A Clinical Trial on Effectiveness and Safety of Hydrogen Generator to Treat Dyspnea for the Patients With Tracheal Stenosis: A Randomized, Double-blind and Single-center Clinical Study

Inclusion Criteria: 1. Aged from 18 to 65; 2. Diagnosed moderate/severe tracheal stenosis by chest CT and/or bronchoscopy; 3. Difficulty breathing symptoms 4. Agree to participate in this trial and sign the informed consent form. Exclusion Criteria: 1. Those who were suffered from respiratory failure or more severe caused by dyspnea; 2. Combined other serious systemic diseases (severe arrhythmia, acute myocardial ischemia, uncontrollable hypertension crisis, active gastric ulcer, uncontrolled diabetes, renal failure, blood system diseases or coagulation dysfunction); 3. Those who were suffered from severe mental illness or could not take care of themselves; 4. Pregnant or lactating women; 5. Those who could not understand the trial procedures and correctly the trial equipment; 6. Those who participated in other clinical trials in the first 3 months before the screening date. Quit criteria 1. The subjects requiring emergency intubation or other intervention or surgical treatment due to worsened tracheal stenosis; 2. Subjects who had severe adverse events during treatment; 3. Subjects who did not want to continue to participate in the trial; 4. The subjects who were necessarily terminated for the trial by the investigators.