Devices that can monitor breathing remotely and accurately: as tested

Continuous monitoring of vital signs is necessary in a variety of clinical settings such as intensive care units, for patients with critical health conditions, health monitoring in aged care facilities and prisons, or in security monitoring situations where drowsiness can lead to accidents.

This is now mostly achieved through wired or invasive contact systems. However, it is inconvenient or, for patients with burns or infants with insufficient skin area, unsuitable.

Scientists at the University of Sydney Nano Institute and the NSW Smart Sensing Network have now developed a photonic radar system that enables highly precise, non-invasive monitoring.

This research was published today in Nature Photonics.

Using a newly developed and patented radar system, the researchers monitored the cane toads and were able to accurately detect pauses in breathing patterns from a long distance. This system is also used in devices that simulate human breathing.

Scientists say this demonstrates a proof-of-principle of using photonic radar which could allow monitoring of multiple patients’ vital signs from a single, centralized station.

University of Sydney Pro-Vice-Chancellor (Research) and lead author of the study, Professor Ben Eggleton said: “Our guiding principle here is to address concerns of convenience and privacy, while providing highly accurate monitoring of vital signs.”

The advantage of this approach is the ability to remotely detect vital signs, eliminating the need for physical contact with the patient. This not only increases patient comfort but also reduces the risk of cross-contamination, making it valuable in environments where infection control is critical.

“Photonic radar uses a light-based photonic system – rather than traditional electronics – to generate, collect and process radar signals. This approach makes it possible to generate extremely wide-band radio frequency (RF) signals, offering extremely precise and simultaneous tracking of multiple subjects,” said lead author Ziqian Zhang, a PhD student in the School of Physics.

“Our system combines this approach with LiDAR – light detection and range. This hybrid approach delivers a vital signs detection system with resolution up to six millimeters with micrometer-level accuracy. It is suitable for a clinical environment.”

Alternative approaches to non-contact monitoring typically rely on optical sensors, using infrared and visible wavelength cameras.

“The camera-based system has two problems. One of them is the high sensitivity to variations in lighting conditions and skin tones. The other is with patient privacy, with high-resolution images of patients being recorded and stored in the cloud computing infrastructure,” said Professor Eggleton who is also co-Director of the NSW Smart Sensing Network.

Radio frequency (RF) detection technology can remotely monitor vital signs without the need for visual recording, providing built-in privacy protection. Signal analysis, including identification of health alerts, can be performed without the need for information storage in the cloud.

Co-author Dr Yang Liu, a former PhD student in Professor Eggleton’s team, now based at EPFL in Switzerland, said: “The real innovation in our approach is complementary: the system we demonstrated has the ability to activate both radar detection and LiDAR simultaneously. It has built-in redundancy; if one of the systems encounters an error, the others continue to function.”

Conventional RF radar systems, which rely heavily on electronics, have a narrow RF bandwidth and therefore lower range resolution. This means they can’t separate closely located targets or distinguish them in cluttered environments.

Relying solely on LiDAR, which uses much shorter wavelengths of light, provides better range and resolution, but has limited penetration through objects such as clothing.

“Our proposed system maximizes the utility of both approaches through the integration of photonics and radio-frequency technologies,” said Zhang.

Working with collaborators and partners in the NSW Smart Sensing Network, the researchers hope this research provides a platform for developing a cost-effective, high-resolution, rapid-response vital signs monitoring system with applications in hospitals and corrective services.

“The next step is to shrink the system and integrate it onto a photonic chip that can be used in handheld devices,” said Zhang.

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INTERVIEW

Professor Ben Eggleton Mr Ziqian Zhang
Sydney Nano and the Sydney Nano School of Physics and the School of Physics
University of Sydney University of Sydney

benjamin(email protected) (email protected)

MEDIA QUESTION

Marcus Storm | +61 423 982 485 | (email protected)

STATEMENT

This research was supported in part by grants from the Australian Research Council, the US Air Force and the US Office of Naval Research.

ADDITIONAL INFORMATION

FOTONIC RADAR Q&A with Ziqian Zhang: HOW IT WORKS

1. What is photonic radar: Photonic radar, also known as microwave photonic radar or photonic-assisted radar, is a radar system that uses photonic technology to enhance the performance of traditional electronic radar systems. This means the system uses photons – light energy at high frequencies – rather than electrons and electricity to generate radio waves. It’s important to realize that even though it incorporates photonic techniques, these systems still rely on radio waves or microwaves for sensing.

1. How it works: Traditional electronic radar systems process and transmit radar signals in the electrical domain, utilizing electronic components. In contrast, photonic radar systems use technology that allows conversion between electronic and optical signals. This allows them to harness the power of modern photonics to process RF (radio frequency) signals in the optical domain. In addition, photonic radar systems can distribute these signals over long distances with minimal loss and distortion, thanks to the properties of fiber optics.
2. What are the advantages: Optical signals can carry much more information than conventional electronic signals. When we use optical signals for the generation, processing, and distribution of radar signals (photonic radar), the systems tend to have a wider radar bandwidth and better signal quality. This provides outstanding range resolution and sensing precision. Range resolution refers to the minimum distance between targets that the radar system can separate. Our photonic system has millimeter-level resolution, allowing it to isolate closely located subjects and extract their vital signs without interfering with one another. Meanwhile, high sensing precision, thanks to high quality signal generation, ensures the accuracy of vital signs detection.
3. Compared to conventional electronic radar systems: The photonic radar system enables distributed multi-band sensing with extended signal range. This results in superior radar performance from a centralized system, facilitating better coordination and lower costs without the need to deploy multiple independent systems and synchronize them simultaneously.
4. Hybrid Radar-LiDAR System: An important innovation in the system we demonstrated was its ability to simultaneously activate radar detection and LiDAR as a sensor fusion system, combining multiple sensor modalities.
   Here are the main advantages:
   Redundancy: If a radar or LiDAR system experiences an error, the others will continue to function, ensuring uninterrupted performance.
   Complementarity: The information gathered from the radar and LiDAR systems can complement each other.
5. What’s next? We may continue to investigate using on-chip components to shrink the device’s footprint or test its performance with human subjects, possibly those with identified lung or heart conditions. Another prospect is studying advanced algorithms to improve system performance for moving subjects in real-world application scenarios, such as in an aged care facility.
6. Potential application scenarios: Our photonic radar sensors offer a wide range of applications spanning the sectors of corrective services, national security, MedTech, aged care, home care, livestock and animal use and healthcare.