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Pediatric Cerebral Hemodynamic Monitoring Goes Wireless

Article In Brief

New research suggests neonatal and pediatric cerebral hemodynamic monitoring is going wireless. The soft, flexible, quarter-size device sends signals via Bluetooth, which will likely broaden its use to a wider array of conditions and settings.

Figure

Schematic illustration and exploded view of (A) a device with (B) a modular, rechargeable coin cell battery. The main body consists of serpentine interconnects between islands of electrical components for wireless operation and optical tissue profiling, with four photodiodes each featuring a distinct source–detector distance. The main body and the modular battery both feature a pair of magnets for mechanical and electrical coupling, all encapsulated within soft, medical-grade silicone. (C) Photograph of the skin-oriented side of the main device unit, with a pair of LEDs and four photodetectors encapsulated between a black silicone optical barrier. (D and E) Photograph of a device upon mechanical stresses of (D) bending and (E) twisting. (F) Computed strain distribution in the copper layers (first Cu layer is the closest to skin) of the device with a bending radius of 2.5 cm. (G) Mechanical characterization of the device main unit compared with pig skin using a three-point flexural test. (H–J) Photographs of a device with a modular battery mounted on the forehead of a 9-week-old infant during (H) resting, (I) feeding, and (J) tummy time.

Pediatric and neonatal cerebral hemodynamic monitoring is going wireless, according to a paper demonstrating a device that is also soft, flexible, the size of a quarter, and nearly as easily applied as a Post-It.

Doing away with the tangle of wires connected to a base station on traditional devices, the wireless monitor sending signals via Bluetooth will likely broaden its use to a wider array of conditions and settings. By permitting free movement and caregiving in hospitals and homes, the device could be of use to patients of any age in need of cerebral monitoring.

“It's far-reaching, not just for premature infants or those with disorders of autonomic regulation,” said one of the study's senior authors, Debra E. Weese-Mayer, MD, chief of the division of pediatric autonomic medicine at Ann & Robert H. Lurie Children's Hospital of Chicago. “It has applications to any area of medicine where there is concern about cerebral bloodflow and oxygenation.”

Neurologists and other physicians who were not involved with the paper, published on November 30 in the Proceedings of the National Academy of Sciences, said they look forward to getting the device.

“I'm a neurointensivist and very much interested in systemic circulation and cerebral hemodynamics,” said Farzaneh Sorond, MD, PhD, chief of stroke and neurocritical care at Northwestern University and Northwestern Medicine. “This kind of work is really a step in the right direction. It makes sense that it starts with infants; they have thinner skin, less fat, thinner skulls. Now that we know the device is accurate in the pediatric ICU, the next step is testing it into the clinics and optimizing it for adults.”

Study Details

Having devoted her career to the study and treatment of respiratory and autonomic disorders of infancy, childhood and adulthood, Dr. Weese-Mayer became interested in finding a way to allow parents and staff to interact with them more normally while still safely monitoring their cerebral hemodynamics.

Such monitoring is especially crucial for infants diagnosed with rapid-onset obesity with hypothalamic dysfunction, hypoventilational and autonomic dysregulation, or with congenital central hypoventilation syndrome, two rare conditions in which she has specialized.

“Parents need to bond with their baby and not be afraid of them,” Dr. Weese-Mayer said. “The tangle of wires can be really enormous. I wanted something that could work not just when the child is in the ICU, but when they're active.”

Four years ago, she met John A. Rogers, PhD, who began his career at the Massachusetts Institute of Technology before joining Bell Laboratories and then the University of Illinois. In September, he was named the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering and founding director of the newly endowed Center on Bio-Integrated Electronics at Northwestern University.

“When we met, it was one of those moments of ‘wow,’ imagining the kinds of work we could do together,” Dr. Weese-Mayer said.

In March of 2019, they coauthored a paper in Science with three dozen collaborators from the University of Illinois, China, Singapore and Korea, demonstrating a pair of ultrathin, soft, skin-like electronic devices capable of coordinated, wireless operation. A year later, they published a follow-up paper in Nature Medicine, describing the device's ability to monitor heart rate, respiration rate, temperature, and blood oxygenation in neonatal and pediatric ICUs. Neither of those papers, however, involved cerebral monitoring.

The first author of the new paper in PNAS, Alina Y. Rwei, PhD, a postdoctoral researcher in Dr. Rogers's laboratory, spent over a year developing and validating the device's cerebral near infrared spectroscopy (NIRS). Despite its tiny size, the system uses a multiple-photodiode array and a pair of light-emitting diodes that measure the amount of light absorbed or scattered by blood and tissue. It can calculate not only the concentration of oxy- and deoxyhemoglobin in arteries and veins directly below the device, but also heart rate, peripheral oxygenation, cerebral pulse pressure, and vascular tone.

