GB2222962A

GB2222962A - Fluid administration filter unit

Info

Publication number: GB2222962A
Application number: GB8919658A
Authority: GB
Inventors: Anthony Frank Davis
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1988-09-07
Filing date: 1989-08-31
Publication date: 1990-03-28
Anticipated expiration: 2009-08-31
Also published as: GB8919658D0; GB8820946D0; IT8921563A0; IT1231391B; GB2222962B

Abstract

A fluid administration unit comprises a fine filter 6, which filters parenteral solutions being administered to a patient, and a coarse filter 8 which enables the unit also to filter blood. The fine filter is located inside and upstream of the coarse filter and is rapidly blocked if blood is delivered through inlet 2, 4, whereupon the fine filter fills and the blood overflows through by-pass holes 7 to reach the coarse filter 8. In an alternative unit the fine filter is arranged at the lower end of the coarse filter and in parallel therewith. The filters may both be polyamide with pores sizes 10-15 microns and 30-220 microns respectively. <IMAGE>

Description

FLUID ADMINISTRATION SET This invention relates to fluid administration sets.

The invention is more particularly concerned with fluid administration sets that can be used to administer and filter both infusion liquid and blood products.

Conventionally when infusing a liquid into a patient, an administration set is placed between the liquid reservoir and the access site to the patient. An administration set usually comprises a filter for the liquid and a drip chamber whereby the rate of administration may be estimated. The inlet of the set usually comprises a spike for connection to the liquid reservoir and the outlet is connected by a length of tubing to an indwelling needle or catheter in the patient.

The filter is an important feature of the administration set since the infusion of particulate material to the patient is undesirable and indeed many countries specify the maximum size of particles which are acceptable. For parenteral solutions such as saline for example, particles greater than 40pm are removed though usually a filter with a pore size of l5jim is used with such solutions. For blood or blood derivatives, filters with larger pores are needed because of the large size of blood cells; these filters are generally in the range 180 to 220pm in diameter, with filters having a pore size of 180pom or 220pm usually being employed. However, it is felt by some authorities that filters containing pores of about 40#um should be used for filtration of blood and blood derivatives.It is clear, nevertheless, that existing administration sets which can be used for parenteral solution can not be used for blood and vice versa, since blood particles would rapidly block the finer filter and the coarser filter would not filter out undesirable particles from the parenteral solution.

It is an object of the present invention to provide an arrangement for an administration set by which means the administration of either parenteral solutions or blood products can be effected by the same set without risk of causing deliterious effects to the patient.

According to one aspect of the present invention there is provided a fluid administration set comprising a chamber having an inlet capable of fluid communication with a source of infusion liquid and an outlet capable of fluid communication with a patient, the chamber containing a first filter with a pore size not more than about 15jim and a second, coarser filter having a pore size which is capable of filtering the liquid when it is blood or a blood derivative, the second filter being in fluid communication with the first filter, and the first filter continuously filtering any non-blood or blood derivative but becoming rapidly blocked by blood or blood derivative causing it to divert through the second filter.

The first filter preferably has a pore size in the range 1 to 5pm and may be of a material which encourages rapid wetting and blocking by blood. The first filter may be of a polyamide.

The second filter preferably has a pore size in the range 30 to 220pm and preferably has a pore size of about 180cm. The area of the second filter may be at least least 32cm and is preferably at least 40cm The first and second filters may be arranged such that the liquid flows through the first filter and then through the second filter if the first filter is not blocked. The first and second filters may be of cylindical shape and arranged vertically. The first filter is preferably located coaxially within the second filter such that if the first filter becomes blocked by blood or a blood derivative it fills the first filter and overflows into the second filter. The second outer filter may be closed at its upper and lower ends.

The inlet may be in the form of a spigot located to direct incoming liquid to flow over a surface of the first filter. The outlet from the chamber containing the filters may be a drip into a drip chamber.

A preferred embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawing which is an exploded view of an administration set.

The administration set 1 is for use with infusion liquids including blood, blood derivatives, parenteral solutions such as saline, intravenous drug solutions and total parenteral nutrition solutions. The set 1 is intended, in use, to hang vertically. The set has a top cap 5 comprising an integral vented spike 2 for piercing an entry port of a conventional parenteral liquid or blood-containing reservoir which may be a glass bottle or a plastic bag (not shown). The spike 2 has two bores.

One bore is connected to a vent 3 containing a membrane filter. This vent permits entry of filtered air into the interior of the liquid container as the liquid flows from the container along the second bore. The liquid flowing along the second bore enters the chamber at a short inlet spigot 4 in the top cap 5.

The top cap 5 is of circular section and seals the upper end of a cylindrical filter chamber 9. The chamber 9 may be injection or blow moulded from a polymer such as polyvinyl chloride, or may be moulded from glass, and is sterilised before use. The lower end of the chamber 9 has an integral drip 10 whereby liquid can pass into a drip chamber 11. The outlet of the drip chamber 11 is connected in the conventional way, via a tube 12 with a needle or indwelling catheter (not shown) in the patient.

The chamber 9 contains two filters 6 and 8 of cylindrical shape which, in use, are arranged vertically.

