WO2001083004A1

WO2001083004A1 - Method and apparatus for dosage of an additive while collecting a liquid

Info

Publication number: WO2001083004A1
Application number: PCT/SE2001/000870
Authority: WO
Inventors: Erik Öhlin; Per Olsson
Original assignee: Bst Blood Saving Technologies Ab
Priority date: 2000-04-28
Filing date: 2001-04-24
Publication date: 2001-11-08
Also published as: AU2001256890A1; SE0001542L; SE0001542D0; SE515605C2

Abstract

The invention relates to a method and an apparatus for collecting and transporting liquids, for instance blood, while at the same time dosing an additive, for instance an anticoagulent agent, in an accurate proportion to the amount of the collected liquid. The liquid or a liquid/air/gas mixture is sucked up by means of a suction nozzle (4) and transported through a suction hose (5). A dosage device (6) comprising an exchangeable, flexible container (23) with said dosing additive, for instance a CPD bag, is connected to the suction hose whereby the pressure levels in the apparatus, provided by connecting the apparatus to a vacuum pump (1), are adjusted in such a way relative to each other that no additive at all is introduced when only air/gas is sucked up in the suction nozzle, whereas dosing additive is introduced into the suction hose (5) as soon as liquid is sucked through the suction nozzle (4) so that the amount of dosage additive is in proportion to the amount of sucked liquid. The invention is characterized by connecting the positive pressure side (30) of the suction source (1) to a pressure bag (31) in order to apply the necessary pressure on the CPD-bag (23), for dosing as soon as liquid has been sucked up by the suction nozzle (4).

Description

Method and apparatus for dosage of an additive while collecting a liquid

^■ .-. nrpsgη inwon-t- .nn roT a oa -J-ri -=» irn-vf- H<-»rf artrt ΛΠ annara πc- for σθl l sσ+* i^rvσ aπ^ 3ⁿSDO'"*' i If l ϊ nπ-ϊ lβ. --.£ war . nija πoa while at the same time dosing an additive in an accurate proportion to the amount of the collected liquid. The invention is specifically useful for handling of blood in connection with a surgical operation, but it can also be used when handling other types of liquids which may be easily damaged, oxidized etc. under the influence of air, gas or the like, for example food stuff liquids, liquids which are corrosive or hazardous to the environment, such as oils, spillage liquids etc.

As the invention has been developed particularly in connection with the handling of blood, in the following it will mainly be described in connection with such handling.

There is always a short supply of blood and large amounts of blood are needed and used for blood transfusions, for instance in connection with surgical operations. Blood is a . ery expensive product, both with respect to the cost for collecting, but also with respect to the costs for testing and storing. During blood transfusions there is also a risque of transfer of jaundice, HIV infection and other diseases. In connection with a surgical operation the patient may lose large quantities of blood. This blood is normally wasted and the patient has to receive the cor- responding amount of blood through transfusions, sometimes as much as several litres.

In order to solve the problem with blood supply it has been previously proposed to collect and intra operatively provide the patient with as much of his own blood as possible from the operation. Such autologous blood collecting devices are previously described in SE 467 725 and EP 0 742 737. According to these devices blood from the surgi- cal operation is continuously sucked up by means of a suction hose and an anticoagulent agent is automatically added in proportion to the amount of sucked up blood. The blood is then caused, in a closed system, to pass suitable defoaming and separation filters and recipients to allow air bubbles included in the blood as well as undesirable particles to be separated from the blood. The blood is then collected in bottles or flexible bags entirely without any admixture of air or any other gas by means of a certain sub-pressure in the system. A suitable sub-pressure in the system can be achieved by connection to a negative pressure source, such as a vacuum pump.

