**Table 1.**

*Indicators of temporal analysis of AOG of healthy, patients with COVID-19 and persons undergoing treatment in a closed department of a psychoneurological hospital and their ratio.*

*Aplication Arterial Oscilography to Study the Adaptive Capacity of Subject with COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.98570*

of the central control circuit, accompanied by increased sympathetic activity and manifested by stabilization of the rhythm, reducing the scatter of the duration of cardio intervals, increasing the number of similar intervals [8, 9, 14, 25, 26, 34]. This is confirmed by the results of our research. A significant decrease in SDSD, pHN50 (**Figures 2**-**1a**), Mo (P < 0.001) (**Figures 2**-**2a**) and an increase in AMo (P < 0, 01), IVR, IN and HVR-index, standard deviation of oscillation amplitudes (P < 0.001) was registered on AOG in patients of group CG 1-c immediately after exercise. After 2 minutes of rest in most of the examined these indicators returned (or approached) to the initial ones (**Figure 2**-**b**).

For example, we demonstrate the dynamics of pNN50 and Mo registered in 30 members of group CG 1-c before, after exercise and in 2 minutes of rest (**Figure 2**).

As can be seen from **Figure 2**, after the Ruffier test, an increase in pNN50 (1) and Mo (2) and a return (approach) to the initial data after 2 minutes of rest is recorded. The observed dynamics of the studied indicators (by analogy with HRV on the ECG) indicates an increase in the tone of the sympathetic link of the ANS and increase the level of centralization of circulatory system management [8, 9, 14, 24–26, 34]. Return to the initial level of the studied indicators after 2 minutes of rest indicates a high level of regenerative capacity of the body after stress [27].

In patients with COVID-19, despite the extremely stressful situation, no similar dynamics of the studied parameters was observed. They were even lower than in healthy people at rest [9, 14, 24, 27, 34].

Patients of CG-2 (patients of psychoneurological hospital). As can be seen from **Table 1**, the results obtained of the temporal analysis of AOG in patients of the closed department in most cases had indicators similar to COVID-19, the difference between them was insignificant, had no reliability. This may indicate the same direction of pathological processes in patients with severe COVID-19 and in patients with mental disorders who are taking neuroleptics and are in a closed stay.

Spectral analysis of AOG indicators of the main and control groups.

The results of spectral analysis of AOG of healthy, patients with COVID-19 and PPNH are presented in **Table 2**.

**Figure 2.**

*Dynamics of pNN50 (1) and Mo (2): a) before and after the Ruffier test; b) before the Ruffier test and after 2 minutes of rest. Note. On the X axis – A representative sample of 30 patients; along the Y axis: in figure 2.1– pNN50 (%); figure 2.2. – Mo (s) in each of the patient. The dash line is before the exercise, the solid line is after it.*


**Table 2.** *Indicators of spectral analysis of AOG of healthy, patients with COVID-19, patients of psychoneurological hospital (PPNH) and their ratios.*

#### *Aplication Arterial Oscilography to Study the Adaptive Capacity of Subject with COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.98570*

Patients with COVID-19 (main group). As can be seen from **Table 2**, there is a specific adaptive pattern in patients with COVID-19. A slight increase in the percentage of high-frequency domain power (% HF) in the total frequency spectrum (compared to healthy ones) is noteworthy. This (as well as the results of temporal analysis) indicates a shift in the autonomic balance in the direction of increasing the activity of the parasympathetic division of the ANS. While the degree of its inhibition (not the growth) is an indicator of increase of the tone of the sympathetic link of the ANS, necessary to maintain homeostasis [8, 9].

This was confirmed by the fact that the percentage of power of the LF spectrum was 10% lower than in healthy people. The LF spectrum is an indicator of the activity of the vasomotor center, reflects the sympathetic and parasympathetic effects from the level above the peripheral and to the centers of autonomic innervation in the medulla oblongata [9, 14, 24–26, 34]. They are regulated by the subcortical nodes and the cerebral cortex [8, 9].

