Clinical ex vivo lung perfusion--pushing the limits

Ex Vivo Optimization of Donor Lungs with Inhaled Sevoflurane during Normothermic Ex Vivo Lung Perfusion (VITALISE): A Pilot and Feasibility Study in Sheep

Volatile anesthetics have been shown in different studies to reduce ischemia reperfusion injury (IRI). Ex vivo lung perfusion (EVLP) facilitates graft evaluation, extends preservation time and potentially enables injury repair and improvement of lung quality. We hypothesized that ventilating lungs with sevoflurane during EVLP would reduce lung injury and improve lung function. We performed a pilot study to test this hypothesis in a slaughterhouse sheep DCD model. Lungs were harvested, flushed and stored on ice for 3 h, after which EVLP was performed for 4 h. Lungs were ventilated with either an FiO2 of 0.4 (EVLP, n = 5) or FiO2 of 0.4 plus sevoflurane at a 2% end-tidal concentration (Cet) (S-EVLP, n = 5). Perfusate, tissue samples and functional measurements were collected and analyzed. A steady state of the target Cet sevoflurane was reached with measurable concentrations in perfusate. Lungs in the S-EVLP group showed significantly better dynamic lung compliance than those in the EVLP group (p = 0.003). Oxygenation capacity was not different in treated lungs for delta partial oxygen pressure (PO2; +3.8 (-4.9/11.1) vs. -11.7 (-12.0/-3.2) kPa, p = 0.151), but there was a trend of a better PO2/FiO2 ratio (p = 0.054). Perfusate ASAT levels in S-EVLP were significantly reduced compared to the control group (198.1 ± 93.66 vs. 223.9 ± 105.7 IU/L, p = 0.02). We conclude that ventilating lungs with sevoflurane during EVLP is feasible and could be useful to improve graft function.

Novel Polymerized Human Serum Albumin For Ex Vivo Lung Perfusion

Ex vivo lung perfusion (EVLP) is a method of organ preservation to expand the donor pool by allowing organ assessment and repair. Perfusion solution composition is crucial to maintaining and improving organ function during EVLP. EVLP compared perfusates supplemented with either polymeric human serum albumin (PolyHSA) or standard human serum albumin (HSA). Rat heart-lung blocks underwent normothermic EVLP (37°C) for 120 minutes using perfusate with 4% HSA or 4% PolyHSA synthesized at a 50:1 or 60:1 molar ratio of glutaraldehyde to PolyHSA. Oxygen delivery, lung compliance, pulmonary vascular resistance (PVR), wet-to-dry ratio, and lung weight were measured. Perfusion solution type (HSA or PolyHSA) significantly impacted end-organ metrics. Oxygen delivery, lung compliance, and PVR were comparable among groups ( P > 0.05). Wet-to-dry ratio increased in the HSA group compared to the PolyHSA groups (both P < 0.05) suggesting edema formation. Wet-to-dry ratio was most favorable in the 60:1 PolyHSA-treated lungs compared to HSA ( P < 0.05). Compared to using HSA, PolyHSA significantly lessened lung edema. Our data confirm that the physical properties of perfusate plasma substitutes significantly impact oncotic pressure and the development of tissue injury and edema. Our findings demonstrate the importance of perfusion solutions and PolyHSA is an excellent candidate macromolecule to limit pulmonary edema. http://links.lww.com/ASAIO/A980.

Diagnostic and Therapeutic Implications of Ex Vivo Lung Perfusion in Lung Transplantation: Potential Benefits and Inherent Limitations

Ex vivo lung perfusion (EVLP), a technique in which isolated lungs are continually ventilated and perfused at normothermic temperature, is emerging as a promising platform to optimize donor lung quality and increase the lung graft pool. Over the past few decades, the EVLP technique has become recognized as a significant achievement and gained much attention in the field of lung transplantation. EVLP has been demonstrated to be an effective platform for various targeted therapies to optimize donor lung function before transplantation. Additionally, some physical parameters during EVLP and biological markers in the EVLP perfusate can be used to evaluate graft function before transplantation and predict posttransplant outcomes. However, despite its advantages, the clinical practice of EVLP continuously encounters multiple challenges associated with both intrinsic and extrinsic limitations. It is of utmost importance to address the advantages and disadvantages of EVLP for its broader clinical usage. Here, the pros and cons of EVLP are comprehensively discussed, with a focus on its benefits and potential approaches for overcoming the remaining limitations. Directions for future research to fully explore the clinical potential of EVLP in lung transplantation are also discussed.

Is there life on the airway tree? A pilot study of bronchial cell vitality and tissue morphology in the ex vivo lung perfusion (EVLP) era of lung transplantation

BACKGROUND

Ex vivo lung perfusion (EVLP) is a relevant procedure to increase the lung donor pool but could potentially increase the airway tree ischemic injury risk.

METHODS

This study aimed to evaluate the direct effect of EVLP on the airway tree by evaluating bronchial cell vitality and tissue signs of injury on a series of 117 bronchial rings collected from 40 conventional and 19 EVLP-treated lung grafts. Bronchial rings and related scraped bronchial epithelial cells were collected before the EVLP procedure and surgical anastomosis.

RESULTS

The preimplantation interval was significantly increased in the EVLP graft group (p < 0.01). Conventional grafts presented cell viability percentages of 47.07 ± 23.41 and 49.65 ± 21.25 in the first and second grafts which did not differ significantly from the EVLP group (first graft 50.54 ± 25.83 and second graft 50.22 ± 20.90 cell viability percentage). No significant differences in terms of histopathological features (edema, inflammatory infiltrate, and mucosa ulceration) were observed comparing conventional and EVLP samples. A comparison of bronchial cell viability and histopathology of EVLP samples retrieved at different time intervals revealed no significant differences. Accordingly, major bronchial complications after lung transplant were not observed in both groups.

CONCLUSIONS

Based on these data, we observed that EVLP did not significantly impact bronchial cell vitality and airway tissue preservation nor interfere with bronchial anastomosis healing, further supporting it as a safe and useful procedure.

