This prospective observational cohort study aims to compare the predictive accuracy of diaphragmatic rapid shallow breathing index (D-RSBI) versus traditional rapid shallow breathing index (RSBI) for predicting weaning success from invasive mechanical ventilation in COPD patients. Diaphragmatic ultrasound measurements will be performed during spontaneous breathing trials, and patients will be followed for 72 hours after extubation to assess weaning outcomes.

Inclusion Criteria:

• Mechanically ventilated COPD patients fulfilling standard weaning readiness criteria.
• Invasive mechanical ventilation for more than 24 hours before spontaneous breathing trial.
• Hemodynamically stable without significant vasopressor support.
• Adequate oxygenation with FiO2 ≤ 0.5 and PEEP ≤ 8 cmH2O .
• Preserved mental status and ability to initiate spontaneous breathing.
• Successful tolerance of spontaneous breathing trial conducted on CPAP mode with pressure support ≤ 8 cmH2O.

Exclusion Criteria:

• Refusal of consent
• Neuromuscular disease, phrenic nerve palsy, or diaphragmatic paralysis.
• Large pneumothorax or pathology interfering with ultrasound assessment.
• Terminal extubation.
• Recent major thoracic surgery.
• Poor sonographic window despite repeated attempts.

Mechanically ventilated adult COPD patients admitted to the intensive care units of Sohag University Hospitals and fulfilling standard weaning readiness criteria.