GB2589689A

GB2589689A - Improved cardiopulmonary bypass device

Info

Publication number: GB2589689A
Application number: GB2013107.4A
Authority: GB
Inventors: P Gunarathne Godallawaththa
Original assignee: Starimedical Ltd
Current assignee: Starimedical Ltd
Priority date: 2019-08-22
Filing date: 2020-08-21
Publication date: 2021-06-09
Anticipated expiration: 2040-08-21
Also published as: GB202013107D0; GB2589689B; GB201912091D0

Abstract

An extracorporeal blood circulation (EBC) device comprises pumping chamber 102, 104 having inlet 110, 112 and outlet valves 114, 116 and a pneumatic drive S1, S2 to apply a positive P1 and a negative pressure P2 (relative to ambient) to the pumping chamber. In a first stage, shown in 104, the drive applies negative pressure to draw blood into the pumping chamber via the inlet, and in a second stage, shown in 102, applies positive pressure driving gas into the pumping chamber to drive blood therein through the outlet. The chambers may be arranged in pairs (shown) and operate alternately and also be arranged concentrically in combination with a buffer tank (206, Fig. 10). Chambers may be arranged with a negative pressure reservoir (24, Fig. 6) in addition to a buffer chamber (24). A wound aspirator 118 may be connected to the reservoir or a pumping chamber via valves 120, 122. In-chamber oxygenators 136, 138 may replace or supplement any system oxygenators, e.g. ECMO 126. The drive may be a simple piston or use theatre pressurised gas blender and wall mounted partial vacuum.

Description

Improved Cardiopulmonary Bypass Device

Field of the Invention

The present disclosure relates to the field of extracorporeal blood circulation, more specifically to devices used in extracorporeal blood circulation.

Background of the Invention

Cardiopulmonary Bypass (CPB) systems, commonly known as Heart-lung machines, are essential in open-heart surgery. The primary function of a CPB system is to take over the function of the heart and lungs during cardiac surgery in maintaining the circulation of blood and the oxygen content of that blood. This is commonly referred to as "Extracorporeal Circulation". Accordingly, these devices may be referred to as extracorporeal blood circulation (EBC) devices.

Presently, there are about 1.75 million operations per year, worldwide. The trend is increasing; with more hospitals and health organisations establishing open-heart surgical facilities worldwide, and due to the increasing prevalence of heart disease.

CPB machines or EBC devices were originally developed and used for heart-surgery in the 1950's. But their core design with respect to providing extracorporeal circulation with mechanical pumping systems virtually remained to the present day, except for incremental progression reaching technological saturation.

Present devices are typically large and bulky, and as a result are unwieldly and difficult to move or transport due at least in part to the need to incorporate one or more reliable pumping devices such as peristaltic pumps or centrifugal pumps. For example, in typical devices there are four or more peristaltic or centrifugal pumps, which include a systemic pump that produces blood flow out into the aorta, an aorta root pump, a cardiotomy pump, a ventricular vent, and a cardioplegia pump. The use of many mechanical pumps of these types results in these devices being large and of significant weight. The use of such mechanical pumping devices can also lead to significant damage to the blood cells (blood trauma) within the blood being pumped, has a high-power consumption and adds to the very high capital cost. Other limitations include the possibility of tube rupture if blocked downstream and the emergence of gaseous micro emboli if blocked upstream in the case of peristaltic pumps; and afterload dependence with the possibility of retrograde flow in the case of centrifugal pumps.

Furthermore, any component of the EBC device that comes into direct contact with blood during a given procedure will need to be replaced, including any centrifugal pump if used, to ensure that there is no risk of contamination between patients.

Accordingly, there is a need for improved EBC devices that overcome at least some of the above limitations.

Summary of the Invention

According to a first aspect, there is presented an extracorporeal blood circulation (EBC) component comprising a pumping chamber, the pumping chamber comprising: an inlet comprising an inlet valve; an outlet comprising an outlet valve; and a pneumatic drive configured to apply a positive pressure and a negative pressure to the pumping chamber, wherein, during use in a first stage the pneumatic drive applies a negative pressure to the pumping chamber to thereby draw blood into the pumping chamber via the inlet, and wherein in a second stage the pneumatic drive applies a positive pressure to the pumping chamber by driving a gas into the pumping chamber to thereby drive blood retained within the pumping chamber out of the outlet.

