Blood collection system and method

A blood collection system comprises a suction unit (11), a hose arrangement (12) connected to the suction unit, means for aspirating blood and air through the suction unit and for pumping said blood and air through the hose arrangement, a flow sensing unit (14) for continuously sensing the blood flow through the hose arrangement, an anticoagulant additive dosing system (15) for continuously dosing an anticoagulant additive into the blood flowed through the hose arrangement in response to the continuously sensed blood flow, a mixing unit (16) for mixing the blood with the anticoagulant additive dosed into the blood, and a collection vessel (17) for collecting the mixed blood and anticoagulant additive. The means for aspirating and pumping the blood and air is a pump system (13) providing a known constant volume flow of the blood and air in the hose arrangement, the flow sensing unit (14) is arranged for continuously sensing the mass flow of blood through the hose arrangement by means of continuously measuring a parameter indicative of the weight of blood in a tubing section (14a), through which the blood is transported, and the anticoagulant additive dosing system comprises a control unit (15d) connected to the flow sensing unit and arranged for automatically controlling the continuously dosing of an anticoagulant additive into the blood flowed through the hose arrangement in response to the continuously sensed mass flow of blood.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase under 35 U.S.C. §371 of PCT International Application No. PCT/SE2013/050845 which has an International filing date of Jul. 2, 2013, which claims priority to Swedish patent application number SE 1250769-5, filed on Jul. 5, 2012; the entire contents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to blood collection systems and methods.

DESCRIPTION OF RELATED ART AND BACKGROUND

In the health services organizations worldwide blood for homologous transfusion has always been and still is in short supply. Considerable amounts are used for transfusions on different indications, e.g., in connection to surgery on humans as mentioned above and in veterinary praxis. Blood is an expensive product due to the costs for collecting, testing and storing the same and the administration of the precise handling of the same. At homologous blood transfusions there is a risk of transferring detrimental diseases such as hepatitis, HIV infections, and different tropical diseases among others.

As an attempt to avoid the risks with homologous blood replacement, autologous blood transfusion has been suggested. In one autologous blood transfusion technique, the patient's own blood is collected during surgery from his surgical wound for a following re-transfusion of the “whole blood” when the patient will best need it. However, blood leaving the vascular bed will also get in contact with injured tissues forming the surgical wound's walls. This contact will activate the blood's coagulation.

When blood is sucked through a tubing system from a surgical wound into a blood collector the activation process will continue unless the internal surface of the tubing is blood compatible or until this process is stopped by an anticoagulant, such as a sodium citrate solution. Furthermore, it can not be avoided that air is also sucked into the system together with the blood. In fact much larger volumes of air are sucked than volumes of blood in the majority of the cases. The result is that almost all blood will pass through the system mixed with air as foam or froth until it has been defoamed.

It is important that the activation process resulting in polymerization or clot formation (coagulation) is stopped as early and complete as possible during that the blood is collected. This can only be achieved if an anticoagulant is added and mixed to the entire blood portion as early as possible during the blood collecting process. It should be noticed that the blood-air interface is not a blood compatible surface.

Beside blood and air the collected material may also contain non-desired tissue fragments from the surgical wound (clots, tissue fragments, fat, bone particles, etc.). These materials will also activate the same coagulation system during the blood collection process until the said system has been stopped (inactivated) by the added anticoagulant.

WO 01/14048 discloses a blood collection system comprising suction means for aspirating blood, a defoaming unit for defoaming the aspirated blood by virtue of subjecting the fluid to a G-force other than the force of gravity, a measuring device for in situ measuring the flow of the defoamed blood, a dosing means for dosing an additive, such as sodium citrate, into the blood at the output of the defoaming unit in dependence of preferably proportional to, the measured flow of the blood, a mixing unit for mixing the blood with the additive by virtue of subjecting the blood and the additive to a G-force other than the force of gravity, and a recipient for collecting the mixed blood and additive. The measuring device is an optical device arranged for measuring the amount of blood and the velocity of said amount, wherein the velocity is measured by recording the amount of blood in a first and in a second one-dimensional cross section of the tubing, located at different positions along the flow direction, at various times, and by correlating the recordings.

SUMMARY

While the technique disclosed in WO 01/14048 seems to take all requirements and limitations into consideration, it has failed in disclosing a measuring device for measuring the flow of blood sufficiently reliably, sufficiently fast, and sufficiently accurately to be used together with the dosing means for dosing the sodium citrate into the blood. Too often the amount of sodium citrate will be too high or too low, and sometimes, the measuring device is not capable to determine a blood flow at all.

