A commercial finger-clip device is being adapted by researchers at the University of Missouri to provide a rapid, non-invasive way to measure and continuously monitor blood pressure.
The device also measures four additional vital signs at the same time, namely heart rate, blood oxygen saturation, body temperature and respiratory rate, said Richard Byfield, a mechanical and aerospace engineering graduate student in the United States. MU College of Engineering, and the study’s lead author published in IEEE Sensors Journal.
“Normally calculating a person’s blood pressure in a hospital or clinic involves the use of an inflatable cuff wrapped around the arm, but there are three problems with that method: It can cause damage to a person’s arteries if used repeatedly within a short period of time. is being done; people’s blood pressure can rise due to nervousness; and can take up to 30 seconds to complete,” Byfield said in a statement. “Our device can record a person’s blood pressure in five seconds by using optical sensors on the fingertip that measure the amount of light reflected from blood vessels beneath the skin’s surface.”
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This process is photoplethysmography (PPG), and the device uses two PPG sensors located at two different points on a finger to capture a person’s pulse to calculate the pulse wave velocity. Once the pulse wave rate data is collected, it is wirelessly sent to a computer for signal processing and blood pressure calculation by a machine learning algorithm. According to the researchers, other studies have shown that pulse wave speed has a strong correlation with blood pressure.
An early test of the device with 26 study participants yielded an accuracy rate of about 90 percent for systolic blood pressure and a 63 percent accuracy rate for diastolic blood pressure. Byfield said accuracy differs between systolic and diastolic because diastolic, which is a person’s minimum blood pressure, can change significantly depending on a person’s age, and can also be controlled by several factors, including age, artery stiffness, overall health, and body weight .
(Image: University of Missouri)
Byfield and colleagues also recognize that there are some difficulties in making PPG sensors work to obtain these measurements.
“Normally there are a few issues with PPG sensors,” Byfield said. “One is called artifact motion – if you move a PPG sensor while it’s reading, it can affect the waves being recorded. In addition, we found that pressure differences can change the waves, but with a finger clip design, a spring provides constant pressure. Another reason why this method hasn’t been explored much before is that these finger clips usually only have one sensor, but we have two sensors in our device.”
The device has a provisional patent pending and the team is developing the device for home use. Their long-term goal includes potential clinical and commercial applications, and Byfield said a clinical application could alleviate some of the burden on nurses dealing with multiple devices to monitor a patient’s vital signs.