A trocar assembly for creating a pneumatic seal during a minimally-invasive surgical procedure. The trocar assembly including an elongated body having a lumen extending therethrough. The proximal end portion of the body defining a housing. A fluid supply plenum is defined in the housing configured to deliver pressurized insufflation fluid to a nozzle. The nozzle configured for directing pressurized fluid into the lumen and creating a pneumatic seal. A fluid return plenum is defined in the housing configured to collect spent insufflation fluid from as patient's abdominal cavity. The fluid return plenum including a plurality of axially and radially oriented elongate vanes configured to permit spent insufflation fluid to proceed between the vanes and direct spent insufflation fluid back to the fluid return plenum.