Preclinical quantification of air leaks in a physiologic lung model: effects of ventilation modality and staple design

Characterisation of pulmonary air leak measurements using a mechanical ventilator in a bench setup

Prolonged air leakage (AL) following pulmonary resections leads to prolonged hospital stay and post-operative complications. Intra- and postoperative quantification of AL might be useful for improving treatment decisions, but these measurements have not been characterised. AL calculations based on inspiratory and expiratory tidal volumes were investigated in an Intensive Care Unit mechanical ventilator circuit (Servo-I). AL was also measured by a digital chest drainage system. This study shows that AL measurements increase in accuracy when corrected for baseline deviations (R: 0.904 > 0.997, p < 0.001). Bland-Altman analysis revealed a funnel-shape, indicative of a detection threshhold. Corrected measurements were most accurate when averaged over five breaths and AL was >500 mL/min, with an estimated mean systemic bias of 7.4% (95%-limits of agreement [LoA]: 1.1%-13.7%) at 500 mL/min air leak. Breath-by-breath analysis showed most accurate results at AL >20 mL/breath (R: 0.989-0.991, p < 0.001) at tidal volumes between 350-600 mL. The digital drain had a mean systemic bias of -11.1% (95%-LoA: -18.9% to -3.3%) with homogenous scatter in Bland-Altman analysis and a strong correlation to the control measurement over a large range (0-2000mL/min, R: 0.999, p < 0.001). This study indicates that the Servo-I can be used for air leak quantification in clinically relevant ranges (>500 mL/min), but is unsuited for small leak detection due to a detection threshold. Researchers and clinicians should be aware of varying accuracy and interoperability characteristics between AL measurement devices.

The role of new staplers in reducing the incidence of air leak

Surgical staplers play an important role in the contemporary minimally invasive thoracic surgery including resection of lung tissue. However, staple line failure resulting in postoperative air leaks is a common complication after lung surgery, that if persist more than five days are defined as prolonged air leaks (PALs). PALs are associated with increased length of stay, patient morbidity and mortality, and hospital costs. To reduce the incidence of PALs, stapler devices underwent in the last years ongoing development aimed at improving device-to-tissue interaction. This clinical practice review explores the most important aspects of the evolution of surgical staplers, based on the review of the available literature. Modern staple cartridges entail small bumps to engage tissue and minimize tissue movement during compression and firing. Staplers with graduated staple heights are advocated to generate less stress on tissue during compression and clamping, thus affording greater perfusion into the staple line. However, air leaks may occur from an appropriate staple line with complete pleural coverage and perfusion due to enlarged staple canals after lung inflation, particularly in case of emphysema. To buttress staple line, thus prevent air leaks in high-risk patients, several types of tissue coverage (bovine pericardium, polytetrafluoroethylene, knitted calcium alginate, bioabsorbable polyglycolic acid) have been successfully developed in the last years. Finally, the most advanced stapler technology is represented by the new energy powered staplers, able to eliminate the manual firing force, monitor tissue compression during firing, and making automatic adjustments to optimize the staple line.

Sound-guided assessment and localization of pulmonary air leak

Pulmonary air leak is the most common complication of lung surgery, with air leaks that persist longer than 5 days representing a major source of post-surgery morbidity. Clinical management of air leaks is challenging due to limited methods to precisely locate and assess leaks. Here, we present a sound-guided methodology that enables rapid quantitative assessment and precise localization of air leaks by analyzing the distinct sounds generated as the air escapes through defective lung tissue. Air leaks often present after lung surgery due to loss of tissue integrity at or near a staple line. Accordingly, we investigated air leak sounds from a focal pleural defect in a rat model and from a staple line failure in a clinically relevant swine model to demonstrate the high sensitivity and translational potential of this approach. In rat and swine models of free-flowing air leak under positive pressure ventilation with intrapleural microphone 1 cm from the lung surface, we identified that: (a) pulmonary air leaks generate sounds that contain distinct harmonic series, (b) acoustic characteristics of air leak sounds can be used to classify leak severity, and (c) precise location of the air leak can be determined with high resolution (within 1 cm) by mapping the sound loudness level across the lung surface. Our findings suggest that sound-guided assessment and localization of pulmonary air leaks could serve as a diagnostic tool to inform air leak detection and treatment strategies during video-assisted thoracoscopic surgery (VATS) or thoracotomy procedures.

Double stapling method for closure of intraoperative alveolar air leakage adjacent to the staple line: a randomized experimental study on ex vivo porcine lungs

Background

Alveolar air leakage from a pleural defect around the staple line is one of the complications after wedge resection of the lung. An intraoperative closure of the pleural defect by suturing can cause additional pleural rupture due to tension of the pleura adjacent to staple lines. Therefore, we have introduced a novel closure method for pleural defect adjacent to the staple line, named the double stapling method. This study compared the efficacy of two closure methods; the double stapling method and conventional suturing method with pledgets using ex vivo porcine lungs.

Methods

The double stapling method involves closing the pleural defect by suturing the two parallel staple lines at both sides of the pleural defect. This method was developed to distribute the pleural tension around the needle holes of suturing. As a model of pleural defect adjacent to the staple line after wedge resection, wedge resection of the caudal lobe of left porcine lungs was performed, and a superficial square pleural defect (10 mm × 10 mm) adjacent to the staple line was made by scalpel. The defect was closed using the following two methods: (I) suturing with pledgets (n=10); and (II) double stapling method (n=10). The lobe was inflated in water at an airway pressure of 20, 25, and 30 cmH₂O; closure success or failure was judged by the absence or presence of air leakage.