The dosing of the anticoagulent agent is effectuated be- fore the blood has reached the defoaming and filtering units . The dosage device is arranged to introduce the additive in an accurate proportion to the amount of the collected (sucked up) blood. This is achieved by providing a certain sub-pressure at different negative pressure levels to the dosage device and the suction nozzle for collecting the liquid. The pressure gradient between these different pressure levels is adjusted in such a way that no additive at all is introduced when there is no liquid (blood) in the suction nozzle, whereas the amount of dosage medium is almost completely in proportion to the amount of sucked liquid when liquid is sucked through the suction nozzle. According to SE 467 725 the dosage device is mounted on a higher level (N) than the suction nozzle and the filter. This level must be adjusted to a preset pressure gradient so that there is a balance between the pressure gradient and the flow resistance in the hose or connection tube between the dosage device with the suction nozzle on one side and the gravitational force which tends to have the liquid column in the connection hose -to flow down into the suction hose on the other side. This requires some kind of mechanism for raising and lowering the dosage device which has been a disadvantage for this types of machines. Some other examples of similar dosage device arrangements are described in EP 0 742 737. However, also in these cases a mechanism is required which can be raised and lowered for the dosage adjustment. The dosage device preferably comprises a flexible container or bag for the anticoagula- tion agent, a so-called CPD-bag, which is enclosed in a stiff casing as illustrated in figure 1 in the EP patent. The container bag is subjected to a sub pressure corresponding to a pressure gradient P2-P3. Alternatively, in the embodiment shown in figure 5, "dosing unit E - outer system", the bag 20" is subjected to atmospheric pressure or under a pressure provided by a load 58. The container bag is mounted on a plate which can be raised and lowered. So also in this case a mechanical adjustment is required when the apparatus is used.

As an adequate and accurate dosing of the additive is very important, particularly in a blood collecting system, it is a disadvantage to have to rely on mechanical adjustment means of the previous type. As blood collecting machines might be mobile, there is also a risque that an adequate adjustment is disturbed when the machine is moved.

It is an object of this invention to solve the problems which have been described above and provide an automatic and accurate dosing of an additive to a sucked up liquid (blood), without mechanical adjustment means and without the use of the gravitational force, which has been the case in the prior platforms or container bags for addi- tives arranged to be raised or lowered.

According to the invention this is achieved by using a separate suction source, for instance a vacuum pump, for sucking the liquid as well as introducing the dosage medi- urn. Then the negative pressure side of the suction source is connected to the liquid collecting system (suction nozzle, blood collecting bags), while the positive pressure side of the suction source is connected to the dosage de- vice in order to apply the necessary pressure on the flexible dosage container, for instance a CPD-bag, for introducing the dosage medium as soon as liquid has been sucked up by the suction nozzle.

According to a preferred embodiment the dosage device comprises a pressure bag, "bellow bag", to which a controlled pressure from the pressure side of the suction source is applied.

In the following the invention will be described more in detail with respect to the accompanying drawings, where

figure 1 shows schematically in the form of a flow chart a blood collecting system for a surgical operation,

figure 2 also shows schematically, but more in detail, the initial situation when applying a pressure on the dosage container in the form of a CPD bag by means of a pressure bag,

figure 3 shows the situation after that pressure has been applied and the CPD bag has been almost drained,

figure 4 is a side view of the dosage box with a cover lid, and

figure 5 shows schematically a pressure container for applying a pressure directly on a dosage container in the form of a CPD bag when placed in the pressure container.

The blood collecting system according to figure 1 comprises a number of main parts which are operating with a certain predetermined pressure gradient in order to provide a sub-pressure (suction) in the system. The system comprises a vacuum pump 1 for creating a suitable sub-pressure. The sucking capacity of the pump could be approximately 2000 ml blood per minute, and the pump is preferably adjustable for different pressure levels by control means 2. As is well-known in the art, the pump has a suction side and a pressure side. The suction side of the pump is primarily connected to the system to provide the required sub-pres- sure in the system similar to the apparatus illustrated in EP 0 742 737. The pump is connected to the different parts in the system by means of a tube- or hose arrangement with valves, manometer and other pressure indicator means 3 which are known per se and therefore will not be described in any detail here.

The system comprises the following main parts: a suction nozzle 4 for sucking up blood at atmospheric pressure, a suction hose 5 connected to a unit 6 for dosing an agent in the form of an anticoagulent, a mixing and defoaming unit (mixer) 7 for admixing of the dosing agent into the blood and separating the foam from the blood, a recipient 8 in the form of a canister bag 9 disposed in a stiff casing 10, and two transfer bags 11, 12 for an automatic col- lection of the blood.

This invention is specifically related to the dosing unit 6 so the other parts in the system will not be described in any detail here. With respect to these parts it is also generally referred to the above-mentioned patent publications SE 467 725 and EP 0 742 737.

As already mentioned, the dosing unit 6 is connected to the suction hose 5 at the inlet end of the mixer 7. The connection conduit is provided with a control and back valve arrangement with a drop chamber 13 for introducing the anticoagulent in accurate proportional , for instance 5-15%, to the amount of liquid. The basic level is adjustable and said proportional preset by using a specific can- nula in the system or by means of the control valve.