Aside from being wireless, Dr. Weese-Mayer said, another benefit of the new device is that, unlike existing stand-alone NIRS devices, it presents the NIRS data synchronized to heart rate, blood pressure, and other vital signs.

“I like to see all my waveforms as time synchronized channels shown one above the next,” she said. “That way, at 5:03:23, I know exactly what happened and I can look for inter-relationships among the measures.”

The investigators tested the device in eight subjects with congenital central hypoventilation syndrome and four with dizziness without other health abnormalities; the children were between the ages of 2 months and 15 years. Results during a variety of challenges were comparable to those using a wired, commercialized NIRS device, the Cerebral/Somatic Oximeter made by Medtronic.

The paper noted that over 900,000 children under the age of 20 in the United States suffer neurological harm linked to irregular cerebral perfusion every year, due to genetic mutations, premature birth, cardiac disease, surgical intervention, or traumatic injury.

Dr. Weese-Mayer said she hopes the wireless device can eventually be used outside the hospital for long-term monitoring in at-risk patients.

“The next logical step is to have it out in the field, including in countries that do not otherwise have the access to advanced care,” she said. “Our big end goal has been to get it into third-world countries, where they do not have ICUs and everything has to be accomplished remotely.”

Expert Commentary

Z. Leah Harris, MD, professor and chair of pediatrics at Dell Children's Hospital and the University of Texas, Austin, called the new device “exciting, compelling and novel. Only ten years ago in ICUs across the country, we started to measure cerebral bloodflow and oxygenation. To have it be wireless changes the game, and for it to be Bluetooth-enabled is huge.”

Dr. Harris said she could envision multiple scenarios in which the device could be useful. “It now allows you to monitor a child outside the ICU, and even outside the hospital,” she said. “You could use this as a surrogate to monitor subclinical breakthrough seizures in sleep. It provides a new tool to study epilepsy, stroke, anything that affects cerebral bloodflow, including sickle-cell disease.”

Dr. Sorond said that “tremendous benefits” could come from use of such devices. “We could, for example, use them to monitor blood pressure in adults,” she said. “Can you imagine having a patient wearing it 24/7? Perhaps we could predict a seizure or stroke before it happens.”

Daniel J. Licht, MD, the Department of Pediatrics Distinguished Endowed Chair and director of the Wolfson Laboratory for Clinical and Biomedical Optics at Children's Hospital of Philadelphia, called the new device “remarkable.”

“What they've done here is created a NIRS device that is small, light, and incredibly wearable,” he said. “There are things you can do with this device that you couldn't with the commercial devices. You could put 20 of these devices on a head and look at regional differences. You could study what happens when kids talk, play, read a book, or fight with each other. And unlike an fMRI, you could do these studies in a normal environment, in real life.”

Dr. Licht pointed out, however, that all NIRS technology requires estimates of oxygenation and deoxygenation, because it cannot directly distinguish between light that is absorbed from that which is diffracted.

“That's a basic problem with NIRS,” he said. As a result, he said, “It's most useful as a trend monitor, to show changes, so you lose a lot of important information.”

A different type of optical device that his group has been working on measures the scattering of light directly, and so produces more accurate results. But, he said, “What we lack are simplicity and inexpensiveness. My device requires a PhD to analyze the data, and the device costs about $150,000. It's far from ready for commercial use.”

Disclosures

Drs. Weese-Mayer, Soround, and Harris had no relevant disclosures.

Link Up for More Information

• Rwei AY, Lu W, Wu C, et al. A wireless, skin-interfaced biosensor for cerebral hemodynamic monitoring in pediatric care https://www.pnas.org/content/117/50/31674. Proc Natl Acad Sci U S A 2020: Epub 2020 Nov 30.
    • Chung HU, Rwei AY, Hourlier-Fargett A, et al. Skin-interfaced biosensors for advanced wireless physiological monitoring in neonatal and pediatric intensive-care units https://www.nature.com/articles/s41591-020-0792-9. Nat Med 2020;26(3):418–429.
      • Chung HU, Kim BH, Lee JY, et al. Binodal, wireless epidermal electronic systems with in-sensor analytics for neonatal intensive care https://science.sciencemag.org/content/363/6430/eaau0780. Science 2019;363(6430):eaau0780.