BLOOD BAG

Abstract: Plastics walls (12) of a blood bag (B) have rough outer surfaces. In order to enable a light beam to be passed through the bag for nonivasively monitoring the contents of the bag, optically clear plastics tablets (16) are bonded to the bag walls in alignment with one another. The tablets also provide means for accurately locating the bag in alignment with an optical system of a monitoring device.

Description: BLOOD BAG It is now conventional for blood components, such as concentrates of blood platelets in plasma to be stored in, and administered to patients from, a flexible bag of generally rectangular shape, .formed between two sheets of plastics material which are welded together to provide a comparatively broad seam around their edges. Various holes and slits are formed in this seam for use in supporting the bag at various stages of use. A number of tubes extend through the seam at a nominal top of the bag to provide plumbing connections to the interior of the bag. A recently developed technique of monitoring non-invasively the viability of blood platelets in a sealed pack is described in EP-A-0141632 (and Japanese published patent application No. 60-113153). That technique involves passing a beam of light through the pack and depends on collecting light transmitted through the pack as a result of scattering by the platelets. When this technique is applied to platelets in a conventional bag of the kind referred to above, appreciable scattering of the light occurs owing to the roughness of the outer surfaces of the plastics walls of the bag and this obscures to a large extent the light transmitted through the bag. The surface of the plastics material from which the bag walls are made is rough or textured to avoid adjacent bags sticking together during manufacture. Roughness on the inner surfaces of the bag walls is unimportant as these surfaces are wholly wetted by the blood plasma. However roughness of the outer surfaces of the bag walls remains a problem which it is the object of the invention to alleviate. In accordance with the present invention, in a blood bag of the kind comprising two walls which are formed by sheets of plastics material sealed together around their edges, at least the outer surfaces of the walls being rough; each of the walls is provided, at least on its outer surface, with means for providing, in use, an optically clear window opposite to that in the other wall. A bag of this construction may be used in the monitoring technique referred to above by positioning the bag so that the beam of light is passed through the two windows. The scattering which occurs will then be dependent almost entirely on the platelets in the bag and therefore on the parameter being monitored. The optically clear windows may extend fully between both surfaces of the bag walls such that they would exist irrespective of any contents in the bag. However, as explained above, liquid such as blood plasma in the bag will fully wet the inner surface of the bag so that no means * need be provided in general for producing an optically clear window at the inner surfaces of the bag walls. There are a number of ways in which the windows may be provided. For example, the outer surface of each bag wall may be touched, during manufacture, with a hot flat surface to provide a smooth shield ■ surrounded by the rough surface of the rest of the bag wall. An alternative solution involves sticking an optically clear member to the outer surface of each bag wall. The member may be a patch of optically clear self adhesive tape, provided that the adhesive is also optically clear. There may however be difficulties in applying the patch accurately in the required position, unless the patch is so large that it covers a large proportion of the surface area of the bag wall, with the disadvantage of inhibiting oxygen diffusion through the wall into the bag for nourishing the platelets. Alternatively, the member may be a comparatively rigid tablet of, for example, clear plastics material, which is heat sealed to the bag wall during manufacture of the bag, or stuck to the outer surface of the wall of the finished bag by means of a contact adhesive, which must also be optically clear and biocompatible in case of leaching of components of the adhesive through the normally permeable wall into the contents. An advantage of providing, on the outer surface of each bag wall, a comparatively rigid member is that the members may be applied to the bag more accurately in position, for example using a jig. A second advantage of using comparatively rigid members is that they may be used for locating the bag accurately in a monitoring device so that the windows provided by the tablets are aligned with an optical system for passing a beam of light through the windows and through the contents in the bag. The invention will now be described by way of example with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a blood bag; Figure 2 is a diagrammatic central cross section through the bag; Figure 3 is a section through a window tablet taken on the line III-III in Figure 2; Figure 4 is a perspective view of a reel of window tablets; Figures 5A, 5B and 5C are perpsective views of an applicator showing successive stages in the application of window tablets to a bag; Figure 6 is a longitudinal cross section through tongs for use with the bag; Figure 7 is a perspective view showing the tongs in association with a bag; and. Figure 8 is a diagrammatic perspective view showing how the tongs are used to locate a bag in a monitoring device. As shown in Figure 1, a conventional blood bag B is formed from two sheets 12 of biocompatible plastics material, which are heat welded or otherwise sealed together around their edges to form a seam 13. Conventional plumbing 14 leads through the top of the seam. A slit 15 is formed in the seam 13 at the bottom of the bag, for use in hanging the bag during clinical dispensing of contents of the bag. The bag walls 12 are comparatively opaque, owing primarily to the outer surface of the walls being rough. Aligned windows are provided through the walls, adjacent to the bottom of the bag, by means, in each case, of a rigid transparent moulded plastics tablet 16 which is bonded to the outer wall surface by means of an optically clear biocompatible adhesive layer 17. As shown in Figure 3, each tablet 16 has a flat inner surface 18 for bonding to the bag wall, and an outer surface with a recessed window portion 19 bounded at each end of the tablet by a raised portion 20, which is chamfered at 21 to avoid obstruction when the bag and tablets are subsequently inserted laterally into the monitoring device shown in Figure 8. The window portion 19 is recessed to avoid scratching of the window surface during handling, or during insertion of the bag into the monitoring device. Each tablet is substantially rectangular in face view and symmetrical about central longitudinal and transverse planes. The tablets are supplied in a reel on a backing release strip 22, as shown in Figure 4 and are peeled off the backing strip to expose the adhesive by drawing the strip under tension over a bar 23. . The tablets are then stuck to the bag walls in precisely correct, mutually aligned positions, by means of the applicator shown in Figures 5. The applicator comprises a base plate 24 with hinge mountings 25 for a pair of plates 26 and 27 which are thus pivotable towards and away from one another and through substantially 180° relatively to the base 24. The base plate is formed with upstanding anvils 28 and 29, the plates 26 and 27 are provided with aligned rectangular openings 30; and the plate 26 is formed with an upstanding rib 31 with a complementary slot 32 in the plate 27. In order to attach the tablets to a bag, the bag is located on the plate 26 with its slit 15 engaging the rib 31, as shown in Figure 5A. The plate 27 is then closed downwards onto the top of the bag B and plate 26 whereupon a tablet 16, which has been taken from the strip 22 is inserted through the hole 30 in the plate 27 and pressed into bonding engagement with the upper wall of the bag, as shown in Figure 5B. At this time the anvil 28 projects through the opening 30 in the plate 26 to provide a support for the bag. The two plates 26 and 27 are then swung over to the position shown in Figure 5C and another tablet 16 is inserted through the opening 30 in the plate 26 and pressed into bonding engagement with the other wall of the bag B. At this time the anvil 29 acts as a support to prevent the previously applied tablet from being pushed down through the opening in the plate 27. In addition to providing optically clear windows through the walls of the bag B, the tablets 16 provide means for locating the bag accurately in the monitoring device of Figure 8. For this purpose the bag is used in association with tongs T, as shown in Figures 6 to 8. The tongs comprise a pair of mutually flexible jaws 33, each of which is provided adjacent to its free end with a rectangular opening 34, which can receive one of the tablets 16 as a close fit. Each jaw also has on its outer surface an elongate rib 35 and buttons 36, one on each side of the respective rib 35. The bag is inserted between the jaws of the tongs, as shown in Figure 7, and the jaws are ■ slightly closed together to cause the tablets 16 to enter the openings 34. The monitoring device has a plurality of pairs of plates, each pair comprising a fixed plate 37 and a movable plate 38. In Figure 8 the plates of one pair are shown an exaggerated spacing apart for clarity of description. Each plate has an open ' ended slot 39 and the slot 39 in the plate 38 has, in its sides, a pair of notches 40. The bag is offered up to the gap between the plates by holding the top of the bag with one hand and squeezing the jaws of the tongs together with the other hand of the operator. The ribs 35 are then inserted into the slots 40 and the squeezing pressure on the jaws released so that the buttons 36 enter the notches 40. At the same time the top of the bag slides behind a clip 41 along the top of the plate 37. The bag B is then securely located between the plates in a precise upright position, which is ensured by the non circular shape of the tablets, with the windows, provided by the tablets, in alignment with an optical system, consisting of a light emitting diode 42 carried by the plate 38, and an opposed photodiode 43, carried by the plate 37. When the moving plate 38 is closed towards . the fixed plate 37, L-shaped projecting rubber ribs 44 on the plates squeeze the bag B between them along a corresponding seal line 44', and separate the interior of the bag into two parts 45 and 46 as shown in Figure 1. The seal line stops short of the bottom of the bag, leaving a channel 47 connecting the two parts 45 and 46. The windows, provided by . the tablets 16 are aligned with this channel 47. A presser 48, which is continually moved to and fro through an operating window 49 in the plate 38, then periodically squeezes the part 45 of the bag against the plate 37 with a frequency of about 2Hz and causes the contents of the bag to move through the channel 47 between the two windows into the part 46. When the squeezing is released, the contents flow back again into the part 45 under the differential hydrostatic pressure across the channel 47. This is indicated by the arrows in Figure 1. Optical readings are then taken in dependence upon a • light transmitted through the bag contents as described in the earlier patent specifications referred to above. Although the invention has been described in the context of a blood bag for a concentrate of blood platelets in plasma, the bag may be used for containing other blood components, where monitoring of the contents by passage of light is necessary.

