Deceptively simple machine performs lungs' complex job
June 15, 2005
The Novalung used to help save Sgt. Chang Wong’s life looks deceptively oversimplified.
A small plastic box with two clear hoses running out of it, the device hardly fits the traditional image of a ventilator: the large bank of equipment with a throat tube snaking out, or a rhythmically whispering pump.
But while those devices are used to keep lungs doing their job — exchanging oxygen for carbon dioxide — the Novalung is designed to help people whose lungs are too damaged to perform. Instead of helping the lungs work, it just does some of the work for them.
“It’s a completely new philosophy,” said one of the inventors of the device, Dr. Thomas Bein, a physician and professor at the Universitätsklinikum in Regensburg, Germany.
To use the Novalung, a physician simply reroutes blood flow from a patient’s major vessels through the box by tapping the femoral artery and vein in the upper thighs. As blood flows from one leg into the box, it passes through a filter that leeches off the carbon dioxide and infuses the cells with oxygen, mimicking the trade-off that should take place in the lungs. It then goes back into the system through the other leg, refreshed.
The Novalung is just becoming available because the technology of the filter is still being perfected, Bein said.
“The key is the membrane,” he said. “The art of this box is that it has a very, very high gas exchange membrane, but a very, very low resistance.”
That is, blood can easily pass through the membrane without a lot of pressure behind it, but can still trade oxygen for carbon dioxide at a very high rate.
The result is a small, portable device that can help sustain a person with critically injured lungs for days without even the need to plug it in somewhere, Bein said.
“The advantage is you can use it even under very poor circumstances,” he said. Circumstances like a field hospital, he suggested, or to transport a patient with damaged lungs by ambulance or plane.
But Bein emphasized that the Novalung is still a new device, and not without its own complications: tapping some of the biggest blood vessels in the body correctly with knitting needle-size tubes is not easy.
“It has to be in the hands of experts and stay in the hands of experts,” he said.