Ex Vivo Lung Perfusion Protocol Research Articles

Determination of Cardiac Output in a Porcine Model for Ex Vivo Pulmonary Perfusion.

Due to their physiological similarities to humans, pigs are used as experimental models for ex vivo lung perfusion (EVLP). EVLP is a technique that perfuses lungs that are not suitable for transplantation via an extracorporeal circulation pump to improve their function and increase their viability. Existing EVLP protocols are differentiated by the type of perfusion solution and perfusion flow, which varies from 40%-100% of the estimated cardiac output (CO) according to the body surface area (BSA). Devices for measuring CO use simple physical principles and other mathematical models. Thermodilution in animal models continues to be the reference standard for estimating CO because of its simplicity and ease of reproduction. Therefore, the objective of this study was to reproduce the measurement of CO by thermodilution in pigs and compare its precision and accuracy with those obtained by the BSA, weight, and Fick's method, to establish perfusion flow during EVLP. In 23 pigs, a thermodilution catheter was placed in the right jugular vein, and the carotid artery on the same side was cannulated. Blood samples were obtained for gasometry, and CO was estimated by thermodilution, adjusted body surface area, Fick's principle, and per body weight. The CO obtained by the BSA was greater (p = 0.0001, ANOVA, Tukey) than that obtained by the other methods. We conclude that although the methods used in this study to estimate CO are reliable, there are significant differences between them; therefore, each method must be evaluated by the investigator to determine which meets the needs of the protocol.

Porcine lungs perfused with three different flows using the 8-h open-atrium cellular ex vivo lung perfusion technique.

The number of lung transplantations is limited due to the shortage of donor lungs fulfilling the standard criteria. The ex vivo lung perfusion (EVLP) technique provides the ability of re-evaluating and potentially improving and treating marginal donor lungs. Accordingly, the technique has emerged as an essential tool to increase the much-needed donor lung pool. One of the major EVLP protocols, the Lund protocol, characterized by high pulmonary artery flow (100% of cardiac output [CO]), an open atrium, and a cellular perfusate, has demonstrated encouraging short-EVLP duration results. However, the potential of the longer EVLP duration of the protocol is yet to be investigated, a duration which is considered necessary to rescue more marginal donor lungs in future. This study aimed to achieve stable 8-h EVLP using an open-atrium cellular model with three different pulmonary artery flows in addition to determining the most optimal flow in terms of best lung performance, including lung electrolytes and least lung edema formation, perfusate and tissue inflammation, and histopathological changes, using the porcine model. EVLP was performed using a flow of either 40% (n = 6), 80% (n = 6), or 100% (n = 6) of CO. No flow rate demonstrated stable 8-h EVLP. Stable 2-h EVLP was observed in all three groups. Insignificant deterioration was observed in dynamic compliance, peak airway pressure, and oxygenation between the groups. Pulmonary vascular resistance increased significantly in the 40% group (p < .05). Electrolytes demonstrated an insignificant worsening trend with longer EVLP. Interleukin-8 (IL-8) in perfusate and tissue, wet-to-dry weight ratio, and histopathological changes after EVLP were insignificantly time dependent between the groups. This study demonstrated that stable 8-h EVLP was not feasible in an open-atrium cellular model regardless of the flow of 40%, 80%, or 100% of CO. No flow was superior in terms of lung performance, lung electrolytes changes, least lung edema formation, minimal IL-8 expression in perfusate and tissue, and histopathological changes.

The impact and relevance of techniques and fluids on lung injury in machine perfusion of lungs.

Primary graft dysfunction (PGD) is a common complication after lung transplantation. A plethora of contributing factors are known and assessment of donor lung function prior to organ retrieval is mandatory for determination of lung quality. Specialized centers increasingly perform ex vivo lung perfusion (EVLP) to further assess lung functionality and improve and extend lung preservation with the aim to increase lung utilization. EVLP can be performed following different protocols. The impact of the individual EVLP parameters on PGD development, organ function and postoperative outcome remains to be fully investigated. The variables relate to the engineering and function of the respective perfusion devices, such as the type of pump used, functional, like ventilation modes or physiological (e.g. perfusion solutions). This review reflects on the individual technical and fluid components relevant to EVLP and their respective impact on inflammatory response and outcome. We discuss key components of EVLP protocols and options for further improvement of EVLP in regard to PGD. This review offers an overview of available options for centers establishing an EVLP program and for researchers looking for ways to adapt existing protocols.