Centralized Organ Recovery and Reconditioning Centers

An increased focus on improving efficiency and decreasing costs has resulted in alternative models of donor management and organ recovery. The specialized donor care facility model provides highly efficient and cost-effective donor care at a free-standing facility, resulting in improved organ yield, shorter ischemic times, decreased travel, and fewer nighttime operations. Ex vivo lung perfusion (EVLP) improves utilization of extended criteria donor lungs, and centralized EVLP facilities have the potential to increase transplant volumes for smaller transplant programs in specified geographic regions. These alternative models are increasingly being used in the United States to improve waitlist mortality and combat the ongoing donor organ shortage.

Impact of ex vivo lung perfusion on brain-dead donor lung utilization: The French experience

Ex vivo lung perfusion (EVLP) is a valuable method for expanding the lung donor pool. Its indications currently differ across centers. This national retrospective cohort study aimed to describe the profile of donors with lungs transplanted after EVLP and determine the effectiveness of EVLP on lung utilization. We included brain-dead donors with at least one lung offered between 2012 and 2019 in France. Lungs transplanted without or after EVLP were compared with those that were rejected. Donor group phenotypes were determined with multiple correspondence analysis (MCA). The association between donor factors and lung transplantation was assessed with a multivariable multinomial logistic regression. MCA revealed that donors whose lungs were transplanted after EVLP had profiles similar to the donors whose lungs were declined and quite different from those of donors with lungs transplanted without EVLP. Donor predictors of graft nonuse included age ≥50 years, smoking history, PaO₂ /FiO₂ ratio ≤300 mmHg, abnormal chest imaging, and purulent secretions. EVLP increased utilization of lungs from donors with a smoking history, PaO₂ /FiO₂ ratio ≤300 mmHg, and abnormal chest imaging.

Reversible occlusion of the pulmonary vasculature by transarterial embolisation with degradable starch microspheres: preclinical assessment in a human isolated lung perfusion model

BACKGROUND

Transpulmonary embolisation (TPE) using degradable starch microspheres (DSM) is a potential approach to treat pulmonary metastases. However, there is a paucity of detailed information on perfusion dynamics. The aim of this study was to establish a human ex vivo isolated lung perfusion (ILP) model to observe and evaluate the effects of DSM-TPE in a near-physiologic setting.

METHODS

ILP was carried out on six surgically resected lung lobes. At baseline, computed tomography (CT), including CT perfusion imaging (CTPI), and histopathological sampling were performed (t30). DSM-TPE was initiated and increased stepwise (t45, t60, t75, and t90) to be followed by CT imaging, histopathological sampling, and pulmonary arterial pressure (PAP). After the last assessment (t90), alpha-amylase was injected into the pulmonary artery to allow for DSM hydrolysation and two additional assessments (t105; t120). Histopathological specimens were evaluated using a semiquantitative ordinal score. CTPI was used for time to peak (TTP) analysis.

RESULTS

After DSM administration, PAP and TTP increased significantly: PAP slope 95% confidence interval (CI) 0.104-0.483, p = 0.004; TTP t30 versus t45, p = 0.046. After the addition of alpha-amylase, functional parameters reverted to values comparable to baseline. In histopathological samples, embolisation grades increased significantly until t90 (slope 95% CI 0.027-0.066, p < 0.001) and decreased after addition of alpha-amylase (slope 95% CI -0.060-0.012, p = 0.165), CONCLUSIONS: The ILP model demonstrated successfully both the physiologic effect of DSM-TPE on human lungs and its reversibility with alpha-amylase. Thus, it can be used as a near-physiologic preclinical tool to simulate and assess later clinical approaches.

Predicting donor lung acceptance for transplant during ex vivo lung perfusion: The EX vivo lung PerfusIon pREdiction (EXPIRE)

Ex vivo lung perfusion (EVLP) has being increasingly used for the pretransplant assessment of extended-criteria donor lungs. Mathematical models to predict lung acceptance during EVLP have not been reported so far. Thus, we hypothesized that predictors of lung acceptance could be identified and used to develop a mathematical model describing the clinical decision-making process used in our institution. Donor lungs characteristics and EVLP physiologic parameters included in our EVLP registry were examined (derivation cohort). Multivariable logistic regression analysis was performed to identify predictors independently associated with lung acceptance. A mathematical model (EX vivo lung PerfusIon pREdiction [EXPIRE] model) for each hour of EVLP was developed and validated using a new cohort (validation cohort). Two hundred eighty donor lungs were assessed with EVLP. Of these, 186 (66%) were accepted for transplantation. ΔPO₂ and static compliance/total lung capacity were identified as independent predictors of lung acceptance and their respective cut-off values were determined. The EXPIRE model showed a low discriminative power at the first hour of EVLP assessment (AUC: 0.69 [95% CI: 0.62-0.77]), which progressively improved up to the fourth hour (AUC: 0.87 [95% CI: 0.83-0.92]). In a validation cohort, the EXPIRE model demonstrated good discriminative power, peaking at the fourth hour (AUC: 0.85 [95% CI: 0.76-0.94]). The EXPIRE model may help to standardize lung assessment in centers using the Toronto EVLP technique and improve overall transplant rates.

Ex vivo lung perfusion: how we do it

Lung transplantation is an established treatment for patients with end-stage lung disease. However, a shortage of donors, low lung utilization among potential donors, and waitlist mortality continue to be challenges. In the last decade, ex vivo lung perfusion (EVLP) has expanded the donor pool by allowing prolonged evaluation of marginal donor lungs and allowing reparative therapies for lungs, which are otherwise considered not transplantable. In this review, we describe in detail our experience with EVLP including our workflow, setup, operative technique, and protocols. Our multidisciplinary EVLP program functions with the collaboration of surgeons, pulmonologists, and EVLP nurses who run the pump. EVLP program has been a valuable addition to our program. Since Food and Drug Administration (FDA) approval in 2019, we experienced incremental increased lung transplant volume of 12% annually.

