GB2122911A - Blood filter - Google Patents

Abstract

A disposable blood filter comprises a chamber having an inlet (12) and an outlet (16) separated by one or more mesh filter elements (18) arranged in pleated preferably tubular form with the folds of the pleats running from top to bottom of the chamber. The filter is generally made from plastics, and the filter element of polyester or nylon meshes interspersed with supporting medium (see Figs. 3 & 4). <IMAGE>

Description

SPECIFICATION Apparatus for use in blood transfusion The invention relates to apparatus for use in blood transfusion, particularly for use in filtering micro-emboli from stored human blood before administration to the patient.

Known apparatus of this type is either bulky in order to maintain a suitable flow rate, a disadvantage being that the volume of the device is somewhat large, or compact but capable of delivering blood at only small flow rates. Some known apparatus utilises filter media lying in horizontal planes and which thus quickly become clogged with debris and micro-bubbles, whilst others have filter media lying in vertical planes but comprise filter media of the "depth" type presenting a greater resistance to flow and increased likelihood of damage to the blood structure and being of small first surface area.

The present invention provides apparatus for use in blood transfusion comprising a chamber, an inlet for blood and an outlet for blood, the apparatus being arranged in use with the inlet higher than the outlet, the chamber being divided into two parts separated from one another by at least one mesh filter element arranged in pleated form with folds of the pleats arranged to extend substantially from a top region to a bottom region of the chamber, the inlet communicating with one part of the chamber and the outlet communicating with the other part.

The term "mesh" as used herein is intended to mean formed from monofilament, as distinct from the "depth" type of element which comprises a fibre mat of relatively large thickness (typically 40-200 ,um) and volume.

Preferably the mesh is supported between two layers of support material, and the mesh size lies in the range 10-70 ym. Desirably two meshes are provided, one of about 50-70 ,*4m, desirably 60 ,um mesh size, the other of mesh size less than 25 ym preferably 23 jum, the meshes being supported between alternate layers of supporting material. If a single mesh is provided, the mesh size is preferably about 40 ,um.

The or each filter element is preferably formed into a pleated tube having a star-shape in cross section, the star having a large number of limbs but not so many that they have surfaces which overlie one another or otherwise obstruct the access of blood and blood clot material to the filter surfaces. Preferably the area inside the starshaped element is substantially unobstructed and forms part of said chamber, desirably the part communicating with the blood outlet. The open ends of the pleated tube are sealed to end plates in fluid-tight manner, preferably by hot melt adhesive, preferably one end plate providing a wall of said chamber and having said outlet therein. If the filter element is made from a flat piece of material having two free ends which are joined together to form the tube, the free ends are preferably joined using a melt-sealing technique or ultrasonic welding.

The supporting material may be polyester, nylon or any other suitable material, and is desirably net-like and of large mesh size relative to the mesh of the filter element.

The filter element is preferably made from polyester or nylon mesh.

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:~ Fig. 1 is a perspective view partly cut away of apparatus according to the invention; Fig. 2 is a schematic cross-sectional view of a lower part of the apparatus shown in Fig. 1; Fig. 3 is a schematic diagram showing the construction of a filter element utilised in the apparatus of Fig. 1; and Fig. 4 is a schematic diagram showing the construction of an alternative filter element to that shown in Fig. 3.

The apparatus shown in Fig. 1 comprises a transparent plastic dome 10 having a blood inlet tube 12 therein, and a plastic base cap 14, which together provide a chamber for blood. The base cap 14 has a blood outlet tube 16 at its centre which communicates with the interior of a tubeshaped, pleated filter element 18 whose ends are sealed by hot melt adhesive 19 to the base cap and a top cap 20 respectively. The space exterior of the filter element 18 communicates with the inlet tube 12. Thus blood entering through the inlet tube 12 can only leave the apparatus through the outlet tube 16 after passing through the filter element 18. The base cap 14 and dome 10 are secured in fluid tight manner by acrylic sealer.On an interior surface of the base cap 1 4 the inlet tube terminates and three support rods 22 with apertures 24, for passage of blood therebetween, extend upwardly to the top cap 20, and are held in spaced apart relation by a web member 26. The top cap 20 has on its underside at the centre a stud (not shown) of circular section which is received in an interference fit between the ends of rods 22 and is secured thereto by hot melt adhesive, so connecting the base cap 14 and the top cap 20. Lower and upper edges of the filter element abutt concentric circular ribs 28 at the base cap 14 and top cap 20 respectively, these ribs helping to form a key for the hot melt adhesive.

