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Reluctant Lungs: How does EVLP save donated lungs that were rejected?
In the world of organ transplantation, lung supply has always been a challenge. With traditional donation methods falling short, scientists have developed technologies marked by extracorporeal lung perfusion (EVLP) to give rejected donated lungs new possibilities. This technology not only prolongs the preservation of donated lungs, but also makes them suitable for transplantation by re-evaluating and repairing damaged lung tissue.
Ex vivo lung perfusion (EVLP) is a mechanical perfusion technique designed to maintain active aerobic cellular metabolism of the lungs outside the donor's body.
Physiological basis of EVLP
The main function of the lungs is to facilitate gas exchange, supply oxygen to the blood, and remove carbon dioxide. This process occurs in the alveoli, where oxygen and carbon dioxide are exchanged between the lungs and the blood.
Perfusion of the lungs refers to the process by which blood circulates through the lungs, and optimized perfusion and ventilation distribution are critical for effective gas exchange. Compared with in vivo perfusion, EVLP provides a controlled external environment, which allows regeneration and repair to proceed without the constraints of the immune system and coagulation system.
Historical background of EVLP
The concept of intravital perfusion was first proposed by Alexis Carrel and Charles Lindbergh in the 1930s, and EVLP was first used in clinical practice by Stijn and his team in 2001. .
Their study shows that even lungs that are initially rejected can be re-evaluated for suitability and successfully transplanted after a short period of EVLP.
Successful regeneration cases provide reliable evidence of the effectiveness of EVLP, showing the potential of this technology.
Main procedures and protocols of EVLP
Multiple EVLP protocols
At present, the most important EVLP agreements include the Toronto Agreement, the Lund Agreement and the Organ Care System Agreement. These methods can be used not only to assess the quality of respiratory organs, but also to realign and repair these organs.
Toronto Agreement
This protocol is currently the most widely used EVLP protocol and is suitable for donated lungs that meet certain conditions.
Lund Agreement
The Lund protocol focuses on regenerating donated lungs once considered unsuitable, enhancing their function through management of the airways and the use of anti-inflammatory drugs.
Organ Care System Agreement
This innovative, portable system is designed to assess lung function during transport, thereby reducing cold ischemia time and having a positive impact on transplant outcomes.
Advantages and Impact of EVLP
Repair a once-rejected donor lung
EVLP can effectively repair lungs affected by pulmonary edema, trauma or infection, making those lungs that have been rejected become usable again. This technology not only solves the problem of alveolar collapse but also reduces infection and inflammation through direct drug delivery.
Improve transplantation results
Lungs treated with EVLP have excellent short- and long-term survival rates. This has led to EVLP being increasingly adopted in transplant procedures, with lungs from high-risk donors performing better after transplantation.
Compared with traditional methods, EVLP can significantly reduce the risk of major graft dysfunction and promote good respiratory capacity.
Risks and challenges of EVLP
Inflammatory response
While EVLP offers multiple advantages, it also comes with potential risks, including inflammatory reactions due to contact with perfused circuit materials. These inflammatory responses can reduce the effectiveness of transplanted organs.
Lung injury caused by ventilation
The process of using a mechanical ventilator may result in ventilation-induced lung injury (VILI), especially if a positive pressure ventilation protocol is applied.
Economic Challenges
According to multi-center observational studies, the cost of EVLP is significantly higher than that of traditional lung transplantation. This high cost is closely related to the operation of machinery, dose replacement, and extended intensive care time.
Conclusion
With the advancement of science and technology, extracorporeal lung perfusion technology has given a new lease of life to donated lungs that were originally rejected. This not only improves the utilization of the donor lung, but also improves the success rate of transplantation. However, the promotion and popularization of this technology still faces many challenges. In the future, how to overcome these obstacles to improve human lung health will be an important question we need to think about.