217.7: Neutrophil Extracellular Traps Removal Using Ex Vivo Lung Perfusion Restored Lung Function in Gastric Aspiration Damaged Porcine Lungs

Background: Lung transplantation (LTx) is an established therapeutic option for end-stage pulmonary disease. However, it remains hampered by donor lung scarcity. Treatments which could regenerate lungs rejected for transplant should be explored in order to combat waiting list mortality. Aspiration induced acute lung injury (ALI) is one of the contributes to the low utilization of donor lungs. Neutrophil extracellular traps (NETs) are implicated in the inflammation profile of ALI. Reduction of NETs could be used as a therapeutic option with the arrival of devices specific to their removal. NucleoCapture device selectively removes NETs from the blood by utilizing human histone H1.3 protein conjugated to polymer beads. This study investigated the impact of the NETs capture device during ex vivo lung perfusion (EVLP) on ALI damaged lungs. Methods: Healthy pigs (n=12) were stratified into two groups, treated (n=6) and not treated (n=6). All animals received 4ml/kg body weight gastric content distributed equally between the different lung segments using a bronchoscopy to induce acute lung injury. Mild to moderate ARDS was developed over 6 hours and confirmed via blood gas values, chest x-ray imaging and histological examination. Lungs were subsequently explanted en bloc and placed on EVLP for 4 hours. Treated lungs were placed in line with a NucleoCapture device connected to the EVLP circuit and the non-treated group underwent the same EVLP protocol without the device. Results: Aspiration induced ALI was induced in all subjects as confirmed by infiltration on chest x-ray, histopathological examination and by PaO2/FiO2 ratio. Following treatment with the NucleoCapture device during 4 hours of EVLP, the PaO2/FiO2 ratio was significantly increased compared to non-treated lungs and was found to surpass the threshold values suitable for transplantation. Furthermore, macroscopic evaluation of the treated lungs demonstrated improvement relative to both the initial injury as well as comparison with the non-treated cohort. Conclusions: Removal of NETs using the NucleoCapture device did restored lung function in aspiration damaged lungs. The amelioration of lung function by removing NETs shows potential clinical use of the device to increase the donor lung pool for lung transplantation.

Successful 3-day lung preservation using a cyclic normothermic ex vivo lung perfusion strategy.

SummaryBackgroundCold static preservation (CSP) at higher temperatures (10°C) has been recently shown as an optimal strategy up to 24-36h of preservation. Here, we hypothesized that alternating 10°C static storage with cycles of normothermic ex vivo lung perfusion (EVLP) would provide conditions for cellular “recharge”, allowing for multi-day lung preservation.MethodsDonor lungs from male Yorkshire pigs were preserved using 10°C CSP with two cycles of 4h EVLP. After a total of 3 days of preservation, a left lung transplant was performed followed by 4h of graft evaluation. As controls, 2 lungs were preserved solely with continuous 10°C preservation for 3 days and transplanted.FindingsFor animals receiving lungs preserved using a cyclic EVLP protocol, lung function and histological structures were stable and the recipient systemic partial pressure of oxygen/fraction of inspired oxygen (P/F Ratio) after excluding the contralateral lung was 422 ± 61 mmHg. In contrast, lungs preserved solely in continuous cold static storage at 10°C for 72h developed massive lung failure, resulting in recipient death. Metabolomic analysis revealed that EVLP plays a critical role in the re-vitalization of key central carbon energy metabolites (Glucose, Succinate, N-Acetyl Aspartate) and reducing the expression of the inflammasome activation marker CASP1.InterpretationIn conclusion, we demonstrate for the first time the feasibility of 3-day lung preservation leading to excellent early post-transplant outcomes. The thoughtful combination of cold storage (10°C) and intermittent EVLP can open new opportunities in organ transplantation.FundingThis work was supported by the UHN Foundation (Grant#1013612).

