This study aims to evaluate whether High-flow Nasal Cannula Oxygen Therapy (HFNC) provides superior respiratory support compared to Conventional Oxygen Therapy (COT) in patients with High-Altitude Pulmonary Edema (HAPE).

Conventional Oxygen Therapy (COT) is the established first-line treatment for High-Altitude Pulmonary Edema (HAPE). Despite the proven efficacy of High-flow Nasal Cannula (HFNC) in treating other forms of acute respiratory failure and pulmonary edema, its clinical role in the context of HAPE remains poorly defined. To address this gap, the investigators conducted a study comparing the efficacy of HFNC versus COT in providing respiratory support and accelerating clinical recovery for patients with HAPE.

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.