Lung transplants are perhaps the most difficult and complex organ transplant procedures. Not only are they vital organs with no artificial replacement, but they are also highly susceptible to infections and failure even after a successful transplant surgery.
The newest member of the lung transplant team at the University of Chicago Medicine, thoracic surgeon Dr. Christopher Wigfield, aims to improve outcomes for transplant recipients through his combination of surgical experience and clinical research in lung transplantation. He also has studied the impact of donor and procurement related issues, and was recently named Director of Educational Affairs at the International Society of Heart and Lung Transplantation.
Science Life spoke to Dr. Wigfield recently about the complexities of lung transplants, and what new technologies are on the horizon that could revolutionize the field. The following is an edited version of that conversation.
Why are lung transplants such a complex procedure?The complexity stems from the fact that you have an organ system that is vital to begin with. For lung function there is still nothing that is similar to an assist device for the heart or a dialysis machine for the kidneys, so if you transplant lungs and they don’t perform immediately, you have a very likely chance of a poor outcome. In addition to that it is very complex surgery—it’s not just connecting a couple of blood vessels and having the tissue perfuse. Lungs, when they’re diseased, tend to get extremely stuck in the patient, and so physically removing them can be the bigger challenge than the actual implantation. In fact, I enjoy implanting lungs because by that point I know I’m on the winning side.
Why are they so difficult to remove?
You have to physically almost chisel them out at times yet avoiding excessive tissue injury. With fibrotic lung diseases and suppurative diseases like cystic fibrosis, patients have been through so many cycles of inflammation and worsening that the lungs are stuck. Most mammalian species have a pleural lining that separates the lung from the inner chest wall. There’s a little fluid that allows it to be slippery, and there’s a “negative pressure” that facilitates this movement. If you have repeated cycles of lung infection or fibrosis, this space is almost completely obliterated. You have to recreate that space in its three dimensional shape and isolate major vascular structures that perfuse the whole cardiac output into the lungs safely, before you ever get near implanting the new lung. Then do it all again on the other side.
What other preparations go into the procedure before implantation?
You have a fair bit of preparation to make the bronchus available for the anastomosis. We allow enough of the vessels coming away from the heart available in a safe fashion to connect recipient with donor. So you’re doing major thoracic surgery, you’re doing major airway surgery, major vascular surgery, and heart-lung bypass at the same time. These operations demand some endurance and perseverance. Even watching can be exhausting. For us it’s always like running a marathon, but you had better be prepared for it.
Aren’t lungs much more prone to infections after the transplant because they’re exposed to air?
Correct, that is one of the long-term issues. Lungs are rejected more than other organs. They are chronically dysfunctional more often than other organ systems, so we expect only 50 percent of our lung transplants to function fully longer than five years. We’ve made a big difference over the last decade, significantly improving survival in the surgical aspects of lung transplantation, but this chronic lung dysfunction that occurs is still not really fully understood. It has to do at least partially with the fact that you breathe airborne toxins, bacteria and other contaminants in with every breath. The lung is a huge immunogenic organ because it’s exposed to the outer atmosphere, like skin. With other organs, they’re implanted and only see what comes through the bloodstream. For lungs it’s both.
How does the multidisciplinary approach to lung transplantation at the University of Chicago appeal to you as a surgeon?
This subspecialty will not be functional if you don’t do it in a truly interdisciplinary setting. You need the whole team on board: pulmonologists, thoracic surgeons, coordinators, and PAs. And you need to have a very low threshold for pulling expertise from all corners, so that you can decide on the adequate candidates for transplantation. Together we provide very adequate surveillance in the long term. Since these patients are more prone to have certain infections because of immunosuppression, we work with infectious disease specialists very closely. They are more prone to have risks of certain cancers, and therefore need close advice of other specialties. They are more prone to have renal dysfunction because of the medications. They also have a chance of developing diabetes because they get steroids, so you can see it goes in all directions. That’s why it has to be a truly multidisciplinary effort. That’s how we can get good results.
Is that something unique to the University of Chicago?
Yes, collaboration is an attraction to work here, but there’s always room for improvement. It starts with selection and ends with surveillance of the patient. Communication with the specialists is vital. An academic setting like this where there’s good collaboration to begin with is the only way to do lung transplantation. Of course the patient has some responsibility as well.
What are some of the research developments you’re looking forward to in the near future?
There are some developments that now bring at least the prospect of an artificial lung to the horizon. It’s not a total artificial lung, and presently a system called ECMO, extra corporeal membrane oxygenation, that over the years has been refined and is now coming to more and more clinical use in these patients. We either bridge them to transplantation, or if the lungs were dysfunctional after transplantation, bridge them to recovery. That used to be a very difficult scenario with poor outcomes, where you had at least 40 to 50 percent mortality at that stage. Those odds are turning more and more in our favor with more experience and more refined technology support. We really have much better systems, and we have them here at UChicago to support patients with ECMO for transplantation when necessary.
Number two is a massive development. It’s really going to bring in a new era of transplantation: optimizing lungs when they come from the donor prior to implantation with a system called Ex-Vivo Lung Perfusion. This should be arriving in major American hospitals within a year. Canadian trials and European trials have proven the feasibility, the efficacy and the superiority of using this system over extended criteria donor lungs. These would normally pose added risk when we transplant. This system is now going through FDA approval, and it’s not a matter of whether we should be doing this, but which system we will adapt. We fully optimize the lungs and utilize the maximum number of lungs to serve our lung transplant candidate population better.
So does this system refurbish the donor lungs before they’re transplanted?
There is more to it than that. It helps you assess the lungs for their function before you even have to intervene. Quite often that tells you that a donor lung is good, although it didn’t look so great when I first assessed it. The whole area of intervention for those lugs is wide open.
This type of preliminary assessment wasn’t possible before?
It wasn’t possible because the systems to take lungs out and perfuse them were purely scientific. This is now a clinical application. The lungs stay sterile and safe. The outcomes the Canadian group published and presented have provided excellent outcomes, scientific data that is very convincing. I’m at a loss as to why the FDA hasn’t already approved this.
What are your plans for implementing it here at the University of Chicago?
It has to be one solution to be considered very seriously. My appointment here may allow us to put that into practice at the University of Chicago. We have an excellent group of surgeons and physicians who have expertise and are very adaptable to this type of procedure. We have a group of extremely experienced perfusionists, and we have a larger group of patients who would benefit from this. If we can distinguish ourselves as a center of excellence in this area, we would be a dominating center in lung transplant. This is an exciting time for lung transplantation.
Find out more about the lung transplant program at the University of Chicago Medicine at uchospitals.edu/specialties/transplant/lung.html.