Hydrogen-oxygen Gas Mixture Inhalation in Patients With Convalescent Coronavirus Disease 2019 (COVID-19)

Subjects in the experimental arm and the control arm will receive hydrogen-oxygen mixed gas inhalation (Hydrogen-Oxygen Generator with Nebulizer, AMS-H-03, output: 3 L/min (hydrogen concentration: 66.7%, oxygen concentration: 33.3%)) and oxygen inhalation (OLO-1 Medical Molecular Sieve Oxygen Generator, output: 3 L/min (oxygen concentration: 33.3%), Shanghai Ouliang Medical Devices Co., Ltd.), respectively; the treatment duration will not be less than 8 hours per day, for 12 weeks. Subjects in the experimental arm and the control arm will also receive other medications (excluding antiviral drugs) by the investigator as clinically indicated. Six visits are required for each subject in this study, including Visit 1 (D-7\~-1), Visit 2 (D1), Visit 3 (D14±3d), Visit 4 (D28±3d), Visit 5 (D56±7d), Visit 6 (D84±7d).