At the University of Missouri, a team of researchers developed a custom finger clip device that can continuously measure a variety of vital signs, including blood pressure. The novel device represents a new way of measuring vital signs and contains two commercial photoplethysmography (PPG) sensors that work at two different points on the finger. This approach allows researchers to simultaneously calculate pulse wave velocity and also measure blood oxygen saturation, body temperature, heart rate, and breathing rate.
Continuous blood pressure measurements can reveal trends that a single measurement can miss. Additionally, taking blood pressure measurements in a doctor’s office can cause an increase in anxiety, leading to a change in blood pressure, a phenomenon known as “white coat syndrome.” It is clear that continuous monitoring, which takes non-invasive and unobtrusive measurements throughout the day, is preferable.
“Typically, in a hospital or clinic, calculating a person’s blood pressure involves the use of an inflatable cuff that is wrapped around their arm, but there are three problems with this method – it can damage a person’s arteries if done in a short period of time is carried out repeatedly; blood pressure may rise due to nervousness; and it can take up to 30 seconds, ”said Richard Byfield, one of the leaders in the development of the new device. “Our device can record a person’s blood pressure in five seconds using optical sensors on the fingertip that measure the amount of light reflected from the blood vessels beneath the surface of the skin.”
As soon as the clip captures the speed data of the pulse wave, it transmits it wirelessly to a computer, where machine learning algorithms interpret it and calculate the blood pressure. So far, the clip has shown in tests with volunteers that it can measure systolic blood pressure with an accuracy of approximately 90% and diastolic pressure with an accuracy of 63%.
The robustness of the clip is key to ensuring that the PPG data is reliable. “Usually there are some problems with PPG sensors,” said Byfield. “It’s called artifact movement – if you move a PPG sensor while reading, it can affect the recorded waves. Additionally, we’ve found that pressure differentials can change the waves, but a finger clip design uses a spring to keep the pressure constant. Another reason this method hasn’t been explored much is that these finger clips usually only have one sensor, but we have two sensors in our device. “
Study in the IEEE Sensors Journal: Towards a robust blood pressure estimate based on pulse wave velocity measured by photoplethysmography sensors
Flashbacks: Precise blood pressure measurement without a cuff on a smartphone; Portable monitor provides continuous blood pressure data
Over: University of Missouri
