Comparative analysis of heart- and pulse-rate variability during mental task execution: the role of pulse transit time variability

Heart rate variability (HRV) analysis is an established method which provides valuable information on the autonomic nervous system’s (ANS) regulation of the cardiac rhythm. HRV is a time- and frequency-domain analysis which is based on the inter-beat interval series of normal sinus rhythm beats. Short-term HRV is computed over time frames of 5 minutes or less. It is widely used in biofeedback applications, in workload assessment and stress management. In recent years different approaches have been proposed, in which the arterial blood pulse generated by cardiac contraction is used instead of the heart beat itself for generating the pulse-series. Although this approach simplifies signal acquisition as it only requires a photo-plethysmographic sensor (PPG) clipped to the earlobe or to a fingertip, the time occurring between heart contraction and propagation of the arterial blood pulse to the peripheral site may determine non-negligible differences between electrocardiogram-derived HRV and PPG-derived HRV indices. Aim of this study is to present a comparative analysis of short-term indices of electrocardiogram-derived HRV and PPG-derived HRV, in an experimental setup reproducing the scenario of a sedentary working activity.