The term "negative pressure" as used herein is intended to refer to a pressure that is lower than the surrounding pressure. More specifically, unless otherwise stated a negative pressure is a negative gauge pressure and is relative to atmospheric pressure. Application of a negative pressure to a chamber may correspond to drawing gas out of that chamber to thereby lower the pressure within that chamber. For example, the application of a negative pressure may correspond to the application of a vacuum source to reduce the pressure within a chamber or vessel such that blood is drawn into the chamber or vessel. Typically, a negative pressure as referred to herein is lower than atmospheric pressure.

The term "positive pressure" as used herein is intended to refer to a pressure that is greater than the surrounding pressure. More specifically, unless otherwise stated a positive pressure is a positive gauge pressure and is relative to atmospheric pressure. For example, application of a positive pressure to a chamber may correspond to driving gas into the chamber to thereby increase the pressure within that chamber. In some instances herein, the application of a positive pressure may correspond to the application of a pressurised gas source to increase the pressure within a chamber or vessel such that blood is driven out of the chamber or vessel.

Typically, a positive pressure as referred to herein is higher than atmospheric pressure.

Typically, the EBC device does not comprise a mechanical pump, such as a peristaltic pump or centrifugal pump or any type of diaphragm pump.

The EBC device of the present aspect accordingly uses pneumatic pressure to drive blood through the device rather than using mechanical pumps such as peristaltic or centrifugal pumps as are commonly known in the art. Further, there are no moving parts of the device that directly contact the blood that is being pumped through the device. The use of pressure rather than mechanical force, for example, may significantly reduce or prevent damage to the blood passing through the EBC device.

Mechanical pumps such as peristaltic pumps or centrifugal pumps are typically large and bulky devices. Existing systems typically use multiple separate pumps for functions including a systemic pump, an aortic root pump, a cardiotomy pump, a ventricle vent and a cardioplegia pump, which makes the systems bulky, heavy and adds significantly to the cost of such systems. Therefore, the provision of an EBC device that does not comprise a mechanical pump allows the EBC device of the present aspect to be less bulky than EBC devices known in the art, thereby improving the portability of the device when compared to EBC devices known in the art.

Furthermore, the lack of one or more mechanical pumps may allow the EBC device of the present aspect to use less electrical power to operate than EBC devices known in the art, making the device more cost effective to operate.

For the avoidance of doubt, the application of positive pressure to the pumping chamber directly contacts blood retained within the pumping chamber with a gas driven into the pumping chamber to thereby drive the retained blood out of the outlet of the pumping chamber without requiring direct contact with any mechanical parts.

In some embodiments, the gas driven into the pumping chamber may be derived from a gas blender. Accordingly, it may be that the pressure driving the gas into the pumping chamber may be the pressure at which the gas is pressurised whilst stored within a container such as a bottle or can or similar. Accordingly, the energy required to pump blood through the EBC device may be at least partially derived from the energy stored within the gas when it is stored at high pressure.

Accordingly, in at least some embodiments, the EBC device may comprise a high pressure gas source. The high pressure gas source may be connected to the pneumatic drive such that the pneumatic drive may allow pressurised gas from the high pressure gas source to enter the pumping chamber to thereby apply positive pressure to the pumping chamber in the second stage.

The gas driven into the pumping chamber to apply positive pressure within the pumping chamber may be an inert gas. For example, the gas may be nitrogen. The gas driven into the pumping chamber to apply positive pressure within the pumping chamber may comprise oxygen. The gas may comprise 20% to 100% oxygen with the balance (where appropriate) comprising a neutral gas and/or optionally a therapeutic gas. The gas may comprise 20% to 50% oxygen with the balance comprising a neutral gas and/or optionally a therapeutic gas. The gas may comprise 20% to 35% oxygen with the balance comprising a neutral gas and/or optionally a therapeutic gas. For example, in one example the gas may comprise 21% oxygen, and the gas may be "medical air" (21% oxygen, 79% nitrogen).

In embodiments where the gas comprises oxygen, the blood being pumped out of the pumping chamber may be at least partially oxygenated by the gas driving the blood from the pumping chamber.

By the term "oxygenated" we refer herein to the process whereby haemoglobin within red blood cells capture and bind molecular oxygen to form the oxygenated form of haemoglobin. This is the process normally carried out in the lungs of a patient.

The inlet may be located at or adjacent to the top of the pumping chamber during use. The outlet may be located at or adjacent to the bottom of the pumping chamber during use.

