Called the ‘Health and Environmental Tracker’ (HET), the system integrates a suite of new sensor devices that monitor a user’s environmental parameters in real time. Included are ozone concentration, temperature, and relative humidity; heart rate via photoplethysmography and electrocardiography and respiratory rate via photoplethysmography; skin impedance, three-axis acceleration, wheezing via heart rate, expiratory airflow, and other environmental and physical aspects.
The researchers plan to begin the next development phase for the device this summer – testing the system on a larger population of trial participants.
According to the Centers for Disease Control and Prevention, asthma affects more than 24 million people in the United States. Most people with asthma currently rely on inhalers to treat their symptoms, which can include frequent 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, an assistant professor of electrical and computer engineering at NC State.
Bozkurt was the principal investigator of a paper published May 26 in the IEEE Journal of Biomedical and Health Informatics describing the HET development team’s work.
The paper, “Low Power Wearable Systems for Continuous Monitoring of Environment and Health for Chronic Respiratory Disease,“ was coauthored by James Dieffenderfer, Henry Goodell, and Brinnae Bent, North Carolina State University and the University of North Carolina at Chapel Hill; Steven Mills, Michael McKnight, Shanshan Yao, Feiyan Lin, Eric Beppler, Bongmook Lee, Veena Misra, Omer Oralkan, Jason Strohmaier, John Muth, and Alper Bozkurt, North Carolina State University; and David Peden, University of North Carolina at Chapel Hill.
The paper explained that the wearable sensor system allows for the correlation of individual environmental exposures to physiologic and subsequent adverse health responses, and that the system permits better understanding of the impact of increased ozone levels and other pollutants on chronic asthma conditions.
The HET system consists of a wristband, a chest patch, and a handheld spirometer. The paper coauthors described preliminary efforts to achieve an energy efficient sub-milliwatt system ultimately to be powered by energy harvested from thermal radiation and motion of the body itself. Primary contributions come from an ultra-low power ozone sensor, a volatile organic compounds sensor, a spirometer, and the integration of other sensors in a multimodal sensing platform.
Data from each sensor are continually streamed to an outside data aggregation device and then transferred to a dedicated server for cloud storage. Future work includes reducing power consumption of the system-on-chip including radio to reduce the entirety of each described system in the sub-milliwatt range.
“Preventing an attack could be as simple as going indoors or taking a break from an exercise routine, said Dieffenderfer, the paper’s lead author.
Dieffenderfer is a graduate research assistant at the NCSU Department of Biomedical Engineering. and the joint biomedical engineering program at NC State and the University of North Carolina at Chapel Hill.
The HET system incorporates a constellation of novel sensing devices incorporated into a wristband and a patch that adheres to the wearer’s chest.
The HET chest patch incorporates sensors that track the wearer’s movement, heart rate, respiratory rate, the amount of oxygen in the blood, skin impedance, and wheezing in the lungs. The wristband mostly monitors environmental factors such as levels of volatile organic compounds and ozone in the air, ambient humidity, and temperature. The wristband also contains additional sensors to monitor motion, heart rate and the amount of oxygen in the blood.
One non-wearable component of the HET system is a spirometer that patients exhale into several times daily 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 the HET is transmitted wirelessly to a computer where custom software collects and records the data.
“The uniqueness of this work is not simply the integration of various sensors in wearable form factors,” says paper coauthor Veena Misra. “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.
Misra is a professor of electrical and computer engineering at NC State’s National Science Foundation Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST).
Misra’s group at NC State researches novel materials and structures to enable scaling of advanced CMOS devices in the nanoscale regime. They also are exploring molecular memories based on redox active molecules which provide certain distinct advantages such as low voltage operation, multiple states, long endurance and compatibility with Silicon.
Additionally, the Misra group explores integration of molecules with silicon membranes and low temperature semiconductor to enable a new class of devices with the goal of applying nanoparticles toward devices ranging from electronic and magnetic memories to biosensors.
“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,” Misra said in a press release. “It enables a pathway to realize the ASSIST Center’s vision of wearable sensors powered by energy from the body in the near future.”
Misra said the system has been tested in the bench-top and on a some human subjects for proof of concept demonstration and confirmation that sensors work, and the system accurately compiles data.
“This summer, we plan to begin testing HET in 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,” Misra said.
When the data is collected, the center will begin developing software to track user data and give users advance warning of asthma attacks, said Bozkurt who is testbed leader of the ASSIST Center and oversees 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,” Bozkurt said.
Research and development for the HET system was done through the ASSIST Center at NC State, under NSF grant number EEC-1160483. The work was also supported by the National Institute of Environmental Health Sciences, under grant number R01ES023349, and by the Environmental Protection Agency, under cooperative agreement number CR 83578501.