Pushing the Envelope for Donor Lungs

The shortage of organ donors remains the major limiting factor in lung transplant, with the number of patients on the waiting list largely exceeding the number of available organ donors. Another issue is the low utilization rate seen in some types of donors. Therefore, novel strategies are continuously being explored to increase the donor pool. Advanced age, smoking history, positive serologies, and size mismatch are common criteria that decrease the rate of use when it comes to organ utilization. Questioning these limitations is one of the purposes of this review. Challenging these limitations by adapting novel donor management strategies could help to increase the rate of suitable lungs for transplantation while still maintaining good outcomes. A second goal is to present the latest advances in organ donation after controlled and uncontrolled cardiac death, and also on how to improve these lungs on ex vivo platforms for assessment and future specific therapies. Finally, pushing the limit of the donor envelope also means reviewing some of the recent improvements made in lung preservation itself, as well as upcoming experimental research fields. In summary, donor lung optimization refers to a global care strategy to increase the total numbers of available allografts, and preserve or improve organ quality without paying the price of early-, mid-, or long-term negative outcomes after transplantation.

Ex vivo lung perfusion in lung transplantation

Lung transplantation is an established life-saving intervention for patients with end-stage lung diseases. The success of lung transplantation mainly depends on the quality and function of the implanted donor lungs, which are frequently subject to brain-death-induced lung injuries and intensive care unit (ICU)-related complications before transplantation. Recent innovations, particularly the development of ex vivo lung perfusion (EVLP), in which donor lungs are ventilated and perfused under normothermic conditions outside the body, have allowed clinicians to more accurately assess the donor lung function prior to transplantation. Therefore, EVLP has been successfully translated into clinical practice with the expansion of the donor lung pool, leading to favorable post-transplant outcomes in a growing number of transplant centers worldwide. The EVLP system and techniques, following the Toronto protocol, have recently been applied for the assessment of extended criteria brain-death donors in clinical lung transplantation in Japan. The advancement of EVLP from organ assessment to organ treatment will be the next challenging stage not only to expand donor lung pool, but also to improve graft survival and long-term outcomes after transplantation.

Common Criteria for Ex Vivo Lung Perfusion Have No Significant Impact on Posttransplant Outcomes

BACKGROUND

Although it is intense in health care resources, by facilitating assessment and reconditioning, ex vivo lung perfusion (EVLP) has the potential to expand the donor pool and improve lung transplant outcomes. However, inclusion criteria used in EVLP trials have not been validated.

METHODS

This retrospective study from 2014 to 2018 reviewed our local state-based donation organization donor records as well as subsequent recipient outcomes to explore the relation between EVLP indications used in clinical trials and recipient outcomes. The primary outcome was primary graft dysfunction grade 3 at 24 hours, with 30-day mortality and posttransplant survival time as secondary outcomes, compared with univariate and multivariate analysis.

RESULTS

From 705 lung donor referrals, 304 lung transplantations were performed (use rate of 42%); 212 of recipients (70%) met at least 1 of the commonly cited EVLP initiation criteria. There was no significant difference in primary graft dysfunction grade 3 or 30-day mortality between recipients with or without an EVLP indication (10.2% versus 7.8%, P = .51; and 2.4% versus 0%, P = .14, respectively). Multivariate analyses showed no significant relationship between commonly cited EVLP criteria and primary graft dysfunction grade 3 or survival time. Recipient outcomes were significantly associated with recipient diagnosis.

CONCLUSIONS

At least 1 commonly cited criterion for EVLP initiation was present in 70% of the transplanted donors, and yet it did not predict clinical results; acceptable outcomes were seen in both subgroups. To discover the true utility of EVLP beyond good clinical management and focus EVLP on otherwise unacceptable lungs, a reconsideration of EVLP inclusion criteria is required.

Impact of normothermic ex vivo lung perfusion on early post-transplantation cytomegalovirus infection

Background

The low acceptance rates in lung transplantation underline the importance to use every potential transplantable organ. With the use of normothermic ex vivo lung perfusion (EVLP) there is a potential to use more donor lungs for transplantation. Aim of this study was to evaluate if EVLP has an effect on cytomegalovirus (CMV) infection after lung transplantation.

Methods

Between May 2016 and October 2018, 57 lung transplants were performed. Out of these 21 extended criteria lungs were evaluated by EVLP and 16 transplanted. In a retrospective study, results of EVLP treated lungs were compared with lungs after cold storage preservation (CSP). Donor/recipient CMV IgG status and seroconversion rate was examined.

Results

Donors were CMV IgG+ in EVLP 69% and CSP 61% (n.s.). Best pO₂ on procurement at FiO₂ 1.0 was in EVLP 278±76 versus CSP 413±96 mmHg (P≤0.05). Recipients were CMV IgG+ in EVLP 38% and CSP 63% (P<0.07). CMV seroconversion: EVLP 12%, CSP 20% (P<0.05), in the CSP group in 5% recipients with more than 1,000 copies/mL were diagnosed by PCR and treated for CMV infection. Procalcitonin (PCT) levels from day 1 to day 5 were significantly lower for CSP group (P<0.05). 30-day mortality was 12% for EVLP recipients.

Conclusions

Normothermic EVLP did not influence CMV infection rate, however early PCT levels were higher in EVLP group. Short-term results were comparable to standard lung transplantation.

Current techniques and the future of lung preservation

Although lung transplant remains the only option for patients suffering from end-stage lung failure, donor supply is insufficient to meet demand. Static cold preservation is the most common method to preserve lungs in transport to the recipient; however, this method does not improve lung quality and only allows for 8 h of storage. This results in lungs which become available for donation but cannot be used due to failure to meet physiologic criteria or an inability to store them for a sufficient time to find a suitable recipient. Therefore, lungs lost due to failure to meet physiological or compatibility criteria may be mitigated through preservation methods which improve lung function and storage durations. Ex situ lung perfusion (ESLP) is a recently developed method which allows for longer storage times and has been demonstrated to improve lung function such that rejected lungs can be accepted for donation. Although greater use of ESLP will help to improve donor lung utilization, the ability to cryopreserve lungs would allow for organ banking to better utilize donor lungs. However, lung cryopreservation research remains underrepresented in the literature despite its unique advantages for cryopreservation over other organs. Therefore, this review will discuss the current techniques for lung preservation, static cold preservation and ESLP, and provide a review of the cryopreservation challenges and advantages unique to lungs.

