Closed, one-handed blood sampling system

A method of flushing a reservoir used in a fluid sampling system, comprising:

• providing a reservoir having a chamber and a displaceable piston having a piston wall facing the chamber and displaceable within the body to vary the volume of the chamber;
• connecting a proximal portion of tubing between a source of flushing fluid and an inlet to the variable volume chamber;
• connecting a distal portion of tubing between a fluid system of a patient and an outlet to the variable volume chamber;
• biasing the piston into a first position within the variable volume chamber with the piston wall adjacent the inlet and outlet ports;
• and
• maintaining a minimum gap between the piston wall and the chamber when the piston is in the first position with structure on either the chamber or the piston, the gap defining a volume to which the inlet and outlet ports communicate and allow fluid to flow from the proximal portion of tubing to the distal portion of tubing.

A reservoir for use in a fluid sampling system, comprising:

• a reservoir body defining a variable volume chamber within, the body having a peripheral wall and a bottom wall;
• a fluid inlet port extending perpendicularly through the bottom wall of the body and open to the chamber;
• a fluid outlet port open to the chamber;
• a piston displaceable within the body from a first position adjacent the bottom wall to a second position spaced farther away from the bottom wall to increase the volume of the chamber, the piston having a pressure surface which is spaced from the bottom wall to form a narrow gap therebetween when the piston is in the first position, the fluid inlet and outlet ports being open to the gap;
• and
• a seal surrounding the pressure surface and providing a fluid-tight seal between the piston against the peripheral wall of the chamber, wherein fluid entering the chamber through the inlet port when the piston is in the first position is directed generally in a 360.degree. sheet across the bottom wall and toward the peripheral wall of the chamber.

A method of sampling fluid from a human, comprising:

• providing a reservoir body defining a variable volume chamber within, the reservoir body having a peripheral wall and a bottom wall;
• connecting the chamber to a vessel of the human by connecting a first conduit to a fluid outlet port open to the chamber;
• connecting the chamber to a source of flushing solution by connecting a second conduit to a fluid inlet port extending perpendicularly through the bottom wall and offset from the peripheral wall;
• providing a piston displaceable within the reservoir body from a first position adjacent the bottom wall to a second position spaced farther away from the bottom wall to increase the volume of the chamber, the piston having a pressure surface facing the bottom wall and including a seal surrounding the pressure surface and providing a fluid-tight seal between the piston against the peripheral wall of the chamber;
• and
• flushing the chamber between the piston and the bottom wall such that fluid entering the chamber through the inlet port when the piston is in the first position is directed generally in a 360.degree. sheet across the bottom wall and toward the peripheral wall of the chamber.