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In patients with severe acute respiratory distress syndrome caused by coronavirus 2019 (COVID-19), mortality remains high despite optimal medical management. Extracorporeal membrane oxygenation (ECMO) has been widely used to support such patients. ECMO is not a perfect solution; however, there are several limitations and serious complications associated with ECMO use. Moreover, the overall short-term mortality rate of patients with COVID-19 supported by ECMO is high (~30%). Some patients who survive severe acute respiratory distress syndrome have chronic lung failure requiring oxygen supplementation, long-term mechanical ventilation, or ECMO support. Although lung transplant remains the most effective treatment for patients with end-stage lung failure from COVID-19, optimal patient selection and transplant timing for patients with COVID-19-related lung failure are not clear. Access to an artificial lung (AL) that can be used for long-term support as a bridge to transplant, bridge to recovery, or even destination therapy will become increasingly important. In this review, we discuss why the COVID-19 pandemic may drive progress in AL technology, challenges to AL implementation, and how some of these challenges might be overcome., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: The role of lung transplantation for coronavirus disease 2019 (COVID-19)-related lung failure is evolving as the pandemic persists., Methods: From January 2021 to April 2022, 20 patients (median age 62 y; range 31-77) underwent lung transplantation for COVID-related lung failure at our institution. We reviewed their clinical and intraoperative characteristics and early outcomes including postoperative complications., Results: Eleven patients (55%) had chronic lung disease when they contracted COVID-19. All 20 patients required hospitalization for antivirus treatment. Median lung allocation score was 74.7 (33.1-94.0). Thirteen patients (65%) underwent single-lung transplants, and 7 patients (35%) underwent double-lung transplants. Concomitant coronary artery bypass graft surgery was performed in 2 (10%) patients because of severe coronary artery disease. Postoperatively, venovenous extracorporeal membrane oxygenation was needed in 3 patients (15%) because of severe primary graft dysfunction; all were eventually weaned. Ten patients (50%) experienced deep venous thrombosis, and 1 eventually developed a major pulmonary embolus. The median intensive care unit stay and hospital stays were 6.5 d (3-44) and 18 d (7-77), respectively. During a median follow-up of 201 d (47-418), we experienced 1 late mortality due to COVID-19-related myocarditis. Among the 13 patients with single-lung transplant, 5 demonstrated improvement in their native lungs., Conclusions: Lung transplantation yielded favorable early outcomes in a heterogeneous patient cohort that included older patients, obese patients, and patients with coronary artery disease or preexisting chronic lung disease. Our data also shed light on the transforming role of lung transplantation for the pulmonary sequelae of a complex multisystem COVID-19 disorder., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Although double lung transplant is recommended in patients with severe secondary pulmonary hypertension (SPH), our institutional experiences suggest a role for single lung transplant in these patients. Here, we review our experience prioritizing single lung transplant in patients with SPH to minimize their surgical burden., Methods: We conducted a retrospective review of our lung transplant database to identify patients with SPH who underwent single lung transplant. Patients were stratified as either mild SPH (mean pulmonary artery pressure 25-40 mm Hg) or severe SPH (mean pulmonary artery pressure >40 mm Hg). Singe lung recipients without PH transplanted over the same time were also examined., Results: Between January 2017 and December 2019, 318 patients underwent single lung transplantation; 217 had mild SPH (68%), and 59 had severe SPH (18.5%). Forty-two patients without PH underwent single lung transplant. When the groups were compared, significantly higher pulmonary vascular resistance was noted in the severe SPH group, and obesity was noted in both the mild and severe SPH groups. Although the severe SPH group required more intraoperative cardiopulmonary support (37.3% versus 10.3% versus 4.7%, P < 0.05), there were no significant differences in most major postoperative parameters, including the duration of postoperative mechanical ventilation or the incidence of severe primary graft dysfunction. Survival 1 y posttransplant was not significantly different among the groups (93.2% versus 89.4% versus 92.9%, P = 0.58)., Conclusions: Our experience supports the option of single lung transplantation with appropriate intraoperative mechanical circulatory support in patients with SPH. This strategy is worth pursuing, especially with ongoing donor lung shortages., Competing Interests: The authors declare no funding or conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Despite the benefits of ex vivo lung perfusion (EVLP) such as lung reconditioning, preservation, and evaluation before transplantation, deleterious effects, including activation of proinflammatory cascades and alteration of metabolic profiles have been reported. Although patient outcomes have been favorable, further studies addressing optimal conditions are warranted. In this study, we investigated the role of the immunosuppressant drug cyclosporine A (CyA) in preserving mitochondrial function and subsequently preventing proinflammatory changes in lung grafts during EVLP., Methods: Using rat heart-lung blocks after 1-hour cold preservation, an acellular normothermic EVLP system was established for 4 hours. CyA was added into perfusate at a final concentration of 1 μM. The evaluation included lung graft function, lung compliance, and pulmonary vascular resistance as well as biochemical marker measurement in the perfusate at multiple time points. After EVLP, single orthotopic lung transplantation was performed, and the grafts were assessed 2 hours after reperfusion., Results: Lung grafts on EVLP with CyA exhibited significantly better functional and physiological parameters as compared with those without CyA treatment. CyA administration attenuated proinflammatory changes and prohibited glucose consumption during EVLP through mitigating mitochondrial dysfunction in lung grafts. CyA-preconditioned lungs showed better posttransplant lung early graft function and less inflammatory events compared with control., Conclusions: During EVLP, CyA administration can have a preconditioning effect through both its anti-inflammatory and mitochondrial protective properties, leading to improved lung graft preservation, which may result in enhanced graft quality after transplantation.