% VLF was lower than in healthy. It reflects the influence of higher autonomic centers on the cardiovascular subcortical center. It can be used as a marker of the degree of connection of autonomous (segmental) levels of blood circulation regulation with suprasegmental, including pituitary–hypothalamic (with its nervous and humoral regulation) and cortical level [9, 24, 34].

It should be noted that according to the literature (according to HRV on the ECG) normally the power of % VLF in the total frequency range is 15–30% [9], that also corresponds to the indicators of our studies. The lack of dynamics of %VLF in patients with severe COVID-19 compared to healthy may indicate a violation of the above connections and functions of the corresponding levels of regulation.

At the same time, the %ULF in the total frequency spectrum is higher than in healthy (26%). The latter integrates and adapts the restructuring of the functional state of the body under the influence of external factors [9, 14, 24–26, 34]. The absence of a significant difference in %HF, %LF, %VLF in patients with COVID-19 and healthy may be due to the inability of the central control loop to integrate and adapt the restructuring of functional activity in severe disease. This can be attributed to the lack of necessary connections and coordination between the levels of regulation of the circulatory system in patients with COVID-19.

Since in this vertical the %VLF is already lower than in healthy ones (−3%), it is possible at this level the connection and coordination between the cortex and the lower levels of regulation of the circulatory system are suppressed.

It should be noted that recently there has been an assumption that patients with SARS-CoV-2 the cause of respiratory failure may be not only "damage to the lungs, but the brain stem, where the command center is located, which provides breathing even in unconsciousness" [36]. Probably, the information noted by us is a direction of markers search of the difficult pathological processes arising at COVID-19. Research is ongoing.

Healthy CG 1-c (Ruffier test). Spectral analysis of oscillograms (**Table 2**) showed that fast (HF) waves (indicator of the state of the parasympathetic link of the ANS) also dominated at rest in the general frequency spectrum.

Exercise helped to increase the percentage of spectrum power of low (%LF – P < 0.01) and ultra-low (%VLF – P < 0.01) frequencies, power of the Theta rhythm spectrum (P < 0.01) and reduce the level of high (%HF, P < 0.01) frequencies in the total frequency spectrum (**Figure 3**) At the same time, the synchronicity of changes in the %VLF and Theta spectra is noteworthy. This indicates an increase in the activity of the sympathetic division of the ANS after exercise, an increase in the centralization of the impact on the activity of the CVS and high stress resistance of the body in the examined patients [8, 9, 14, 24–26, 34]. After rest (**Figure 3**), the studied indicators returned (or approached) to the initial, which confirm the high

#### **Figure 3.**

*Dynamics of VLF (left column) and Theta spectrum (right column) before, after the Ruffier test and after 2 minutes of rest. Note. On the X axis – A representative sample of 30 people, on the Y axis – The power of the spectrum (ms2 ); top line – Before and after exercise. Bottom line – Before exercise and after 2 minutes of rest. Before exercise – A dash line, after exercise – A solid line.*

adaptability of the body of the patients [8, 9, 14, 24–26, 34]. Its slowing down is about the decrease of functional reserves and low stress resistance of the organism, which is a vegetative marker of anxiety [9, 10, 19, 24, 34].

It was noteworthy that (despite the difficult stressful situation due to the severe course of the disease) in patients with COVID-19 the marked direction of the adaptive response of the healthy body was not observed. This confirms the violation of function, coordination and communication in the hierarchical regulation of the circulatory system, which leads to a decrease in functional reserves and low stress resistance of the body.

