Blood Pressure Measurement Based on the Camera and Inertial Measurement Unit of a Smartphone

Abstract BackgroundThis study assessed the accuracy of AlwaysBP (test) in blood pressure (BP) measurement compared with the standard cuff-based manual method of brachial BP measurement (reference). AlwaysBP is a smartphone software that estimates systolic BP (SBP) and diastolic BP (DBP) based on the pulse transit time (PTT). The PTT was calculated from the finger photoplethysmogram using the camera and from seismocardiogram using the inertial measurement unit sensor of a commercially available smartphone.MethodsA total of 87 participants without known cardiovascular disease were enrolled in the study. The primary analysis aimed to evaluate the accuracy of the test method compared with the reference method in the entire study population. The secondary analysis was performed to confirm the stability of the test method for up to 4 weeks in 15 subjects. At enrollment, the gender, arm circumference, and BP distribution were considered according to the current guidelines.ResultsAmong the study subjects, 45 (51.7%) individuals were male and the average age was 35.6 ± 10.4 years. Hypertension was diagnosed in 14 subjects (16.1%) prior to the study. The mean test and reference SBP were 120.0 ± 18.8 and 118.7 ± 20.2 mmHg, respectively, and the difference was 1.2 ± 7.1 mmHg (r = 0.935, P < 0.001). The mean test and reference DBP were 80.1 ± 12.6 and 81.1 ± 14.4 mmHg, respectively, and the difference was −1.0 ± 6.0 mmHg (r = 0.911, P < 0.001). At the 4-week time point, the differences between SBP and DBP were 0.1 ± 8.8 and −2.4 ± 7.6 mmHg.ConclusionsThe AlwaysBP software exhibited acceptable accuracy regarding SBP and DBP measurement compared with the standard BP measurement method. This technology can be easily applied in everyday life and may improve the general population’s awareness of hypertension, thus helping to control it.