pleural stress in the development of post-lobectomy air leak.

Methods

Preoperative characteristics and postoperative data from 367 consecutive video assisted thoracic surgery (VATS) lobectomy resections from one centre were collected prospectively between January 2014 and March 2017. Computer modelling of a lung model using finite element analysis (FEA) was used to calculate pleural stress in differing areas of the lung.

Results

Air leak following upper lobectomy was significantly higher than after middle or lower lobectomy (6.3% versus 2.5%, P=0.044), resulting in a significant six-day increase in mean hospital stay, P=0.004. The computer simulation model of the lung showed that an apical bullet shape was subject to eightyfold higher stress than the base of the lung model.

Conclusions

After upper lobectomy, the bullet shape of the apex of the exposed lower lobe was associated with high pleural stress, and a reduction in mechanical support by the chest wall to the visceral pleura due to initial post-op lack of chest wall confluence. It is suggested that such higher stress in the lower lobe apex explains the higher parenchymal air leak post-upper lobectomy. The pleural stress model also accounts for the higher incidence of right-sided prolonged air leak post-resection.

Pressure-decay testing of pleural air leaks in intact murine lungs: evidence for peripheral airway regulation

The critical care management of pleural air leaks can be challenging in all patients, but particularly in patients on mechanical ventilation. To investigate the effect of central airway pressure and pleural pressure on pulmonary air leaks, we studied orotracheally intubated mice with pleural injuries. We used clinically relevant variables - namely, airway pressure and pleural pressure - to investigate flow through peripheral air leaks. The model studied the pleural injuries using a pressure-decay maneuver. The pressure-decay maneuver involved a 3 sec ramp to 30 cmH2 0 followed by a 3 sec breath hold. After pleural injury, the pressure-decay maneuver demonstrated a distinctive airway pressure time history. Peak inflation was followed by a rapid decrease to a lower plateau phase. The decay phase of the inflation maneuver was influenced by the injury area. The rate of pressure decline with multiple injuries (28 ± 8 cmH2 0/sec) was significantly greater than a single injury (12 ± 3 cmH2 O/sec) (P < 0.05). In contrast, the plateau phase pressure was independent of injury surface area, but dependent upon transpulmonary pressure. The mean plateau transpulmonary pressure was 18 ± 0.7 cm H2 O. Finally, analysis of the inflation ramp demonstrated that nearly all volume loss occurred at the end of inflation (P < 0.001). We conclude that the air flow through peripheral lung injuries was greatest at increased lung volumes and limited by peripheral airway closure. In addition to suggesting an intrinsic mechanism for limiting flow through peripheral air leaks, these findings suggest the utility of positive end-expiratory pressure and negative pleural pressure to maintain lung volumes in patients with pleural injuries.

Functional Mechanics of a Pectin-Based Pleural Sealant after Lung Injury

Pleural injury and associated air leaks are a major influence on patient morbidity and healthcare costs after lung surgery. Pectin, a plant-derived heteropolysaccharide, has recently demonstrated potential as an adhesive binding to the glycocalyx of visceral mesothelium. Since bioadhesion is a process likely involving the interpenetration of the pectin-based polymer with the glycocalyx, we predicted that the pectin-based polymer may also be an effective sealant for pleural injury. To explore the potential role of an equal (weight%) mixture of high-methoxyl pectin and carboxymethylcellulose as a pleural sealant, we compared the yield strength of the pectin-based polymer to commonly available surgical products. The pectin-based polymer demonstrated significantly greater adhesion to the lung pleura than the comparison products (p < 0.001). In a 25 g needle-induced lung injury model, pleural injury resulted in an air leak and a loss of airway pressures. After application of the pectin-based polymer, there was a restoration of airway pressure and no measurable air leak. Despite the application of large sheets (50 mm2) of the pectin-based polymer, multifrequency lung impedance studies demonstrated no significant increase in tissue damping (G) or hysteresivity (η)(p > 0.05). In 7-day survival experiments, the application of the pectin-based polymer after pleural injury was associated with no observable toxicity, 100% survival (N = 5), and restored lung function. We conclude that this pectin-based polymer is a strong and nontoxic bioadhesive with the potential for clinical application in the treatment of pleural injuries.

CT-guided percutaneous laser ablation of metastatic lung cancer: three cases report and literature review

Objective

To report the efficacy and safety of CT-guided percutaneous laser ablation (PLA) for metastatic lung tumors.

Methods

Three cases of metastatic lung cancer underwent CT-guided PLA, and we searched for previously published articles on the minimally invasive CT-guided RFA or MWA for lung tumors in recent five years.

Results

With the guidance of CT, all lesions had good prognosis under laser ablation. Case 1 suffering from severe pulmonary dysfunction and diffuse pulmonary bullae, had small pneumothorax. CT scan obtained four months following the ablation showed two lesions had complete responses and one partial response. Case 2 had successful complete response with absent lung mass, and also had a good postoperative condition without any discomfort in the two-month follow-up. Case 3 showed partial response and improved greatly after five months. 962 cases (mean age of 45.7 years, 62.2% male) of 1297 lung tumors with detailed information were identified from 27 articles. Of these cases, the minority manifested complications such as pneumothorax, hemoptysis, hemothorax, pneumonia, pain and fever.