Early pulmonary function and mid-term outcome in lung transplantation after ex-vivo lung perfusion - a single-center, retrospective, observational, cohort study

Outcomes after transplantation of lungs (LuTX) treated with ex-vivo lung perfusion (EVLP) are debated. In a single-center 8 years of retrospective analysis, we compared: donors' and recipients' characteristics, gas exchange and lung mechanics at ICU admission, 3, 6, and 12 months, and patients' survival of LuTX from standard donors compared with EVLP-treated grafts. A total of 193 LuTX were performed. Thirty-one LuTX, out of 50 EVLP procedures, were carried out: 7 from nonheart beating and 24 from extended criteria brain-dead donors. Recipients' characteristics were similar. At ICU admission, compared with standard donors, EVLP patients had worse PaO₂ /FiO₂ [276 (206; 374) vs. 204 (133; 245) mmHg, P < 0.05], more frequent extracorporeal support (18% vs. 32%, P = 0.053) and longer mechanical ventilation duration [28 days of ventilator-free days: 27 (24; 28) vs. 26 (19; 27), P < 0.05]. ICU length of stay [4 (2; 9) vs. 6 (3; 12) days, P = 0.208], 28-day survival (99% vs. 97%, P = 0.735), and 1-year respiratory function were similar between groups. Log-rank analysis (median follow-up 2.5 years) demonstrated similar patients' survival (P = 0.439) and time free of chronic lung allograft disease (P = 0.484). The EVLP program increased by 16% the number of LuTX. Compared to standard donors, EVLP patients had worse respiratory function immediately after LuTX but similar early and mid-term outcomes.

Prolonged Cold Ischemia Induces Necroptotic Cell Death in Ischemia-Reperfusion Injury and Contributes to Primary Graft Dysfunction after Lung Transplantation

Primary graft dysfunction (PGD) is a major cause of morbidity and mortality after lung transplantation. Ischemia-reperfusion injury (IRI) is a key event that contributes to PGD, though complex interactions affect donor lungs status, such as preceding brain death (BD), hemorrhagic shock (HS), and pre-engraftment lung management, the latter recognized as important risk factors for PGD. We hypothesized that a multi-hit isogenic mouse model of lung transplantation is more closely linked to PGD than IRI alone. Left lung transplants were performed between inbred C57BL/6 mice. A one-hit model of IRI was established by inducing cold ischemia (CI) of the donor lungs at 0°C for 1, 72, or 96 hours before engraftment. Multi-hit models were established by inducing 24 hours of HS and/or 3 hours of BD before 24 hours of CI. The recipients were killed at 24 hours after transplant and lung graft samples were analyzed. In the one-hit model of IRI, up to 72-hour CI time resulted in minimal cellular infiltration near small arteries after 24-hour reperfusion. Extension of CI time to 96 hours led to increased cellular infiltration and necroptotic pathway activation, without evidence of apoptosis, after 24-hour reperfusion. In a multi-hit model of PGD, "HS + BD + IRI" demonstrated increased lung injury, cellular infiltration, and activation of necroptotic and apoptotic pathways compared with IRI alone. Treatment with an inhibitor of receptor-interacting protein kinase 1 kinase, necrostatin-1, resulted in a significant decrease of downstream necroptotic pathway activation in both single- and multi-hit models of IRI. Thus, activation of necroptosis is a central event in IRI after prolonged CI, though it may not be sufficient to cause PGD alone. Pathological evaluation of donor lungs after CI-induced IRI, in conjunction with pre-engraftment donor lung factors in our multi-hit model, demonstrated early evidence of lung injury consistent with PGD. Our findings support the premise that pre-existing donor lung status is more important than CI time alone for inflammatory pathway activation in PGD, which may have important clinical implications for donor lung retrieval.

Increased Arginase Expression and Decreased Nitric Oxide in Pig Donor Lungs after Normothermic Ex Vivo Lung Perfusion

An established pig lung transplantation model was used to study the effects of cold ischemia time, normothermic acellular ex vivo lung perfusion (EVLP) and reperfusion after lung transplantation on l-arginine/NO metabolism in lung tissue. Lung tissue homogenates were analyzed for NO metabolite (NOx) concentrations by chemiluminescent NO-analyzer technique, and l-arginine, l-ornithine, l-citrulline and asymmetric dimethylarginine (ADMA) quantified using liquid chromatography-mass spectrometry (LC-MS/MS). The expression of arginase and nitric oxide synthase (NOS) isoforms in lung was measured by real-time polymerase chain reaction. EVLP preservation resulted in a significant decrease in concentrations of NOx and l-citrulline, both products of NOS, at the end of EVLP and after reperfusion following transplantation, compared to control, respectively. The ratio of l-ornithine over l-citrulline, a marker of the balance between l-arginine metabolizing enzymes, was increased in the EVLP group prior to reperfusion. The expression of both arginase isoforms was increased from baseline 1 h post reperfusion in EVLP but not in the no-EVLP group. These data suggest that EVLP results in a shift of the l-arginine balance towards arginase, leading to NO deficiency in the lung. The arginase/NOS balance may, therefore, represent a therapeutic target to improve lung quality during EVLP and, subsequently, transplant outcomes.

