The primary objective of this study is to compare gravity-driven versus wall suction-driven large volume therapeutic thoracentesis on the development of chest discomfort during the procedure.

This study is a multicenter, single-blinded, randomized controlled trial designed to compare chest discomfort between gravity-driven and wall suction-driven therapeutic thoracentesis. Patients will be stratified by study centers, and randomly assigned to intervention and control arms; and will remain blinding to their group assignment during the procedure.

Aims and Objectives:

The primary objective of this study is to compare gravity-driven versus wall suction-driven large volume therapeutic thoracentesis on the development of chest discomfort during the procedure.

Expected Outcomes:

We anticipate that gravity driven therapeutic thoracentesis will result in improved clinical outcomes compared to wall suction driven thoracentesis, defined by less chest discomfort throughout the procedure as measured at 5 minutes post-procedure (primary endpoint).

Primary endpoint:

The Global Pain Score will be determined at 5 minutes post-procedure using a VAS 0-100 and represents the pain experienced by the patient during the entire procedure from the beginning to the 5-minute post-procedure assessment ("On average, how much discomfort have you felt during the procedure?"). The primary endpoint is defined as the overall procedural chest pain scored 5 minutes following the procedure.

This study is a randomized controlled trial designed to compare the changes of chest pain scores between gravity-driven therapeutic thoracentesis and wall suction-driven thoracentesis. The estimated minimal clinically important difference of the change is 10.

Secondary endpoints:

1. Duration of procedure timed from the beginning of fluid drainage to catheter removal.
2. Differences in narcotics used after the procedure.
3. Incidence of pneumothorax detected on the post procedural CXR
4. Incidence of clinically apparent re-expansion pulmonary edema
5. Incidence of radiographically apparent re-expansion pulmonary edema detected on the post procedural CXR

Inclusion criteria:

1. Referral to pulmonary services for large-volume thoracentesis

2. Presence of a symptomatic moderate or large free-flowing (non-septated) pleural effusion on the basis of:

   1. Chest radiograph: effusion filling ≥ 1/3 the hemithorax, OR
   2. CT-scan: maximum AP depth of the effusion ≥ 1/3 of the AP dimension on the axial image superior to the hemidiaphragm, including atelectatic lung completely surrounded by effusion, OR Ultrasound: effusion spanning at least three interspaces, with depth of 3 cm or greater in at least one intercostal space, while the patient sits upright.

3. Age >/= 18

Exclusion criteria:

1. Inability to provide informed consent

2. Study subject has any disease or condition that interferes with safe completion of the study including:

   1. Coagulopathy, with criteria left at the discretion of the operator
   2. Hemodynamic instability with systolic blood pressure <90 mmHg or heart rate > 120 beats/min, unless deemed to be stable with these values by the attending physicians

3. Pleural effusion is smaller than expected on bedside pre-procedure ultrasound

4. Referral is for diagnostic thoracentesis only

5. Presence of more than minimal septations and/or loculations( more than 3) on bedside pre-procedure ultrasound

6. Inability to sit for the procedure

7. Pregnancy