Conclusions

Percutaneous CT-guided PLA could be a safe and promising minimally invasive treatment for patients with primary lung cancer or unresectable pulmonary metastases, especially multineedle PLA in large tumors, which still needs more large-scale prospective studies to convince this method in the future.

[Application of Digital Drainage System in Postoperative Refractory Prolonged Air Leaks after Pulmonary Surgery]

背景与目的

术后持续性肺漏气是肺部手术后最常见的并发症之一。数字化胸腔引流系统（digital drainage system, DDS）被认为具有准确、客观、舒适、患者耐受性好、经济等优点。本研究旨在总结DDS用于肺部手术后难治性持续性大量漏气的临床疗效。

方法

术后5天和7天分别是胸腔镜和开胸术后持续性肺漏气（prolonged air leak, PAL）的界限；本研究将难治性持续性大量漏气定义为达到PAL时间2倍及以上且漏气持续达2度以上，可伴有明显皮下气肿或纵隔气肿等相关并发症。2016年1月-2016年12月间，应用数字化胸腔引流系统结合胸膜固定术治疗符合上述标准的病例共8例，收集相关临床资料并总结分析。

结果

本组病例中肺叶切除术6例，肺段切除2例。平均术后持续漏气（17.3±5.1）d，DDS平均使用时间（5.6±3.7）d。平均术后引流量（3, 550.6±1, 881.1）mL。应用DDS前后的平均引流量为（2, 615.6±1, 741.2）mL和（935.0±242.7）mL。平均住院时间（18.1±5.0）d。

结论

数字化胸腔引流系统用于肺部手术后难治性持续性大量漏气安全可行，可提供更大的负压吸引值，从而促使患肺复张为后继的胸膜固定术创造条件，并缩短引流天数和住院时间。

Optimal age for elective surgery of asymptomatic congenital pulmonary airway malformation: a meta-analysis

Controversy exists on the optimal age for elective resection of asymptomatic congenital pulmonary airway malformation. Current recommendations vary widely, highlighting the overall lack of consensus. A systematic search of Embase, MEDLINE, CINAL, and CENTRAL was conducted in January 2016. Identified citations were screening independently in duplicate and consensus was required for inclusion. Results were pooled using inverse variance fixed effects meta-analysis. Meta-analysis results indicate no statistically significant differences for complications within the 3-month and 6-month age comparison groups [odds ratio (OR) 4.20, 95% confidence interval (CI) 0.78-22.77, I ² = 0%; OR 2.39, 95% CI 0.63-9.11, I ² = 0%, respectively]. Older patients were significantly favoured for 3-month and 6-month age comparison groups for length of hospital stay [mean difference (MD) 4.13, 95% CI 2.31-5.96, I ² = 0%; MD 3.38, 95% CI 0.44-6.31, I ² = 0%, respectively]. Borderline statistical significance was observed for chest tube duration in patients ≥6 months of age (MD 1.06, 95% CI 0.02-2.09, I ² = 0%). No mortalities were recorded. Surgical treatment appears to be safe at all ages, with no mortalities and similar rates of complications between age groups. The included evidence was not sufficient to make a conclusive recommendation on optimal age for elective resection.

Pleural pressure theory revisited: a role for capillary equilibrium

BACKGROUND

Theories elucidating pleural pressures should explain all observations including the equal and opposite recoil of the chest wall and lungs, the less than expected pleural hydrostatic gradient and its variation at lobar margins, why pleural pressures are negative and how pleural fluid circulation functions.

METHODS

A theoretical model describing equilibrium between buoyancy, hydrostatic forces, and capillary forces is proposed. The capillary equilibrium model described depends on control of pleural fluid volume and protein content, powered by an active pleural pump.

RESULTS

The interaction between buoyancy forces, hydrostatic pressure and capillary pressure was calculated, and values for pleural thickness and pressure were determined using values for surface tension, contact angle, pleural fluid and lung densities found in the literature. Modelling can explain the issue of the differing hydrostatic vertical pleural pressure gradient at the lobar margins for buoyancy forces between the pleural fluid and the lung floating in the pleural fluid according to Archimedes' hydrostatic paradox. The capillary equilibrium model satisfies all salient requirements for a pleural pressure model, with negative pressures maximal at the apex, equal and opposite forces in the lung and chest wall, and circulatory pump action.

CONCLUSIONS

This model predicts that pleural effusions cannot occur in emphysema unless concomitant heart failure increases lung density. This model also explains how the non-confluence of the lung with the chest wall (e.g., lobar margins) makes the pleural pressure more negative, and why pleural pressures would be higher after an upper lobectomy compared to a lower lobectomy. Pathological changes in pleural fluid composition and lung density alter the equilibrium between capillarity and buoyancy hydrostatic pressure to promote pleural effusion formation.