Increasing Lung Transplant Availability with Normothermic Ex Vivo Lung Perfusion (EVLP) at a Dedicated Facility and a Centralized Lung Evaluation System (CLES): 3-Year Outcomes

<h3>Purpose</h3> This study is the first prospective, multicenter trial to examine the safety and feasibility of a dedicated EVLP facility to evaluate lungs declined for standard transplantation in the US. <h3>Methods</h3> Seven transplant centers from the Midwest and Eastern US referred 105 lungs that had been rejected by standard transplant criteria to a dedicated EVLP facility (NCT02234128). Lungs were perfused and ventilated using the Toronto EVLP protocol. Following EVLP, 63 were accepted for transplantation (utilization rate of 60%). The matched control group consisted of 49 lungs transplanted without the use of EVLP. Bronchiolitis Obliterans Syndrome (BOS) was defined per protocol as airflow limitation in the absence of other etiologies and did not require histopathology documenting BOS. BOS diagnosis was graded in accordance with 2014 ISHLT guidelines as follows: forced expiratory volume in 1 second (FEV₁) 66-80% of baseline was grade 1, FEV₁ 51-65% of baseline was grade 2, and FEV₁ <50% of baseline was grade 3. <h3>Endpoints</h3> The primary endpoints were the proportion of recipients with bronchiolitis obliterans syndrome (BOS) grade (1, 2, or 3), time to death, and mortality rate at three years post-transplant.

Clinical Outcomes of the Lund, Toronto, and Organ Care System Protocols for Normothermic Ex Vivo Lung Perfusion: A Systematic Review and Pursuit of Network Meta-Analysis

Purpose Ex Vivo Lung Perfusion (EVLP) is an excellent method to preserve and recondition donor lungs, thus increasing the lung donor pool. This systematic review summarizes studies comparing both primary graft dysfunction (PGD) and survival between EVLP and conventional lung transplantation (c-LTx), or between different EVLP protocols. The objective is to evaluate outcomes of the three main EVLP protocols: ‘Lund’, ‘Toronto’ and ‘Organ Care System’ (OCS), through a network meta-analysis (NMA). Methods A systematic search was performed in Pubmed, Embase, the Cochrane library and Web of Science. Studies performing EVLP on initially discarded donor lungs were independently assessed for eligibility by two researchers. Data on study design, participants, and EVLP methods were extracted, together with outcomes such as survival and PGD. The generated database was assessed on meeting the assumptions for NMA. Results Nine studies were included: two non-randomised clinical trials (n = 240), and four prospective (n = 1360) and three retrospective observational cohort studies (n = 540). The study protocols could be divided into: Toronto (5/9), Lund (3/9) and OCS (1/9). Most frequently reported outcomes were PGD grade 3 at 72 hours post-LTx, and one-month and one-year survival. All included studies compared EVLP to c-LTx, providing solely indirect evidence for comparison between protocols and thus no loops within the NMA model. In the absence of loops, consistency within the model cannot be statistically assessed. Thus, thorough examination for differences that could modify the treatment effect is required. Substantial variations were found in study design, type of LTx, and participant characteristics. It was therefore not feasible to construct a subset of studies that met the similarity and consistency assumptions of NMA. Conclusion Currently, no substantiated statistical comparison can be made between different EVLP protocols. Further attempts at NMA are dependent on the introduction of studies comparing multiple EVLP protocols, or an increase in randomised controlled trials performing EVLP on standard donor lungs. Alternatively, collaborative data management between EVLP centres would be a promising way to explore the effect of different protocols, and their individual components, on patient outcomes.

