| 摘要 |
A needle assembly for use in preventing backflow of blood being collected from a patient comprises a housing with a chamber therein, and including first and second access openings through the housing in fluid communication with the chamber. A cannula extends outwardly from the first access opening and is adapted for insertion into a patient. The chamber has a volume sufficiently large to store blood therein collected from the patient and to delay blood from backflowing from the second access opening into the first access opening under normal patient blood flow conditions due to the large amount of blood which must first be displaced from the chamber. In another embodiment of the present invention, the chamber includes flow resistance elements positioned in the chamber to provide flow resistance in the flow of blood from the chamber toward the first access opening. These objects may include tapered cones to favor flow of blood in one direction but not the other direction. |
