Tech Briefs

Sensors are built into a wristband and a chest patch.

Researchers have developed an integrated, wearable system that monitors a user’s environment, heart rate, and other physical attributes to help predict and prevent asthma attacks. The system, called the Health and Environmental Tracker (HET), is composed of a suite of new sensor devices and was developed by researchers from the National Science Foundation’s Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) at North Carolina State University. The researchers plan to begin testing the system on a larger subject population this summer.

Fig.1 – A prototype of the HET chest patch. (Credit: James Dieffenderfer)

According to the Centers for Disease Control and Prevention, asthma affects more than 24 million people in the United States. Asthma patients currently rely on inhalers to deal with their symptoms, which can include debilitating asthma attacks.

“Our goal was to design a wearable system that could track the wellness of the subjects, and in particular provide the infrastructure to predict asthma attacks, so that the users could take steps to prevent them by changing their activities or environment,” said Alper Bozkurt, assistant professor of electrical and computer engineering at N.C. State. “Preventing an attack could be as simple as going indoors or taking a break from an exercise routine,” said James Dieffenderfer, a Ph.D. student in the joint biomedical engineering program at N.C. State and the University of North Carolina at Chapel Hill, and a former winner of the Create the Future Design Contest presented by Tech Briefs Media Group.

How It Works

The HET system incorporates a collection of novel sensing devices integrated into a wristband and a patch that adheres to the chest. The patch includes sensors that track a patient’s movement, heart rate, respiratory rate, the amount of oxygen in the blood, skin impedance, and wheezing in the lungs. (See Figure 1) The wristband focuses largely on environmental factors, monitoring volatile organic compounds and ozone in the air, as well as ambient humidity and temperature. The wristband includes additional sensors to monitor motion, heart rate, and the amount of oxygen in the blood. (See Figure 2)

The system also has one non-wearable component—a spirometer that patients breathe into several times a day to measure lung function. “Right now, people with asthma are asked to use a peak flow meter to measure lung function on a day-to-day basis,” Dieffenderfer said. “That information is used to inform the dosage of prescription drugs used in their inhalers. For HET, we developed a customized self-powered spirometer, which collects more accurate information on lung function and feeds that data into the system.” Data from all of these sensors is transmitted wirelessly to a computer, where custom software collects and records the data.

Fig.2 – A prototype of the HET wristband. (Credit: N.C. State University)

“The uniqueness of this work is not simply the integration of various sensors in wearable form factors,” said Veena Misra, a professor of electrical and computer engineering at N.C. State. “The impact here is that we have been able to demonstrate power consumption levels that are in the sub-milliwatt levels by using nano-enabled novel sensor technologies. Comparable, existing devices have power consumption levels in the hundreds of milliwatts.

“This ultra-low power consumption is important because it gives the devices a long battery life, and will make them compatible with the power generated by the body—which is not a lot,” said Misra, who is also the director of the ASSIST Center. “It enables a pathway to realize the ASSIST Center’s vision of wearable sensors powered by energy from the body in the near future.” Energy from the body is harvested from thermal radiation and motion of the body.

Researchers have tested the system in the benchtop and on a limited number of human subjects for proof-of-concept demonstration, and have confirmed that all of the sensors work and the system accurately compiles the data. Re searchers plan to begin testing HET this summer. They will use a controlled environment with subjects suffering from asthma and a control group in order to identify which environmental and physiological variables are effective at predicting asthma attacks.

“Once we have that data, the center can begin developing software that will track user data automatically and give users advance warning of asthma attacks,” said Bozkurt, who as testbed leader of the ASSIST Center is overseeing HET system integration. “And that software will allow users to synch the HET to their smartphones so that they can monitor their health on the go. After these tests are completed, and the prediction software created, we are hoping that a fully functional HET system will be available.”

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