AsianScientist (Feb. 16, 2023) – What do body temperature, blood pressure, pulse and respiration rates have in common? They are all vital signs that indicate human health. Monitoring these vital signs is a common and crucial component of patient care and can be instrumental in detecting or preventing life-threatening events. The measurements also offer clinicians the necessary information to make informed decisions that can enhance patient care and outcomes.
Typically, healthcare professionals measure these vital signs with a myriad of methods. However, going to a healthcare professional can be inconvenient and even difficult—particularly for vulnerable groups like the elderly and infants.
To make vital signs monitoring more available, researchers have designed accurate, low-cost devices for real-time monitoring. For example, many of today’s monitoring techniques employ photoplethysmography (PPG)—a non-invasive, simple, and low-cost optical method that can detect changes in blood volume below the skin surface.
The volume of blood flow in the arteries changes each time the heart beats. Using light-emitting diodes (LED) and a photodetector, a PPG sensor will detect these changes by shining light on the skin and measuring the amount of light not absorbed by melanin and reflected from the skin’s surface. The process results in PPG signals that can be analyzed to determine a person’s health condition.
To what degree the light of a PPG sensor enters the skin is subject to its wavelength. Red and near-infrared (NIR) LEDs have longer wavelengths and are less easily absorbed by melanin, so they penetrate the skin deeper. Green and blue LEDs have shorter wavelengths and relatively shallower penetration. As such, pulse oximeters in clinical settings often use red and NIR LEDs, while commercially available PPG wearables that measure heart and respiration rates adopt green LEDs.
Innovative medical devices harnessing PPG are an important part of the global digital health ecosystem, which is projected to have a market value of US$1.04 billion by 2030. These gadgets are on track to transform how quality healthcare is delivered, vastly improving accessibility and affordability for all.
A good night’s sleep
If you still feel exhausted even after a full night’s sleep, there is a chance you might have sleep apnea. A serious sleep disorder that happens when a person’s breathing is interrupted repeatedly during slumber, sleep apnea affects a significant percentage of the global population. If left untreated, the disorder can precipitate severe health problems, like high blood pressure and heart trouble.
To easily monitor vital signs during sleep, a Hong Kong-based innovation has equipped hearables with PPG. What sets this innovation apart is that the PPG measurement is done inside the ear canal—with the PPG device inherently constrained within the ear canal, interference from user movements can be minimized. In addition, the use of proprietary algorithms further removes unwanted signals. This effectively filters the “noise” to preserve raw, detailed information, which is then translated to various physiological data, such as heart and respiratory rate and sent to users’ smartphones for easy monitoring.
These non-intrusive smart hearables can also send vocal cues to users when an apnea episode is detected, gently waking them for a change in sleep posture. Small and lightweight, PPG-based hearables can help those experiencing sleep apnea get the quality sleep they need.
Simple blood-pressure monitoring
Another important vital sign to measure is blood pressure, which provides tell-tale signs of an individual’s heart condition. High blood pressure, or hypertension, indicates the risk of developing heart attack, stroke and other life-endangering health issues. While the conventional method of using an inflating cuff to measure blood pressure is already non-invasive, continuous monitoring is not possible and neither is taking measurements during sleep or exercise.
Circumventing the usage of cuffs, small and easy-to-use wearables can detect the user’s PPG signals and derive the user’s blood pressure using sophisticated algorithms in these PPG signals. Operating the system requires calibrating it against a medical-grade blood pressure measurement device. Successive measurements are then relative to the calibration point, while its connectivity to consumer devices like smartphones or smartwatches makes readings effortlessly available to users. This empowers users to continuously monitor and analyze any notable changes in their health data, providing early indications of heart or blood pressure issues that could allow for early, life-saving interventions.
Some technology companies are also incorporating machine learning to remove the need for calibrating PPG signals altogether. This innovation can enable continuous blood pressure monitoring and open avenues for cuffless measurements.
Smartphones offer contactless monitoring
To make these wearables even more convenient, researchers are harnessing the power of smartphones. From boosting productivity to providing entertainment and polishing photography skills, the palm-sized gadget is nothing short of a modern marvel. With healthcare thrown into the mix, many mobile applications include features to allow users to manage their well-being.
Making use of a smartphone camera as the sensor, Singapore-based innovators have developed a remote-PPG (rPPG) technology that employs proprietary computer-vision algorithms and signal-processing techniques to measure users’ vital signs through the light reflected from their faces. This process can be done remotely by analyzing pre-recorded or real-time videos of users to monitor their heart and respiration rates through facial blood flow and volume changes based on reflected light. The technology’s advanced video-processing method includes capturing regions of interest (in this context, the face), filtering signals and increasing the signal-to-noise ratio of PPG signals.
While using NIR light enables more accurate measurements, ambient light is sufficient to obtain PPG signals through rPPG technology. In addition to heart and respiration rates, rPPG technology can also derive stress levels from heart-rate-variability measurements.
From wellness and medical applications to non-healthcare industries, the applications of this rPPG-based monitoring technology are wide-ranging. Significantly, the innovation can help improve medical accessibility for individuals living in remote locations, extending telemedicine to a larger population base. In a post-COVID world where an increasing number of people are less keen to visit clinics physically, these tech offers can be great home-based solutions for individuals who want to take charge of their health.
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