In some embodiments, the inlet valve may be a unidirectional valve such that fluid is only allowed to flow through the inlet valve in a single direction. Typically, the inlet valve only allows fluid to flow into the pumping chamber through the inlet and does not allow fluid to flow out of the pumping chamber through the inlet. The outlet valve may be a unidirectional valve such that fluid is only allowed to flow through the outlet valve in a single direction. Typically, the outlet valve only allows fluid to flow out of the pumping chamber through the outlet valve and does not allow fluid to flow into the pumping chamber through the outlet valve. Accordingly, the inlet valve and the outlet valve may automatically open and close when appropriate during the first and second stages.

In some embodiments, the inlet valve and/or the outlet valve may be a controlled valve that can be opened and closed, or partially opened or partially closed on command. Accordingly, during use in a first stage the inlet valve may be opened and the outlet valve may be closed and the pneumatic drive may apply a negative pressure to the pumping chamber to thereby draw blood into the pumping chamber via the inlet. In a second stage, the inlet valve may be closed and the outlet valve may be opened and the pneumatic drive may apply a positive pressure to the pumping chamber by driving a gas into the pumping chamber to thereby drive blood retained within the pumping chamber out of the outlet.

The pneumatic drive may comprise a vacuum inlet and a pressure inlet. During use, the pneumatic drive may be operable to switch between the vacuum inlet and the pressure inlet such that gas is drawn from the pumping chamber through the vacuum inlet to thereby apply a negative pressure to the pumping chamber, or gas is driven into the pumping chamber through the pressure inlet to thereby apply a positive pressure to the pumping chamber. The pneumatic drive may be operable to switch to a neutral position such that the pumping chamber is not exposed to either negative pressure or positive pressure. Accordingly, the pneumatic drive may have an "or position.

In some embodiments the pneumatic drive may comprise a pressure inlet valve and a vacuum inlet valve. The pressure inlet valve may be configured to allow the rate of gas flow into the pumping chamber through the pneumatic drive to be controlled. The vacuum inlet valve may be configured to allow the rate of gas flow out of the pumping chamber through the pneumatic drive to be controlled. Accordingly, the pneumatic drive may be configured to apply a desired positive pressure or a desired negative pressure to the pumping chamber.

Typically, during operation the EBC component continuously switches between the first stage and the second stage such that the pumping chamber is sequentially exposed to negative pressure and positive pressure to continuously draw blood into the pumping chamber and to then subsequently drive the retained blood out of the pumping chamber. Accordingly, blood is continually drawn into the pumping chamber during the first stage and subsequently driven out of the pumping chamber during the second stage.

In some embodiments the pneumatic drive may comprise a pressure conduit. The pneumatic drive may comprise a single pressure conduit. The pressure conduit may be configured to act as a pressure inlet. The pressure conduit may be configured to act as a vacuum inlet. The pressure conduit may be configured to act as a pressure inlet and a vacuum inlet.

The pneumatic drive may comprise a drive unit. The drive unit may be configured in a first mode to draw gas from or apply a negative pressure to the pumping chamber to thereby reduce the pressure within the pumping chamber through the pressure conduit. The drive unit may be configured in a second mode to drive gas into the pumping chamber through the pressure conduit. The drive unit may be configured to cycle between the first mode and the second mode. Accordingly, the drive unit may continuously reduce pressure and then increase pressure in the pumping chamber.

The drive unit may comprise a gas inlet. The gas inlet may be located adjacent to the pressure conduit. Accordingly, during the first mode gas may be drawn into the drive unit from the gas inlet rather than from the pressure conduit. As a result, the pressure within the pumping chamber may be increased during consecutive cycles without drawing gas from the pumping chamber.

The drive unit may comprise a gas outlet. The gas outlet may be located adjacent to the pressure conduit. Accordingly, during the second mode gas may be driven out of the drive unit through the gas outlet rather than through the pressure conduit. As a result, the pressure within the pumping chamber may be reduced during consecutive cycles without driving gas into the pumping chamber.

