Noninvasive and cuffless blood pressure measurement: The effects of contacting force and dynamic exercise.

摘要

Approximately 1 billion people around the world are suffering from hypertension. The monitoring of blood pressure is vitally important in order to identify hypertension and treat them earlier before serious health problems are developed. Cuffless blood pressure measurement has been proposed in recent years to realize continuous monitoring of blood pressure. The primary objective of this research is to solve two major issues related to noninvasive and cuffless blood pressure measurement using pulse transit time: (1) the effect of contacting force between the sensor unit and the measurement site on blood pressure estimation and (2) the estimation of blood pressure after dynamic exercise.;In order to understand the effect of contacting force on pulse transit time and to develop a blood pressure estimation method robust to contacting force, a model-based study is carried out. The theoretical analysis is verified by an experiment carried out on 30 subjects and a repeatability study on 10 subjects. Based on theoretical simulation and experimental verification, DC component of the photoplethysmographic signals is used as an indication of contacting force and to compensate the effect of it on pulse transit time. The developed method is tested by 248 trials obtained from 30 subjects and more accurate estimation of blood pressure is achieved.;To extend the applicability of cuffless blood pressure measurement to post-exercise situations, heart rate information is studied and proposed to compensate the estimated blood pressure for post-exercise. With falling time compensation, the accuracy of blood pressure estimation immediately after exercise is improved, especially for systolic blood pressure after vigorous exercise (12 subjects, 156 trials). The difference between the estimated and the measured blood pressure is improved from -3.43 +/- 9.41mmHg to -1.42 +/- 7.64mmHg (p = 0.048) for the estimation of SBP and from -2.55 +/- 8.15mmHg to -3.56 +/- 6.54mmHg (p = 0.245) for DBP. Comparing with the AAMI standard, satisfactory results are achieved with falling time compensation. The possibility of blood pressure estimation by timing feature of the photoplethysmographic pulses is also explored. Using a logarithmic relationship, rising time can give comparable blood pressure estimation results with pulse transit time at rest and during the late recovery phase.