Northwestern researchers created a new hair-thin device that measures the vital signs of fetuses in a collaborative effort with Ann & Robert H. Lurie Children’s Hospital of Chicago.
A Jan. 26 study published in the Nature Biomedical Engineering journal details how researchers at the Querrey Simpson Institute for Bioelectronics made the device. According to the study, the tool measures heart rate, temperature, blood oxygen levels and heart rate variability by going through small ports in the body created for fetal surgery.
McCormick Prof. John Rogers, who serves as the director of the Institute and authored the study, said there is currently no way to continuously measure these vital signs in fetuses, unlike with surgery on a baby or adult.
Rogers added that having constant vital sign measurements is useful for tracking the health of patients during surgery.
“You’d like to be able to track the patient’s status throughout the surgery, so that you could detect any kind of adverse effect as soon as possible, so that the surgeon could take corrective action,” Rogers said. “But that’s currently not possible with this particular type of fetal surgery.”
He added that the device measures vitals through “extremely miniaturized” sensors. He said small balloons on the device are used to maneuver it through the ports in the body as well as to create the necessary level of contact with the fetus.
Steven Papastefan, a general surgery resident at Northwestern Medicine and an author of the study, said while surgery on a fetus is uncommon, it is advantageous to operate before birth in certain cases.
The current type of ultrasound used to measure heart rate in current fetal surgeries, transuterine echocardiography, is limited, Papastefan said, as it can only be performed every ten minutes due to the constraints of surgical environments.
“We’ll check its heart rate to make sure it’s okay, and then we’ll keep operating for another ten minutes or so, and we’ll take a break, and then just hope for the best,” Papastefan said. “What this (device) allowed us to do is to basically continuously monitor the fetus throughout the operation so that we know on a second-by-second basis how it’s doing.”
Papastefan said most fetal surgeries are intended to prevent ongoing damage during growth that could be irreversible after the baby is born, citing twin-twin transfusion syndrome and spina bifida as examples.
Aimen Shaaban, the director of the Chicago Institute for Fetal Health at Lurie Children’s Hospital and an author of the study, said spina bifida is an opening in the spine that can lead to a variety of neurological problems, including paralysis of the legs and hydrocephalus in the brain. Shaaban said closing this opening prior to birth can reduce the risk of complications for these problems after birth.
“The baby can have stronger legs and potentially avoid the severity of hydrocephalus,” Shaaban said. “So those are real benefits to the baby, but they require an operation on the mom in order to do it.”
Shaaban said the process of developing the device was “good old-fashioned collaboration” between his and Rogers’ teams.
Papastefan said one method of testing the device was through surgery on lambs. He said they would create spina bifida in lamb fetuses, close the fetus and then use the device in the repair operation a few weeks later.
While the device has not been tested in humans yet, Rogers said he estimates the first human test could happen two to three years after the FDA approval process begins.
Shaaban said at Lurie Children’s Hospital, fetal surgeries are performed once or twice a week. He said the device will allow surgeons to get insight into the health of the patient during surgery.
“It’s really going to change the way we actually care for the patients and give us just a greater insight into what we’re actually doing,” Shaaban said. “We think we do a good job, but when we have the data in front of us, then we’ll know, and we’ll be able to do a better job regardless.”
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