The drive unit may comprise a drive chamber. The drive chamber may change volume during use. During the first mode the drive chamber may increase in volume. During the second mode the drive chamber may reduce in volume. The drive unit may comprise a drive piston. The drive piston may be located within the drive chamber. The drive piston may be configured to move along the drive chamber to reduce or increase the volume of the drive chamber adjacent to the pressure conduit. The drive piston may be configured to move along the drive chamber to reduce or increase the volume of the portion of the drive chamber adjacent to the pressure conduit. For example, the drive piston and drive chamber may form a piston-cylinder arrangement. A positive stroke of the piston may reduce the volume of the drive chamber to apply positive pressure to the pumping chamber. A negative stroke of the piston may increase the volume of the drive chamber to apply negative pressure to the pumping chamber. The positive pressure applied by the drive unit to the pumping chamber may be determined by the extent of the positive stroke. The negative pressure applied by the drive unit to the pumping chamber may be determined by the extent of the negative stroke. The positive stroke may be defined with respect to the neutral pressure point (i.e. zero gauge pressure). The negative stroke may be defined with respect to the neutral pressure point.

The drive unit may substantially not require an external pressure source and/or an external vacuum source. Accordingly, the drive unit may effectively provide a closed-circuit pressure source.

In some embodiments, the required magnitude of the positive gauge pressure applied to the pumping chamber may be different to the required magnitude of the negative gauge pressure applied to the pumping chamber. Accordingly, the extent of the positive stroke may be different to the extent of the negative stroke. Therefore, the neutral point of the drive piston within the drive chamber may be offset from the mid-point of the drive chamber.

In some embodiments, the required magnitude of the positive gauge pressure applied to the pumping chamber may be substantially the same as the required magnitude of the negative gauge pressure applied to the pumping chamber. Accordingly, the extent of the positive stroke may be substantially the same as the extent of the negative stroke. Therefore, the neutral point of the drive piston within the drive chamber may be at approximately the mid-point of the drive chamber.

In some embodiments the pumping chamber comprises at least one pressure sensor configured to detect the pressure within the pumping chamber. The pumping chamber may comprise a port for connection to the at least one pressure sensor. The at least one pressure sensor may allow the pneumatic drive to determine the pressure within the pumping chamber.

Accordingly, the pneumatic drive may control the pressure within the pressure chamber to ensure that a target pressure is maintained within the pumping chamber during the first stage and/or the second stage.

The pumping chamber may comprise at least two pressure sensors. The pumping chamber may comprise at least two ports for connection to the at least two pressure sensors. A first pressure sensor may be located adjacent to the top of the pumping chamber. A second pressure sensor may be located adjacent to the bottom of the pumping chamber. The difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the liquid level within the pumping chamber. The derivative of the difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the flow rate of liquid out of the pumping chamber and/or the flow rate of liquid into the pumping chamber. For example, during the first stage the derivative may relate to the flow rate of liquid into the pumping chamber and during the second stage the derivative may relate to the flow rate of liquid out of the pumping chamber.

The first pressure sensor and second pressure sensor may be characterised prior to use and the gain and offset of the first pressure sensor and/or second pressure sensor may be adjusted such that the characteristics of the first pressure sensor and the second pressure sensor are the same or similar.

The pumping chamber may comprise at least one sensor to determine the level of blood within the pumping chamber. The pumping chamber may comprise at least one sensor located at a level that corresponds to a maximum desired level of blood within the pumping chamber such that during use the pneumatic drive may switch from applying negative pressure to the pumping chamber in the first stage to applying positive pressure to the pumping chamber in the second stage. The pumping chamber may comprise at least one sensor located at a level that corresponds to a minimum desired level of blood within the pumping chamber such that during use the when the pneumatic drive may switch from applying positive pressure to the pumping chamber in the second stage to applying negative pressure to the pumping chamber in the first stage.

The pumping chamber may comprise an oxygenator. The oxygenator may be located within the pumping chamber such that during use the oxygenator is submerged or substantially submerged beneath blood retained within the pumping chamber during at least the first stage or the second stage. The oxygenator may be located within the pumping chamber such that during use the oxygenator is below a minimum level of blood in the pumping chamber during use. Accordingly, the oxygenator may always be surrounded by blood during operation of the EBC device.

The oxygenator may be connected to an oxygen gas source such that during use oxygen or a gas comprising oxygen is driven through the oxygenator and into the blood retained within the pumping chamber.

The oxygenator may be connected to a supply of pressurised oxygen or a pressurised gas comprising oxygen.

The oxygen or gas comprising oxygen may pass through the oxygenator into the pumping chamber through the blood retained within the pumping chamber. The oxygen or gas comprising oxygen may at least partially apply a positive pressure to the pumping chamber.