Use of metabolomics to identify strategies to improve and prolong ex vivo lung perfusion for lung transplants

Normothermic ex vivo lung perfusion (EVLP) allows for functional assessment of donor lungs; thus has increased the use of marginal lungs for transplantation. To extend EVLP for advanced organ reconditioning and regenerative interventions, cellular metabolic changes need to be understood. We sought to comprehensively characterize the dynamic metabolic changes of the lungs during EVLP, and to identify strategies to improve EVLP. Human donor lungs (n = 50) were assessed under a 4-hour Toronto EVLP protocol. EVLP perfusate was sampled at first (EVLP-1h) and fourth hour (EVLP-4h) of perfusion and were submitted for mass spectrometry-based untargeted metabolic profiling. Differentially expressed metabolites between the 2 timepoints were identified and analyzed from the samples of lungs transplanted post-EVLP (n = 42) to determine the underlying molecular mechanisms. Of the total 312 detected metabolites, 84 were up-regulated and 103 were down-regulated at EVLP-4h relative to 1h (FDR adjusted p < .05, fold change ≥ |1.1|). At EVLP-4h, markedly decreased energy substrates were observed, accompanied by the increase in fatty acid β-oxidation. Concurrently, accumulation of amino acids and nucleic acids was evident, indicative of increased protein and nucleotide catabolism. The uniform decrease in free lysophospholipids and polyunsaturated fatty acids at EVLP-4h suggests cell membrane remodeling. Untargeted metabolomics revealed signs of energy substrate consumption and metabolic by-product accumulation under current EVLP protocols. Strategies to supplement nutrients and to maintain homeostasis will be vital in improving the current clinical practice and prolonging organ perfusion for therapeutic application to further enhance donor lung utilization.

A CLUE for better assessment of donor lungs: Novel technique in clinical ex vivo lung perfusion

The direCt Lung Ultrasound Evaluation (CLUE) technique was proven to be an accurate method for monitoring extravascular lung water in donor lungs during ex vivo lung perfusion (EVLP) in an experimental model. The aim of this study was to examine the application of CLUE in the clinical setting. Lungs were evaluated using acellular EVLP protocol. Ultrasound images were obtained directly from the lung surface. Images were graded according to the percentage of B-lines seen on ultrasound. CLUE scores were calculated at the beginning and end of EVLP for the whole lung, each side, and lobe based on the number (No.) of images in each grade and the total No. of images taken and evaluated retrospectively. A total of 23 EVLP cases were performed resulting in 13 lung transplants (LTxs) with no hospital mortality. Primary graft dysfunction (PGD) occurred in only 1 recipient (PGD3, no PGD2). Significant differences were found between suitable and non-suitable lungs in CLUE scores (1.03 vs 1.85, p < 0.001), unlike the partial pressure of oxygen/fraction of inspired oxygen ratio. CLUE had the highest area under the receiver operating characteristic curve (0.98) compared with other evaluation parameters. The initial CLUE score of standard donor lungs was significantly better than marginal lungs. The final CLUE score in proned lungs showed improvement when compared with initial CLUE score, especially in the upper lobes. The CLUE technique shows the highest accuracy in evaluating donor lungs for LTx suitability compared with other parameters used in EVLP. CLUE can optimize the outcomes of LTx by guiding the decision making through the whole process of clinical EVLP.

Normothermic machine perfusion of donor-lungs ex-vivo: promoting clinical adoption.

Lung transplantation offers the only realistic therapeutic option for patients with end-stage lung disease. However, this is impacted by a shortfall in availability of suitable donor-lungs. Normothermic machine perfusion of donor-lungs outside the donor body also known as ex-vivo lung perfusion (EVLP) offers a potential solution through objective assessment, reconditioning and treatment of donor-lungs initially deemed unsuitable for use. This review discusses key advances and challenges in the wider clinical adoption of this technology. This review will summarize key research within the following areas: recent clinical trials utilizing EVLP, logistical challenges, EVLP protocol innovations, novel assessment methods and current research into therapeutic modulation of lung function during EVLP. Normothermic machine perfusion of donor-lungs ex-vivo offers a promising platform to assess and modulate donor-lung quality prior to transplantation. Consensus on how and when to best utilize EVLP is yet to be reached, meaning that widespread clinical adoption of the technology has not yet become a reality. Further work is needed on agreed indications, perfusion protocols and organization of services before becoming a regularly used procedure prior to lung transplantation.

