Abstract: ABSTRACT The amplitude parameters of blood pressure (BP) and heart rate (HR) oscillations in the low-frequency (LF, frequency of baroreflex waves, ~ 0.1 Hz) and high-frequency (HF, corresponding to the respiratory frequency, 0.2-0.25 Hz) ranges are widely used to assess the state of the cardiovascular system of astronauts and patients suffering from orthostatic instability. To increase the information content of the traditional approach we analyzed time (phase) relationships between blood pressure and heart rate oscillations. A passive tilt test was performed (transition from a lying position to an orthostatic position, 65 degrees), during which the person maintained a constant and comfortable breathing rate. Software has been developed to set the breathing rhythm, record and analyze experimental data. Narrow-band components extracted by digital filtering from the obtained time series of BP and HR were presented in the form of an analytic signal, that allowed us to determine their phases and then calculate phase difference and phase synchronization in different frequency ranges. It was shown that in healthy people the degree of synchronization of LF oscillations in blood pressure and heart rate increases during orthostasis, while at the same time there is a sharp decrease in the time lag (phase difference) of HF oscillations of blood pressure and heart rate. After a 1-2 week stay in “dry” immersion (the period of the most pronounced dysregulation of the cardiovascular system), the effects described above disappear, which indicates an impairment of the nervous regulation of heart rate. Thus, complex analysis of the time relationships of blood pressure and heart rate oscillations in the LF and HF ranges can be used to assess the nervous regulation of the heart during simulated gravitational unloading. This approach might be used in the development of countermeasures to prevent orthostatic intolerance. FUNDING The work is performed with financial support of the Russian Science Foundation, grant # 23-25-00293

Cite: Vinogradova O.L. , Borovik A.S. , Zhedyaev R.Y. , Tarasova O.S.
Synchronization Of Blood Pressure And Heart Rate Oscillations In Different Frequency Ranges As A Measure Of Disturbances In The Regulation Of Systemic Hemodynamics During Tilt Test
43rd Annual the International Society of Gravitational Physiology Meeting 26-31 May 2024