IE41543B1 - Apparatus for use in blood transfusion - Google Patents

Description

In the administration of whole blood to a patient it is desirable, if not necessary, to filter the blood as it is being administered. The debris which is to be removed by the filter will vary depending upon the length of time the blood has been stored. Over the years, many different filter media have been developed which are specifically useful in filtering debris from whole blood. Although the engineering of the filter media and the filter efficiency is extremely important there is a number of other problems involved with filtering blood during blood transfusions.

First, in administering blood to the patient and in filtering this blood, the flow rate should be known and controlled The filtration unit should be readily insertable into a blood reservoir, usually a blood bag, and the necessary administration sets for administering blood to the patient easily and readily connected to the filtration unit in a manner that does not disrupt or change the flow of the blood. The filtration unit must be constructed so not to collect or entrap micro-gas bubbles which might be adminis20 tered inadvertently to the patient. The unit itself should have a low total volume so the blood is not retained in the unit and all of the blood from a blood bag is administered to the patient. The filtration unit should be easily and readily primed and primed in such a manner as not to entrap - 2 41543 gas bubbles. Along with all of these problems whioh should be overcome, the unit should have excellent filtering efficiency, do as little damage to the blood components as possible, and be usable for multiple blood transfusions to a single patient in order to be reasonably economical.

In Patent Specification No. we claim a blood filtration unit comprising a housing, a drip chamber disposed at an upper portion within said housing, a blood inlet opening into said drip chamber, one end of said inlet extend10 ing into the chamber and the opposite end of said inlet being attachable to a reservoir for blood, a filter cartridge fitted into said housing, said cartridge comprising a top end cap, a bottom member, and an elongated annular filter element comprising filter material, the filter element being sealed between said top end cap and bottom member, said top end cap being solid and having a multipointed transverse crosssection, said filter element having substantially the same cross-sectional shape as the top end cap, the diameter of the top end cap being substantially the same as the inside diameter of the housing such that the points thereof engage the inside surface of the housing, said bottom member having a centrally located blood outlet, one end of said outlet communicating with the space inside the filter element, the other end of said outlet being adaptable to connect with a blood administration set, and said housing being secured to said bottom member at the periphery of said bottom member.

The flow of blood through the abovementioned unit is measurable and known. The manner in which the filter medium is used in the unit is more efficient, and the possible blockage of the medium is reduced. Our filter unit does little, if any, damage to the blood components being filtered. In certain embodiments of our filter unit, it may be readily and easily primed or filled without entrapping gas bubbles and filtered blood may be drained from the unit so there is very little blood held-up or retained in the unit and substantially all the blood is available to the patient. In other embodiments of our filtration unit administration sets are easily insertable into the filtered blood outlet in a manner that ensures a uniform flow rate and reduces the possibility of entrapment of micro-gas bubbles by the filtered blood stream. Our blood filtration unit may be used for multiple administration of units of blood and is economical.

In one embodiment of the blood filtration unit the blood inlet extends into the drip chamber at its one end and is diagonally cut at its opposite end for easy insertion into a blood reservoir such as a bag of blood. In use, blood flows from the blood bag to the drip chamber, down through the spaces around the multipointed filter cartridge which serve as filtration compartments, through the filter element into the hollow centre core and out through the blood outlet in the bottom end member.

According to the present invention we provide apparatus for use in blood transfusions, which comprises a housing having a drip chamber in an upper portion thereof and adapted to have a blood filter element fitted into the housing downstream of the drip chamber, the drip chamber having an opening in its side wall for the passage of air into or out of the drip chamber, an air valve for closing the opening and an air filter element surrounding the opening and positioned adjacent the valve whereby when the valve is opened air passing through the valve also passes through the air filter element. Preferably the valve comprises a resilient member deformable to open the valve, said member extending through said side wall opening and normally sealing the inside of the wall to an inner part of the resilient member, the air filter element being annular and disposed between said wall and a part of the resilient member outside said wall.

The filtered air valve is placed in the side wall of the drip chamber so the unit may be readily primed and filled and entrapped gas evacuated. When the blood bag is emptied, the valve may be opened and the filtration unit drained to allow administration of substantially all of the filtered blood. When the air valve is opened, the incoming air is filtered.

In certain embodiments of the blood filtration unit of Patent Specification No. ifthe blood outlet has a shoulder on its inlet side. The inside diameter of the outlet measured at this shoulder is the same as the inside diameter of the tubing of the administration set to be used with the unit to administer blood to a patient. This construction reduces the possibility of micro-gas emboli being entrapped in the area where the blood outlet and the administration set meet. This construction also provides for a uniform and constant flow rate of blood to the patient.

The invention will be further described in conjunction with the accompanying drawings wherein:Figure 1 is an exploded view in perspective showing the assembly of the various parts of an apparatus for use in blood transfusion^ Figure 2 is a cross-sectional view of the apparatus j Figure 3 is an enlarged cross-sectional view of an air valve incorporating a filter in accordance with the present invention with the valve in the closed position; Figure 4 is an enlarged, cross-sectional view of the air vent valve shown in Figure 3 with the valve in the open position? and Figure 5 is a cross-sectional view taken along line -5 of Figure 3.

The same numeral has been used for similar parts throughout the Figures.