The oxygen or gas comprising oxygen may pass through the oxygenator into the pumping chamber through the blood retained within the pumping chamber in the first stage. Accordingly, a greater negative pressure may be required to be applied. The oxygen or gas comprising oxygen may pass through the oxygenator into the pumping chamber through the blood retained within the pumping chamber in the second stage. Therefore, a lower positive pressure may be required to be applied by the pneumatic drive. Alternatively, if the oxygen or gas comprising oxygen passing through the oxygenator into the pumping chamber results in the pressure within the pumping chamber exceeding the required pressure in either of the first stage or second stage of operation the pneumatic drive may vent the excess gas to bring the pressure back to the required level.

The pumping chamber may comprise a gas diffuser. The gas diffuser may mitigate agitation of the blood retained within the pumping chamber that may be caused by sudden changes in pressure from negative pressure and positive pressure in the first stage and second stage respectively. The gas diffuser may be structured such that the gas enters into the pumping chamber via a plurality of inlets. Accordingly, the gas may be driven into the pumping chamber more evenly thereby reducing the rate of gas flow from any one inlet mitigating agitation that may be caused by gas from a single inlet impacting the surface of the blood retained within the pumping chamber.

The FOB component may comprise a relief valve. The relief valve may be configured to connect the pumping chamber and/or the pneumatic drive to the atmosphere. The relief valve may be configured to connect the pumping chamber and/or pneumatic drive to the atmosphere when a pressure within the pumping chamber and/or pneumatic drive exceeds a maximum pressure. The relief valve may be configured to connect the pumping chamber and/or pneumatic drive to the atmosphere when a pressure within the pumping chamber and/or pneumatic drive drops below a minimum pressure.

The relief valve may be located adjacent to the pneumatic drive. The relief valve may be located adjacent to the pumping chamber.

The relief valve may be opened prior to use to set the neutral pressure point of the drive unit.

The relief valve may be opened to allow the piston of the drive unit to be moved to set the neutral pressure point of the drive unit. The neutral pressure point of the drive unit may be moved closer to the maximum positive stroke point of the drive piston. The neutral pressure point of the drive unit may be moved closer to the minimum positive stroke point of the drive piston.

The inlet may comprise a filter. Accordingly, blood entering the pumping chamber through the inlet during the first stage may be filtered to remove any impurities or particulates that may be present.

During the first stage the negative pressure applied to the pumping chamber may be a pressure of about -0.7 kPa (-0.1 PSI) to about -69.0 kPa (-10 PSI). The negative pressure applied to the pumping chamber may be a pressure of about -3.4 kPa (-0.5 PSI) to about -34.5 kPa (-5 PSI). The negative pressure applied to the pumping chamber may be a pressure of about -6.9 kPa (-1 PSI) to about -20.7 kPa (-3 PSI). For example, the negative pressure applied to the pumping chamber may be a pressure of about -6.9 kPa (-1 PSI), -13.8 kPa (-2 PSI), or -20.7 kPa (-3 PSI) or values therebetween.

During the second stage the positive pressure applied to the pumping chamber may be a pressure of about 6.9 kPa (1 PSI) to about 69.0 kPa (10 PSI). The positive pressure applied to the pumping chamber may be a pressure of about 6.9 kPa (1 PSI) to about 46.3 kPa (7 PSI). The positive pressure applied to the pumping chamber may be a pressure of about 20.7 kPa (3 PSI) to about 46.3 kPa (7 PSI). For example, the positive pressure applied to the pumping chamber may be a pressure of 20.7 kPa (3 PSI), 27.6 kPa (4 PSI), 34.5 kPa (5 PSI), 41.4 kPa (6 PSI) or 46.3 kPa (7 PSI), or values therebetween. The positive pressure applied to the pumping chamber may be a pressure of 27.6 kPa (4 PSI), 34.5 kPa (5 PSI) or 41.4 kPa (6 PSI) or values therebetween.

According to a second aspect there is provided an EBC device comprising a reservoir, an EBC component according to the first aspect and a buffer chamber, the reservoir comprising a reservoir inlet comprising an inlet valve, a reservoir outlet, and a vacuum regulator configured to apply a negative pressure to the reservoir during use, wherein the reservoir outlet is fluidly connected to the inlet of the pumping chamber of the EBC component such that during the first stage blood is drawn into the pumping chamber from the reservoir through the reservoir outlet, the buffer chamber comprising: a buffer inlet; a buffer outlet comprising an outlet valve; and a pressure regulator configured to apply a positive pressure to the buffer chamber during use, wherein the buffer inlet is fluidly connected to the outlet of the pumping chamber such that during the second stage blood is driven out of the pumping chamber to the buffer chamber through the buffer inlet of the buffer chamber.

