Patients with acute respiratory failure (ARF) who were receiving mechanical ventilator support, had significant pleural effusion (both transudates and exudates) and drainage plan were evaluated. Decision to drain, timing and duration of drainage were made by primary physician according to the intensive care unit (ICU) protocols.The estimated amount of effusion (mL) was calculated as the maximum pleura-lung distance (mm) x 20 and significant effusion is accepted as ≥ 800 mL according to thoracic ultrasonography (USG) performed by the intensivist. The amount of effusion drained, mechanical ventilator parameters, arterial blood gas results and hemodynamic data were recorded before, at the 1st hour and at the end of drainage up to 30 days after drainage.

Inclusion Criteria:

• Patients on mechanical ventilation due to acute respiratory failure
• Estimated effusion > 800 ml according to USG
• Have drainage plan according to ICU protocols decided by primary physician

Exclusion Criteria:

• Have absolute drainage indication (empyema, hemothorax or chylothorax)
• predicted duration of mechanical ventilation less than 72 hours
• contraindications to drainage,
• underlying disease, which prevents lung expansion (chest deformity, central atelectasis)
• malignant effusions

Critical care patients on mechanical ventilation due to acute respiratory failure and have significant pleural effusion who had drainage plan according to İCU protocols decided by primary physician were enrolled for the study