Approximately 20% of patients in the intensive care unit (ICU) requiring mechanical ventilation (MV) experience difficulty and prolonged weaning. Early spontaneous breathing trials (SBT) and timely extubation are essential to avoid complications such as diaphragmatic dysfunction, ventilator-associated pneumonia, and airway trauma.

Mechanical ventilation is a vital supportive therapy in critical care. However, both delayed weaning and premature discontinuation are associated with poor outcomes and prolonged ICU stay. Prolonged MV may lead to complications including respiratory muscle dysfunction, ventilator-associated lung injury, and increased healthcare costs, emphasizing the importance of optimal timing of weaning.

Ultrasonography (US) has emerged as a rapid, non-invasive bedside tool for real-time assessment of respiratory muscle function. It allows evaluation of muscle thickness and contractility, aiding in the detection of diaphragmatic dysfunction.

In cases of diaphragmatic impairment, accessory respiratory muscles, particularly the parasternal intercostal muscles, play a compensatory role. Measurement of parasternal intercostal muscle thickness fraction (PICTF%) has been proposed as a predictor of weaning failure.

Additionally, composite indices such as the rapid shallow breathing index (RSBI) and compliance, rate, oxygenation, and pressure (CROP) index are widely used to assess weaning readiness. A recently proposed composite index combining PICTF (>9%) and diaphragmatic excursion (<15 mm) demonstrated high predictive value for failure of non-invasive ventilation.

Therefore, the present study aims to evaluate the effectiveness of this novel composite index in predicting weaning failure in mechanically ventilated patients.

Inclusion Criteria:

• Age ≥ 18 years old.
• Both sexes.
• Patients who have been mechanically ventilated for more than 48 h.

Exclusion Criteria:

• All the patients with difficulty in obtaining an appropriate ultrasound window (diaphragmatic paralysis/injury, ascites, thoracotomy, pneumothorax, pleural effusion, flail chest, and rib fractures).
• Neuromuscular diseases.
• Severe head injury.
• Pregnant and lactating women.

• All the patients with difficulty in obtaining an appropriate ultrasound window (diaphragmatic paralysis/injury, ascites, thoracotomy, pneumothorax, pleural effusion, flail chest, and rib fractures).
• Neuromuscular diseases.
• Severe head injury.
• Pregnant and lactating women.