Photonic radar can remotely monitor breathing without privacy concerns
Researchers have created a device that uses photonic radar to remotely and accurately monitor breathing, even distinguishing between more than one patient. They say their device might one day be used in hospitals, aged care facilities and at home to provide contactless monitoring of people with respiratory concerns.
Monitoring a patient’s vital signs is, well, vital to tracking their health and bodily functions. Many current methods used in hospitals require wired contact with the patient – think of those sticky electrodes placed across the chest that record heart and respiratory rates – which can be problematic if a patient is burned, for example, and has little accessible skin.
A contactless alternative is camera-based monitoring systems, but they are sensitive to light conditions and skin color and raise privacy issues if used in a healthcare setting. Now, researchers at the University of Sydney have developed a system to accurately monitor breathing that doesn’t require patient contact.
“Camera-based systems have two problems,” said Ben Eggleton, corresponding author of the study. “One is high sensitivity to variations in lighting conditions and skin color. The other is with patient privacy, with high-resolution images of patients being recorded and stored in cloud computing infrastructure.”
To overcome these problems, the researchers turned to photonics. Photonic radars, or microwave photonic radars, use photons – light energy at high frequency – rather than electrons and electricity to generate radio waves. A photonic transceiver creates a microwave signal through a pulsed laser, which returns the signal to a photonics-based receiver after hitting the target.
Conventional radio frequency (RF) radars that rely on electronics have a narrow bandwidth and reduced range resolution. As a result, they can’t distinguish between targets placed close together.
“Photonic radar uses a light-based, photonics system – rather than traditional electronics – to generate, collect and process the radar signals,” said Ziqian Zhang, the study’s lead author. “This approach allows for a very wideband generation of radio frequency (RF) signals, offering highly precise and simultaneous, multiple tracking of subjects.”
The researchers complemented their photonic system with light detection and ranging (LiDAR), which uses pulsed light waves to measure distance. While LiDAR alone provides good range and resolution, its ability to penetrate through objects such as clothing is limited. Incorporating radar and LiDAR provides the device with the advantages of both, as well as an inbuilt backup system.
“A real innovation in our approach is complementarity: our demonstrated system has the capacity to simultaneously enable radar and LiDAR detection,” said Yang Liu, a co-corresponding author. “This has inbuilt redundancy; if either system encounters a fault, the other continues to function.”
The researchers first tested their device using two human breathing simulators. They found that the radar could accurately detect the respiration rate of two targets about 3.9 in (10 cm) apart in real-time. It detected irregular breathing patterns at the millimeter level, including longer inhalations and shorter exhalations, as well as pauses in breathing.
Next, they tested their device on a living creature, using a cane toad as a human proxy. The toad was placed approximately 39 in (1 m) from the radar, with the beam focused on its buccal region, which moves during breathing. Compared to the human chest, the toad’s buccal region is not even an inch – or a couple of centimeters – squared.
A video recording of the toad’s breathing was cross-referenced with the real-time data extracted from the device. It accurately measured the animal’s respiration rate, including the intermittent breathing common to amphibians.
Moving forward, the researchers see a number of options for improving their device.
“We could continue investigating the use of on-chip components to shrink the device’s footprint or test its performance with human subjects, possibly those with identified lung diseases or heart conditions,” said Zhang. “Another prospect is delving into advanced algorithms to boost the system’s performance for moving subjects in real-world application scenarios, such as in aged-care facilities.”
They say that their device’s ability to measure breathing from a distance enhances patient comfort and reduces the risk of cross-contamination. Further, it would enable the monitoring of multiple patients from a single, centralized station. Ultimately, they see a range of applications for it, including in healthcare, the prison sector, aged and home care, as well as veterinary and livestock uses.
The study was published in the journal Nature Photonics and the below short video, produced by the University of Sydney, shows how the device monitored the cane toad’s breathing.
Source: University of Sydney