inclusion criteria: written informed consent to participate in the study; age 40 and over; male and female; one or more cardiovascular pathologies in the anamnesis: a reliably confirmed diagnosis of hypertension, stage i-iii (the diagnosis was made in accordance with the national clinical guidelines - 2019); stable angina pectoris i-iii functional class, confirmed by complaints, anamnesis and physical examination and with the help of diagnostic tests (bicycle ergometry or daily electrocardiography monitoring); confirmed diagnosis of arrhythmias and conduction disorders based on electrocardiography data and 24-hour holter monitoring (premature depolarization, supraventricular tachycardia, atrial fibrillation, sick sinus syndrome, atrioventricular block i-ii, bundle branch blocks); chronic heart failure stage i-iib, i-iii functional class (new york heart association functional classification), confirmed by the presence of clinical signs and at least one of two criteria: myocardial dysfunction of left ventricle or / and an increase in the level of the n-terminal fragment of brain natriuretic peptide over 125 pg / ml; the presence of signs of systolic or diastolic dysfunction of the left ventricle according to echocardiography. covid-19 infection confirmed by laboratory tests (polymerase chain reaction testing, enzyme-linked immunosorbent assay (positive result at least 1 time) with a ct degree of 3 or higher. non-inclusion criteria: acute infectious diseases, tuberculosis; chronic somatic diseases in the acute stage; congenital anomalies of the heart and large vessels; valvular heart defects (congenital and acquired); severe atherosclerosis of the lower extremities'vessels (chronic ischemia of the lower extremities,stage 3-4); acute decompensated heart failure (ii-iv class according to killip classification); chronic heart failure iv functional class (new york heart association functional classification classification); secondary arterial hypertension; acute coronary syndrome within 4 weeks before the start of the study; life-threatening rhythm and conduction disturbances; bronchial asthma with the development of respiratory failure ii-iii degree; acute cerebrovascular accident within the last 4 months; chronic kidney disease (glomerular filtration rate<30 ml / min / 1.73 m2 via ckd-epi (chronic kidney disease epidemiology collaboration) formula); pregnancy; mental illness (severe dementia, schizophrenia, severe depression, manic-depressive psychosis); oncology, diagnosed within a year or receiving a course of radiation / chemotherapy for cancer at the present time; severe cognitive impairment (mos) and clinically significant anxiety and / or depression (hads) interfering with observation; individual intolerance to oxygen deficiency.

inclusion criteria: written informed consent to participate in the study; age 40 and over; male and female; one or more cardiovascular pathologies in the anamnesis: a reliably confirmed diagnosis of hypertension, stage i-iii (the diagnosis was made in accordance with the national clinical guidelines - 2019); stable angina pectoris i-iii functional class, confirmed by complaints, anamnesis and physical examination and with the help of diagnostic tests (bicycle ergometry or daily electrocardiography monitoring); confirmed diagnosis of arrhythmias and conduction disorders based on electrocardiography data and 24-hour holter monitoring (premature depolarization, supraventricular tachycardia, atrial fibrillation, sick sinus syndrome, atrioventricular block i-ii, bundle branch blocks); chronic heart failure stage i-iib, i-iii functional class (new york heart association functional classification), confirmed by the presence of clinical signs and at least one of two criteria: myocardial dysfunction of left ventricle or / and an increase in the level of the n-terminal fragment of brain natriuretic peptide over 125 pg / ml; the presence of signs of systolic or diastolic dysfunction of the left ventricle according to echocardiography. covid-19 infection confirmed by laboratory tests (polymerase chain reaction testing, enzyme-linked immunosorbent assay (positive result at least 1 time) with a ct degree of 3 or higher. non-inclusion criteria: acute infectious diseases, tuberculosis; chronic somatic diseases in the acute stage; congenital anomalies of the heart and large vessels; valvular heart defects (congenital and acquired); severe atherosclerosis of the lower extremities'vessels (chronic ischemia of the lower extremities,stage 3-4); acute decompensated heart failure (ii-iv class according to killip classification); chronic heart failure iv functional class (new york heart association functional classification classification); secondary arterial hypertension; acute coronary syndrome within 4 weeks before the start of the study; life-threatening rhythm and conduction disturbances; bronchial asthma with the development of respiratory failure ii-iii degree; acute cerebrovascular accident within the last 4 months; chronic kidney disease (glomerular filtration rate<30 ml / min / 1.73 m2 via ckd-epi (chronic kidney disease epidemiology collaboration) formula); pregnancy; mental illness (severe dementia, schizophrenia, severe depression, manic-depressive psychosis); oncology, diagnosed within a year or receiving a course of radiation / chemotherapy for cancer at the present time; severe cognitive impairment (mos) and clinically significant anxiety and / or depression (hads) interfering with observation; individual intolerance to oxygen deficiency.