Non-Contact Assessment of Blood Pressure Pulse Wave by Means of Vibrocardiography

Central Blood Pressure (BP) has a well-known predictive value for many cardiovascular pathologies. The carotid artery pressure pulse is related to BP and can be measured without contact by Vibrocardiography (VCG), the vibrational signal associated to the heartbeat acquired by means of a Laser Doppler Vibrometer (LDV). In this paper, we aim to present an accurate measurement method, which allows us to obtain the relationship between the VCG signal and BP without contact. The VCG signal requires calibration, in order to get pressure absolute values. To this aim, an exponential calibration scheme has been applied. Diastolic and systolic blood pressure values have been assessed by means of a standard oscillometric method, while mean arterial pressure has been derived with an empirical formula. The VCG test bench has been optimized by the use of an infra-red thermal camera, which makes the identification of the best measurement point possible. Results confirm the effectiveness of thermal imaging with respect to accuracy of the measurement point for the LDV on the skin overlying the carotid artery. The proposed method allows us to estimate BP and other important cardiovascular features (i.e. heart rate, heart rate variability, QT-interval, etc.) in a subject without contact.