The inner filter 6 is of smaller diameter than the outer filter 8 and is arranged coaxially within it. At its lower end, the inner filter 6 is closed and at its upper end it is open. The top cap 5 is spaced from the upper end of the inner filter 6 by a downwardly extending axial ring 17 which is sealed to the top margin of the inner filter and has several gaps around its circumference defining overflow outlets or ports 7 for the passage of liquid overflowing from the inner filter. The inlet spigot 4 is located within the ring 17 but offset radially in order to encourage the incoming liquid to flow down the material of the inner filter 6 to avoid causing the incoming liquid to drip or foam. The inlet spigot 4, by virtue of its length, prevents incoming liquid from flowing or tracking directly through the ports 7 and thereby avoiding passage through filter 6.The relative position of the lower end of the inlet spigot 4 and the upper margin of the inner filter 6 also prevents incoming liquid from dripping directly through the ports 7 should the administration set 1 not be suspended in a truly vertical position.

The inner filter 6 has a pore size in the range 1 to l5#m and, for example, may be lpm, 5#m or lOum.

Preferably, the pore size is not greater than 5jim. The area of the inner filter 6 is sufficient to give with solutions, an adequate flow rate, of about 60 drops/min.

The filter 6 is made of a lay-flat polyamide tubing which encourages rapid wetting of the filter and also encourages rapid blocking when the liquid is blood or the like.

Alternative materials compatible with both blood and solution could be used, such as various metals, ceramics and polymers including polyesters.

The outer filter 8 is sealed at its upper end to the top cap 5 and is closed at its lower end. The pore size of the outer filter 8 is greater than 30pm and is preferably in the range 40rim to 220pm, typically being 180um. The pore size is such that the outer filter 8 is effective in filtering blood or blood derivatives without blocking. The outer filter 8 is made of polyamide and has an area of at least 32cm# and preferably more than 40cm .

The inner filter 6 extends deep into the outer filter 8 to reduce dripping, splashing and foaming when liquid passes through the inner filter.

In use with parenteral liquids, the liquid continuously passes into and through the wall of the inner, finer filter 6, through the wall of the outer, coarser filter 8 and exits via the drip 10 into the chamber 11, and thence to the patient. The finer filter 6 is such that it cannot be blocked by any particles present in non-blood or blood derivatives.

When, however, it is used with blood or blood derivatives, the inner filter rapidly becomes blocked thereby allowing it to fill, overflowing its upper margin via the ports 7 and flowing into the space between the inner filter 6 and outer filter 8. The outer filter 8 removes particles larger than l8O#m but allows passage of blood into the drip chamber 11.

The fine and coarser filters need not necessarily be arranged coaxially, one within the other. In an alternative arrangement (not shown), the filter assembly is also cylindrical in shape but the fine filter is located at the lower end of the assembly with the coarser filter located directly above it and sealed at its upper end to the top cap. In use, the infusion liquid enters the inside of the assembly. If the liquid is a parenteral solution then it is filtered by the lower, finer filter.

If the liquid is blood or a blood derivative then the lower filter becomes blocked, allowing the liquid to rise up the inside of the filter assembly until it reaches the level of the upper, coarser filter. The liquid then flows out of the assembly through the coarser filter and thence flowing to the outlet drip.

Claims

1. A fluid administration set comprising a chamber having an inlet capable of fluid communication with a source of infusion liquid and an outlet capable of fluid communication with a patient, wherein the chamber contains a first filter with a pore size not more than about lSpm and a second, coarser filter having a pore size which is capable of filtering the liquid when it is blood or a blood derivative, wherein the second filter is in fluid communication with the first filter, and wherein the first filter continuously filters any non-blood or blood derivative but becomes rapidly blocked by blood or blood derivative causing it to divert through the second filter.

2. A fluid administration set according to Claim 1, wherein the first filter has a pore size in the range 1 to 5pm.

3. A fluid administration set according to Claim 1 or 2, wherein the first filter is of a material which encourages rapid wetting and blocking by blood.

4. A fluid administration set according to Claim 3, wherein the first filter is of a polyamide.

5. A fluid administration set according to any one of the preceding claims, wherein the second filter has a pore size in the range 30 to 220cm.

6. A fluid administration set according to Claim 5, wherein the second filter has a pore size of about 180pom.

7. A fluid administration set according to any one of the preceding claims, wherein the area of the second filter is at least 32 cm

8. A fluid administration set according to Claim 7, wherein the area of the second filter is at least 40cm .

9. A fluid administration set according to any one of the preceding claims, wherein the first and second filters are arranged such that liquid flows through the first filter and then through the second filter if the first filter is not blocked.

10. A fluid administration set according to any one of the preceding claims, wherein the first and second filters are of cylindrical shape and are arranged vertically.

11. A fluid administration set according to Claims 9 and 10, wherein the first filter is located coaxially within the second filter such that if the first filter becomes blocked by blood or a blood derivative it fills the first filter and overflows into the second filter.

12. A fluid administration set according to Claim 11, wherein the second outer filter is closed at its upper and lower ends.

13. A fluid administration set according to any one of the preceding claims, wherein the inlet is in the form of a spigot located to direct incoming liquid to flow over a surface of the first filter.

14. A fluid administration set according to any one of the preceding claims, wherein the outlet from the chamber containing the filters is a drip into a drip chamber.

15. A fluid administration set substantially as hereinbefore described with reference to the accompanying drawing.

16. Any novel feature or combination of features as hereinbefore described.