Therefore, it is an object of the invention to provide a blood collection system and a blood collection method, by which a correct amount of anticoagulant additive, such as e.g. sodium citrate, always can be added to the blood at an early stage during blood collection.

It is a further object of the invention to provide such blood collection system and method, by which the blood flow can be established reliably, fast, and accurately.

It is yet a further object of the invention to such blood collection system and method, which are robust, easy, fast and flexible to set up and use, of small size, reliable, and of low cost.

Various aspects of the invention are found in the appended patent claims.

In one aspect a blood collection system is provided, which comprises a suction unit, a hose arrangement connected to the suction unit, means for aspirating blood and air through the suction unit and for pumping said blood and air through the hose arrangement, a flow sensing unit for continuously sensing the blood flow through the hose arrangement, an anticoagulant additive dosing system for continuously dosing an anticoagulant additive into the blood flowed through the hose arrangement in response to the continuously sensed blood flow, a mixing unit for mixing the blood with the anticoagulant additive dosed into the blood, and a collection vessel for collecting the mixed blood and anticoagulant additive.

The means for aspirating and pumping the blood and air is a pump system providing a known constant volume flow of the blood and air in the hose arrangement, the flow sensing unit is arranged for continuously sensing the mass flow of blood through the hose arrangement by means of continuously measuring a parameter indicative of the weight of blood in a tubing section, through which the blood is transported, and the anticoagulant additive dosing system comprises a control unit connected to the flow sensing unit and arranged for automatically controlling the continuously dosing of an anticoagulant additive into the blood flowed through the hose arrangement in response to the continuously sensed mass flow of blood.

The tubing section may be pivotably suspended and the flow sensing unit may comprise a weight sensing arrangement for continuously sensing the parameter indicative of the weight of blood in the pivotably suspended tubing section. Further, the tubing section may have two open ends in fluid communication with the hose arrangement, wherein the tubing section can be pivotably suspended at an inner end thereof, which comprises the two open ends. Still further, the pivotably suspended tubing section may comprise a U-shaped tubing section.

The weight sensing arrangement may comprises a cantilever provided with at least one strain gauge wherein the pivotably suspended tubing section is resting on the cantilever, e.g., about halfway between the inner end of the tubing section and an outer end thereof. In one version, the weight sensing arrangement comprises four strain gauges connected in a bridge, wherein two of the strain gauges are mounted on an upper side of the cantilever and two of the strain gauges are mounted on a lower side of the cantilever.

In another aspect a blood collection method is provided, which comprises the steps of: pumping blood and air through a hose arrangement; continuously sensing the blood flow through the hose arrangement; continuously dosing an anticoagulant additive into the blood flowed through the hose arrangement in response to the continuously sensed blood flow; mixing the blood with the anticoagulant additive dosed into the blood; and collecting the mixed blood and anticoagulant additive in a collection vessel. The blood and air are pumped through the hose arrangement by means of a pump system providing a known constant volume flow of the blood and air in the hose arrangement. The mass flow of blood through the hose arrangement is continuously sensed by means of continuously measuring a parameter indicative of the weight of blood in a tubing section, through which the blood is transported. Finally, the continuously dosing of an anticoagulant additive into the blood flowed through the hose arrangement is controlled in response to the continuously sensed mass flow of blood.

Advantages of the aspects above include the following:

The blood collection system and method may prevent activation of the coagulation of blood, add automatically adequate amounts of anticoagulant additive to the collected blood concomitant with the collection independent on whether the blood is mixed with air in a foam or not, mix the anticoagulant additive instantaneously, defoam and filter the collected blood, not deteriorate the blood quality, and be easy to operate and cost-efficient.

Collected blood can be transferred to blood storage units/traditional blood bags immediately ready for use or delayed re-transfusion.

Further, the blood collection system and method may collect blood from a surgical or trauma wound during surgery similar to traditional suction techniques, have high degree of reliability of operation, and possess high precision of the dosing of the anticoagulant additive. The dosing of anticoagulant additive cannot be disturbed by any accidental compressions in the hose arrangement through which the blood is pumped.

Yet further, the blood collection system is safe, movable, flexible, staff economizing, and well adapted to the user. It is not bulky and can be placed in operation theaters at a distance where the system will not intrude on the limited space close to the operation table. The use of it does not affect the common surgical routines, does not require any advanced training, or does not require any expanding of power resources existing in most operation theaters.

