Indirect measurement of the carotid arterial pressure from vibrocardiographic signal: Calibration of the waveform and comparison with photoplethysmographic signal

The detection of arterial Blood Pressure waveform provides important information about the subject health status. Laser Doppler Vibrometry (LDV) is a non-contact technique with high sensitivity able to detect mechanical movements of the arterial wall; several previous studies have shown that LDV is able to characterize cardiac activity. Photoplethysmogram (PPG) quantifies the digital volume artery pulse, which has been demonstrated to be closely related to the pressure signal measured by an arterial tonometer. In this paper, an indirect measurement of carotid arterial pressure by means of LDV is presented. Moreover, a comparison between LDV and PPG is conducted in order to estimate the time interval between opening and closing of the aortic valve, that is the Left Ventricular Ejection Time (LVET). Results show an average reduction of around 20% of the systolic pressure derived from LDV signal measured over the carotid artery with respect to the systolic pressure measured at brachial level (i.e. peripheral pressure value). Finally, the comparison between LDV and PPG in the estimation of LVET shows a mean percentage deviation <10%. So, in conclusion, it can be stated that LDV technique has the potential of providing a displacement waveform that, adequately calibrated, can furnish significant information about pressure waveform.