This is a prospective, multicenter, randomized, controlled, superiority clinical trial, with the test group expected to be superior to the control group in the primary evaluation endpoints (changes in Borg score and PSQI index at 3 months after the start of the treatment). The test group will use the investigational device Hydrogen-Oxygen Generator with Nebulizer (manufactured by Shanghai Asclepius Meditec Co., Ltd.) + basic treatment (supportive treatment determined by the investigator based on the condition of the patients), and the control group will use basic treatment only, to evaluate of effectiveness and safety of the investigational device Hydrogen-Oxygen Generator with Nebulizer for rehabilitation treatment of dysfunctions in discharged patients who are previously hospitalized due to 2019 novel coronavirus pneumonia (COVID-19).

A total of 216 eligible subjects will be randomly assigned to the test group and the control group in a 1:1 ratio to receive corresponding treatment (treatment in both groups will last for 12 months), and the subjects will then be followed up for 12 months from the start of treatment after enrollment.

All subjects enrolled in this study will receive seven visits, including the screening visit (within 14 days before the enrollment), randomization and treatment visit (Day 0), visits at 1 month after the start of the treatment (± 7 days), 2 months after the start of the treatment (± 7 days), 3 months (± 14 days) after the start of the treatment, 6 months (± 14 days) after the start of the treatment, and 12 months (± 30 days) after the start of the treatment.

The following indicators of the two groups will be collected and analyzed in this study: the primary effectiveness evaluation indicator: changes in Borg score and PSQI index at 3 months after the start of the treatment; secondary effectiveness evaluation indicators: 1) Pulmonary function assessment indicators (forced expiratory volume in one second [FEV1], ratio of forced expiratory volume in one second to forced vital capacity [FEV1/FVC], 25/50/75% maximal mid expiratory flow [MMEF 25/50/75], and fractional exhaled nitric oxide [FeNO]); 2) Lung imaging changes; 3) Neurological and psychological function assessment indicators (Mini-Mental State Examination Scale [MMSE] score, Generalized Anxiety Disorder Scale [GAD-7] score, Depression Screening Scale [PHQ-9] score, Post-Traumatic Stress Disorder Checklist [PCL-C]); 4) Inflammatory indicators (neutrophil-to-lymphocyte ratio [NLR], C-reactive protein [CRP], interleukin-6 [IL-6]); 5) Evaluation of device usability, and the safety evaluation indicators: incidence of AEs and SAEs, and incidence of device deficiencies.

When all enrolled subjects have completed the follow up at 3 months after the start of the treatment, an analysis will be performed for application to the National Medical Products Administration (NMPA) for registration of the investigational medical device, while the 6- and 12-month follow up will be continued spontaneously.

Inclusion Criteria:

• Male and female subjects aged between 18 and 75 years old (inclusive);
• Subjects previously hospitalized due to COVID-19, who are recovered and discharged with negative results for COVID-19 and released from quarantine;
• Known symptoms of respiratory dysfunctions (such as dyspnea), and / or neurological/psychological dysfunction (such as sleep disorders, anxiety, and depression) and / or somatic dysfunction (such as fatigue);
• Borg dyspnea or fatigue score before study treatment ≥ 1 (please refer to Appendix 2: Borg Scale for specific information), and PSQI score ≥ 2 (please refer to Appendix 3: PSQI Scale for specific information);
• Subjects who are willing to participate and provided written informed consent form.

Exclusion Criteria:

• Subjects with known malignant tumor;
• Subjects with known moderate or severe pulmonary infection;
• Subjects with mucosa injury in upper respiratory tract, for whom no inhalation treatment can be provided;
• Subjects who are intolerable to inhalation treatment;
• Subjects with moderate or severe disabilities;
• Subjects with mental disorders or cognitive impairment who are unable to provide consent;
• Subjects with neurological disease accompanied with sleep disorders for which medical intervention is provided before the diagnosis of COVID-19.
• Subjects with any immunodeficiency (for example, subjects requiring chronic treatment with any corticosteroid or other immunosuppressants) judged by the investigator;
• Allergy to any component of the investigational product that have contact with human body;
• Complicate severe cardiac, hepatic or renal insufficiency;
• Expected life expectancy < 1 year;
• Subjects who are participating in any other clinical study of any investigational drug or medical device;
• Pregnant or lactating women, or women who plan to become pregnant within the following one year;
• Any other condition judged as inappropriate to participate in this study by the investigator.