  Pulse transit time (PTT) has been widely used for cuffless blood pressure
(BP) measurement. But, it requires more than one cardiovascular signals
involving more than one sensing device. In this paper, we propose a method for
continuous cuffless blood pressure measurement with the help of left
ventricular ejection time (LVET). The LVET is estimated using a signal obtained
through a micro-electromechanical system (MEMS)-based accelerometric sensor.
The sensor acquires a seismocardiogram (SCG) signal at the chest surface, and
the LVET information is extracted. Both systolic blood pressure (SBP) and
diastolic blood pressure (DBP) are estimated by calibrating the system with the
original arterial blood pressure values of the subjects. The proposed method is
evaluated using different quantitative measures on the signals collected from
ten subjects under the supine position. The performance of the proposed method
is also compared with two earlier approaches, where PTT intervals are estimated
from electrocardiogram (ECG)-photoplethysmogram (PPG) and SCG-PPG,
respectively. The performance results clearly show that the proposed method is
comparable with the state-of-the-art methods. Also, the computed blood pressure
is compared with the original one, measured through a CNAP system. It gives the
mean errors of the estimated systolic BP and diastolic BP within the range of
-0.19 +/- 3.3 mmHg and -1.29 +/- 2.6 mmHg, respectively. The mean absolute
errors for systolic BP and diastolic BP are 3.2 mmHg and 2.6 mmHg,
respectively. The accuracy of BPs estimated from the proposed method satisfies
the requirements of the IEEE standard of 5 +/- 8 mmHg deviation, and thus, it
may be used for ubiquitous long term blood pressure monitoring.