Referring to the drawings in Figure 1, there is shown an apparatus for use in blood transfusion. At the top of the apparatus is the blood inlet 11. One end 12 of the blood inlet is tapered or diagonally cut for easy insertion into a reservoir of blood such as a plastics blood bag commonly in use. The blood bag contains a weakened portion, circular in shape, and the tapered spike-like inlet is readily insertable into this weakened portion. The opposite end of the blood inlet extends into the drip chamber 13 which is at the top of the housing 14 of the unit. As may be more clearly seen in Figure 2, the extension 15 into the drip chamber 13 allows blood to drip into the unit and the number of drops may be counted and metered as desired. The height of the drip chamber should be as small as possible to reduce the impact force of the blood droplets on the distribution surface and minimize the blood-air interface contact time in order to reduce blood trauma.

Disposed in the side wall of the drip chamber is an air valve 17. The valve is more clearly shown in Figures 3, 4 and 5. The valve comprises a resilient member 18 which extends through a hole 19 in the wall 20 of the drip chamber and expands outwardly to seal along the inside surface of the wall. On the outside surface of the wall and around the entry hole is a circular ledge 21. An annular shaped filter element 22 is positioned within the circular ledge. One end of the element contacts the wall surface and the other end contacts the resilient member.

The circular ledge has an opening 23 to allow air to escape or enter through the valve. When the apparatus unit is to be filled from a blood bag the resilient member is pushed in as shown in Figure 4, allowing air within the apparatus to escape out through the hole 19 and the opening in the circular ledge. A number of stops 24 are disposed about the hole 19 to prevent sealing of the hole when pushing in the resilient member. When the apparatus is filled to a desired level with blood, the valve is released and automatically closes. To drain the apparatus after the blood bag has been emptied, the valve is pressed inwardly to allow air to enter the apparatus and allow the apparatus to drain. The air entering the apparatus is filtered through the annular filter element.

The filter cartridge itself comprises annular filter element 25 comprising filter material, a top end cap 26 and a bottom member 27. The top end cap is solid and multi pointed or star-shaped. It is preferred that the end cap have from four to ten points to produce between four and ten segmental filter compartment areas in the caftridge. The 5 element 25 is in the form of an elongated member having a hollow centre core. Its cross-sectional shape is the same as the multipoint shape of the top end cap. If desired, a permeable centre core 28 may be disposed in the element 25 for structural purposes and such a core may be wrapped with an additional fine filter medium to aid in the filtration as desired. One end of the element 25 is sealed by the top end cap and the other end of the element 25 is sealed into the bottom member. The outer periphery 29 of the bottom member 27 is attachable to the housing 14. The bottom member contains a centrally located outlet 30 which communicates with the centre core of the medium at one end the other end 31 being adaptable to connect with various types of administration sets or administration set tubing.

In one embodiment the blood outlet is constructed as shown in Figure 2. Within the blood outlet 30 there is a small shoulder 33. The inside diameter of this shoulder is exactly the same as the inside diameter of the tubing 34 of the administration set to be used. The tubing is inserted in the downstream end of the outlet up against the shoulder. If desired, the tubing may be adhered or bonded to the inside surface of the outlet. Also, if desired, the outlet may be slightly tapered to aid in insertion.

An advantage of this construction is that no air can be entrapped where the tubing and the blood outlet meet and - 8 41543 this eliminates the possibility of entrapping small air bubbles during administration of the blood. This configuration also provides a uniform diameter from the filter cartridge to the needle administering blood to the patient and a constant and uniform blood flow.

The housing of the apparatus may be made from any of the plastics materials which are inert and have no effect on blood. Examples of such materials are the polycarbonates and the butadiene-styrene copolymers. Similar materials may be used for the top end cap and the bottom end member. Generally, it is preferred to use clear materials for the housing.

The filter material of element 25 may be any of the various depth, semi-depth, or sieve type media or various combinations of these media. Suitable media are woven fabrics made from synthetic filaments, foam materials, and nonwoven fabrics. A preferred filter material for the transfusion of blood has as a first filter layer in the direction of blood flow a woven polyester fabric having a mean pore size opening of 160 to 180 microns and as the second filter layer a needle-punched nonwoven fabric of polyester fibres weighing about nine ounces per square yard.

The layers may be separated by an open plastics mesh material for support and stability. In some instances, a third filter layer may be used such as a woven nylon fabric having a mean pore size rating of about 20 microns. This last-mentioned layer is used to prevent lint or fibres which may slough off or be removed from the nonwoven fabric layer from entering the bloodstream. If desired this said last- 9 mentioned layer may be wrapped around a supporting core to act in the way described.

The air valve is made from resilient material which is inert to blood such as natural, synthetic or silicone 5 rubber. The valve is resiliently deformable and provides a good seal with the material from which the housing is made. The air filter element used with the valve may be any of the standard air filtration materials such as a needle-punched polyester or other synthetic fiber batts.

Claims (2)

1. CLAIMS:1. Apparatus for use in blood transfusion, which comprises a housing having a drip chamber in an upper portion thereof and adapted to have a blood filter element 5 fitted into the housing downstream of the drip chamber, the drip chamber having an opening in its side wall for the passage of air into or out of the drip chamber, an air valve for closing the opening and an air filter element surrounding the opening and positioned adjacent the valve 10 whereby when the valve is opened air passing through the valve also passes through the air filter element.

2. Apparatus according to claim 1, wherein the valve comprises a resilient member deformable to open the valve, said member extending through said side wall opening and 15 normally sealing the inside of the wall to an inner part of the resilient member, the air filter element being annular and disposed between said wall and a part of the resilient member outside said wall.