Background: Compromised microvasculature resulting from disrupted bronchial arterial circulation appears to trigger chronic lung allograft dysfunction. Maintaining the microvasculature throughout the transplant process could improve the long-term health of transplanted lungs. We recently developed a bronchial-arterial-circulation-sparing (BACS) lung preservation approach and tested whether this approach would decrease microvascular damage and improve allograft function., Methods: The lungs of Lewis rats were procured using either the BACS approach, where the bronchial and pulmonary arteries were synchronously perfused; a conventional approach, where only the pulmonary artery was perfused; or a conventional approach with a prostaglandin flush. After 4 hours of cold ischemia, physiologic function and vascular tone of the grafts were evaluated during ex vivo lung perfusion (EVLP), and microvasculature damage was assessed using 2-photon microscopy analysis. Lung function was compared after transplant among the groups., Results: After 4 hours of cold ischemia, the BACS group exhibited significantly higher adenosine triphosphate levels and lower expression of phosphorylated myosin light chain, which is essential for vascular smooth muscle contraction. On EVLP, the BACS and prostaglandin groups showed lower pulmonary vascular resistance and less arterial stiffness. BACS attenuated microvasculature damage in the lung grafts when compared with conventional preservation. After transplantation, the lungs preserved with the BACS approach exhibited significantly better graft function and lower expression of phosphorylated myosin light chain., Conclusions: Our data suggest that BACS lung preservation protects the dual circulation inherent to the lungs, facilitating robust microvasculature in lung grafts after transplantation, leading to better posttransplant outcomes.

Chronic allograft dysfunction (CLAD) remains a major complication, causing the poor survival after lung transplantation (Tx). Although strenuous efforts have been made at preventing CLAD, surgical approaches for lung Tx have not been updated over the last 2 decades. The bronchial artery (BA), which supplies oxygenated blood to the airways and constitutes a functional microvasculature, has occasionally been revascularized during transplants, but this technique did not gain popularity and is not standard in current lung Tx protocols, despite the fact that a small number of studies have shown beneficial effects of BA revascularization on limiting CLAD. Also, recent basic and clinical evidence has demonstrated the relationship between microvasculature damage and CLAD. Thus, the protection of the bronchial circulation and microvasculature in lung grafts may be a key factor to overcome CLAD. This review revisits the history of BA revascularization, discusses the role of the bronchial circulation in lung Tx, and advocates for novel bronchial-arterial-circulation sparing approaches as a future direction for overcoming CLAD. Although there are some already published review articles summarizing the surgical techniques and their possible contribution to outcomes in lung Tx, to the best of our knowledge, this review is the first to elaborate on bronchial circulation that will contribute to prevent CLAD from both scientific and clinical perspectives: from bedside to bench to bedside, and beyond.

