Comparison of cuffless blood pressure measurement using an electrocardiogram monitor with photoplethysmography function with measurement by the Korotkov method: a pilot study

The aim. To evaluate the reliability of blood pressure (BP) measurement results using a cuffless blood pressure device (CardioQVARK®) in comparison with the values obtained using the Korotkov method.

Materials and methods. An observational cross-sectional study of 50 patients (25 men, mean age 60 ± 14 years) with arterial hypertension was performed. Blood pressure was measured by the Korotkov method as a standard method, and a CardioQVARK® device, made in the form of a smartphone case, was used as a new method. The device records the electrocardiogram and the photoplethysmogram. Based on the parameters of the electrocardiogram and the photoplethysmogram the systolic and diastolic blood pressure (SBP and DBP) is calculated. Correlation analysis, Student’s t-test, Bland-Altman method were used for comparing the two methods, the standard deviation of the difference and a 95% confidence interval (95% CI) were calculated.

Results. There were no statistically significant differences in the mean values of SBP and DBP for the two methods. There was a strong direct relationship between SBP (r = 0.976, p < 0.0001) and DBP (r = 0.817, p < 0.0001), measured by two methods. Bias for SBP and DBP measured by the new method was: –0.5 mm Hg (95% CI: –1.7; 0.7) and –0.3 mmHg (95% CI: –1.4; 0.7), respectively. The difference in DBP measurements depended on the blood pressure level (r = 0.302, p = 0.03). The underestimation of DBP values was more pronounced for low blood pressure from 55 to 75 mm Hg. At the time of the study, 13 (26%) patients had an increase in blood pressure. The sensitivity of the new method in detecting arterial hypertension was 77% (95% CI: 46; 95), specificity 100% (95% CI: 91; 100), accuracy 94% (95% CI: 83; 99).

Conclusion. The blood pressure measurement method based on the analysis of the electrocardiogram and photoplethysmogram showed reliable blood pressure measurement results in comparison with the Korotkov method.