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Health Care at Your Finger Tips

Researchers develop smartphone app that monitors respiration rates

By Carol Nelson

What if a simple smartphone app could alert you or your doctor to a health issue based upon the detection of a change in your respiration or heart rates?

Researchers in the Auburn University Wireless Engineering Research and Education Center are working to make this a reality.

Shiwen Mao and graduate students Xuyu Wang, Runze Huang and Chao Yang are developing two systems with applications in health care: SonarBeat, an ultrasound-based smartphone app that is used to monitor respiration rates; and PhaseBeat, a Wi-Fi-based technology that can monitor both respiration and heart rates.

“We use an acoustic signal to detect respiration rates of a patient,” said Mao, Samuel Ginn Professor and director of the Wireless Engineering Research and Education Center. “Rather than using sensors that attach to the chest or clip to your fingertips, the technology is contact-free, low-cost, easy to deploy and suitable for long-term monitoring of a patient’s conditions.”

The SonarBeat system is implemented in the form of an Android smartphone app to transmit signals into open space through the phone’s speaker.

“The signal hits on the chest of the patient — there is a chest movement induced by breathing — and the acoustic signal changes,” Mao said. “Those chest movements change the feature characteristics of the signal. The smartphone microphone picks up the reflected signal, and the signal processing software is executed to detect the small variations induced by the movements. We are then able to make accurate estimates of respiration rates, with a median error around 0.3 beats-per-minute.”

The smartphone app-based system has been tested in a living room, an office and even a crowded movie theater.

“It has been found to be quite robust when it comes to interfering noises and different environments, largely due to the short propagation range of acoustic signals,” Mao said.

The PhaseBeat system employs the ubiquitous Wi-Fi infrastructure for contact-free health sensing, transmitting Wi-Fi signals from devices such as wireless routers, smartphones or laptop computers.

“Again, the signal hits the patient’s chest, and the reflected signal, along with signals from the line-of-sight path and reflected from other obstacles, are received by another device equipped with an IEEE 802.11n card with three antennas,” Mao said. “The received signal is calibrated and analyzed, with the small vital sign signals detected. It works the same way to detect heartbeat signals to measure heart rates, working over a longer distance and even through a wall.”

Mao said the technology will eventually be available for use in the home to assist those who are living alone, without the necessity of specialized or expensive equipment.

“We can use what is monitored to detect an issue or to compare with certain features that can indicate certain types of disease,” he said. “By comparing the data, we can detect anomalies and send alarms to the doctor or directly to the patient.

“In addition, the wireless system’s signal is able to penetrate obstacles and could be used to locate survivors in the aftermath of a disaster or to detect breathing patterns and sound an alarm to wake a tired driver.”

Mao said the next step to making that a reality is to pursue collaborations for testing the technology with researchers in industry or medical schools.

“By comparing the data, we can detect anomalies and send alarms to the doctor or directly to the patient."

“Both SonarBeat and PhaseBeat can capture vital sign signals over an extended period of time,” he said. “Once equipped with the medical knowledge through such collaborations, the team aims to develop algorithms to detect signature features or symptoms in captured vital sign signals for diseases, such as sudden infant death syndrome or apnea. The system also can be used for activity recognition, to detect various activities of a patient, such as a fall, and trigger a warning message to doctors or family members.”

Additionally, the team is collaborating with researchers at the Auburn University MRI Research Center to use the captured respiration signal to control the MRI scanner. If successful, patients would not be required to hold their breath during an MRI scan, making the procedure more comfortable for the elderly and patients with certain diseases.

Mao and his team were honored last fall at an international conference for their work on the SonarBeat technology. Their presentation of “SonarBeat: Sonar Phase for Breathing Beat Monitoring with Smartphones” earned the Best Demo Award at the Institute of Electrical and Electronics Engineers International Conference on Sensing, Communication and Networking. The conference focuses on novel communication technologies and emerging applications and services involving mobile sensing and communication, and ubiquitous and pervasive computing.