Inflammatory Response after Immediate versus Delayed Ex-Vivo Lung Perfusion in a Porcine Cardiac Arrest Donation Model

Ex Vivo Lung Perfusion (EVLP) is a promising tool for evaluation and reconditioning in marginal donor lungs. However, the optimal protocol is discussed controversially. It is our hypothesis that different EVLP protocols and different perfusion solutions result in different cytokine patterns during EVLP. Following cardiac arrest and 30 min of no-touch warm ischemia, pig lungs were harvested, flushed and stored in cold preservation solutions. Different groups were processed as immediate long EVLP (I-EVLP, 12 h), delayed short EVLP (4 h) after 9 hours of cold storage (D-EVLP). Lungs were perfused with different acellular solutions: Steen solution or modified HTK solution containing either dextran(CD) or dextran and albumin (CDA). Pulmonary gas exchange, biochemical and structural parameters were recorded hourly. Cytokine / chemokine levels were analyzed in perfusates at baseline and after 1 and 4 h of EVLP. ∆ pO2 (pulmonary venous - pulmonary arterialpO2) was higher in D-EVLP group, especially at h 1: I-EVLP: 259 ± 132, D-EVLP: 291 ± 96 and h 2: I-EVLP: 228 ± 125, D-EVLP: 252 ± 116 (n.s.). Compared to D-EVLP, lungs that underwent EVLP with CD and CDA showed significantly higher oxygen capacity (∆ pO2 CD: 402.79 +30.33 mmHg, CDA: 414.86 + 9.77 mmHg). Within 4 h ELVP, concentrations of IFN-γ, TNF-a, IL-1α/β, IL-10, CXCL8 (IL-8) and IL-18 increased significantly (all p<0.05) in the four groups. Of note, no significant differences could be detected between I- vs. D-EVLP lungs and CD vs. CDA solutions. In a non-heart beating porcine lung donor model with relevant ischemic tissue damage, lungs were perfused with normothermic EVLP. Even after 9 hours cold static preservation (CSP) and 4 hours EVLP lung, function is comparable to direct EVLP. The modified HTK solution with dextran and dextran/ albumin had significantly better oxygenation. Cytokines and chemokines including the cell death marker IL-18 increase during 4 h of EVLP but a delay before EVLP may not dramatically worsen the inflammatory response.

The Assessment of Lobe Oxygenation by Differential Blood Gas Analysis on Ex-Vivo Lung Perfusion May Predict Postoperative Outcomes

Lung assessment of marginal donor lungs on ex vivo lung perfusion (EVLP) can be challenging due to limited objective parameters. Currently, the significance of isolated differential analysis of blood gas (ABG) from each lobar pulmonary vein is not clear. The aim of this study is to identify the impact of differential ABG (D-ABG) on EVLP evaluation, and compare the D-ABG with the post-transplant outcomes. From Feb 2016 to August 2019, 110 EVLP lungs from 57 donors were analyzed for this study. Donor lungs were perfused with an acellular EVLP protocol, and transplant suitability of lungs was evaluated based on standard EVLP parameters. D-ABGs were taken from each pulmonary vein at the same time of standard evaluation. In transplanted EVLP lungs, primary graft dysfunction (PGD) was assessed at 72 hours. In the favorable group (defined as PGD grade 0-1), both PaO2/FiO2 (P/F) ratio at left atrium (P/F LA) and P/F ratio at lower lobe pulmonary vein (P/F LPV) were significantly higher than that of the unfavorable group (non-suitable or PGD grade 2-3) [LA, 526 (466-574) vs. 437 (386-499) mmHg, P < 0.001; LPV, 409 (349-452) vs. 332 (250-364) mmHg, p <0.001]. In receiver operating characteristic curve analysis for unfavorable, P/F ratio LPV showed the highest AUC with threshold of 384, sensitivity 0.88 and specificity 0.63 than that of other standard parameters (Table 1). Regarding PGD at 72 hours in transplanted lungs, P/F LA on EVLP assessment was not different between PGD≥2 and PGD≤1 groups [526 (466-574) vs. 510 (433-513) mmHg, p = 0.307, Figure], while P/F LPV in PGD≥2 was significantly lower than that in PGD≤1 [352 (334-398) vs. 409 (349-452) mmHg, p = 0.046]. These results suggest that D-ABG on EVLP could provide additional, valuable information for evaluation. The deterioration of lobe oxygenation might be masked throughout whole lung ABG; however, low D-ABG of the lower lobe may predict a greater incidence of high-grade PGD after lung transplantation.

