Patent ID: 7691093

Claim:
A method of controlling the fluid flow rate in an extension tube of an introducer needle assembly for confirmation flashback, the introducer needle assembly having a catheter attached to a catheter hub with a side port, an extension tube attached to the side port on the catheter hub at least a portion of which is translucent, and an introducer needle with a notch adapted to be inserted into a bore in the catheter, wherein the needle has an outer diameter smaller than the diameter of the bore such that an annular space is defined between the catheter and the needle, the method including: selecting a preferred fluid flow front rate of a fluid through the extension tube, wherein the fluid is at a pressure and has a viscosity when it is accessed by the needle; and selecting a needle assembly from a plurality of needle assemblies capable of producing the preferred fluid flow front rate, wherein each needle assembly of the plurality of needle assemblies includes a distinct combination of needle assembly properties, including the sizing of the notch, the internal diameter of the extension tube, and the annular space, and wherein each distinct combination provides a distinct fluid flow rate through the extension tube based on the pressure and viscosity of the fluid when accessed by the needle.