Typically, the blood collection system is provided as a two-part system comprising one disposable unit (consisting of hoses and possibly plastic bags and parts of the flow sensing unit) and one non-disposable unit, a console, into which the disposable unit is mounted fast and easily.

Further characteristics and advantages will be evident from the following detailed description given hereinafter and the accompanyingFIGS. 1-4, which are given by way of illustration only, and shall thus not limit the scope of the present invention.

Identical reference numerals are used throughout the Figures to denote identical or similar components, portions, details and the like of the various embodiments.

DETAILED DESCRIPTION

The blood collection system ofFIG. 1comprises a suction unit11, a first hose arrangement12, a first pump system13, a flow sensing unit14, an anticoagulant additive dosing system15, a mixing and defoaming unit16, and a filter unit or collection vessel17. Optionally, the blood collection system also comprises a second hose arrangement18, a second pump system19, directing means, preferably a clamp arrangement20, and a blood storage arrangement21.

The suction unit11may comprise an elongated rigid, preferably transparent, tube11a, e.g., made of plastic having an inlet end11band a hole (e.g. a no-return air valve unit)11c, which can be covered by a finger tip during operation to concentrate all suction force to the inlet end11b.

The first hose arrangement12may comprise three hose portions: a first portion12ainterconnecting the suction unit11and the flow sensing unit14, a second portion12binterconnecting the flow sensing unit14and the anticoagulant additive dosing system15, and a third portion12cinterconnecting the anticoagulant additive dosing system15and the collection vessel17. Each of the hose portions12a-cmay be made of a transparent flexible plastic.

The first pump system13may comprise a peristaltic or roller pump13a, e.g., controlled by a control unit13b, and may be arranged upstream of the flow sensing unit14, and may thus be arranged to provide an under pressure in the suction unit11for aspirating blood and air through the inlet end11bof the suction unit11and into the hose portion12aand an over pressure downstream of the first pump system13for pumping blood and air through the hose portions12a-cand into the collection vessel17. The first pump system13is arranged to provide a known constant volume flow of the blood and air in the first hose arrangement12. The blood and air is present as blood foam. When lifting the suction unit11from where the blood foam is aspirated, typically only air is sucked into the first hose arrangement12.

The flow sensing unit14is arranged to continuously sense the mass flow of blood through the first hose arrangement12by means of continuously measuring a parameter indicative of the weight of blood in a tubing section14a, through which the blood is transported by means of a weight sensing arrangement schematically indicated at14b. Flow sensing units14, which can be used with the blood collection system ofFIG. 1, will be described in detail later with reference toFIGS. 2a-band3.

The anticoagulant additive dosing system15comprises a control unit15dconnected to the flow sensing unit14, i.e. to the weight sensing arrangement14bthereof, and is arranged to automatically control the continuously dosing of an anticoagulant additive into the blood flowed through the first hose arrangement12in response to the continuously sensed mass flow of blood. The anticoagulant additive dosing system15may thus comprise a storage unit15afor the anticoagulant additive, a hose portion15binterconnecting the anticoagulant additive storage unit15aand the first hose arrangement12between the second and the third hose portions12b-c. A pump, such as e.g. a peristaltic pump15c, may be operatively connected to the hose portion15bof the anticoagulant additive dosing system15in order to pump the anticoagulant additive into the blood flowed in the first hose arrangement12under control of the control unit15dof the anticoagulant additive dosing system15.

Further, The first pump system13and the anticoagulant additive dosing system15may be provided with an adjustment device15efor manually adjusting the volume flow of the blood and air in the first hose arrangement12and consequently the dosing of the anticoagulant additive depending on the particular circumstances during operation, i.e. different suction forces may be desirable during operation.

The mixing and defoaming unit16is arranged to mix the blood with the anticoagulant additive dosed into the blood and may comprise a device16aarranged to automatically move a portion of the third hose portion12cback and forth, i.e. shaking the portion of the third hose portion12c, which device16amay be provided with an adjustment device16bfor manually adjusting an operation parameter such as shaking frequency or shaking amplitude. Typically, the mixing unit16is arranged to at least partly defoam the blood.

The filter unit or collection vessel17is arranged to collect the mixed blood and anticoagulant additive. It may comprise a valve17afor letting air out and a filter arrangement17barranged to filter the mixed blood and anticoagulant collected in the collection vessel17. The filter arrangement may comprise one or more filters arranged to separate foam, particles, bone residuals, eventually existing coagulum etc. Typically the filter arrangement may comprise three fabrics of different mesh size.

