Apparatus and method of fluid aspiration

An in-line sampling syringe for selectively introducing a fluid to and aspirating a fluid from a downstream fluid conduit connected to a catheterized patient, said syringe comprising:

• a. a housing defining a closed system composed of a fluid chamber having a first opening into which fluid is aspirated and an air chamber having a second opening in which a relief element is positioned;
• b. a volume regulator mounted in said housing composed of a sealing gasket interposed between the fluid chamber and the air chamber and a drive mechanism connected to the sealing gasket for moving the sealing gasket for adjusting the volume of said fluid chamber;
• c. a rigid fluid line mounted in a fixed position in said housing through which fluid flows relative to a downstream fluid conduit via said first opening, said rigid fluid line passing through the sealing gasket in a slidably sealed manner, and said rigid fluid line terminating adjacent to said first opening;
• d. wherein said drive mechanism connected to the sealing gasket is mounted for linear sliding movement in said housing relative to said rigid fluid line;
• and e. a rotatably mounted control member, which can be operated manually single handedly, is operatively connected to said drive mechanism for:
• i. selectively controlling fluid flow relative to said rigid fluid line;
• and, ii. selectively linearly shifting said volume regulator relative to said housing to adjust the volume of said fluid chamber.