Use of Phosphodiesterase Inhibition During Ex-Vivo Lung Perfusion of Donor Lungs Unsuitable for Transplantation

Purpose Primary Graft Dysfunction after lung transplantation is characterised by inflammatory cascade activation, vascular leak and pulmonary oedema. Nitric oxide signalling plays a critical role in pulmonary vascular homeostasis. Reduced cyclic guanosine monophosphate (cGMP) following ex-vivo lung perfusion (EVLP) is associated with increased microvascular permeability. Phosphodiesterase-5 inhibitors e.g. Sildenafil prevent cGMP breakdown causing pulmonary vasodilation and reduced pulmonary vascular resistance (PVR). We investigated the effects of Sildenafil during EVLP on physiology, inflammatory status and endothelial activation markers. Methods Five human, clinically unused donor lungs, underwent acellular EVLP with 40% predicted cardiac output and a closed left atrium. Following 30 minutes of stable EVLP, a 10mg Sildenafil (Revatio; Pfizer) bolus was administered. Haemodynamic data was continuously monitored and perfusate sampled at intervals and evaluated via a MSD pro-inflammatory panel.Physiological data was compared using ANOVA method. Inflammatory protein concentrations were compared with DEVELOP-UK historical control data and analysed by multiple unpaired t-tests. Results Following Sildenafil administration, rapid development of alveolar oedema was observed. No measured effects on pulmonary haemodynamics including flow, PAP, PVR and oxygenation were seen. The overall trends for the pro-inflammatory cytokines (IL-1β, IL-6, IL-8 and TNF-α) were similar in both groups. Significance was observed at the final 120-minute time-point; with higher levels of IL-8 and TNF-α following Sildenafil. The treatment group had significantly decreased expression of soluble tight junctional proteins (VE-cadherin, thrombomodulin and VWF) compared to the control group. Conclusion Sildenafil didn't improve pulmonary physiology as expected and appeared to promote the development of alveolar oedema. While the mechanism for this remains unclear, we observed significantly lower concentrations of the endothelial damage markers in the Sildenafil group. This difference may be confounded by the control group being a historical cohort which used a different EVLP protocol, limiting comparison. We conclude that Sildenafil failed to have the hypothesised therapeutic effects and is detrimental to lungs undergoing EVLP.

Perfusate-adsorption during ex vivo lung perfusion improves early post-transplant lung function

Objective: Improvement in ex vivo lung perfusion (EVLP) protocols could increase the number of donors available for transplantation and protect the lungs from primary graft dysfunction. We hypothesize that perfusate adsorption during EVLP reconditions the allograft to ischemia-reperfusion injury after lung transplantation. Methods: Donor pig lungs were preserved for 24h at 4°C, followed by 6h of EVLP according to the Toronto protocol. The perfusate was additionally adsorbed through a CytoSorb adsorber in the treatment group, whereas control lungs were perfused according to the standard protocol (n = 5, each). EVLP physiology and biochemistry were monitored. Upon completion of EVLP, a left single lung transplantation was performed. Oxygenation function and lung mechanics were assessed during a 4-hour reperfusion period. The inflammatory response was determined during EVLP and reperfusion. Results: The cytokine concentrations in the perfusate were markedly lower with the adsorber, resulting in improved EVLP physiology and biochemistry during the 6-hour perfusion period. Post-transplant dynamic lung compliance was markedly better during the 4-hour reperfusion period in the treatment group. Isolated allograft oxygenation function and dynamic compliance were continued to be superior in the adsorber group at the end of reperfusion accompanied by a markedly decreased local inflammatory response. Conclusions: Implementation of an additional cytokine adsorber has refined the standard EVLP protocol. Furthermore, cytokine removal during EVLP improved immediate post-transplant graft function together with a less intense inflammatory response to reperfusion in pigs. Further studies are warranted to understand the beneficial effects of perfusate adsorption during EVLP in the clinical setting.

