Limb Cardiovasculature System Identification Using Adaptive Filtering

An approach is proposed to determine the transfer function of the human heart-to-finger upper-limb vascular segment. The instant of occurrence of the left ventricular blood pressure was estimated using simultaneous electrocardiography and photoplethysmography (PPG). A well-established, generic shape is assumed for the left-ventricular pressure. The weights of an adaptive finite impulse response filter were tuned using a least mean-square algorithm so that the output of the model fitted measured peripheral volume change pulses. Results show that the above iterative system identification scheme eventually converges to a set of filter coefficients representing the subject’s vascular segment. A potential application of this technique is to gain more insight into the mechanical properties of the arterial wall, namely compliance.