Mechanical device resembling badminton birdie placed in inferior vena cava below level of renal veins; used to block passage of large emboli to heart and lungs; also indicated as prophylaxis against development of pulmonary emboli in patients who cannot be anticoagulated or who have had pulmonary emboli while being anticoagulated. Patients should always be asked about presence of this device before central line is placed using Seldinger technique with wire (to avoid catching wire on device).