The inlet valve of the reservoir may be a flow-control valve. The outlet valve of the buffer chamber may be a flow-control valve. The flow-control valves of the inlet and/or outlet may regulate flow rates of blood regardless of source pressure fluctuations applied within the EBC device. In some embodiments the pneumatic drive may comprise control valves to regulate the flow rate of gas into or out of the pumping chamber.

Additionally, one or more chamber may be fitted with a release valve. The release valve may automatically open if the pressure within the one or more chamber exceeds a predetermined threshold pressure. The release valve may be opened manually.

CPB pumping requirements can be basically divided into two groups: that which require a driving mechanism that drives blood out into the body and the heart; and that which require suction. The systemic pump and the cardioplegia pump belong to the first category and the aortic root and cardiotomy pump belongs to the second category.

The pumping chamber of the EBC device of the present aspect uses a source of positive pneumatic pressure, such as that provided from the pressurised gas blender in the operating theatre, and a source of negative pressure such as that in the wall mounted partial vacuum source in the operating theatre.

The pumping chamber of the EBC device may comprise a drive unit as described in the first aspect. In some embodiments, the drive unit may comprise a drive piston provided within a drive chamber. Movement of the drive piston within the drive unit may apply positive pressure to the pumping chamber in a second mode by the piston reducing the volume of the drive chamber. Movement of the drive piston within the drive unit may apply a negative pressure to the pumping chamber in a first mode by the piston increasing the volume of the drive chamber.

The reservoir is typically maintained at a negative pressure and a flow-control valve at the inlet of the EBC device regulates the blood intake from the vina cava to maintain the blood level within desired limits in the reservoir while ensuring the limits of venal blood pressure as kept within the safe limits. The negative pressure applied to the reservoir may be about -0.5 kPa to about -10 kPa. The negative pressure applied to the reservoir may be about -0.5 kPa to about -7 kPa. The negative pressure applied to the reservoir may be about -3 kPa to about -5 kPa The flow path from the inlet of the EBC device and the outlet of the EBC device may comprise unidirectional valves. The EBC device may comprise a unidirectional valve between each chamber of the EBC device (i.e. the reservoir, the pumping chamber and the buffer chamber) to ensure that the flow of blood through the EBC device is only permitted in a single direction.

The reservoir may provide all other suction requirements of the EBC device. The flow of blood between the chambers of the EEC device (reservoir, pumping chamber and buffer chamber) may be decoupled and may therefore be set to required suction or pumping rates independently.

The reservoir may comprise a drive unit as described in the first aspect. The drive unit may be configured to apply a negative pressure to the reservoir. The drive unit may comprise a pressure outlet. The drive unit may comprise an inlet. The inlet may connect the drive unit to the reservoir. The inlet may comprise a valve that allows the passage of gas into the drive unit through the inlet from the reservoir. The valve may prohibit the passage of gas from the drive unit to the reservoir. In some embodiments, the drive unit may comprise a drive piston provided within a drive chamber. Retraction of the drive piston within the drive unit may apply a negative pressure to the reservoir in a first mode by the piston increasing the volume of the drive chamber. Movement of the drive piston within the drive chamber may apply a positive pressure to the pumping chamber in a second mode by the piston increasing the volume of the drive chamber. The movement of the drive piston in the second mode may drive gas from within the drive chamber through the pressure outlet.

The above arrangement of the EBC of the present aspect therefore replaces all multiple pumping requirements of the CPB with one single integrated system.

The inlet may be located at or adjacent to the top of the reservoir during use. The outlet may be located at or adjacent to the bottom of the reservoir during use.

The reservoir may comprise at least one pressure sensor configured to detect the pressure within the reservoir. The at least one pressure sensor may allow the vacuum regulator to control the pressure within the reservoir to ensure that a target pressure is maintained within the reservoir.

The reservoir may comprise at least two pressure sensors. A first pressure sensor may be located adjacent to the top of the reservoir. A second pressure sensor may be located adjacent to the bottom of the reservoir. The difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the liquid level within the reservoir. The derivative of the difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the flow rate of liquid out of the reservoir and/or the flow rate of liquid into the reservoir.

The reservoir may comprise at least one sensor to determine the level of blood within the reservoir. The reservoir may comprise at least one sensor located at a level that corresponds to a maximum desired level of blood within the reservoir such that during use the vacuum regulator may apply a negative pressure to the reservoir to draw blood into the reservoir until the maximum level is reached. The reservoir may comprise at least one sensor located at a level that corresponds to a minimum desired level of blood within the reservoir such that during use the vacuum regulator may apply a greater negative pressure to draw more blood into the reservoir than is being drawn out of the reservoir into the pumping chamber.

