When performing pleurodesis through a chest tube, we recommend small-bore tubes (14F) or an existing TPC (previously placed). The argument for the use of a larger-bore catheter is based on Poiseuille law, which suggests better flow rates with a larger inner diameter. In an in vitro study, when draining simple fluid, the maximum flow rate plateaus with catheters smaller than 9F.3 More viscous substances (abscess fluid) would have diminishing returns starting with 12F catheters. In addition, other factors may include catheter length, material (collapsibility), number and style of fenestrations within the catheter, and requirement for a three-way stopcock, which often is smaller than the inner diameter of the catheter. Many available small-bore (14F) catheter designs allow for MPE sampling through a three-way stopcock, which also allows for flushing and instilling thrombolytic and sclerosing agents.