Ex Vivo Lung Perfusion: A Review of Research and Clinical Practices

End-stage lung disease is ultimately treated with lung transplantation. However, there is a paucity of organs with an increasing number of patients being diagnosed with end-stage lung disease. Ex vivo lung perfusion has emerged as a potential tool to assess the quality and to recondition marginal donor lungs prior to transplantation with the goal of increasing the donor pool. This technology has shown promise with similar results compared with the conventional technique of cold static preservation in terms of primary graft dysfunction and overall outcomes. This review provides an update on the results and uses of this technology. The review will also summarize clinical studies and techniques in reconditioning and assessing lungs on ex vivo lung perfusion. Last, we discuss how this technology can be applied to fields outside of transplantation such as thoracic oncology and bioengineering.

[Current developments in lung transplantation]

BACKGROUND

Lung transplantation is the established treatment of benign end-stage pulmonary diseases after failure of alternative surgical and medical treatment options. The aim of this paper is to provide an overview of current developments in selected fields of lung transplantation.

METHODS

A selective literature search was conducted.

RESULTS

Lung transplantation in Germany is currently limited by a donor organ shortage. Measures to increase organ donation rates and to optimize the use of available donor organs are required. Ex-vivo lung perfusion, currently mainly used to re-evaluate marginal donor organs, has the potential to increase the available donor pool and to serve as a platform for additional therapies.

CONCLUSIONS

Refinements in organ allocation, perioperative management, immunosuppression, and in the understanding of acute cellular and humoral rejection as well as chronic lung allograft dysfunction contributed to improvements in long-term outcome after lung transplantation.

Progress of Clinical Application for Ex Vivo Lung Perfusion (EVLP) in Lung Transplantation

In recent years, medical advances make lung transplantation become a standard treatment for terminal lung diseases (such as emphysema, pulmonary fibrosis, pulmonary cystic fibrosis, and pulmonary arterial hypertension) that cannot be cured by drugs or surgery (Lund et al., J Heart Lung Transplant 34:1244, 2015). However, the current number of donor lungs that meet the transplant criteria is no longer sufficient for transplanting, causing some patients to die while waiting for a suitable lung. Current methods for improving the situation of shortage of lung transplant donors include the use of donation after cardiac death (DCD) donors, smoker donors, and Ex Vivo Lung Perfusion (EVLP). Among them, EVLP is a technique for extending lung preservation time and repairing lung injury in the field of lung transplantation. By continuously assessing and improving the function of marginal donor lungs, EVLP increases the number of lungs that meet the transplant criteria and, to some extent, alleviates the current situation of shortage of donor lungs. This chapter reviews the clinical application and research progress of EVLP in the field of lung transplantation.

Ex-vivo lung perfusion versus standard protocol lung transplantation-mid-term survival and meta-analysis

Background

While extended criteria lung donation has helped expand the lung donor pool, utilization of lungs from donors of at least one other solid organ is still limited to around 15-30%. Ex-vivo lung perfusion (EVLP) offers the ability to expand the number of useable lung grafts through assessment and reconditioning of explanted lungs, particularly those not initially meeting criteria for transplantation. This meta-analysis aimed to examine the mid- to long-term survival and other short-term outcomes of patients transplanted with EVLP-treated lungs versus standard/cold-storage protocol lungs.

Methods

Literature search of ten medical databases was conducted for original studies involving "ex-vivo lung perfusion" and "EVLP". Included articles were assessed by two independent researchers, survival data from Kaplan-Meier curves digitized, and individual patient data imputed to conduct aggregated survival analysis. Meta-analyses of suitably reported outcomes were conducted using a random-effects model.

Results

Thirteen studies met inclusion criteria, with a total of 407 EVLP lung transplants and 1,765 as per standard/cold storage protocol. One study was a randomized controlled trial while the remainder were single-institution cohort series of varying design. The majority of donor lungs were from brain death donors, with EVLP lungs having significantly worse PaO₂/FiO₂ ratio and significantly greater rate of abnormal chest X-ray. Aggregated survival analysis of all included studies revealed no significant survival difference for EVLP or standard protocol lungs (hazard ratio 1.00; 95% confidence interval: 0.79-1.27, P=0.981). Survival at 12, 24, and 36 months for the EVLP cohort was 84%, 79%, and 74%, respectively. Survival at 12, 24, and 36 months for the standard protocol cohort was 85%, 79%, and 73%, respectively. Meta-analysis did not find a significant difference in risk of 30-day mortality or primary graft dysfunction grade 3 at 72 hours between cohorts.

Conclusions

There was no significant difference in mid- to long-term survival of EVLP lung transplant patients when compared to standard protocol donor lungs. The incidence of 30-day mortality and primary graft dysfunction grade 3 at 72 hours did not differ significantly between groups. EVLP offers the potential to increase lung donor utilization while providing similar short-term outcomes and mid- to long-term survival.

Normothermic ex vivo lung perfusion: Does the indication impact organ utilization and patient outcomes after transplantation?

BACKGROUND

Ex vivo lung perfusion (EVLP) is being increasingly applied as a method to evaluate and treat donor lungs for transplantation. However, with the previous limited worldwide experience, no studies have been able to evaluate the impact of indication for EVLP on organ utilization rates and recipient outcomes after lung transplantation (LTx). We examined these outcomes in a large-cohort, single-center series of clinical EVLP cases.

METHODS

All EVLP procedures performed at our institution between October 2008 and December 2017 were examined. The EVLPs were divided into 4 groups based on the indication for the procedure: group 1, high-risk brain death donors (HR-BDD); group 2, standard-risk donation after cardiac death (S-DCD); group 3, high-risk donation after cardiac death (HR-DCD); and group 4, logistics (LOGISTICS, the need for prolongation of preservation time or organ retrieval by a different transplantation team).

