Intravenous solution set having an air access site and constricted inner diameter portion

Claim 1

In a parenteral liquid infusion set which comprises flexible flow tubing, means for connection at one end of said flow tubing with blood vessel penetrating means, means for connection with a parenteral liquid source at the other end of said tubing, drip chamber means having a tubular, drop-forming member at an upper end thereof of reduced inner diameter relative to the inner diameter of said flow tubing, and an intermediately-positioned site providing potential access of air to the interior of said set from the exterior, said site being positioned downstream from said drip chamber, the improvement comprising, in combination: a portion of said flexible fluid flow tubing positioned downstream from said access site defining a bore of reduced diameter, when compared with the bore size of the remainder of said flow tubing, said reduced diameter bore being of a length and diameter to cause the overall frictional pressure drop of water in the portion of said set which is upstream from and including said intermediately-positioned site to be less than the frictional pressure drop of water through the portion of said set which is downstream from said intermediately-positioned site when said set is extended in a fully vertical position, and said means for connection with a parenteral liquid source is connected with a vented solution container in which the liquid level of solution in said container is no higher than the upper end of said means for connection with the parenteral liquid source, and while no outside clamping restriction to flow is applied to said set.