The blood is sucked up by means of the suction nozzle 4 which has a finger hole 14, and transferred via said sue- tion hose 5 to the mixer which could be of the type shown in EP 0 742 737. The mixer has a mixing hose 15 which has a larger diameter than the suction hose 5 and whicl is rotated in the known way for admixing the dosing anticoagu- lent agent with the blood and separating air bubbles from the blood.

The centrifugated blood is then sucked via a filter arrangement 16, which in this case comprises a filter 17 with a mask size of approximately 150-250 μm and a fine filter 18 with a mask size of approximately 30-40 μm, and collected in the canister bag 9 which may have a volume of about 2000 ml. A photo optical sensor Si indicates when the collected blood has reached a volume of approximately 700 ml. Then a magnet valve 19 opens and approximately 500 ml blood is allowed to flow into the transfer bag 11. When this bag is full a sensor S2 gives a signal to the control panel of the system for opening of the magnet valve 20 and closing the magnet valve 19. Also the hose valve 42 is closed and instead the hose valve 43 is opened for filling of the transfer bag 12. When also this bag is full this is indicated by light or alarm signals in the same way by means of a sensor S3. The suction system can be used without interruption during the exchange of the transfer bags as the canister bag 9 has an extra capacity of minimum 1300 ml. Of course the transfer bags can be exchanged several times which makes the capacity of the apparatus substantially unlimited.

Another photo optical sensor S4 in the recipient 8 indicates a certain minimum level in the canister bag 9. The canister bag 9 and the passage of the blood to the transfer bags 11 and 12 are described more in detail in our parallell patent application PCT/SE01/00868.

The apparatus blood flow passageways - such as suction nozzle, suction hose, mixer hose, filter arrangement and transfer system - has a layer of a blood compatible mate- rial as known in the art.

The dosing unit 6 comprises a holder or box 27 with a stiff casing 21 and with an inner spacing 22 for a CPD bag or another flexible container from which the anticoagulent is supplied to the suction hose 5 , see figure 2 and 3. The anticoagulent is supplied through a connection conduit 24 which is connected to the filled CPD bag 23 and the suction hose 5. The holder or box 27 can be mounted on the outside of the apparatus so that it is easily accessible when changing CPD bag. The holder or box has a swing-lid 25 with snap-in locking means 28 for opening and closing the holder or box when changing CPD bags, see figure 4. The dosing unit is connected to the vacuum pump 1 via a hose system 29, 30.

As mentioned in the introductory portion it is important that the anticoagulent is dosed continuously and in an accurate proportional to the sucked up blood. When the appa- ratus is sucking only an air/gas-mixture the pressure in the suction hose is higher than the pressure in the dosing unit 6 which prevents the dosing agent to flow from the bag into the mixer hose. As soon as a liquid is sucked up through the suction hose the dosing agent supply should no more be prevented. In this situation the pressure in the suction hose is substantially reduced as the sucked up liquid stops air from flowing in and the pressure difference is so small that the dosing agent can be arranged to flow down through the connection conduit 24. Previously this has been achieved by means of the gravity force. According to the invention the vacuum pump 1 is used for this purpose. By connecting the dosing container to the pressure side of the vacuum pump a sufficient hydrostati- cal pressure is obtained to allow dosing agent supply.

According to a preferred embodiment the pressure is applied through a pressure bag 31 which is also placed in the dosing container or box and connected to the vacuum pump by a hose system 29,30. The hose 29 is connected to the suction side of the vacuum pump and the hose 30 is connected to the pressure side of the pump. The pressure bag is preferably placed beside the filled bag 23, as il- lustrated in figure 2. The two bags are orientated vertically, side by side, with the pressure bag located in the innermost position, as illustrated in figures 2 and 3, preferably fixed by means of resilient bands or any other type of attaching means 32 to rest with one side against the inner wall of the box, so that it is remained in the apparatus (box), but free to expand against the CPD bag when subjected to a pressure. The pressure bag then functions according to the "bellows principle". When connected to the suction side of the vacuum pump (hose 29), due to the sub-pressure, the bag 31 is pressed together against the wall of the box as illustrated in figure 2. This is the initial situation in which a filled CPD bag is disposed in the box beside the empty and by the sub-pressure flattened out pressure bag so that this bag is pressed against the inner wall of the box. In this position, instead the pressure side of the vacuum pump is connected to the pressure bag 31 so that the bag is subjected to a pressure which in this case can be around 20 mbar. The bag is filled up and then provides a pressure on the filled CPD bag, as illustrated in figure 3. This pressure is sufficient to allow the dosing agent to flow into the suction hose 5 as soon as the liquid (blood) is sucked into the suction nozzle. The flow is related to the actual, non- balanced pressure gradient between the suction hose and the dosing container. However, the pressure is low enough to prevent the dosing agent to be supplied if the suction nozzle is sucking air/gas only. Also, the pressure can be adjusted by control means 33 in the pressure hose 30. In order to reduce possible sound effects due to pressure variations in the system, sound absorbing means 44 are arranged on the pressure side. The connecting suction hose arrangement comprises a nozzle valve 45 and a safety valve 46. The switching from suction function to pressure function can be effectuated mechanically by means of suitable switching means in the hose 29, for instance by means of a hose clip 34 that chokes the suction function so that the pressure through the conduit 30 instead is allowed to act upon the pressure bag. This has been indicated by a constriction of the hose in figure 1. In figures 2 and 3 the hose clip is shown open and closed, respectively. As an alternative the lid 25 of the box can be arranged to squeeze and choke the hose 29 into the box when the lid is closed, after a new CPD bag is on place. A standard CPD bag is normally sufficient for 2,5 liter of blood.