An observational study of Donor Ex Vivo Lung Perfusion in UK lung transplantation: DEVELOP-UK.

Many patients awaiting lung transplantation die before a donor organ becomes available. Ex vivo lung perfusion (EVLP) allows initially unusable donor lungs to be assessed and reconditioned for clinical use. The objective of the Donor Ex Vivo Lung Perfusion in UK lung transplantation study was to evaluate the clinical effectiveness and cost-effectiveness of EVLP in increasing UK lung transplant activity. A multicentre, unblinded, non-randomised, non-inferiority observational study to compare transplant outcomes between EVLP-assessed and standard donor lungs. Multicentre study involving all five UK officially designated NHS adult lung transplant centres. Patients aged ≥ 18 years with advanced lung disease accepted onto the lung transplant waiting list. The study intervention was EVLP assessment of donor lungs before determining suitability for transplantation. The primary outcome measure was survival during the first 12 months following lung transplantation. Secondary outcome measures were patient-centred outcomes that are influenced by the effectiveness of lung transplantation and that contribute to the health-care costs. Lungs from 53 donors unsuitable for standard transplant were assessed with EVLP, of which 18 (34%) were subsequently transplanted. A total of 184 participants received standard donor lungs. Owing to the early closure of the study, a non-inferiority analysis was not conducted. The Kaplan-Meier estimate of survival at 12 months was 0.67 [95% confidence interval (CI) 0.40 to 0.83] for the EVLP arm and 0.80 (95% CI 0.74 to 0.85) for the standard arm. The hazard ratio for overall 12-month survival in the EVLP arm relative to the standard arm was 1.96 (95% CI 0.83 to 4.67). Patients in the EVLP arm required ventilation for a longer period and stayed longer in an intensive therapy unit (ITU) than patients in the standard arm, but duration of overall hospital stay was similar in both groups. There was a higher rate of very early grade 3 primary graft dysfunction (PGD) in the EVLP arm, but rates of PGD did not differ between groups after 72 hours. The requirement for extracorporeal membrane oxygenation (ECMO) support was higher in the EVLP arm (7/18, 38.8%) than in the standard arm (6/184, 3.2%). There were no major differences in rates of chest radiograph abnormalities, infection, lung function or rejection by 12 months. The cost of EVLP transplants is approximately £35,000 higher than the cost of standard transplants, as a result of the cost of the EVLP procedure, and the increased ECMO use and ITU stay. Predictors of cost were quality of life on joining the waiting list, type of transplant and number of lungs transplanted. An exploratory model comparing a NHS lung transplant service that includes EVLP and standard lung transplants with one including only standard lung transplants resulted in an incremental cost-effectiveness ratio of £73,000. Interviews showed that patients had a good understanding of the need for, and the processes of, EVLP. If EVLP can increase the number of usable donor lungs and reduce waiting, it is likely to be acceptable to those waiting for lung transplantation. Study limitations include small numbers in the EVLP arm, limiting analysis to descriptive statistics and the EVLP protocol change during the study. Overall, one-third of donor lungs subjected to EVLP were deemed suitable for transplant. Estimated survival over 12 months was lower than in the standard group, but the data were also consistent with no difference in survival between groups. Patients receiving these additional transplants experience a higher rate of early graft injury and need for unplanned ECMO support, at increased cost. The small number of participants in the EVLP arm because of early study termination limits the robustness of these conclusions. The reason for the increased PGD rates, high ECMO requirement and possible differences in lung injury between EVLP protocols needs evaluation. Current Controlled Trials ISRCTN44922411. This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 85. See the NIHR Journals Library website for further project information.

