**3. Analytical methods**

Systolic and diastolic AP (АPs and АPd, respectively) were measured with Korotkov auscultation method by mercury tonometer ("Riester", Germany). Mean arterial pressure (APm) was calculated with Hickam formula; blood struck volume (BSV) with Kubichek formula [55] by the signals of differentiated impedance rheogram by all the realizations (beat-to-beat) during 5 minutes.

With the help of a rheographer and pneumograph, only cardiointervalograms and pnevmograms were recorded. Cardiointervalograms were recorded using Caspico [56] in MS DOS mode. For this, a cardiac sensor T31 (Polar Electro OU, Finland) was applied to the thoracic cell, which formed 8 ms pulses at the top of the QRS complex. These impulses were telemetrically perceived by the pulse meter A1 and, together with the pnevmogram signal, were transmitted to a 5 kV galvanic switch comparator, which closed the contacts on the LPT port of the computer. The program scanned the device with a frequency of 1000 times per second. The power of R-R and BSV oscillations spectrum was calculated in standard frequency ranges of very low frequencies of 0–0.04 Hz (VLF), low frequencies of 0.04–0.15 Hz (LF), high frequencies of 0.15–0.4 Hz (HF), general oscillation power of 0–0.4 Hz (TP), and normalized power in the range of 0.15–0.4 Hz (HFnorm). Besides, spectral and cross-spectral density and the frequency of the highest amplitude oscillation peak of t-R-R and BSV in the LF range were estimated in the prone position at rest for 5 minute records, at tilt test from the 2nd till the 5th minute and in psycho-emotional test from the 3rd till 7th minute [10].

The method of impedance reopeltysmography was used to calculate cardiac output [57], associated with it indicators of relative blood flow to the body of the chest.

Signals of differentiated ECG and rheograms were fixed with the aid of a biopower RA-5-01 (Kyiv Research Institute of Radio-measuring Equipment). The spring electrodes of rheograms were standardized [10]. The frequency of the reagent's probe signal was 70 kHz.

The pnevmogram signal was obtained from a piezoelectric sensor placed directly in front of the subject (nostrils of the nose).

All these signals were "digitized" through an analog-to-digital converter ADC-1280 (Holit Data Systems, Kiev) with a sampling rate of 860 times per second. The digital signals were stored on the hard disk of the computer for further processing. To analyze signals, identify critical points on them, and export them to spreadsheets, Bioscan [10] was used.