The at least one sensor may be a pressure sensor, an ultrasonic sensor, a conductive sensor, an optical sensor and a capacitive sensor. Accordingly, the at least one sensor may be any sensor that configured to determine the level of blood within a chamber.

In some embodiments the EEC device may comprise an aspirator. The aspirator may be configured to apply suction to a wound during surgery, for example. The aspirator may comprise a fluid channel through which fluid may be drawn. The aspirator may be connected to the reservoir. Blood drawn into the aspirator through the fluid channel may pass into the reservoir. The reservoir may comprise a secondary inlet through which blood drawn into the aspirator passes into the reservoir. The secondary inlet may comprise a filter to ensure that the blood passing into reservoir is filtered.

The aspirator may comprise a gas outlet, and during use the gas outlet of the aspirator may be configured to direct gas at a target area. The gas may be selected from the group consisting oxygen, carbon dioxide and a neutral gas such as nitrogen or a gas comprising one or more of the same. For example, the gas outlet may be configured to direct oxygen or an oxygen containing gas at a target area. In another example, the gas outlet may be configured to direct carbon dioxide or a carbon dioxide containing gas at a target area.

The aspirator may comprise a valve control configured to allow a user to turn the aspirator on or off as required during a surgical procedure, for example. The valve control may allow a user to control the degree of suction applied by the aspirator.

In some embodiments the reservoir may comprise an oxygenator. The oxygenator may be located within the reservoir such that during use the oxygenator is submerged or substantially submerged beneath blood retained within the reservoir during use. In some embodiments the oxygenator may be located within the reservoir such that the oxygenator is located below a minimum desired level of blood within the reservoir.

The oxygen or gas comprising oxygen may pass through the oxygenator into the reservoir through the blood retained within the reservoir. The oxygen or gas comprising oxygen may pass through the oxygenator into the reservoir through the blood retained within the reservoir. The oxygen or gas comprising oxygen may pass through the oxygenator into the reservoir through the blood retained within the reservoir.

In embodiments where the EBC device comprises an aspirator connected to the reservoir, the aspirator may be additionally connected to the supply of pressurised oxygen or pressurised gas comprising oxygen. The aspirator may be connected to a supply of pressurised carbon dioxide or pressurised gas comprising carbon dioxide. The aspirator may be configured to allow oxygen or gas comprising oxygen, carbon dioxide or gas comprising carbon dioxide to be directed onto a surgical wound area during a surgical procedure, for example. The direction of gas onto a surgical wound area may form a barrier around or over the surgical wound. The aspirator may allow gas to be directed onto a wound through the fluid channel. Accordingly, the aspirator may comprise a control to allow a user to switch functionality of the aspirator from suction to gas flow. Alternatively, the aspirator may comprise a gas channel through which a gas may pass. The gas channel may be parallel to the fluid channel. The gas channel may be arranged concentrically around the fluid channel.

In some embodiments the reservoir may surround or at least partially surround the pumping chamber. Accordingly, the pumping chamber may be surrounded around at least one side by the reservoir.

During use blood may be driven into the buffer chamber during the second stage. Due to the positive pressure being applied by the pressure regulator, blood may be constantly driven from the buffer chamber through the outlet. Accordingly, during use the flow rate of blood out of the outlet of the buffer chamber may be constant irrespective of whether the pumping chamber is in the first stage or second stage of operation. Typically, the flow rate of blood out of the outlet of the buffer chamber is lower than the flow rate of blood into the buffer chamber from the pumping chamber during the second stage so that the buffer chamber is recharged adequately after supplying the outlet flow during the first stage. Accordingly, the buffer chamber regulates the flow of blood being driven from the EBC device. The buffer chamber may also act as a bubble trap.

The pressure regulator may apply positive pressure to blood retained within the buffer chamber by driving gas into the buffer chamber.

The inlet may be located at or adjacent to the top of the buffer chamber during use. The outlet may be located at or adjacent to the bottom of the buffer chamber during use.

The buffer chamber may comprise at least one pressure sensor configured to detect the pressure within the buffer chamber. The at least one pressure sensor may allow the pressure regulator to control the pressure within the buffer chamber to ensure that a target pressure is maintained within the buffer chamber.

