Noninvasive Cuffless Blood Pressure Estimation Using Pulse Transit Time and Impedance Plethysmography.

Objective: To demonstrate the feasibility of everaging impedance plethysmography (IPG) for detection of pulse transit time (PTT) and estimation of blood pressure (BP). Methods: We first established the relationship between BP, PTT, and arterial impedance (i.e., the IPG observations). The IPG sensor was placed on the wrist while the photoplethysmography sensor was attached to the index finger to measure the PTT. With a cuff-based BP monitoring system placed on the upper arm as a reference, our proposed methodology was evaluated on 15 young, healthy human subjects leveraging handgrip exercises to manipulate BP/PTT and compared to several conventional PTT models to assess the efficacy of PTT/BP detections. Results: The proposed model correlated with BP fairly well with group average correlation coefficients of ${\text{0.88}}\pm {\text{0.07}}$ for systolic BP (SBP) and ${\text{0.88}}\pm {\text{0.06}}$ for diastolic BP (DBP). In comparison with the other PTT methods, PTT-IPG-based BP estimation provided a lower root-mean-squared-error of ${\text{8.47}}\pm {\text{0.91}}\,{\text{mmHg}}$ and ${\text{5.02}}\pm {\text{0.73}}\,{\text{mmHg}}$ for SBP and DBP, respectively. Conclusion: We conclude that the measurement of arterial impedance via IPG methods is an adequate indicator to estimate BP. The proposed method appears to offer superiority compared to the conventional PTT estimation approaches. Significance: Using impedance magnitude to estimate PTT offers promise to realize wearable and cuffless BP devices. [ABSTRACT FROM AUTHOR]