GB2325726A - Infusion device - Google Patents

Abstract

An infusion device has an upper filter chamber 4 opening into a lower drip chamber 5 via an inlet spigot 84. A float 40 in the lower chamber 5 occludes the inlet 84 at high liquid levels. The outlet 3 of the lower chamber 5 has four pegs (37, figure 2) projecting up around the outlet opening 35 so as to support the float 40 above the opening at low liquid levels and prevent occlusion. The wall 7 of the lower chamber 5 is bendable so that the chamber 5 can be squeezed to expel liquid through the outlet 3. The area between the projecting pegs (37) is about one and a half times the area of the outlet.

Description

INFUSION DEVICE This invention relates to infusion devices.

Fluid, such as saline, blood or the like, can be infused into a patient from a reservoir suspended above the patient, via a drip chamber by which the flow of fluid can be seen. The drip chamber often includes a float valve floating on fluid in the chamber, which blocks flow into the chamber when the level of fluid in the chamber is too high. Examples of such drip chambers are described in, for example, W096/35465, EP228802, EP674910, GB2147087, GB2266842, GB2028975 and US4055176. In many cases, the float valve in such drip chambers is also arranged to block the outlet from the chamber when the level of fluid in the chamber falls below a certain level. This can be a problem in some cases because the flow of fluid out of the chamber can cause the float valve to be pulled down and shut off flow through the valve, even when there is still some fluid remaining in the chamber.

It is an object of the present invention to provide an improved infusion device.

According to the present invention there is provided an infusion device including a chamber having an inlet at its upper end and an outlet at its lower end, and a float member arranged to float in liquid in the chamber and to move up or down the chamber as the level of liquid rises or falls, the float member being arranged to impede flow of liquid into the chamber from the inlet at high liquid levels, the chamber being configured in the region of the outlet to maintain a fluid flow passage between the outlet and the float member when the float member is at its lowest point in the chamber.

The chamber preferably has a plurality of projections in the region of the outlet arranged to support the float member spaced above the outlet. The projections are preferably four pegs spaced from one another around the outlet. The area between the projections when contacted by the float member is preferably about one and a half times the area of the outlet.

The inlet may have a projecting spigot arranged for engagement by the float member at high liquid levels. The chamber preferably has a bendable wall whereby the chamber can be squeezed to expel liquid from the outlet. The device may include an upper filter chamber mounted at the inlet of the lower chamber containing the float member, the filter chamber being arranged to filter liquid supplied to the inlet. The device may include two cylindrical walls forming walls of the upper and lower chambers respectively, and a connection piece joining the two walls together and providing the inlet of the lower chamber. The float member is preferably a spherical ball.

An infusion device including a drip chamber according to the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional side elevation view of the infusion device; Figure 2 is an enlarged sectional side elevation view of the base of the device; Figure 3 is a plan view of the base of the device; and Figure 4 is a perspective view of the base of the device.

With reference first to Figure 1, there is shown an infusion device 1 with an inlet 2 at its upper end for connection to a blood bag via inlet tubing (not shown). At its lower end, the device 1 has an outlet 3 for connection to a patient via outlet tubing (not shown). The infusion device 1 is of tubular shape having a filter chamber 4 at its upper end communicating with a drip chamber 5 at its lower end. The outer wall of the device 1 is provided by two cylindrical sleeves 6 and 7 of a transparent, bendable plastics joined end-to-end by a central connection piece 8.

The upper sleeve 6 forms the wall of the filter chamber 4 and is sealed at its upper end to a cap 9 having an axial, upwardly-projecting spigot 10 forming the inlet 2 of the device.

The filter chamber 4 may be of conventional form and contains a tubular filter element 40 sealed with the inside of the cap 9 so that any solid matter or clots are removed from blood flowing through the filter element.

The central connection piece 8 is moulded from a substantially rigid plastics material and has an upwardly-projecting collar 80 and a downwardly-projecting collar 81 separated by an internal transverse plate 82, which also projects outwardly of the sleeves to form a flange 83. The lower end of the upper sleeve 6 is a push fit on the collar 80, abutting the flange 83 and is retained in place by a solvent, adhesive or by welding. Similarly, the upper end of the lower sleeve 7 is fitted on the downwardly-projecting collar 81. The plate 82 has a spigot 84 in its centre projecting downwardly into the drip chamber 5, providing a drip inlet into the chamber.

The outlet 3 of the drip chamber 5 is provided by a base member 30 shown in more detail in Figures 2 to 4. The base member 30 has a co-axial inner and outer collar 31 and 32 forming an annular recess 33 therebetween, in which the lower end of the sleeve 7 is retained.

