Investigators aim to study the effectiveness and safety of inhaling hydrogen-oxygen which produced by a hydrogen generator with nebulizer to decreases inspiratory effort for the patients with tracheal stenosis.

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.