Background: The role of the circulating leukocytes in lungs and their relationship with circulating proinflammatory cytokines during ischemia-reperfusion injury is not well understood. Using ex vivo lung perfusion (EVLP) to investigate the pathophysiology of isolated lungs, we aimed to identify a therapeutic target to optimize lung preservation leading to successful lung transplantation., Methods: Rat heart-lung blocks were placed on EVLP for 4 hours with or without a leukocyte-depleting filter (LF). After EVLP, lung grafts were transplanted, and posttransplant outcomes were compared., Results: Lung function was significantly better in lung grafts on EVLP with a LF than in lungs on EVLP without a LF. The interleukin (IL)-6 levels in the lung grafts and EVLP perfusate were also significantly lower after EVLP with a LF. Interestingly, IL-6 levels in the perfusate did not increase after the lungs were removed from the EVLP circuit, indicating that the cells trapped by the LF were not secreting IL-6. The trapped cells were analyzed with flow cytometry to detect apoptosis and pyroptosis; 26% were pyroptotic (Caspase-1-positive). After transplantation, there was better graft function and less inflammatory response if a LF was used or a caspase-1 inhibitor was administered during EVLP., Conclusions: Our data demonstrated that circulating leukocytes derived from donor lungs, and not circulating proinflammatory cytokines substantially impaired the quality of lung grafts through caspase-1-induced pyroptotic cell death during EVLP. Removing these cells with a LF and/or inhibiting pyroptosis of the cells can be a new therapeutic approach leading to long-term success after lung transplantation.

Background: Adult lung transplant recipients with small chests have traditionally received lungs from pediatric donors, placing an additional strain on the already restricted pediatric donor pool. Performing lobar lung transplantation (LLT) can circumvent issues with donor-recipient size mismatch; however, LLT imparts additional risks. Here, we review our experience using LLT and standard lung transplantation using a pediatric donor (PDLT) for adults with small chests., Methods: We retrospectively reviewed consecutive patients with end-stage lung disease and a height of 65 inches or less who underwent LLT (n = 15) or PDLT (n = 15) between 2006 and 2012 at our institution, a high-volume lung transplant center., Results: Lobar lung transplantation recipients were older (54 ± 10 vs 48 ± 8 years) and had higher pulmonary pressure (57 ± 11 vs 52 ± 27 mmHg) and higher lung allocation scores (70 ± 9 vs 51 ± 8) than PDLT recipients (all P < 0.05). Mean waiting time was 62 days for PDLT and 9 days for LLT. Postoperatively, the incidence of severe primary graft dysfunction and the incidence of acute renal insufficiency were higher, and the mean intensive care unit stay was longer in the LLT group, but the incidence of bronchial anastomotic complications was higher in the PDLT group because of significant size discrepancy in the main bronchus (P < 0.05). Interestingly, long-term functional outcomes and survival rates were similar between the groups., Conclusions: Both LLT and PDLT are viable surgical options for adult patients with small chests. Because of the potential impact on posttransplant outcomes, the technical complexity of transplantation, decisions regarding the best surgical approach should be made by experienced surgeons.

Background: A shortage of donors has compelled the use of extended-criteria donor organs in lung transplantation. The purpose of this study was to evaluate the impact of using older donors on outcomes after lung transplantation using current protocols., Methods: From January 2003 to August 2009, 593 lung transplants were performed at our institution. We compared 87 patients (14.7%) who received lungs from donors aged 55 years or older with 506 patients who received lungs from donors less than 55 years old. We also examined risk factors for mortality in recipients of lungs from older donors., Results: The incidence of major complications including severe primary graft dysfunction and early mortality rates were similar between the groups. However, posttransplant peak FEV1 was lower in the patients who received lungs from older donors (71.7% vs. 80.7%, P<0.05). In multivariate analysis, recipient pulmonary hypertension (transpulmonary pressure gradient >20 mm Hg) and prolonged intraoperative cardiopulmonary bypass were significant risk factors for mortality in the recipients of lungs from older donors., Conclusions: This large, single-center experience demonstrated that transplanting lungs from donors older than 55 years did not yield worse short- or long-term outcomes as compared with transplanting lungs from younger donors. However, transplanting lungs from older donors into recipients with pulmonary hypertension or recipients who required prolonged cardiopulmonary bypass increased the risk for mortality. Although lungs from older donors should not be excluded because of donor age alone, surgeons should carefully consider their patient selection criteria and surgical plans when transplanting lungs from older donors.

