High-flow Nasal Cannula Oxygen Therapy Versus Conventional Oxygen Therapy in High-altitude Pulmonary Edema

Inclusion Criteria: 1. Aged 18 years or older; 2. Onset of symptoms related to HAPE (including dyspnea at rest, cough, or exercise intolerance) within 7 days of ascending to high altitude (≥2500m); 3. Diagnosis of HAPE according to the STAR data reporting guidelines, requiring at least two symptoms (dyspnea at rest, cough, weakness/decreased exercise performance, or chest tightness/congestion) and two clinical signs (rales or wheezing in at least one lung field, central cyanosis, tachypnea, or tachycardia); 4. Radiographic evidence of pulmonary edema on chest X-ray or CT; 5. Refusal or inability to undergo immediate descent at the time of presentation; 6. Capability and willingness to provide written informed consent. Exclusion criteria: 1. Known or clinically confirmed pregnancy; 2. Requirement for emergency intubation (as assessed by the treating clinician) due to cardiac/respiratory arrest, hemodynamic instability, airway compromise, severe hypoxia, or impaired consciousness, etc; 3. Pulmonary edema or hypoxemia resulting from other medical conditions (e.g., cardiogenic pulmonary edema, sepsis, chronic obstructive pulmonary disease (COPD), pneumothorax, massive pleural effusion, chest trauma, etc.); 4. Glasgow Coma Scale (GCS) score ≤ 12; 5. PaCO₂ \> 55 mmHg; 6. Presence of high-altitude cerebral edema; 7. Receipt of any respiratory support therapy (other than conventional oxygen therapy) prior to admission; 8. Presence of any contraindication to conventional or nasal oxygen therapy; 9. Presence of severe medical conditions or abnormal clinical laboratory findings that, in the investigator's judgment, may pose a risk to the patient's safety or interfere with the study's execution and participant completion; 10. Current participation in other clinical trials; 11. Refusal to sign the informed consent form.