Ultrasonic tech provides high-resolution contactless respiration monitoring

Chronic respiration diseases represent a major health problem for populations across the planet. Sleep apnea has been linked to hypertension, heart disease, diabetes and stroke, while chronic obstructive pulmonary disease kills upward of 3 million people annually. In the early stages of these afflictions, most sufferers exhibit abnormal respiration, which makes continuous respiration monitoring crucial for detecting troublesome warning signs and preventing sudden death.

As alternatives to expensive and invasive monitoring methods, contactless sensing technologies have been explored, including the use of acoustic beams that produce real-time, high-ranging resolution and detect small distance transformations in the respiratory system. However, these typically have insufficient sampling rates, poor synchronization, and imprecise ranging resolutions.

Wang et al. introduced a novel ultrasonic-based, high-resolution contactless monitoring system supported by an acoustic transceiver platform with universal audio architecture to achieve submillimeter ranging and continuous respiratory wave recovery.

“The platform is equipped with an FPGA soundcard and tweeter that can customize the transmission and reception of broadband ultrasound for high sampling rates and transceiver synchronization,” said author Zhisheng Wang. “Its design resolves some practical challenges associated with existing platforms, and the cross-correlation-based delay estimation enables better ranging and further recovery of the respiration wave.”

In tests, the new platform achieved a distance estimation median error within a 1-meter range of 0.45 mm.

“The experimental results show our system can exactly monitor participants’ respiration, adapting to different sleep postures as well as maintaining long-term continuous monitoring and apnea detection, with a median error of 0 breaths per minute and a maximum error of only 0.58 breaths per minute,” said Wang.

Source: “Ultrasonic-based submillimeter ranging system for contactless respiration monitoring,” by Zhisheng Wang, Shangyu Li, Zongfeng Li, Shunli Wang, and Junning Cui, AIP Advances (2023). The article can be accessed at http://doi.org/10.1063/5.0156997 .