The second hose arrangement18may interconnect the collection vessel17and the blood storage arrangement21, and the second pump system19may be arranged to pump the mixed blood and anticoagulant additive from the collection vessel17to the blood storage arrangement21by means of creating an under pressure in the collection vessel17to suck the mixed blood and anticoagulant additive from there and creating an over pressure downstream of the second pump system19to pump the mixed blood and anticoagulant additive to the blood storage arrangement21.

The second pump system19may comprise a pump, e.g. a peristaltic pump19a, and a control unit19barranged to control the second pump system19.

The blood storage arrangement21may comprises a plurality of blood bags21a-bconnected in parallel via the second hose arrangement18and the clamp arrangement20may comprise clamps20a-bconnected to a control unit20cfor the control thereof, wherein the clamps20a-bcan be used to selectively direct the mixed and filtered blood and anticoagulant additive from the collection vessel17to a selected one of the blood bags21a-b. It shall be appreciated that the blood storage arrangement21may comprise any number of blood collection units, such as blood bags, connected in parallel via the second hose arrangement18to the collection vessel17. Similarly, the clamp arrangement20may comprise one clamp for each such parallel fluid path.

When a blood collection unit/blood bag is full it is exchanged for a new empty blood collection unit/blood bag. In such a manner any required number of blood collection units/blood bags can be filled by the blood collection system.

With reference next toFIGS. 2a-band3, which are schematic perspective, side elevation, and top views, respectively, of a flow sensing unit which can be used with the blood collection system ofFIG. 1. InFIG. 2ais also shown the anticoagulant additive dosing system15with its storage unit15a, hose portion15b, pump15c, and control unit15d.

The flow sensing unit may comprise a rigid base tubing section141which is connected to the first and second hose portions12a-bof the first hose arrangement12and to the tubing section14a, which may be essentially U-shaped, via flexible hose portions142a-b. The U-shaped tubing section14a, which is rigid, is thus pivotably suspended at142a-b, i.e. at an inner end portion of the U-shaped tubing section14a, and rests onto the weight sensing arrangement14bschematically indicated inFIG. 2a. The flexible hose portions142a-bmay be made of a flexible plastic or rubber material.

The weight sensing arrangement14bas seen inFIG. 2bcomprises a cantilever143provided with at least one strain gauge144a-b, wherein the pivotably tubing section14ais resting on the cantilever143. Preferably, the pivotably suspended tubing section14ais resting on the cantilever143about halfway between the inner end of the U-shaped tubing and an outer end thereof. By such provisions, if the pivotably suspended tubing section is filled with a mix of blood and air, the entire weight of the blood is sensed (compared to only half the weight of the blood if the pivotably suspended tubing section14ais resting on the cantilever143at the outer end thereof). A casing of the flow sensing unit14is denoted by145.

In one embodiment, the weight sensing arrangement14bcomprises two strain gauges connected in a bridge, wherein one of the strain gauges are mounted on an upper side143aof the cantilever and one of the strain gauges are mounted on a lower side143bof the cantilever143.

Typically, each of the strain gauges is mounted on the cantilever143close to where the cantilever143is attached.

In another embodiment, the weight sensing arrangement14bcomprises four strain gauges connected in a bridge, wherein two of the strain gauges are mounted on an upper side143aof the cantilever and two of the strain gauges are mounted on a lower side143bof the cantilever.

FIG. 4is an enlarged schematic cross-sectional view of a part of an alternative flow sensing unit which can be used with the blood collection system ofFIG. 1.

The flow sensing unit may comprise a rigid base tubing section141which is connected to the first and second hose portions12a-bof the first hose arrangement12and to the tubing section14a, which may be essentially U-shaped, via flexible hose portions (only142bshown inFIG. 4). The U-shaped tubing section14a, which is rigid, is thus pivotably suspended at142a-b, i.e. at an inner end portion of the U-shaped tubing section14a, and rests onto a weight sensing arrangement (not illustrated). The flexible hose portions142bmay be made of a flexible plastic or rubber material.

The joints between each of the flexible hose portions142band the rigid base tubing section141and the U-shaped tubing section14amay be formed as follows. The inner diameter of the flexible hose portions142bis identical with or somewhat larger than the outer diameter of the rigid base tubing section141and the U-shaped tubing section14a. Each joint is formed by an overlap between one of the flexible hose portions142band the rigid base tubing section141or the U-shaped tubing section14a, in which overlap a glue line147a-bis applied. In order to form a strong joint, a respective shrink hose portion146a-bis threaded around the overlap and is treated, e.g. heated, to shrink and press against the overlap. A protection tubing148may be arranged around each of the flexible hose portions142bat an appropriate distance in order to avoid explosion of any of the flexible hose portions142bdue to an over pressure within the flexible hose portion.

