Intermittent Hypoxic-hyperoxic Training in Patients With Cardiovascular Pathology After COVID-19 Infection.

Aim of this prospective, interventional, single-centered, randomized study is to evaluate the efficacy and safety of intermittent hypoxic-hyperoxic training as a rehabilitation method in patients with cardiovascular pathology in the early period after coronavirus infection. The study will include 60 patients with cardiovascular pathology who underwent confirmed by laboratory tests COVID-19 infection (polymerase chain reaction (PCR) testing, enzyme-linked immunosorbent assay (positive result at least 1 time)) 1-3 months ago with the degree of lung lesion CT3, CT4, who were admitted to the University Clinical Hospital No. 4 of I.M. Sechenov First Moscow State Medical University. Patients will be randomized via the random number table method into two groups, comparable by gender, age and comorbidity: Intermittent hypoxic-hyperoxic training (intervention group) group, 30 patients who will receive 15 IHHT sessions, 40-minutes long each (5 workouts per week) for 3 weeks. Patients in the IHHT group will inhale hypoxic gas mixtures (10-12% O2) followed by exposure to a hyperoxic gas mixture with 30-35% O2. A control group of 30 patients will undergo a simulated IHHT course with the same "exposure" time and number of sessions. Patients of this group will breathe normoxic gas mixture using the same equipment; ordinary humidified air is supplied through the mask during the entire session. Patients eligible for inclusion will undergo the following investigations: * Anamnesis and complaints collection; physical examination; * Assessment of the quality of life and psycho-emotional status using the Short Form-36 (SF36) and Hospital Anxiety and Depression Scale (HADS) questionnaires, as well as the six-minute walk test; * General and biochemical blood tests , urine analysis, , determination of markers of inflammation (ferritin, C-reactive protein, D-dimer, fibrinogen, interleukin-1, interleukin-6, interleukin-18 and tumor necrosis factor), the level of Endothelin-1 and nitric oxide (NO) in the blood; * Electrocardiography, a flow mediated dilatation procedure for endothelial function assessment,transthoracic echocardiography to identify the structural and functional features of the myocardium, spiroergometry to determine the patient's oxygen consumption. The statistical processing will be performed using the Python Software Foundation version 3.8 for Windows (Delaware, USA). Estimated result of the study is to confirm or refute the hypothesis of the study that a three-week course of IHHT in patients with cardiovascular pathology in the early stages after suffering a coronavirus infection can improve exercise tolerance, as well as the quality of life and psychoemotional status, and affect the dynamics of laboratory and instrumental parameters.