Background: Although the benefits of ex vivo lung perfusion (EVLP) have been globally advocated, the potentially deleterious effects of applying EVLP, in particular activation of proinflammatory cascades and alteration of metabolic profiles, are rarely discussed. This study examined proinflammatory events and metabolic profiles in lung grafts on EVLP and tested whether preconditioning lung grafts with inhaled hydrogen, a potent, cytoprotective gaseous signaling molecule, would alter the lungs' response to EVLP., Methods: Rat heart-lung blocks were mounted on an acellular normothermic EVLP system for 4 hr and ventilated with air or air supplemented with 2% hydrogen. Arterial and airway pressures were monitored continuously; perfusate was sampled hourly to examine oxygenation. After EVLP, the lung grafts were transplanted orthotopically into syngeneic rats, and lung function was examined., Results: Placing lung grafts on EVLP resulted in significant upregulation of the messenger RNAs for several proinflammatory cytokines, higher glucose consumption, and increased lactate production. Hydrogen administration attenuated proinflammatory changes during EVLP through upregulation of the heme oxygenase-1. Hydrogen administration also promoted mitochondrial biogenesis and significantly decreased lactate production. Additionally, in the hydrogen-treated lungs, the expression of hypoxia-inducible factor-1 was significantly attenuated during EVLP. These effects were maintained throughout EVLP and led to better posttransplant lung graft function in the recipients of hydrogen-treated lungs., Conclusions: Lung grafts on EVLP exhibited prominent proinflammatory changes and compromised metabolic profiles. Preconditioning lung grafts using inhaled hydrogen attenuated these proinflammatory changes, promoted mitochondrial biogenesis in the lungs throughout the procedure, and resulted in better posttransplant graft function.

Background: Lung volume reduction surgery (LVRS) as a bridge to lung transplantation was first advocated in 1995 and published studies have supported the concept but with limited data. The risk-benefit tradeoffs of the combined procedure have not been thoroughly examined, although substantial information regarding LVRS has emerged., Methods: Of 177 patients who underwent lung transplantation for end-stage emphysema between 2002 and 2009 at our center, 25 had prior LVRS (22 bilateral and 3 unilateral). Lung transplantation was performed 22.9±15.9 months after LVRS. We compared in-hospital morbidity, functional capacity, and long-term outcomes of patients who underwent LVRS before lung transplantation with a matched cohort of patients without prior LVRS to assess the influence of LVRS on posttransplantation morbidity and mortality., Results: The incidence of postoperative bleeding requiring reexploration and the incidence of renal dysfunction requiring dialysis were higher in patients with LVRS before lung transplantation. Posttransplantation peak forced expiratory volume in 1 s was worse in patients with LVRS before lung transplantation (56.7% vs. 78.8%; P<0.05). Five-year survival was not significantly different (59.7% in patients with LVRS before lung transplantation vs. 66.2% in patients with lung transplantation alone). In multivariate analysis, age more than 65 years, prolonged cardiopulmonary bypass time, and severe pulmonary hypertension were significant predictors for mortality (P<0.05)., Conclusions: Although LVRS remains a viable option as a bridge to lung transplantation in appropriately selected patients, LVRS before lung transplantation can impart substantial morbidity and compromised functional capacity after lung transplantation. LVRS should not be easily considered as a bridge to transplantation for all lung transplant candidates.

