First-in-human study for evaluating the accuracy of blood pressure measurement using the ring-type device with a photoplethysmography

Abstract

Abstract Background Early diagnosis of hypertension and optimal blood pressure (BP) control are important for prevention of cardiovascular morbidity and mortality. The 24-hour BP is better predictive of cardiovascular outcome than the office BP. However, conventional non-invasive BP measurement by sphygmomanometer has limitations in obtaining continuous BP and its variability in daily life. Recently, a ring-type BP measuring device, CART-I Plus (Sky Lab Inc, South Korea) without a cuff has been developed. Purpose This study was a prospective, single arm, first-in-human pivotal trial to evaluate accuracy of blood pressure measurement by the new device. Methods The ring-type smart wearable blood monitoring device measures photoplethysmography signals from the proximal phalanx and transmits the data wirelessly to the connected smartphone, to monitor the BP (Figure 1). A cuff was worn on arm to check the reference BP by auscultation, while the test device was worn on the finger of the opposite arm to check the test BP simultaneously. Measurements were repeated for up to three sets each on the left and right arms. The primary outcome measure was mean error and standard deviation of BP differences between the test device and the reference readings. Results The final analysis included 89 subjects, 47% of whom were male, with a mean age of 40.1 years. We collected 526 sets of systolic BP (SBP) and 513 sets of diastolic BP (DBP), with ranges of 80 to 175 mmHg and 43 to 122 mmHg, respectively. In sample-wise comparison (Figure 2), the mean error between the test device and the reference was 0.16 ± 5.90 mmHg (95% limit of agreements [LOA] -11.41 to 11.72) in SBP and -0.07 ± 4.68 (95% LOA -0.26 to 9.10) in DBP. The test device showed a good correlation with the reference for SBP (r=0.94, p<0.001) and DBP (r=0.95, p<0.001). In subject-wise comparison, the test device showed a good correlation with the reference for SBP (r=0.98, p<0.001) and DBP (r=0.98, p<0.001), with a mean error of 0.17 ± 3.67 mmHg (95% LOA -7.04 to 7.7) in SBP and 0.02 ± 3.21 mmHg (95% LOA -6.27 to 6.31) in DBP. Conclusion The new ring-type BP measuring device had a good correlation for SBP and DBP with minimal bias compared with a auscultation method. It has the potential to provide accurate BP in daily life.