This randomized controlled trial investigates the effects of prone positioning versus lateral positioning at different angles (30°, 90°, 120°) on pulmonary function improvement in patients with acute respiratory distress syndrome (ARDS). Utilizing electrical impedance tomography (EIT) technology, the study monitors key parameters including ventilation distribution and ventilation-perfusion matching in real time, while integrating respiratory mechanics and blood gas analysis data to comprehensively evaluate the therapeutic efficacy of positional adjustments. The study hypothesizes that high-angle lateral positioning may reduce adverse complications associated with prone positioning while effectively improving oxygenation and pulmonary function. The ultimate objective is to provide a safer and more personalized positional therapy regimen for clinical practice, optimizing ARDS treatment strategies to reduce mortality and enhance patient survival outcomes.

Inclusion Criteria:

1. Age >= 18 years.
2. Diagnosis of ARDS according to the Berlin Definition (2023 update).
3. Clinically evaluated as suitable for positional therapy by physicians.
4. Signed informed consent obtained from the patient or legal representative.
5. Absence of severe spinal deformities or musculoskeletal disorders that may compromise safe high lateral positioning.
6. No severe skin conditions (e.g., extensive open wounds or pressure ulcers) that may affect the feasibility of lateral positioning.

Exclusion Criteria:

1. Pregnant or lactating women.
2. Severe cardiac diseases (e.g., unstable arrhythmia or heart failure) that may worsen with positional changes.
3. Severe coagulation disorders with increased bleeding risk.
4. Known allergy to the EIT device or any of its components.
5. Severe psychiatric disorders impairing study compliance.
6. Current participation in experimental therapies that may affect pulmonary function.
7. Severe active infections requiring special isolation measures.
8. Anticipated need for emergency surgery or life-threatening complications within 24 hours.