RESULTS

During the study period, a total of 1106 lung transplants were performed in our institution. In this period, 372 EVLPs were performed, 255 (69%) of which were accepted for transplantation, resulting in 262 transplants. Utilization rates were 70% (140 of 198) for group 1, 82% (40 of 49) for group 2, 63% (69 of 109) for group 3, and 81% (13 of 16) for group 4 (P = .42, Fisher's exact test). Recipient age (P = .27) and medical diagnosis (P = .31) were not different across the 4 groups. Kaplan-Meier survival by EVLP indication group demonstrated no differences. Thirty-day mortality was 2.1% in group 1, 5% in group 2, 2.9% in group 3, and 0% in group 4 (P = .87, Fisher's exact test). The median days of mechanical ventilation, intensive care unit stay, and hospital stay were 2, 4, and 21 in group 1; 2, 3, and 21 in group 2; 3, 5, and 28 in group 3; and 2, 4, and 17 in group 4 (P = .29, .17, and .09, respectively, Kruskal-Wallis rank-sum test).

CONCLUSIONS

Clinical implementation of EVLP has allowed our program to expand the annual lung transplantation activity by 70% in this time period. It has improved confidence in the utilization of DCD lungs and BDD lungs, with an average 70% utilization of post-EVLP treated donor lungs with excellent outcomes, while addressing significant challenges in donor lung assessment and the logistics of "real-life" clinical lung transplantation.

The Conversional Efficacy of Ex Vivo Lung Perfusion and Clinical Outcomes in Patients Undergoing Transplantation of Donor Lungs by Ex Vivo Lung Perfusion: A Meta-Analysis

Background

Ex vivo lung perfusion (EVLP) is a relatively new technique that can be used to assess and repair the donor lungs, increasing the utilization of high-risk lungs. However, its effect on outcomes of lung transplantation patients is uncertainty. This meta-analysis is conducted to assess the impact of EVLP on donor lungs and outcomes of recipients compared with the standard lung transplantation.

Material/Methods

We systematically searched for studies comparatively analyzing the efficacy of EVLP and standard cold storage in lung transplantation. The hazard ratio (HR), relative risk (RR), and weighted mean difference (WMD) were used as the effect size (ES) to evaluate the survival outcomes, categorical variables, and continuous variables respectively.

Results

A total of 20 published articles (including 2574 donors and 2567 recipients) were eligible. The chest x-ray manifestations and PaO₂/FiO₂ 100% were more deficient in the EVLP group than the standard group. EVLP improved the function of high-risk donor lungs with the conversion rate ranging from 34% to 100%. The EVLP group had a lower incidence of primary graft dysfunction 3, but longer intensive care unit stay. Other clinical outcomes between the 2 groups were similar.

Conclusions

The pooled results indicated that EVLP could be used to assess and improve high-risk donor lungs and had non-inferior postoperative outcomes compared with the standard cold storage. EVLP not only increased the utilization of marginal donors, but also could extend preservation time and reduce the total ischemia time of donors.

Bilateral lung transplantation on intraoperative extracorporeal membrane oxygenator: An observational study

OBJECTIVE

Intraoperative extracorporeal membrane oxygenation (ECMO) is usually reserved to support patients during complex lung transplantation. We hypothesized that a routine application of intraoperative ECMO in all patients improves primary graft function.

METHODS

Patients receiving a bilateral lung transplantation between November 2016 and July 2018 at the Medical University of Vienna were included in this prospective, single-center observational study. All transplantations were uniformly performed on central venoarterial ECMO support, with the possibility to extend ECMO into the early postoperative period whenever graft function did not meet established quality criteria at the end of implantation. Primary graft dysfunction (PGD) grades were evaluated at 24, 48, and 72 hours after transplantation. Perioperative complications and survival outcome were assessed.

RESULTS

A total of 159 patients were included in the study. At 24 hours post-transplantation, 38.4% (n = 61) of patients were already extubated, 48.4% (n = 77) were classified as PGD0, 4.4% (n = 7) as PGD1, 3.1% (n = 5) as PGD2, 2.5% (n = 4) as PGD3, and 3.1% (n = 5) were "ungradable" due to prophylactic postoperative prolongation of ECMO. At 72 hours after transplantation, 76.7% (n = 122) of the patients were extubated, as opposed to only 1.3% (n = 2) of patients classified as PGD3. The median time of mechanical ventilation was 29 hours (interquartile range, 17-58). The 90-day-mortality was 3.1%, and 2-year survival was 86%.

CONCLUSIONS

Routine use of intraoperative ECMO resulted in excellent primary graft function and mid-term outcome in patients undergoing lung transplantation. To the best of our knowledge, the herein measured PGD rates are the lowest reported in the literature to date. Our results advocate a routine intraoperative use of ECMO in bilateral lung transplantation.

Implementation of an experimental isolated lung perfusion model on surgically resected human lobes

Isolated lung perfusion (ILP) is an ideal model to study treatment effects on a variety of pathologies. As published research mostly relies on rejected donor lungs or animal organs, this study investigates the use of surgically resected human lobes as an alternative and novel model for personalized experimental research. Ten surgically resected lobes were perfused in acellular and normothermic condition. The indication for surgery was lung cancer. Perfusion and ventilation were adapted to the size of the lobes and both functional and metabolic parameters were assessed during ILP. Patients (age 67.5 y (59–81)|♀n = 3|♂n = 7) underwent anatomic pulmonary lobectomy. Ischemic time between arterial ligation and ILP was 226 minutes (161–525). Median duration of ILP was 135 (87–366) minutes. Gas exchange and mechanical respiratory parameters remained steady during ILP (pulmonary venous pO₂ 196(151–219) mmHg | peak AWP: 14.5(11–22) cmH₂O). Metabolism stayed constant during ILP (Glucose consumption: 1.86 mg/min/L_TLC (95%CI: −2.09 to −1.63) | lactate production: 0.005 mmol/min/ L_TLC (95%CI: 0.004 to 0.007)). ILP of surgically resected human lobes is a feasible and promising method. By maintaining a near physiological setting, this model may pave the way for future experimental lung research including cancer research, transplantation, physiology, pharmacology and mechanical ventilation.

