This paper describes in detail a new method proposed by authors for quantitative estimation of the strength of synchronization between the low-frequency oscillations (with the main frequency of about 0.1 Hz) in the heart rate variability (HRV) and photoplethysmogram (PPG). Calculation of index value is followed by statistical significance control. The proposed method is applied for the analysis of 1056 pairs of HRV and PPG signals obtained from patients having different clinical status. Methodological recommendations are developed for method application in clinical studies.
Anton R. Kiselev, Anatoly S. Karavaev, Vladimir I. Gridnev, Mikhail D. Prokhorov, Vladimir I. Ponomarenko, Ekaterina I. Borovkova, Vladimir A. Shvartz, Yurii M. Ishbulatov, Olga M. Posnenkova, Boris P. Bezruchko Method of estimation of synchronization strength between low-frequency oscillations in heart rate variability and photoplethysmographic waveform variability // Russian Open Medical Journal, Vol. 5, Issue 1, 2016, pp. 0-0

The research work provides current understanding of the functional organization of vegetative regulation of cardiovascular system. The basic oscillatory processes in vegetative regulation system have been determined, and the information about their functional properties has been generalized. The most significant oscillatory processes are main heart rhythm, respiration and low-frequency oscillations in vegetative regulation of cardiovascular system. The article considers intersystem interactions involving the vegetative regulation of cardiovascular system
Kiselev A.R., Gridnev V.I. Oscillatory processes in vegetative regulation of cardiovascular system (Review) // Saratov Journal of Medical Scientific Research, Vol. 7, Issue 1, 2011, pp. 34-39