Claims: CLAIMS 1. A blood bag (B) of the kind comprising two walls (12), which are formed by sheets of plastics material sealed together along their edges, at least the outer surfaces of the walls being rough; each of the walls being provided, at least on its outer surface, with means (16) for providing, in use, an optically clear window opposite to that in the other wall. 2. A bag according to claim 1, wherein each window is provided by a smooth heat formed shield on the outer surface of the respective bag wall, the shield being surrounded by the rough surface of the rest of the bag wall. 3. A bag according to claim 1, wherein each window is provided by an optically clear member (16) bonded to the outer surface of the respective bag wall. 4. A bag according to claim 3, wherein the optically clear member is a comparatively rigid tablet (16) which is arranged, in use, to locate the bag in a monitoring device with the tablets aligned with an optical system for passing a beam of light through the tablets and through contacts in the bag. ' 5. A bag according to claim 4, wherein the tablet is of a clear plastics material which is heat sealed to the respective bag wall. 6. A bag according to claim 3 or claim 4, wherein the optically clear member (16) is bonded to the respective bag wall by an adhesive (17) which is also optically clear and biocompatible.

Inventors: BELLHOUSE BRIAN JOHN, PUGH SYDNEY MERVYN, BELLHOUSE, BRIAN, JOHN, PUGH, SYDNEY, MERVYN
Applicants: BELLHOUSE MED PROD LTD, BELLHOUSE MEDICAL PRODUCTS LIMITED
Application year: 1985
Main classification: A61J1
IPC codes: A61J1, G01N21