Drainage Of Pleural Effusions in the Intensive Care Unit (DOPE-ICU) - Feasibility Trial

Inclusion Criteria: * Acute admission to the ICU. * Age ≥ 18 years. * Pleural effusion ≥ 2 cm in either pleural cavity assessed by ultrasonography, computed tomography or magnetic resonance imaging (measured between the parietal and visceral pleura perpendicularly to the chest wall at the largest-separation point). * Respiratory failure defined as one or more of the following: any oxygen supplementation in an open system, invasive or non-invasive mechanical ventilation (including non-intermittent mask CPAP), or most recent arterial blood gas analysis with arterial partial pressure of carbon dioxide (PaCO2) \> 6.0 kPa and pH \< 7.35. Exclusion Criteria: * Mediastinal drain or pleural drain in situ on either side. * Suspected or confirmed haemothorax (e.g., due to recent thoracic trauma or intrathoracic surgery). * Suspected or confirmed pneumothorax (e.g., by anamnesis, on radiographic or ultrasonographic assessment, or by clinical presentation, e.g., due to presence of subcutaneous emphysema). * Suspected or confirmed pleural empyema (e.g., by anamnesis or clinical presentation, or on CT, MRI or ultrasonographic assessment). * Pleural malignancy (suspected or confirmed pleural lymphoma, pleural metastases or direct pleural invasion, or malignant mesothelioma). * Antithrombotic treatment or coagulation deficiency incompatible with conducting pleural drainage as by local recommendations, and contraindications to reversal of this (clinical assessment). * Clinically assessed absolute indication for therapeutic pleural drainage and: * invasive or non-invasive mechanical ventilation or mask CPAP with PaO2/FiO2 ratio ≤ 13.3 kPa in the most recent ABG analysis. * high-flow humidified oxygen therapy with a flow ≥ 50 L/min and a PaO2/FiO2 ratio ≤ 13.3 kPa in the most recent ABG analysis. * persistent respiratory acidosis with a pH \< 7.25 and a PaCO2 \> 6.0 kPa in the most recent ABG analysis in spite of non-invasive ventilation for \> 1 hour. * Withdrawal from active therapy or brain death deemed imminent. * Expected ICU stay \< 24 hours from randomisation. * Pregnancy (in females \< 60 years of age, non-pregnancy must be confirmed by a negative urine or plasma human chorionic gonadotropin, or presence a condition incompatible with pregnancy, e.g., previous hysterectomy, or conducted caesarean section during current hospitalisation). * Under coercive measures (i.e., ongoing involuntary hospital admission or under correctional authorities' jurisdiction). * Consent not obtainable as per Danish legislation. * Previously randomised in the DOPE-ICU feasibility trial.