Blood sampling device

Claim 1

A syringe device for drawing an arterial blood sample including a hollow barrel open at one end and having a hypodermic needle removably mounted at the other end, a plunger assembly within the open end of said barrel for slidable reciprocating movement therein, said plunger assembly including a hollow piston with a first annular fitting within said hollow piston having an external diameter smaller than said hollow piston and of a dimension to allow it to be fixedly mounted within the distal end of said hollow piston, an integral skirt of a lesser diameter dependent therefrom, a second annular fitting comprising a cylindrical upper section having an internal diameter to cooperate with and receive said dependent integral skirt for a force fit therebetween and of an external diameter to form a force fit within said hollow piston, said second annular fitting also including an inner shoulder and an outer shoulder, said outer shoulder being adapted to receive a sealing ring for sealing the space between the hollow barrel and piston when said hollow barrel and second annular fitting are assembled, said internal shoulder cooperating with the dependent skirt of said first annular fitting for supporting and fixedly maintaining a membrane element therebetween, said membrane element being pervious to the passage of air therethrough but impervious to the passage of liquid after being wetted.