Ex vivo lung perfusion prior to transplantation: an overview of current clinical practice worldwide

Lung transplantation is a lifesaving treatment in numerous forms of end-stage lung disease but organ shortage remains nowadays his biggest issue. Ex vivo lung perfusion (EVLP) has recently emerged as a solution to this problem and begins to be accepted is clinical practice. In this review, we will focus on his experience worldwide. We would like to describe the technique and the criteria used to select the donors and the transplantable lungs. We will also browse the acceptance rate described in literature as well as numerous other aspects of this new tool.

Lung transplantation after ex vivo lung perfusion in two Scandinavian centres

OBJECTIVES

We reviewed our combined clinical outcome in patients who underwent lung transplantation after ex vivo lung perfusion (EVLP) and compared it to the contemporary control group.

METHODS

At 2 Scandinavian centres, lungs from brain-dead donors, not accepted for donation but with potential for improvement, were subjected to EVLP (n = 61) and were transplanted if predefined criteria were met. Transplantation outcome was compared with that of the contemporary control group consisting of patients (n = 271) who were transplanted with conventional donor lungs.

RESULTS

Fifty-four recipients from the regular waiting list underwent transplantation with lungs subjected to EVLP (1 bilateral lobar, 7 single and 46 double). In the EVLP and control groups, arterial oxygen tension/inspired oxygen fraction ratio at arrival in the intensive care unit (ICU) was 30 ± 14 kPa compared to 36 ± 14 (P = 0.005); median time to extubation was 18 h (range 2-912) compared to 7 (range 0-2280) (P = 0.002); median ICU length of stay was 4 days (range 2-65) compared to 3 days (range 1-156) (P = 0.002); Percentage of expected forced expiratory volume at 1s (FEV1.0%) at 1 year was 75 ± 29 compared to 81 ± 26 (P = 0.18); and the 1-year survival rate was 87% [confidence interval (CI) 82-92%] compared to 83% (CI 81-85), respectively. Follow-up to a maximum of 5 years did not show any significant difference in survival between groups (log rank, P = 0.63).

CONCLUSIONS

Patients transplanted with lungs after EVLP showed outcomes comparable to patients who received conventional organs at medium-term follow-up. Although early outcome immediately after transplantation showed worse lung function in the EVLP group, no differences were observed at a later stage, and we consider EVLP to be a safe method for increasing the number of transplantable organs.

Extended criteria donor lung reconditioning with the organ care system lung: a single institution experience

Lung transplantation is a life-saving procedure limited by donor's availability. Lung reconditioning by ex vivo lung perfusion represents a tool to expand the donor pool. In this study, we describe our experience with the OCS™ Lung to assess and recondition extended criteria lungs. From January 2014 to October 2016, of 86 on-site donors evaluated, eight lungs have been identified as potentially treatable with OCS™ Lung. We analyzed data from these donors and the recipient outcomes after transplantation. All donor lungs improved during OCS perfusion in particular regarding the PaO₂ /FiO₂ ratio (from 340 mmHg in donor to 537 mmHg in OCS) leading to lung transplantation in all cases. Concerning postoperative results, primary graft dysfunction score 3 at 72 h was observed in one patient, while median mechanical ventilation time, ICU, and hospital stay were 60 h, 14 and 36 days respectively. One in-hospital death was recorded (12.5%), while other two patients died during follow-up leading to 1-year survival of 62.5%. The remaining five patients are alive and in good conditions. This case series demonstrates the feasibility and value of lung reconditioning with the OCS™ Lung; a prospective trial is underway to validate its role to safely increase the number of donor lungs.

Recent advances in lung transplantation

Lung transplantation can improve quality of life and prolong survival for individuals with end-stage lung disease, and many advances in the realms of both basic science and clinical research aspects of lung transplantation have emerged over the past few decades. However, many challenges must yet be overcome to increase post-transplant survival. These include successfully bridging patients to transplant, expanding the lung donor pool, inducing tolerance, and preventing a myriad of post-transplant complications that include primary graft dysfunction, forms of cellular and antibody-mediated rejection, chronic lung allograft dysfunction, and infections. The goal of this manuscript is to review salient recent and evolving advances in the field of lung transplantation.

Ex Vivo Modeling of Perioperative Air Leaks in Porcine Lungs

OBJECTIVE

A novel ex vivo model is described to advance the understanding of prolonged air leaks, one of the most common postoperative complications following thoracic resection procedures.

METHODS

As an alternative to in vivo testing, an ex vivo model simulating the various physiologic environments experienced by an isolated lung during the perioperative period was designed and built. Isolated porcine lungs were perfused and ventilated during open chest and closed chest simulations, mimicking intra and postoperative ventilation conditions. To assess and validate system capabilities, nine porcine lungs were tested by creating a standardized injury to create an approximately 250 cc/min air leak. Air leak rates, physiologic ventilation, and perfusion parameters were continuously monitored, while gas transfer analysis was performed on selected lungs. Segmental ventilation was monitored using electrical impedance tomography.

RESULTS

The evaluated lungs produced flow-volume and pressure-volume loops that approximated standard clinical representations under positive (mechanical) and negative (physiological) pressure ventilation modalities. Leak rate was averaged across the ventilation phases, and sharp increases in leak rate were observed between positive and negative pressure phases, suggesting that differences or changes in ventilation mechanics may strongly influence leak development.

CONCLUSION

The successful design and validation of a novel ex vivo lung model was achieved. Model output paralleled clinical observations. Pressure modality may also play a significant role in air leak severity.

SIGNIFICANCE

This work provides a foundation for future studies aimed at increasing the understanding of air leaks to better inform means of mitigating the risk of air leaks under clinically relevant conditions.

One-year experience with ex vivo lung perfusion: Preliminary results from a single center

Objective:

To enlarge the donor pool for lung transplantation, an increasing number of extended criteria donor lungs are used. However, in more than 50% of multi-organ donors the lungs are not used. Ex vivo lung perfusion offers a unique possibility to evaluate and eventually recondition the injured donor lungs. The aim of our study was to assess the enlargement of the donor pool and the outcome with extended criteria donor lungs after ex vivo lung perfusion.

