Could smartphones be used to measure blood pressure? Canadian and Chinese researchers are suggesting that the smartphone camera could be used to make it easier to check blood pressure.
Scientists at Hangzhou Normal University, Hangzhou, China, and the University of Toronto, Canada, believe they have found a faster and more practical way to measure blood pressure. They rely on the power of Transdermal Optical Imaging, which uses short, selfie-like facial images to measure blood pressure, and the smartphone's optical sensors detect blood flow patterns under the outer layer of skin.
Professor Kang Lee, the lead study author, explained that "cuff-based blood pressure monitors are very accurate but impractical and uncomfortable. In addition, users tend not to perform the recommended number of measurements." For this reason, Professor Lee's team saw the need to find a more convenient solution for blood pressure measurements.
To test their ideas, the researchers recruited 1,328 study participants in Canada and China. The respondents were instructed to sit in front of smartphones that were set to record with the front camera. They had 5 minutes to acclimatize, and the recording itself took 2 minutes.
At the same time, the researchers used regular blood pressure methods to compare the values with the predictions of the Transdermal Optical Imaging. Using the data, the researchers also learned to make more accurate predictions for blood pressure and pulse measurements based on facial blood flow patterns.
On average, the new method succeeded in detecting systolic blood pressure with an accuracy of 95% and diastolic blood pressure and pulse pressure with an accuracy of almost 96%. Professor Lee noted that the accuracy of these values was consistent with the accuracy of current international blood pressure measurement methods.
However, it will be some time before imaging technology can find a widespread application reachable to the general public. The researchers admit that their study still has some limitations and that the results obtained so far may only be applicable to certain groups and specific settings.
For example, the images were taken in an environment with fixed light and temperature conditions, which could lead to different results if the user is at home and or on the move. In addition, there were no persons with very dark or very light skin tones among the study participants. Also, the blood pressure values of all those examined were in the normal range, which is why the researchers are uncertain as to whether the new technique can also accurately detect signs of hypertension.
The research team aims to reduce the video running time from 2 minutes to 30 seconds, as it could be exhausting to stand still for a long period of time during the measurements. Professor Lee is nevertheless optimistic: "If future studies confirm our results and prove that clinically high or low blood pressure can be measured with this method, we may have the possibility of contactless, non-invasive and practical blood pressure measurement anywhere and anytime".
Hong Luo et al., Circulation: Cardiovascular Imaging. 2019;12: https://doi.org/10.1161/CIRCIMAGING.119.008857