A sensor S5 indicates when the amount of dosing anticoagulent in the bag has reached a certain minimum level, i.e. when the bag is almost empty, for instance when there is only 5% left in the bag (30-40 ml). The sensor can also be arranged to give alarm if there is no bag in the contain- er. The sensor and contacting means can be of different types, preferably in the form of a spring-loaded switch which is actuated by the pressure bag, when this bag has expanded to a predetermined position, as indicated by reference numeral 35 in figure 3. For this reason the pres- sure bag can be provided with a band, plate or the like which actuates a switch when it has reached its end position 35 for the expansion. In this way a more distinct contact function is achieved.

According to an alternative embodiment the holder or box 27 can be made as a closed container or can 36, a pressure chamber, having a lid and a spacing for a filled CPD bag, see figure 5. In this case the pressure is applied directly into the container or can so that there is an overpres- sure on the filled CPD bag which allows the dosing agent to flow down into the suction hose 5 in the same way as in the first embodiment. The lid 37 is preferably made as a unit with a peripheral sealing ring 38 for contact against the wall of the pressure container and a central bushing 39 with a hose system having one end in the form of a spike 40 connected to the CPD bag and another end 41 connected to the connection conduit 24.

The invention is not limited to the examples which have been illustrated in the figures, but can be varied within the scope of the accompanying claims.

Claims

1. Method for collecting and transporting liquids, for example blood, while at the same time dosing an additive in an accurate proportion to the amount of the collected liquid, whereby the liquid or a liquid/air/gas mixture is sucked up by means of a suction nozzle (4) and transported through a suction hose (5) and that a dosage device (6) comprising an exchangeable, flexible container (23) with said dosing additive is connected to the suction hose and whereby the pressure levels in the system, provided by connecting the system to a suction source ( 1 ) , are ad usted in such a way relative to each other that no additive at all is introduced when only air/gas is sucked up in the suction nozzle, whereas dosing additive is introduced into the suction hose as soon as liquid is sucked through the suction nozzle so that the amount of dosage additive is in proportion to the amount of sucked liquid c h a r a c t e r i z e by connecting the positive pressure side (30) of the suction source (1) to the dosage device (6) in order to apply the necessary -pressure on the flexible dosage container (23), for instance a CPD-bag, for introducing the dosage additive as soon as liquid has been sucked up by the suction nozzle (4).

2. Method according to claim I c har a c t e r i z e d by connecting the positive pressure side (30) of the suction source (1) to a pressure bag (31) arranged in the dosage device (6), -which pressure bag applies said pres- sure on the flexible dosage container (23) nf en dosing the dosing additive.

3. Method acording to claim 1 c h ara ct e r i z ed by connecting the positive pressure side ( 3ϋ ) of the suc- tion source (I) to a tight container, a pressure chamber, τ(36) rπanged in the dosage device (6), which pressure chamber applies said pressure on a dosage container (23) arranged in the pressure chamber for dosing the dosing ad- ditive .

4. Method according to claim 2 c h a r a c t e r i z e d by connecting the negative pressure side, suction side (29) , of the suction source (1) to the pressure bag (31) before the dosing in order to allow a filled dosage bag (23) to be disposed in a holder or box (27) beside the empty and by the sub-pressure flattened out pressure bag (31).