As can be seen from Fig. 1 , the filter element is of tubular pleated shape and is constructed from support mesh and filter mesh, the tube being formed from a sheet whose ends are secured to make the tube by ultrasonic welding in fluid-tight manner. Fig. 3 shows a preferred filter element construction comprising from the upper blood inlet side, a first supporting mesh 30a of widely spaced polyester monofilament, a first polyester filter mesh 32 of 60 Mm, a second polyester supporting mesh 30b, a second filter polyester mesh 34 of 23 #m, and finally a third polyester supporting mesh 30c.Fig. 4 shows an alternative filter element comprising first and second polyester support meshes 30a and 30b respectively between which is sandwiched a nylon filter element 36 of 40 ,um. The supporting meshes are 800 Mm mesh size.

In operation, blood flows through inlet tube 12 through filter element 18 where micro-emboli is separated out, tending to fall to the base of the apparatus in regions 38, through the apertures 24 between rods 22 and thence out through the outlet tube 16.

Various modifications may be made to the apparatus without departing from the scope of the invention, for example the filter element may comprise any suitable number of layers of mesh, and the various parts of the apparatus may be secured together by any convenient means which does not adversely affect the blood being filtered.

The filter element should have surfaces which are generally upright when the apparatus is in use so that separated debris does not generally lie over the mesh to impede blood flow. The volume of the apparatus is as small as possible consistent with a reasonable flow rate, and the filter is pleated to give a large filter surface area. The filter element is made with monofilament filter meshes in one or more layers, and desirably the supporting meshes are made of polyester monofilament, the filter meshes being made of polyester or nylon. It is intended that the apparatus according to the invention will be disposable after use.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to whether or not particular emphasis has been placed thereon.

When the apparatus is used with a second or subsequent batch of blood, the configuration of the apparatus is such that any air micro-bubbles introduced into the apparatus will not impede the flow of blood to the filter.

The support mesh is desirably of polyester material. Where a single filter mesh is provided as hereinbefore described the filter mesh is preferably of nylon material. Where two filter meshes are provided these are preferably of polyester material.

Claims (18)

1. Apparatus for use in blood transfusion comprising a chamber, an inlet for blood and an outlet for blood, the apparatus being arranged in use with the inlet higher than the outlet, the chamber being divided into two parts separated from one another by at least one mesh filter element arranged in pleated form with folds of the pleats arranged to extend substantially from a top region to a bottom region of the chamber, the inlet communicating with one part of the chamber and the outlet communicating with the other part of the chamber.

2. Apparatus as claimed in Claim 1, in which a single mesh filter element is provided, the mesh size lying in the range 15-70 #m.

3. Apparatus as claimed in Claim 2, in which the mesh size of the filter element is 40 #m.

4. Apparatus as claimed in Claim 1, in which two filter elements are provided, the mesh size of the first being in the range 50~70,um and that of the second being less than 25 ym.

5. Apparatus as claimed in Claim 4, in which the mesh size of the first element is 60 Mm.

6. Apparatus as claimed in Claim 4 or Claim 5, in which the mesh size of the second element is 23 jut.

7. Apparatus as claimed in any of Claims 4 to 6, in which the first filter element is on the blood inlet side of the apparatus and the second filter element on the blood outlet side.

8. Apparatus as claimed in any preceding Claim, in which the or each filter element is provided with at least one monofilament supporting mesh of large mesh size.

9. Apparatus as claimed in Claim 8, in which the or each filter element is sandwiched between two monofilament supporting meshes of large mesh size.

10. Apparatus as claimed in Claim 8 or Claim 9, in which the mesh size of the supporting mesh is of the order of 1 millimetre.

11. Apparatus as claimed in Claim 8, 9 or 10, in which the monofilament supporting mesh is made from polyester material.

12. Apparatus as claimed in any preceding claim, in which the apparatus comprises a dome part having one of said blood inlet or blood outlet therein and a base part having the other of said blood inlet or blood outlet therein.

13. Apparatus as claimed in Claim 12, in which the dome part is made of transparent material.

14. Apparatus as claimed in Claim 12 or Claim 13, in which the or each filter element is sealingly secured at one of its open ends to the base part, and at another open end to a cap member secured in spaced relation to said base part within the dome part.

15. Apparatus as claimed in Claim 13 in which said base part has the blood outlet therein, said blood outlet communicating with a space in the interior of the or each tubular filter element.

16. Apparatus as claimed in any preceding claim, in which the apparatus is made of plastics material.

1 7. Apparatus as claimed in any preceding claim, in which the or each filter element is made from polyester monofilament.

18. Apparatus as claimed in any preceding claim, in which the or each filter element is made from nylon monofilament.

1 9. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.