The internal diameter of the base member 30 within the inner collar 31 is about 16mm. The base member 30 has an spigot 34 projecting downwardly externally of the chamber, which provides the outlet over which outlet tubing is fitted. The spigot 34 opens at its upper end through a central opening 35 about 3mm in diameter. The inside of the base member 30 has a floor 36 tapering down towards the central opening 35, forming a frusto-conical surface. Four pegs 37 project vertically upwardly from the floor 36 of the base member, each being about 3.4mm high and of circular section with a diameter of about 1.75mm. The pegs 37 are equally spaced from one another around the central opening 35 and are located with their centres on a coaxial circle of diameter d, about 8.6mm, so that the inside edge of the pegs lies on a circle of diameter d2 of about 6.85mm. The top of each peg 37 has a rounded edge.

The drip chamber 5 also contains a float member in the form of a spherical ball 40 of diameter about 10.5 mm and of a material that will float on the surface of blood in the drip chamber. The diameter of the ball 40 is selected so that it locates squarely on the bottom of the spigot 84 when the level of blood in the drip chamber 5 is high. The locations and height of the pegs 37 is selected so that the ball 40 sits squarely on the tops of the four pegs with the bottom of the ball being spaced above the opening 35 when the level of blood in the drip chamber 5 is low. The height of the pegs 37 is selected so that, when the ball is sitting on top of the pegs, the area for flow between the pegs is equal to about one and a half times the area of the outlet opening 35. Because this area is greater than that of the outlet opening, flow is not significantly impeded by the inclusion of the pegs. It has been found preferable to use four pegs 37, rather than three, because they reduce the risk of the ball being trapped between the pegs and the lower end of the sleeve. The pegs 37 are spaced away from the opening 35 to ensure that any clots that might form on the pegs do not block the opening.

In operation, blood from the blood bag flows through the inlet tubing into the inlet 2 of the filter chamber 4, to fill the bottom of the chamber. Blood then drips through the drip inlet 84 into the drip chamber 5 so that the level of blood in the chamber is somewhere between its upper and lower limits. The ball 40 floats on the surface of the blood without providing any significant obstacle to flow.

If the level of blood should rise to that indicated by the line "U" in Figure 1, the upper surface of the ball 40 will engage the lower end of the drip inlet 84 and prevent any further significant flow into the drip chamber 5 until the level falls again. In some circumstances it is necessary to pump the drip chamber 5 manually to increase flow or to prime the outlet tubing.

This is done by squeezing the sleeve 7 of the drip chamber 5 to compress the chamber and force blood through the outlet 3. When this is done, the ball float 40 seals with the drip inlet 84 to prevent blood flowing in the opposite direction.

If the level of blood should fall to that indicated by the lower line "L" the ball 40 will seat on the pegs 37. As mentioned above, in this position, the ball 40 is spaced above the opening 35 so that any residual blood can flow around the pegs 37, under the ball and out of the outlet. This arrangement ensures that the float can never occlude the outlet, such as might otherwise be caused at high flow rates and low levels of blood in the drip chamber. The pegs 37 have also been found to create a spiralling vortex flow of blood through the outlet 35, which enables increased flow rates to be achieved.

Instead of pegs, there are various other ways in which the chamber could be configured in the region of the outlet to maintain a fluid flow passage between the outlet and the float member when the float member is at its lowest point in the chamber. For example, the floor of the chamber could be formed with ridges or grooves to provide a flow passage under the float. The float member need not be spherical but could be of other shapes.

Claims (11)

1. An infusion device including a chamber having an inlet at its upper end and an outlet at its lower end, and a float member arranged to float in liquid in the chamber and to move up or down the chamber as the level of liquid rises or falls, the float member being arranged to impede flow of liquid into the chamber from the inlet at high liquid levels, wherein the chamber is configured in the region of the outlet to maintain a fluid flow passage between the outlet and the float member when the float member is at its lowest point in the chamber.

2. A device according to Claim 1, wherein the chamber has a plurality of projections in the region of the outlet arranged to support the float member spaced above the outlet.

3. A device according to Claim 2, wherein the projections are four pegs spaced from one another around the outlet.

4. A device according to Claim 2 or 3, wherein the area between the projections when contacted by the float member is about one and a half times the area of the outlet.

5. A device according to any one of the preceding claims, wherein the inlet has a projecting spigot arranged for engagement by the float member at high liquid levels.

6. A device according to any one of the preceding claims, wherein the chamber has a bendable wall whereby the chamber can be squeezed to expel liquid from the outlet.

7. A device according to any one of the preceding claims including an upper filter chamber mounted at the inlet of the lower chamber containing the float member, and wherein the filter chamber is arranged to filter liquid supplied to said inlet.

8. A device according to Claim 7, wherein said device includes two cylindrical walls forming walls of the upper and lower chamber respectively, and a connection piece joining said two walls together and providing the said inlet of said lower chamber.

9. A device according to any one of the preceding claims, wherein said float member is a spherical ball.

10. An infusion device substantially as hereinbefore described with reference to the accompanying drawings.

11. Any novel and inventive feature or combination of features as hereinbefore described.