The sad reality of terminal lung illnesses is that there are simply far more patients than there are donor lungs available. This isn’t just because of the low number of donors, which would be problem enough, but many donor lungs are significantly damaged, rendering them unusable.
By using a new experimental technique, though, such a damaged lung has now been restored to function – by sharing its circulatory system with that of a living pig. This leverages the body’s self-repair mechanisms to exceed the capabilities of current donor lung restoration techniques.
“It is the provision of intrinsic biological repair mechanisms over long-enough periods of time that enabled us to recover severely damaged lungs that cannot otherwise be saved,” say the lead researchers, surgeon Ahmed Hozain and biomedical engineer John O’Neill of Columbia University.
The underlying principle is similar to an existing donor lung restoration technique called ex vivo lung perfusion (EVLP), which involves placing a lung in a sterile dome attached to a ventilator, pump, and filters.
The lung’s temperature is maintained at human body temperature, and a bloodless solution containing oxygen, nutrients, and protein is circulated through it. That circulation, when liquid is pumped through the organ, is the perfusion part.
EVLP has helped save lives by keeping donor lungs stable and even repairing them a little. But the time window afforded by the technique is somewhat limited – it can only be conducted for up to eight hours, which is not a lot of time for the biological repair functions to kick in.
It’s that precious time that the research team has bought with their pigs, and years of research.
In 2017, O’Neill led the development of the xenogeneic (cross-species) cross-circulation platform. Last year, two of the researchers, biomedical engineer Gordana Vunjak-Novakovic of Columbia University and surgeon Matthew Bacchetta of the Vanderbilt Lung Institute, led a study in which they restored damaged pig lungs by attaching them to other pigs.
Earlier this year, the team extended the operation time of the platform to four days.
Now, the researchers have revealed that they have successfully used the same technique to repair five damaged human lungs by connecting them to pigs, including one severely injured lung that had failed to recover function using EVLP.
“We were able to recover a donor lung that failed to recover on the clinical ex vivo lung perfusion system, which is the current standard of care,” Vunjak-Novakovic said. “This was the most rigorous validation of our cross-circulation platform to date, showing great promise for its clinical utility.”
