May 9, 2012 |
A new prototype device lifts weight from the abdomens of obese patients who might otherwise have trouble breathing during surgery.
The respiratory assist device built by engineering students at Rice University uses suction cups attached to a horizontal beam and tied into a vacuum pump to gently lift the abdomens of patients who are on their backs and under light sedation.
Though the suspension device would not be suitable for patients under heavy sedation or who are undergoing abdominal surgery, it could be invaluable to surgeons performing operations that involved the upper or lower body.
The students—Gabriel Ochoa, Marisa Prevost, Norman Truong, Daeun Yoon, and Justin Yun—accepted the challenge last fall as their senior design capstone project, required of most graduates of Rice University’s George R. Brown School of Engineering.
Mehdi Razavi, director of electrophysiology clinical research at the Texas Heart Institute (THI), brought his idea to the school last year. He had had success in the past working with students at the Oshman Engineering Design Kitchen (OEDK).
Razavi, a co-adviser on the project with Maria Oden, OEDK director and a professor in the practice of engineering education, found his inspiration on the job.
“Almost all of these ideas come during a procedure, when you have the ‘What if?’ moment,” Razavi says. “I was in the midst of a surgical procedure on a very obese patient when he started snoring, which implies the airway may be a little bit occluded. We could see that his oxygen levels were going down, and he was trying to push against his abdominal contents to breathe.
“I thought if there was a way to support his belly, he would probably do much better and there would be less chance of having to declare an emergency and put a breathing tube in,” he says.
Razavi envisioned a device that could not only help patients breathe by gently relieving pressure on the abdomen, but would also save hospitals money. “Hospitals aren’t reimbursed by the insurance companies for medical complications,” he says. “This could help avoid the cost of having to put a breathing tube in, which is not going to be reimbursed.”
The doctor’s pitch to the students “sounded a little weird,” Truong says. But a search of the literature by Razavi and the team turned up no evidence that such a device already existed.
“I would have heard about it,” Razavi says.
“We asked around to see if doctors were interested,” Prevost says. “It seems like it’s an issue they just deal with. They get assistants to hold up the weight or pick it up themselves, but when we asked them if they’d be interested in a device, they said, ‘Yeah, that would be good.’”
Razavi, a cardiologist, installs pacemakers through the chest and gains access to arteries to the heart through the groin. He says he would use a respiratory assist device “for everything I do. A lot of the time, the abdominal content pushes down and distorts the whole anatomy of the groin, so I could use this to hold it back. But I can see it being used in any number of ways, not only in hospitals and cardiac catheterization labs but also in outpatient clinics.”
Once they decided noninvasive suction was the proper approach, the students needed suction cups that would treat the skin gently, without bruising it while maintaining the vacuum. “The cups we used come from breast pumps,” Yoon explains. “They have flexible rubber rims that conform to the contours of the skin, so they keep a good seal.”
The cups, which would link to an operating room’s vacuum system, are suspended from a horizontal beam that bears the weight.
The 40-pound test
The students and Razavi served as test subjects for the prototype by lying on their backs with a weighted slab of silicone, which mimics human tissue, on their chests.
“It was a simple, nothing-can-go-wrong test,” Ochoa says. “We had the subjects lie down on a table, and we put 40 pounds of weight on their stomachs to see how their vitals changed. We expected their CO2 levels to drop—we had a pulse oximeter on them—but we didn’t find a statistically significant change. But we did find their heart rates increasing quite a bit to compensate.”
“I got the full 40-pound treatment,” says Razavi, who also had the cups attached to his real skin. “The suction was a concern; they left it on for, I think, a good hour.”
The doctor said he took “a good dose” of aspirin the day before to mimic the condition of patients likely to be on blood thinners and whose skin would be extra sensitive as a result. “At the end, my skin was a little red, but there was no bruising,” he says, either after the test or the next morning.
A provisional patent has been filed for the invention, which may be developed by Saranas, a medical device company founded by Razavi and recent alumnus Alex Arevalos.
The students say their prototype cost less than $200 to make. The most expensive components were the custom-printed plastic connectors fabricated on the OEDK’s 3-D printer. Injection molding those parts would cut the cost even further, they say.
“The device will be very cheap, and the amount of training required to use it will be nominal,” Razavi says. “And the approval process, the regulatory pathway, is likely to be quite straightforward. I’ve run this by a regulatory specialist, and we believe strongly that it’s going to be an FDA Class 1, which is basically more paperwork than anything else.”
Razavi is encouraging the team to show the device at the American Heart Association Scientific Sessions in Los Angeles in November. “If we get a spotlight there, it will spur a lot of studies,” Yoon says.
The team members, who graduate this week, took the prize for best pitch in the Rice Undergraduate Venture Challenge.