Background: Early major neurologic complications after lung transplantation represent a major source of morbidity for patients and compromise their quality of life; however, the mechanisms underlying neurologic complications and their impact on outcomes in lung transplantation remain largely unknown., Methods: Patients who received lung transplants at our institution between January 2004 and December 2010 were identified (n=759). Data on complications including occurrence, timing, management, and outcome were extracted from our transplant database and medical record review. Major neurologic complications were defined as those that were potentially life threatening, required urgent treatment/intubation, or required admission to the intensive care unit., Results: Seventy (9.2%) patients experienced major neurologic complications within 2 weeks after lung transplantation. Most common complications were stroke (41%) and severe toxic/metabolic encephalopathy (37%). Multivariate analysis demonstrated that advanced age, history of coronary artery disease, prolonged use of cardiopulmonary bypass, and severe primary graft dysfunction increased the risk for death in patients with early major neurologic complications (P<0.05). There was a significant difference in survival between patients with neurologic complications and without (90-day mortality: 15% of patients who developed neurologic complications versus 4% of patients who did not; P=0.03; 5-year survival: 51.1% in patients who developed neurologic complication versus 62.1% in patients who did not; P<0.05)., Conclusions: Early major neurologic complications after lung transplantation are common and carry substantial morbidity and mortality. Given the risk factors identified in this study, additional pretransplantation workup and intraoperative and postoperative monitoring for high-risk patients may help reduce the incidence of neurologic complications.

Background: When selecting a donor for lung transplantation, it is generally believed that the best outcomes occur when the donor has no smoking history. Because we experienced unexpected adverse outcomes after transplant of lungs from teenaged donors with no smoking history, this study revisited the effects of donor smoking history in relation to age on transplant outcomes., Methods: We conducted a retrospective review of 532 consecutive lung transplants performed at our institution. Most donors (293, 55%) had a history of smoking; 239 donors were nonsmokers. The smoking donors were further subgrouped based on consumption (<20, 20-40, or >40 pack-years). The nonsmoking donors were subgrouped by age (<20 years or ≥20 years). Recipients' characteristics and outcomes were compared., Results: The recipients of lungs from donors with a smoking history showed better 5-year survival than recipients of lungs from nonsmokers (65.8% vs. 48.3%, P<0.05), but recipients of lungs from heavy smokers (>40 pack-years smoking history) exhibited a significantly higher incidence of severe primary graft dysfunction and higher short- and long-term mortality than the recipients of lungs from donors who smoked less. Surprisingly, recipients of lungs from teenaged donors with no smoking history exhibited a higher morbidity and mortality than recipients of lungs from adult nonsmoking donors but did not exhibit decreased posttransplant forced expiratory volume in 1 sec., Conclusions: In this large, single-center experience, the absence of smoking history in the donor did not result in better long-term outcomes after lung transplantation. Potential problems with lungs from teenaged donors with no smoking history were suggested.

Background: Successful abrogation of ischemia/reperfusion (I/R) injury of lung grafts could significantly improve short- and long-term outcomes for lung transplant (LTx) recipients. Hydrogen gas has potent antioxidant and antiapoptotic properties and has been recently used in number of experimental and clinical studies. The purpose of this research was to investigate whether inhaled hydrogen gas could reduce graft I/R injury during lung transplantation., Methods: Orthotopic left LTxs were performed in syngenic Lewis rats. Grafts were perfused with and stored in low potassium dextran solution at 4°C for 6 hr. The recipients received 100% O2 or 98% O2 with 2% N2, 2% He, or 2% H2 during surgery and 1 hr after reperfusion. The effects of hydrogen were assessed by functional, pathologic, and molecular analysis., Results: Gas exchange was markedly impaired in animals exposed to 100% O2, 2% N2, or 2% He. Hydrogen inhalation attenuated graft injury as indicated by significantly improved gas exchange 2 hr after reperfusion. Graft lipid peroxidation was significantly reduced in the presence of hydrogen, demonstrating antioxidant effects of hydrogen in the transplanted lungs. Lung cold I/R injury causes the rapid production and release of several proinflammatory mediators and epithelial apoptosis. Exposure to 2% H2 significantly blocked the production of several proinflammatory mediators and reduced apoptosis with induction of the antiapoptotic molecules B-cell lymphoma-2 and B-cell lymphoma-extra large., Conclusion: Treatment of LTx recipients with inhaled hydrogen can prevent lung I/R injury and significantly improve the function of lung grafts after extended cold preservation, transplant, and reperfusion.