Optimal ex vivo lung perfusion techniques with oxygenated perfusate

Accumulating evidence supports an increasing role of ex vivo lung perfusion (EVLP) in clinical lung transplantation. However, EVLP has adverse effects on the quality of lung grafts, which have rarely been discussed. Careful optimization of current EVLP protocols might improve outcomes. This study examined effects of different levels of oxygenation of the perfusate circulated through the lungs during EVLP and the impact on post-transplant functional outcomes. We compared results of 4 different oxygenation levels in the perfusate during EVLP: 6% oxygen (O2), 40% O2, 60% O2, and 100% O2. We evaluated lung function, compliance, and vascular resistance and levels of glucose and other markers in the perfusate. After EVLP, lung grafts were transplanted, and post-transplant outcomes were compared. Lungs perfused with 40% O2 on EVLP had the lowest glucose consumption compared with the other perfusates. Lungs treated with 40% O2 or 60% O2 exhibited significantly less inflammation, as indicated by reduced pro-inflammatory cytokine messenger RNA levels compared with lungs perfused with 6% O2 or 100% O2. Significantly more oxidative damage was noted after 4 hours of EVLP perfused with 100% O2. After transplantation, lungs perfused with 40% O2 during EVLP had the best post-transplant functional outcomes. Optimization of O2 levels in the perfusate during EVLP improved outcomes in this rat model. Deoxygenated perfusate, the current standard during EVLP, exhibited significantly more inflammation with compromised cellular metabolic activity and compromised post-transplant outcomes.

Animal models of ex vivo lung perfusion as a platform for transplantation research

Ex vivo lung perfusion (EVLP) is a powerful experimental model for isolated lung research. EVLP allows for the lungs to be manipulated and characterized in an external environment so that the effect of specific ventilation/perfusion variables can be studied independent of other confounding physiologic contributions. At the same time, EVLP allows for normal organ level function and real-time monitoring of pulmonary physiology and mechanics. As a result, this technique provides unique advantages over in vivo and in vitro models. Small and large animal models of EVLP have been developed and each of these models has their strengths and weaknesses. In this manuscript, we provide insight into the relative strengths of each model and describe how the development of advanced EVLP protocols is leading to a novel experimental platform that can be used to answer critical questions in pulmonary physiology and transplant medicine.

A New Lung Preservation Technique through Bronchial Artery Perfusion on Ex-Vivo Lung

Purpose Airway hypoxia due to microvascular loss may be a predisposing factor for subsequent fibrotic remodeling in allografts, resulting in suboptimal transplant outcomes in lung transplantation. Ex-vivo lung perfusion (EVLP) is a novel strategy for lung allograft preservation that keeps the organs at physiological protective conditions. Modifying EVLP strategy, we have developed a new lung preservation technique focusing on airway protection through bronchial artery perfusion. Methods and Materials Using heart-lung blocks harvested from Lewis rats, we have developed a model where bronchial circulation (using another cannula from descending aorta, retrogradely) was synchronously perfused in addition to pulmonary circulation with acellular Steen solution on EVLP (the scheme of the model is shown in Fig 1 ). Rat lungs after 1 hour cold preservation, perfused and ventilated on EVLP for 4 hours were evaluated and lungs with bronchial artery perfusion were compared with those without bronchial perfusion on EVLP. The studies were performed based on our rat EVLP protocol that has proven to be reliable with at least 4 hours of duration with stable results. Results At 4 hours on EVLP, bronchial artery perfusion was associated with significantly better preserved oxygenation and better compliance in lung allografts through reduced glucose consumption and increased ATP level as compared to the control group. Conclusions Bronchial artery perfusion on EVLP may be a new lung preservation strategy that breaks through the current major limitation in hypoxic transplant airways after lung transplantation.