EARLY-VENT is a multicenter, open-label, three-period cluster-randomized crossover trial designed to evaluate whether early transition from controlled to assisted ventilation improves outcomes in critically ill patients. The study will enroll approximately 1,600 adult patients across 10 ICUs who are expected to require mechanical ventilation for at least 48 hours and meet specific stability criteria (e.g., hemodynamically stable, light sedation). Participating centers will alternate between an experimental strategy, where patients transition to an assisted mode (preferably Pressure Support Ventilation) within 6 hours of eligibility, and a control strategy based on standard care practices. The primary endpoint is the rate of successful extubation at day 28, aiming to demonstrate that transition from controlled to assisted ventilation can reduce ventilation duration and improve prognosis compared to delayed transition.

Inclusion Criteria:

• Age ≥ 18 years.
• Expected ICU stay and mechanical ventilation (MV) ≥ 48 hours.
• Currently receiving controlled ventilation mode
• No neuromuscular blocking agents in use, and sedation level RASS ≥ -3.
• P/F ≥ 150 mmHg.

Exclusion Criteria:

• Severe end-stage irreversible respiratory, cardiac, or neurologic disease that may lead to long-term/chronic ventilator dependence or inability to wean from MV (e.g., interstitial lung disease/pulmonary fibrosis, cardiomyopathy, valvular disease, severe traumatic brain injury, Guillain-Barré syndrome, amyotrophic lateral sclerosis, multiple sclerosis, high cervical spinal cord injury, or other restrictive diseases).
• Expected death or transfer out of the ICU within 48 hours.
• Hemodynamic instability judged by the treating clinician.
• Pregnancy.
• Currently participating in other clinical studies related to mechanical ventilation.
• Any other condition considered unsuitable for participation by the investigator.

Written informed consent not obtained.