Wireless oxygen sensor inspired by researcher’s sick baby

WPI professor develops wireless oxygen sensor
WPI professor Ulkuhan Guler shows off an early prototype of the miniaturized, wearable device that will one day monitor infants’ blood oxygen levels. (Worcester Polytechnic Institute)

There’s an expression that necessity is the mother of invention, and for Ulkuhan Guler, assistant professor of electrical and computer engineering and director of WPI’s (Worcester Polytechnic Institute's) Integrated Circuits and Systems Lab, the necessity was the well-being of her infant son over a decade ago.

Inspired by the experience of her sick newborn son laying in a neonatal intensive care unit in Istanbul, Guler has teamed with several researchers to create a miniaturized wireless oxygen sensor that would enable infants to leave the hospital and still be safely monitored from home.

The miniature wearable sensor, the size of a Band-Aid, measures blood gases diffusing through the skin and reports the data wirelessly. By using this flexible miniaturized device, babies can be untethered from medical monitors, enabling nurses, doctors, and parents to more easily and safely examine and hold them. Untethered from these medical machines, an infant could be taken home, with doctors receiving data on its respiratory function and alerts if the condition worsens.

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Guler, who had limited personal contact with her infant son when he was born, understands how important the sensor can be.

“Extended stays in the hospital are costly and can be a strain on families,” said Guler in an article appearing on WPI’s website. “And studies have shown that babies’ health improves when they are with their families. Our goal with this affordable, mobile device is to give doctors more flexibility in monitoring their patients both in the hospital and at home.”

Typically, measuring oxygen molecule levels transcutaneously involves using a system with a 5-lb. monitor plugged into an electrical outlet, and sensors that generally are wired to the monitor. Guler’s healthcare device will use wireless power transfer. It also will be connected to the Internet wirelessly, so an alarm on a monitor in a doctor’s office or smartphone app would notify medical personnel and family members if the baby’s oxygen level begins to drop.

The device is designed to measure PO2, or the partial pressure of oxygen, which indicates the amount of oxygen dissolved in the blood—a more accurate indicator of respiratory health than a simple oxygen saturation measurement, which can be easily taken with a pulse oximetry device gently clamped on a finger. Measuring the PO2 level via a noninvasive device attached on the skin is as accurate as a blood test.

The wearable baby oxygen monitor also would be useful for adults, especially people with severe asthma and seniors with COPD, or Chronic Obstructive Pulmonary Disease, an incurable, progressive lung disease and the third leading cause of death in the United States, according to the Centers for Disease Control and Prevention. Guler will modify the wearable for adults, and create a related smartphone app, in another phase of her research.

Guler is collaborating with Pratap Rao, associate professor of mechanical engineering at WPI, and Lawrence Rhein, MD, chair of the department of pediatrics and an associate professor at the University of Massachusetts Medical School. Ian Costanzo and Devdip Sen, both graduate students in electrical and computer engineering at WPI, also are working with Guler to create a chip that will eventually act as the heart for the wearable device.

“The concept of the technology is that if we have more accessible data for a person of any age, we’ll be able to better take care of these patients,” said Rhein, who has served as an advisor to Guler. “The idea of noninvasive, untethered, accessible data collection opens up a whole new world of care.”

The chip, designed to work inside the wearable oxygen monitor, activates the optical sensors, captures analog signals from the sensor, handles power management, and contains required circuitry. Guler and the team have custom designed the individual circuits, such as signal capturing circuits and driver circuits for optical based read-out circuits. In the next phase of the research project, they plan to equip the chip with more circuits to digitize the analog signals, transmit the captured and digitized data, and create power from a wireless link.

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