The goal of this observational study is to learn about the function of lung and diaphragm ultrasound during weaning from mechanical ventilation in COVID-19 patients. The aim of this study was that the lung ultrasound score and diaphragm muscle mobility could be a potential predictive factor of weaning success.

Inclusion Criteria:

• age > 18 years,
• critically ill patients with COVID-19 (defined as those requiring mechanical ventilation due to respiratory failure), and eligible for their first SBT according to the attending physician's judgement that the underlying disease which led to intubation had sufficiently resolved.

Exclusion Criteria:

• patients with previous cardiothoracic surgery or pleurodesis and patients who presented with stridor (due to upper airway involvement) as a cause of extubation failure
• neuromuscular disease

admission to a COVID-19 ICU with hypoxemic respiratory failure； start of weaning from mechanical ventilation