Abstract: A system, device, and method to determine a dominant activity observed from body-worn sensors and accurately characterize the activity. Various embodiments may include using Periodicity Transform (PT) along with Partial Cycle Measurement (PCM) calculations to detect a dominant activity associated with a data interval from one or more data channels. For example, in a body-worn sensor (e.g., chest-worn, limb-worn, etc.), there may be contradictory signals that overlap in time, frequency, amplitudes, and/or the like, and this overlapping data may convey the specific dominant information in a mixed way. Various embodiments described herein seek to determine the dominant source of information from any channel by using fractional cycles and periodicity transforms.

Abstract: Generalized transfer functions are available to mathematically derive the more relevant central blood pressure waveform from a more easily measured radial blood pressure waveform. However, these transfer functions are population averages and therefore may not adapt well to variations in pulse pressure amplification (ratio of radial to central pulse pressure). An adaptive transfer function was developed. First, the transfer function is represented in terms of the wave travel time and wave reflection coefficient parameters of an arterial model. Then, the model parameters are estimated from only the radial blood pressure waveform by exploiting the frequent observation that central blood pressure waveforms exhibit exponential diastolic decays.

Abstract: A method is provided for determining pulse transit time of a subject as a function of blood pressure. The method includes: measuring a proximal waveform indicative of the arterial pulse at a proximal site of the subject; measuring a distal waveform indicative of the arterial pulse at a distal site of the subject; defining a relationship between the proximal waveform and the distal waveform in terms of unknown parameters of a nonlinear model; determining the unknown parameters of the nonlinear model from the measured proximal waveform and the measured distal waveform; and determining pulse transit time for the subject as a function of blood pressure from the parameters of the nonlinear model. The nonlinear model can account for arterial compliance and peripheral wave reflection, where the arterial compliance depends on blood pressure.

Abstract: Methods are presented for determining pulse transit time (PTT) and/or pulse wave velocity (PWV) of a subject by application of parametric system identification to proximal and distal arterial waveforms. The two waveforms are measured from the subject. A system is defined that relates the proximal arterial waveform to the distal arterial waveform (or vice versa) in terms of the unknown parameters of a parametric mathematical model. The model parameters are determined from the measured waveforms using system identification. PTT between the proximal and distal arterial sites is then determined from the system model. PWV may also be determined by dividing the distance between measurement sites (D) by PTT.

Abstract: A method is provided for determining pulse transit time of a subject as a function of blood pressure. The method includes: measuring a proximal waveform indicative of the arterial pulse at a proximal site of the subject; measuring a distal waveform indicative of the arterial pulse at a distal site of the subject; defining a relationship between the proximal waveform and the distal waveform in terms of unknown parameters of a nonlinear model; determining the unknown parameters of the nonlinear model from the measured proximal waveform and the measured distal waveform; and determining pulse transit time for the subject as a function of blood pressure from the parameters of the nonlinear model. The nonlinear model can account for arterial compliance and peripheral wave reflection, where the arterial compliance depends on blood pressure.

Abstract: Methods are presented for determining pulse transit time (PTT) and/or pulse wave velocity (PWV) of a subject by application of parametric system identification to proximal and distal arterial waveforms. The two waveforms are measured from the subject. A system is defined that relates the proximal arterial waveform to the distal arterial waveform (or vice versa) in terms of the unknown parameters of a parametric mathematical model. The model parameters are determined from the measured waveforms using system identification. PTT between the proximal and distal arterial sites is then determined from the system model. PWV may also be determined by dividing the distance between measurement sites (D) by PTT.