| 摘要 |
A needle assembly for facilitating the collection of a blood sample from a patient into an evacuated collection container and indicating when a venipuncture has been accomplished and preventing flow of fluid from the collection container into the patient during and after collection of the blood sample. The assembly includes a housing having a chamber therein, a forward penetrating end including a cannula extending from the housing for penetration into the blood vessel of a patient, and a rearward end including a cannula extending from the housing and adapted to be coupled in fluid communication with the interior of an evacuated collection container. Surfaces of the assembly form a passageway for directing blood from the blood vessel through the housing to the collection container when the forward end is in the blood vessel and the rearward end is in the container. A valve assembly is mounted in the chamber in the housing and normally is in the unarmed position with passages therein to permit blood to flow from the vein into the chamber upon venipuncture. The assembly is shiftable to an armed position to close the passageway from the vein into the chamber by means of a resilient elastomeric valve member in the chamber. The valve member is adapted to be responsive to a reduction in fluid pressure at the rearward end to deform and automatically open the passageway and permit blood to flow from the blood vessel to the rearward end. Thereafter, the valve member is responsive to a predetermined increase in fluid pressure at the rearward end to automatically return to the closed position to thereby prevent flow of fluid from the rear end of the assembly to the blood vessel. |
