New study improves respiratory rate measurements

By WILLIAM XIE | October 12, 2017

Researchers at University College London (UCL) have recently designed a system to monitor respiratory rates using affordable thermal cameras.

The thermal cameras were attached to mobile devices to constantly track respiratory rates. The researchers analyzed the nostrils’ region of interest (ROI) by using thermal imaging to formulate respiratory information.

Thermal cameras are devices that use infrared rays to form images.

The combination of a thermal camera and ambient light, like natural sunlight or indoor lighting, can create a photoplethysmography (PPG) sensor, which senses the rate of blood flow.

The ability to monitor blood flow can also be used to monitor periodic respiratory cycles. Because of this, the researchers were able to use mobile thermal devices to track the respiration of subjects without contact.

Traditional methods of tracking respiratory rates use physical instruments such as chest-belts and oronasal probes. These physical systems can cause issues ranging from mild inconveniences to serious medicals conditions.

According to the researchers’ paper published by The Optical Society, the alternatives to physical systems include PPG and Doppler radar, which are common thermal imaging systems.

Nadia Bianchi-Berthouze, a professor in affective computing and interaction at UCL was the leader of the research team. She spoke about bringing this technology to others.

“By using low-cost thermal cameras, our work is a first step toward bringing thermal imaging into people’s everyday lives,” Bianchi-Berthouze said in a press release. “This approach can be used in places other sensors might not work or would cause concern.”

There were three major challenges that the researcher’s faced using the mobile thermal camera technique.

First, incoming data becomes difficult to study in a general environment with different ambient light sources. Second, it can be difficult to quantify themal patterns while studying environments with varying temperatures.

Additionally, nostril movement caused by breathing or body motion (e.g., laughing) makes it difficult to extract physiological information.

Researchers employed several solutions to confront those challenges: optimal quantization, thermal gradient flow and thermal voxel.

All of these methods improve the respiratory information at the ROI and the ability to track respiratory rate.

Researchers also developed a tracking algorithm that may be implemented outside the nostril ROI. Large thermal ranges and environmental noise degrade the performance of the designed tracking system.

Extreme cases of environmental change, such as leaving a heated room in the winter or entering a swimming pool, influence the temperature distribution.

Youngjun Cho, an author of the paper, spoke to ScienceDaily about how researchers previously had to use large expensive imaging systems to measure breathing. Cho explained that while using mobile devices for this research was more convenient, there were still issues to be addressed.

“We wanted to use the new portable systems to do the same thing by creating a smart-phone based respiratory tracking method that could be used in almost any environment or activity,” Cho said. “However, we found that in real-world situations this type of mobile thermal imaging was affected by changes in air temperature and body movement.

Nevertheless the researchers concluded in their paper that their nostril tracking technique works better than state of the art algorithms in high thermal range environments. The technique also generally achieved high accuracy in tracking respiratory rates.

The ability to remotely monitor respiratory rates generates various benefits ranging from early treatment and diagnosis of lung and cardiovascular conditions. This technology can also monitor babies at risk of sudden infant death syndrome.

Applications of the techniques created by the researchers will expand as the efficiency and accuracy of the mobile trackers improve.

“As thermal cameras continue to get smaller and less expensive, we expect that phones, computers and augmented reality devices will one day incorporate thermal cameras that can be used for various applications,” Bianchi-Berthouze said.

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