State of Oxygen Metabolism, Cardiovascular and Respiratory System Reserve Capacity in Patients Who Underwent COVID-19

This clinical study will create an evidence base for rehabilitation approach, which will be used for restoration of pulmonary ventilation and gas exchange, increase of tolerance to physical load reduced in patients who underwent COVID-19.

The aim of the present clinical study is to evaluate the effectiveness of medical rehabilitation of COVID-19 patients based on the study of individual physiological parameters of oxygen metabolism and reserve capabilities of the cardiovascular and respiratory systems.

After an interview about the possibility of taking part in the study, the patient is presented with an informed consent form, explaining all the questions of interest. In the case of consent to participate in the study, the patient and the researcher fill out all the necessary fields of the two copies of the informed consent and sign it. If necessary, the researcher re-explains any information about the study. One copy of the informed consent remains with the patient, and the second copy is kept by the investigator, as required by Good Clinical Practice.

Once informed consent is obtained, an Individual Registration Card (IRC) is completed for the patient enrolled in the study. Completion of the IRC also continues until completion of the second phase of rehabilitation.

Pulmonary functional tests, cardiopulmonary stress testing (CPT) are performed on day 1 or 2 of inclusion of the patient in the rehabilitation program of "Federal Research Center for Fundamental and Translational Medicine" (FRC FTM) using MasterScreen Pneumo (Jaeger, Germany) and Oxycon Pro ergospirometry systems (Jaeger, Germany), in accordance with international standards. The indexes of external respiration are brought to BTPS conditions, and gas exchange - STPD. The protocol of stress testing is chosen individually, based on the proper values in accordance with the age, sex and anthropometric data of the patient. The study is conducted up to the individual maximum, followed by a recovery period. The anaerobic threshold is determined using the V-slope method. After peak load is reached, it is gradually reduced. Observation is continued until complete recovery of hemodynamic parameters, gas exchange, in case of adverse symptoms - until their disappearance. Repeated testing is performed after the rehabilitation program, before discharge from the FTC MTF.

Thoracic MSCT is performed on day 1-2 of inclusion of a patient into the rehabilitation program of the FRC FTM to assess the lesion of the bronchopulmonary system after COVID-19.

Questionnaires describing the severity of the underlying disease (mMRC respiratory impairment scale, BODE pulmonology risk scale, SMRT-CO respiratory support need scale), and SF-36 quality of life questionnaire are completed at study inclusion and after the rehabilitation program, before discharge from the FRC FTM.

Eligibility Criteria:
Inclusion Criteria:

* pneumonia or acute respiratory distress syndrome caused by SARS-CoV-2
* referral for a second phase of rehabilitation
* signed informed consent of the patient to participate in the study

Exclusion Criteria:

* mental and/or locomotor disorders that make it impossible to adequately perform an exercise test, cooperate with the patient, and interpret the results
* conditions and diseases requiring emergency surgical intervention and/or observation and treatment in the ICU
* patient's refusal to participate in this clinical trial at any stage of the study.