Evaluation of the coherence between the control of the variability of the photoplethysmographic pulse amplitude and the heart rate variability Coherence in PPGAV and HRV

Heart rate variability (HRV) is an analysis tool through which is possible to analyze the autonomic nervous system (ANS) in its two sympathetic and parasympathetic pathways. Photoplethysmography (PPG) has been used to determine beat-to-beat blood volume changes in both arterial and surrounding tissues. In this work we used a characteristic of the pulsatile signal, mainly associated with the changes in the arterial diameters, the amplitude of the photoplethysmographic beat to beat pulse (PPGAV) and its corresponding association with the modification of the ANS activity. In this study participated a group of thirty volunteers (15M, 15F, 22.9 +/- 1.95 years). In order to stimulate the ANS we used the five minutes clinostatism to orthostatism maneuver by which we obtained the tachograms and the amplitudes of the PPG pulses. Later the frequency domain analysis was carried out by Statistica Software, determining the high and low frequency components for both maneuvers. To establish the linear relationship in the frequency domain, the spectral coherence function was used. The analysis of HRV and PPGAV in this group of volunteers revealed that there is a decrease in the PPG amplitude at the clinostatism / orthostatism postural change, suggesting an increase of the sympathetic activity towards the blood vessels, which causes vasoconstriction, thus reflecting a decrease in the value of the spectral coherence in response to the stimulus caused by the maneuver.