It is important that all parts coming into contact with blood are disposable parts or are easy to sterilize. This put restrictions on the design of the flow sensing unit. The above design enables the use of simple parts (the base tubing section141, flexible hose portions142a-b, and the pivotably suspended tubing section14a) that can easily be exchanged, while the weight sensing arrangement14bhas no contact with the blood and thus not need to be exchanged for that reason.

All surfaces of part that risk to come in contact with blood such as e.g. the interior walls of the parts, i.e. the suction unit11, the first hose arrangement12, the base tubing section141, flexible hose portions142a-b, and the pivotably suspended tubing section14aof the flow sensing unit14, the collection vessel17, the second hose arrangement and the blood bags21a-bof the blood storage arrangement21, should be blood compatible, i.e. made of or treated by a blood compatible material.

In one embodiment the interior walls of some or all of the above parts are heparinized or otherwise treated, e.g., as disclosed in U.S. Pat. No. 4,613,665, the contents of which being hereby incorporated by reference.

It shall further be appreciated that the blood collection system may be provided with a number of sensors, by which automatic safety operations can be performed.

The first pump system13may comprise a sensor13carranged to continuously sense whether a level of anticoagulant additive left in the anticoagulant additive dosing system15falls below a first threshold level, wherein the control unit13bof the first pump system13can be arranged to automatically shut down the first pump system13, i.e. stopping the pump13aof the first pump system13, in case the level of anticoagulant additive left in the anticoagulant additive dosing system15falls below the first threshold level. Hereby, under dosing of anticoagulant additive can be avoided. When the anticoagulant additive dosing system15runs short of of anticoagulant additive, the aspiration of blood is automatically halted.

Further, the control unit13bof the first pump system13and the control unit15dof the anticoagulant additive dosing system15may be connected to one another, wherein the control unit13bof the first pump system13can be arranged to automatically inform the control unit15dof the anticoagulant additive dosing system15when shutting down the first pump system13, in response to which the control unit15dof the anticoagulant additive dosing system15can be arranged to automatically stop the dosing of the anticoagulant additive into the blood flowed through the first hose arrangement12. Hereby, over dosing of anticoagulant additive can be avoided. When the aspiration/pumping of blood through the first hose arrangement12is halted, the dosing of anticoagulant is automatically halted.

Further, the first pump system13may comprise a sensor13darranged to continuously sense whether a level of mixed blood and anticoagulant additive in the collection vessel17rises above a second threshold level, wherein the control unit13bof the first pump system13can be arranged to automatically shut down the first pump system13, i.e. stopping the pump13aof the first pump system13, in case the mixed blood and anticoagulant additive in the collection vessel rises above the second threshold level. Hereby, overflow of blood and anticoagulant additive in the blood collection system can be avoided. When the collection vessel17is close to become full, the aspiration of blood is automatically halted.

Yet further, the second pump system19may comprise a sensor19carranged to continuously sense whether a level of mixed blood and anticoagulant additive in the collection vessel17falls below a third threshold level, wherein the control unit19bof the second pump system19can be arranged to automatically shut down the second pump system19in case the level of mixed blood and anticoagulant additive in the collection vessel17falls below the third threshold level. Hereby, it can be safeguarded that when the collection vessel17is close to become empty, the pumping by the second pump system19is automatically halted.

Still further, the clamp arrangement20may, for each of the blood bags21a-b, comprise a sensor20d,20earranged to continuously sense whether a level of mixed blood and anticoagulant additive in the blood bag21a-brises above a fourth threshold level, wherein the control unit20cof the clamp arrangement20can be arranged to automatically control the clamps20a-bsuch that mixed blood and anticoagulant additive from the collection vessel17is not directed to a blood bag21a-bin case the level of mixed blood and anticoagulant additive in that blood bag21a-brises above the fourth threshold level. Hereby, it can be ensured that when each of the blood bags21a-bbecomes full, a respective clamp20a-bcloses the fluid communication between the collection vessel17and that blood bag21a-b.

It shall be appreciated that the blood collection system may comprise less or more sensors, based on the sensing of which various actions may be taken. In such a manner an entirely automated blood collection system can be provided. Optionally, or alternatively, some or all of the sensors are connected to alarms, which may be triggered based on the sensing of the sensors.

It will be obvious that the invention may be varied in a plurality of ways within the scope of the appended patent claims.