5. Method according to claim 4 c h a r a c t e r i z e d by switching to the pressure side (30) of the suction source (1) by choking the suction hose connection (29), for instance by means of a hose clip (34).

6. Method according to claim 4 c h a r a c t e ri z e d by switching to the pressure side (30) of the suction source by choking the suction hose connection (29) by means of the lid (25) of the holder or box (27) for the dosing additive when the lid is closed after a filled dosing bag has been placed in the holder or box.

7. Method according to claim 1 c h a r a c t e r i z e d by providing the connection conduit (24) to the—suction hose (5) with a control valve (13) for introducing the amount of dosing additive in an accurate proportional to the amount of liquid.

8. Method according to claim 1 c h a r a c t e r i z e d by adjusting the pressure on the pressure side (30) of the suction source (1) by control means (33).

9. Apparatus for collecting and transporting liquids, for example blood, while at the same time dosing an additive in an accurate proportion to the amount of the collected liquid, comprising a suction nozzle (4) for sucking up the liquid or a liquid/air/gas mixture, a suction hose (5) for transporting the sucked up liquid and a dosage device (6) connected to said suction hose (5) comprising an exchangeable, flexible container (23) with said dosing additive whereby the pressure levels in the apparatus are provided by a suction source ( 1) connected to the apparatus and ad- justed in such a way relative to each other that no additive at all is introduced when only air/gas is sucked up in the suction nozzle, whereas dosing additive is introduced into the suction hose (5) as soon as liquicl is sucked through the suction nozzle (4) so that the amount of dosage additive is in proportion to the amount of sucked liquid c h a r a c t e r i z e d i n that the positive pressure side (30) of the suction source (1) is connected to the dosage device (6) in order to apply the necessary pressure on the flexible dosage container (23), for instance a CPD-bag, for introducing the dosage additive as soon as liquid has been sucked up by the suction nozzle (4).

10. Apparatus according to claim 9 c h ar ac te r - i z e d i n that the positive pressure side (30) of the suction source (1) is connected to a pressure bag (31) arranged in the dosage device (6) , which pressure bag is arranged to apply said pressure on the flexible dosage container (23) when dosing the additive.

11. Apparatus acording to claim 9 c harac ter i z e i that the positive pressure side (30) of the suction source (1) is connected to a tight container, a pressure chamber, (36) arranged in the dosage device (6) to apply said pressure on a dosage bag (23), arranged in the pressure chamber, for dosing the additive.

12. Apparatus according to claim 10 c har ac te r i z e d in that the negative pressure side, suction side (29), of the suction source (1) is connected to the pressure bag (31) before the dosing in order to allow a filled dosage bag (23) to be disposed in a holder or box (27) beside the empty and by the sub-pressure flattened out pres- sure bag (31) .

13. Apparatus according to claim 12 c har ac te ri z e d by switching means (34) arranged in the suction hose connection (29) for the dosage device (6) for switching between suction and pressure connection of the pressure bag (31).

14. Apparatus according to claim 13 c har ac te r- i z e d in that said switching means comprises a hose clip (34).

15. Apparatus according to claim 13 c h ar a c te r i z e d in that the lid (25) of the holder or box (27) for the dosing additive is arranged to squeeze and choke the suction connection hose (29) when the lid is closed, after a new dosing bag (23) has been placed in the holder or box.

16. Apparatus according to claim 9 c har ac te r i z e d by a control valve (13) for introducing the amount of dosing additive in an accurate proportional to the amount of sucked up liquid arranged in the connection conduit (24) from the dosage device (6) to the suction hose (5).

17. Apparatus according to claim 9 c har ac te ri z e d by control means (33) for adjusting the pressure on the dosage device (6) arranged on the pressure side (30) of the suction source (1).

18. Apparatus according to claim 9 c harac te r i z e d by a sensor (S5) arranged in the dosage device (6) for indicating when the amount of dosing additive in the flexible dosing bag has reached a certain minimum level, for instance when there is only 5% of the dosing liquid left.

19. Apparatus according to claim 18 c ha r ac te r i z e d i n that the sensor comprises switching means actuated by a band, plate or the like on the pressure bag (31) which actuates the switching means when the pressure bag has expanded to a predetermined end position (35) due to the applied pressure and a corresponding squeeze of the dosing bag (23).

20. Apparatus according to claim 9 c har ac te r- i z e d i n that, in case the liquid consists of blood, the apparatus blood flow passageways - such as suction nozzle, suction hose, mixer hose, filter arrangement and transfer system - has been coated with a layer of a blood compatible material.