August 06, 2019
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Novel technology with smartphone camera may measure BP

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Kang Lee

The use of a novel smartphone-based technology — transdermal optical imaging — to measure BP fell within 5 mm Hg of reference measurements in adults who were normotensive, according to a study published in Circulation: Cardiovascular Imaging.

“Current methods are quite accurate but still not convenient for monitoring blood pressure,” Kang Lee, PhD, professor and Canada Research Chair Tier 1 at the Dr. Eric Jackman Institute of Child Study at University of Toronto, told Cardiology Today. “Our study is a proof of concept that for the first time shows we can use a regular smartphone to perform blood pressure measurement in a contactless, noninvasive and convenient fashion without the need of any additional equipment.”

Novel technology

Hong Luo, MD, PhD, of The Affiliated Hospital of Hangzhou Normal University in Zhejiang, China, and colleagues analyzed data from 1,328 adults who were normotensive. Patients were either part of the training set (70%), the testing set (15%) or the validation set (15%).

Transdermal optical imaging via a smartphone was used to measure BP. The camera on the front of an iPhone was used to record video for 2 minutes. Machine learning was also used to assess the video and to generate prediction models for systolic BP, diastolic BP and pulse pressure.

“In the last 10 years or so, I have been trying to detect children’s lies in a contactless manner and invented a new imaging method called transdermal optical imaging,” Lee said in an interview. “In the middle of doing this, we discovered the same technology can be used to detect blood pressures. Instead of pursuing a contactless lie detector for children, we decided to develop a contactless blood pressure monitoring system because it will benefit more people in the world, including my father who is hypertensive.”

The average accuracy of predicting systolic BP was 94.81%, 95.71% for diastolic BP and 95.75% for pulse pressure. The average prediction biases for systolic BP was 0.39 mm Hg, –0.2 mm Hg for diastolic BP and 0.52 mm Hg for pulse pressure.

“Although our method can be used conveniently to measure blood pressure, it does not mean that we should use our smartphone to replace trained nurses and doctors to perform clinical measurements and diagnosis,” Lee told Cardiology Today. “Rather, the real advantage of our technology is to make you aware of your blood pressure and health conditions so that you can manage your health and wellness and seek professional help when needed.”

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Potential impact

“The study of Luo et al represents an auspicious start for video camera BP measurement,” Ramakrishna Mukkamala, PhD, cardiovascular researcher and signal processing instructor at Michigan State University College of Engineering in East Lansing, wrote in a related editorial. “In addition to including heterogenous subjects, future studies should focus on extracting all potential BP-related information from facial video including the imperceptible head movements with each heartbeat (head ballistocardiography) and even facial expressions. Such rich information in facial video may render this video camera approach to be more promising for BP measurement than a contact measurement of the finger [photo-plethysmography] waveform.” – by Darlene Dobkowski

For more information:

Kang Lee, PhD, can be reached at Dr. Eric Jackman Institute of Child Study, University of Toronto, 45 Walmer Road, Toronto, ON M5R 2X2, Canada; email: kang.lee@utoronto.ca.

Disclosures: Lee reports he holds a patent for the transdermal optical technology. Luo reports no relevant financial disclosures. Mukkamala reports he received grants from the NIH and holds several issued and pending patents on cuffless BP measurement, some of which have been licensed to Digitouch Health. Please see the study for all other authors’ relevant financial disclosures.