The effects of pleural drainage on lung mechanics are unknown. Insertion of esophageal balloon will allow us to measure and assess pleural pressure, and thus assess any possible effects of pleural fluid drainage may have on lung mechanics.

Esophageal balloon will be inserted prior to pleural fluid drainage.

Inclusion Criteria:

• Mechanically ventilated patients with significant pleural fluid documented by CT scan or US.who are candidates for pleural fluid drainage.

Exclusion Criteria:

• Patients with any of the following were excluded from the study. Previous lung or chest wall surgery, previous esophageal surgery, known Achalasia or any other esophageal motility or spasm disorder, presence of chest thoracostomy tube, and any significant chest wall abnormality such as kyphoskoliosis.

Mechanically ventilated patients with significant pleural fluid documented by CT scan or US.