Patients of CG-2 (PPNH). Frequent analysis of AOG of PPNH (**Table 2**) revealed a slight decrease in the percentage of weight of the spectrum of high (HF), low (LF) and a significant increase in the percentage of VLF (49%) and ULF (41%) frequencies compared to healthy. The last two reflect the activity of the central control circuit by the functional capacity of the cardiovascular system [12, 13, 28–30]. Their activities are closely related to psycho-emotional tensions [9]. It should be noted that in the norm, the power of the central control circuits occurs as a result of the reaction to a stressful situations and disappears in their absence [12, 13, 28–30], confirmed by the results of our (Ruffier test) studies. It is possible to predict that long tension of activity of the central contour of regulation integrating and adapting reorganization of functional activity of the body, can cause mental disorders of the presented group of patients.

When comparing the spectral analysis of patients with COVID-19 and PPNH, the long-term tension of %ULF in the total frequency spectrum was common, which can be associated with the presence of mental disorders.

#### **3.1 Correlation analysis of AOG of the examined patients in main and control groups**

Patients with COVID-19 (main group). Analysis of correlations in COVID-19 showed a limitation in their number. If in healthy people (group CG 1-c) 28 pairs

#### *Aplication Arterial Oscilography to Study the Adaptive Capacity of Subject with COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.98570*

of correlates were registered, in patients with COVID-19 – only 10. There were no temporal analysis indicators in the correlation pairs. Waves LF, VLF, HF occurred, respectively, in 15, 15, 5 percent of cases. Among the indicators of brain activity in pairs of correlates Theta rhythm was most common, Alpha, Beta, Gamma (20%, 15%, 10%, 5% – respectively) – less common. The highest aspect that connects the waves of brain activity with human health is the ability to change these states according to the requirements of the situation [24, 34, 39, 40]. In patients with COVID-19, only maximal compression provoked a slight inclusion in the correlations of brain activity, indicating a profound violation of the ability to adapt to external factors.

Healthy, CG 1-c (Ruffier test). Before exersice, correlations were recorded in 28 pairs of correlates, mainly between the temporal parameters of the oscillogram: Mo, AMo, NN50, IVR. In addition, between the waves of high (HF) and the slowest (VLF) frequency of spectral analysis and with temporal parameters in different numerical and percentage values and periods of compression.

Immediately after the Ruffier test, 19 pairs of correlates were recorded. The correlations of rest mostly disappeared. Participation in HF correlates also decreased from 16 to 8 cases. New ones appeared – most often between the absolute and percentage content of Theta, Alpha, Beta, Delta brain rhythms. They occurred (respectively) in 16%, 13%, 8%, 8% of cases and were registered during the entire shoulder compression. Gamma waves were not met.

The obtained results indicate an increase in the rhythms of brain and cardiac activity in healthy people after exercise of coordinated wave activity. Two minutes after the squats, the restoration of the vast majority of correlations inherent in the indicators before exercise was registered in the examined patients.

If we compare the results of the correlation analysis of AOG of healthy people after physiological stress (exercise) and patients with COVID-19, the main differences are that the number of correlates in healthy people is greater, they include indicators of temporal, spectral analysis and brain activity. The reaction in healthy people was manifested from the beginning to the end of compression, in patients – only in its last phases, with maximum compression of the shoulder.

Patients of CG-2 (PPNH). Surveys showed that among the 4 departments of the psycho-neurological hospital on AOG, the fewest correlations were registered in patients treated in a closed department. Actually, they were subject to study. The most common components of 12 correlation pairs were: Beta (20%), Gamma (14%), Delta (11%) rhythms of brain activity. In correlation pairs, Beta and Gamma, VLF and LF were combined. Ultra-low frequencies (VLF) occurred in 20%, %LF and %HF – once. The correlations is noticeable only in the last phases of shoulder compression.

If we compare the correlation portraits of patients with COVID-19 and the closed department, the Theta waves predominate in the first and Beta and the appearance of Gamma waves – in the second. The limited number of correlations between the rhythms of brain and heart activity in both groups was noteworthy. At the same time, they appeared only in the last phases of shoulder compression, which indicates a deep violation of the adaptive capacity to the influence of external factors. According to the results of research, we can predict the common pathogenetic mechanisms of mental disorders in patients with COVID-19 and PPNH [5–7].