Patients and Methods:

Data were prospectively collected in our lung transplant database. We compared the results of lung transplants after ex vivo lung perfusion with those after conventional cold static preservation. In total, 11 extended criteria donor lungs processed with ex vivo lung perfusion and 41 cold static preservation lungs transplanted consecutively between May 2016 and May 2017 were evaluated. Normothermic ex vivo lung perfusion was performed according to the Toronto protocol for 4 h. Cold static preservation lungs were stored in low-potassium dextran solution.

Results:

Ex vivo lung perfusion lungs before procurement had significantly lower PaO2/FiO2 (P/F) ratios and more X-ray abnormalities. There were no statistically significant differences for pre-donation ventilation time, smoking history, or sex. After reconditioning with ex vivo lung perfusion, 9 out of 11 processed lungs were considered suitable and successfully transplanted. The mean postoperative ventilation time and in-hospital stay were not significantly different in ex vivo lung perfusion and cold static preservation recipients.

Conclusion:

Ex vivo lung perfusion can safely be used in the evaluation of lungs initially considered not suitable for transplantation. The primary outcome was not negatively affected and normothermic ex vivo lung perfusion is a useful tool to increase the usage of potentially transplantable lungs.

Application of ex vivo lung perfusion (EVLP) in lung transplantation

Lung transplantation was the ultimate method to treat the end-stage benign lung diseases. Although the lung transplantation has been increasing quickly in the past 30 years, the shortage of donor lung still limited its development. Ex vivo lung perfusion (EVLP) was a promising technique that could provide the platform to preserve, evaluate and repair the donor lung graft. In this article, we give a general review of the development of EVLP, its clinical application and the animal model. With the increasing experience of clinical EVLP, some pre-identified unsuitable donor lungs have been re-evaluated and accepted for transplantation. EVLP have now been considered to be an effective way to expand the donor pool.

Machine perfusion of thoracic organs

This article summarizes recent knowledge and clinical advances in machine perfusion (MP) of thoracic organs. MP of thoracic organs has gained much attention during the last decade. Clinical studies are investigating the role of MP to preserve, resuscitate, and assess heart and lungs prior to transplantation. Currently, MP of the cardiac allograft is essential in all type DCD heart transplantation while MP of the pulmonary allograft is mandatory in uncontrolled DCD lung transplantation. MP of thoracic organs also offers an exciting platform to further investigate downregulation of the innate and adaptive immunity prior to reperfusion of the allograft in recipients. MP provides a promising technology that allows pre-transplant preservation, resuscitation, assessment, repair, and conditioning of cardiac and pulmonary allografts outside the body in a near physiologic state prior to planned transplantation. Results of ongoing clinical trials are awaited to estimate the true clinical value of this new technology in advancing the field of heart and lung transplantation by increasing the total number and the quality of available organs and by further improving recipient early and long-term outcome.

Treatment of infected lungs by ex vivo perfusion with high dose antibiotics and autotransplantation: A pilot study in pigs

The emergence of multi-drug resistant bacteria threatens to end the era of antibiotics. Drug resistant bacteria have evolved mechanisms to overcome antibiotics at therapeutic doses and further dose increases are not possible due to systemic toxicity. Here we present a pilot study of ex vivo lung perfusion (EVLP) with high dose antibiotic therapy followed by autotransplantation as a new therapy of last resort for otherwise incurable multidrug resistant lung infections. Severe Pseudomonas aeruginosa pneumonia was induced in the lower left lungs (LLL) of 18 Mini-Lewe pigs. Animals in the control group (n = 6) did not receive colistin. Animals in the conventional treatment group (n = 6) received intravenous application of 2 mg/kg body weight colistin daily. Animals in the EVLP group (n = 6) had their LLL explanted and perfused ex vivo with a perfusion solution containing 200 μg/ml colistin. After two hours of ex vivo treatment, autotransplantation of the LLL was performed. All animals were followed for 4 days following the initiation of treatment. In the control and conventional treatment groups, the infection-related mortality rate after five days was 66.7%. In the EVLP group, there was one infection-related mortality and one procedure-related mortality, for an overall mortality rate of 33.3%. Moreover, the clinical symptoms of infection were less severe in the EVLP group than the other groups. Ex vivo lung perfusion with very high dose antibiotics presents a new therapeutic option of last resort for otherwise incurable multidrug resistant pneumonia without toxic side effects on other organs.

Intraoperative extracorporeal membrane oxygenation and the possibility of postoperative prolongation improve survival in bilateral lung transplantation

OBJECTIVES

The value of intraoperative extracorporeal membrane oxygenation (ECMO) in lung transplantation remains controversial. In our department, ECMO has been used routinely for intraoperatively unstable patients for more than 15 years. Recently, we have extended its indication to a preemptive application in almost all cases. In addition, we prolong ECMO into the early postoperative period whenever graft function does not meet certain quality criteria or in patients with primary pulmonary hypertension. The objective of this study was to review the results of this strategy.

METHODS

All standard bilateral lung transplantations performed between January 2010 and June 2016 were included in this single-center, retrospective analysis. Patients were divided into 3 groups: group I-no ECMO (n = 116), group II-intraoperative ECMO (n = 343), and group III-intraoperative and prolonged postoperative ECMO (n = 123). The impact of different ECMO strategies on primary graft function, short-term outcomes, and patient survival were analyzed.

RESULTS

The use of intraoperative ECMO was associated with improved 1-, 3-, and 5-year survival compared with non-ECMO patients (91% vs 82%, 85% vs 76%, and 80% vs 74%; log-rank P = .041). This effect was still evident after propensity score matching of both cohorts. Despite the high number of complex patients in group III, outcome was excellent with higher survival rates than in the non-ECMO group at all time points.

CONCLUSIONS

Intraoperative ECMO results in superior survival when compared with transplantation without any extracorporeal support. The concept of prophylactic postoperative ECMO prolongation is associated with excellent outcomes in recipients with pulmonary hypertension and in patients with questionable graft function at the end of implantation.