Results

The closure success was confirmed in 2 (20%) out of 10 cases in the suturing with pledgets group and 9 (90%) out of 10 in the double stapling method group (P=0.007). In 4 out of 10 cases in the suturing with pledgets group, new pleural clefts longer than 3 mm were created around the needle holes of suturing.

Conclusions

Ex vivo experiments have suggested the superiority of the double stapling method for the intraoperative closure of alveolar air leakage adjacent to the staple line after wedge resection, compared to conventional suturing with the pledget method.

Comparative study of hydrophobically modified gelatin-based sealant with commercially available sealants

Air leakage is one of the major complications related to pulmonary surgeries. To reduce this complication, we developed a decyl group (C10)-modified Alaska pollock gelatin (ApGltn) (C10-ApGltn) sealant and evaluated its practical performance against commercially available sealants, Beriplast® and DuraSeal®. C10-ApGltn was synthesized by reductive amination of the amino groups in ApGltn with decanal. C10-ApGltn was crosslinked with a poly(ethylene glycol)-based crosslinker to form a tissue sealant. The crosslinking time of the C10-ApGltn sealant was fast enough for curing on tissue and application as a spray system. Although the percent swelling of C10-ApGltn and DuraSeal was significantly greater than Beriplast, C10-ApGltn and DuraSeal exhibited excellent tissue sealing properties on pleura tissue under a long-term moist condition. Additionally, C10-ApGltn and DuraSeal did not cause severe inflammatory responses in a rat subcutaneous example. Therefore, C10-ApGltn sealant had comparable tissue sealing properties to DuraSeal under a moist condition, indicating the potential of C10-ApGltn sealant for pulmonary surgeries.

Air leaks: Stapling affects porcine lungs biomechanics

During thoracic operations, surgical staplers resect cancerous tumors and seal the spared lung. However, post-operative air leaks are undesirable clinical consequences: staple legs wound lung tissue. Subsequent to this trauma, air leaks from lung tissue into the pleural space. This affects the lung's physiology and patients' recovery. The objective is to biomechanically and visually characterize porcine lung tissue with and without staples in order to gain knowledge on air leakage following pulmonary resection. Therefore, a syringe pump filled with air inflates and deflates eleven porcine lungs cyclically without exceeding 10 cmH₂O of pressure. Cameras capture stereo-images of the deformed lung surface at regular intervals while a microcontroller simultaneously records the alveolar pressure and the volume of air pumped. The raw images are then used to compute tri-dimensional displacements and strains with the Digital Image Correlation method (DIC). Air bubbles originated at staple holes of inner row from exposed porcine lung tissue due to torn pleural on costal surface. Compared during inflation, left upper or lower lobe resections have similar compliance (slope of the pressure vs volume curve), which are 9% lower than healthy lung compliance. However, lower lobes statistically burst at lower pressures than upper lobes (p-value<0.046) in ex vivo conditions confirming previous clinical in vivo studies. In parallel, the lung deformed mostly in the vicinity of staple holes and presented maximum shear strain near the observed leak location. To conclude, a novel technique DIC provided concrete evidence of the post-operative air leaks biomechanics. Further studies could investigate causal relationships between the mechanical parameters and the development of an air leak.

Clinical and economic benefits associated with the use of powered and tissue-specific endoscopic staplers among the patients undergoing thoracoscopic lobectomy for lung cancer

Background: Thoracoscopic lobectomy for lung cancer is a complex procedure where endoscopic staplers play a critical role in transecting the lung parenchyme, vasculature, and bronchus. This retrospective study was performed to investigate the economic benefits of powered and tissue-specific endoscopic staplers such as gripping surface technology (GST) and powered vascular stapler (PVS) compared to standard staplers.Methods: Two hundred and seventy-five patients who received a thoracoscopic lobectomy between 2008 and 2016 were included. Group 1 (n = 117) consisted of patients who received the operation with manual endoscopic staplers, whereas Group 2 (n = 158) consisted of patients who received the operation with GST and PVS.Results: Patient demographics and clinical characteristics were comparable, except smoking history, pulmonary function, and pleural adhesion. All patients received the operation successfully without mortalities and broncho-pleural fistula. Operation time and blood loss were higher in Group 1. Pleurodesis was performed less in Group 2 than in Group 1 (18.0% vs 3.8%, p < 0.0001). Group 2 had statistically significant lower adjusted hospital costs (Korean Won, 14,610,162 ± 4,386,628 vs 12,876,111 ± 5,010,878, p < 0.0001), lower adjusted hemostasis related costs (198,996 ± 110,253 vs 175,291 ± 191,003, p = 0.0101); lower cartridge related adjusted costs (1,105,091 ± 489,838 vs 839,011 ± 307,894, p < 0.0001) compared to Group 1. As well, Group 2 showed ∼12% lower adjusted total hospital costs compared to Group 1. Multivariable analysis revealed that Group 1 was related to increased hospital costs.Conclusions: This study showed that thoracoscopic lobectomy with powered and tissue-specific endoscopic staplers were associated with better clinical outcomes and reduced adjusted hospital costs when compared in Korean real-world settings.