The positive pressure applied to the buffer chamber may be a pressure of about 6.9 kPa (1 PSI) to about 69.0 kPa (10 PSI). The positive pressure applied to the buffer chamber may be a pressure of about 6.9 kPa (1 PSI) to about 46.3 kPa (7 PSI). The positive pressure applied to the buffer chamber may be a pressure of about 20.7 kPa (3 PSI) to about 46.3 kPa (7 PSI). For example, the positive pressure applied to the buffer chamber may be a pressure of 20.7 kPa (3 PSI), 27.6 kPa (4 PSI), 34.5 kPa (5 PSI), 41.4 kPa (6 PSI) or 46.3 kPa (7 PSI), or values therebetween. The positive pressure applied to the buffer chamber may be a pressure of 27.6 kPa (4 PSI), 34.5 kPa (5 PSI) or 41.4 kPa (6 PSI) or values therebetween.

The buffer chamber may comprise at least two pressure sensors. A first pressure sensor may be located adjacent to the top of the buffer chamber. A second pressure sensor may be located adjacent to the bottom of the buffer chamber. The difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the liquid level within the buffer chamber. The derivative of the difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the flow rate of liquid out of the buffer chamber and/or the flow rate of liquid into the buffer chamber. The derivative of the difference in pressure recorded by the first pressure sensor and the second pressure sensor may be related to the difference in flow rate into and out of the buffer chamber. For example, during the second stage the derivative may relate to the instantaneous difference in flow rate of liquid into and out of the buffer chamber, and during the first stage the derivative may relate to the flow rate of liquid out of the buffer chamber.

The buffer chamber may comprise at least one sensor to determine the rate of blood flow out of the buffer chamber. The EBC device may comprise a flow sensor downstream of the outlet of the buffer chamber.

The pressure regulator may be configured to adjust the pressure being applied to blood retained within the buffer chamber to ensure that the rate of blood flow out of the buffer chamber is maintained within a defined range. The pressure regulator may be configured to adjust the pressure of gas being applied to the buffer chamber to thereby adjust the rate of blood flow out of the buffer chamber. In embodiments where the buffer chamber outlet valve is a flow-control valve, the rate of blood flow out of the buffer chamber is maintained by the flow-control valve. The rate of blood flow out of the buffer chamber may be adjusted or changed in response to a change in demand from the body of the patient, for example.

The buffer chamber may comprise a drive unit as described in the first aspect. The drive unit may be configured to apply a positive pressure to the buffer chamber. The drive unit may comprise a vacuum outlet. The drive unit may comprise an inlet. The inlet may connect the drive unit to the buffer chamber. The inlet may comprise a valve that allows the passage of gas from the drive unit through the inlet to the buffer chamber. The valve may prohibit the passage of gas from the buffer chamber to the drive unit. In some embodiments, the drive unit may comprise a drive piston provided within a drive chamber. Movement of the drive piston within the drive unit may apply a positive pressure to the buffer chamber in a first mode by the piston reducing the volume of the drive chamber.

In some embodiments the buffer chamber may be surrounded or at least partially surrounded by the pumping chamber. In embodiments the pumping chamber may be surrounded or at least partially surrounded by the reservoir. The pumping chamber may be concentric about the buffer chamber. The reservoir may be concentric about the pumping chamber. The reservoir may be concentric about the buffer chamber. The reservoir and the pumping chamber may be concentric about the buffer chamber. The reservoir and pumping chamber may form concentric rings about the buffer chamber. The inlets of the reservoir, the pumping chamber and the buffer chamber may be located on a first side of the EBC device. The or each source of oxygen or a gas comprising oxygen may be located on the first side of the EBC device. Accordingly, the inlets of the reservoir, the pumping chamber and the buffer chamber may be located on the same side of the EBC device as the or each source of oxygen or gas comprising oxygen.

The buffer chamber outlet may direct blood to flow to the aorta of the patient during use and may direct blood to flow to the heart through the cardioplegia circuit. Accordingly, the buffer chamber outlet may bifurcate into a systemic blood flow outlet and a cardioplegia blood flow outlet. The systemic blood flow outlet may comprise a first control valve and the cardioplegia blood flow outlet may comprise a second control valve. Accordingly, the EBC device of the present aspect provides both systemic blood flow and cardioplegia blood flow independently of the positive pressure applied to the buffer chamber by adjustment of the first control valve and the second control valve. Furthermore, the flow rate of blood through the systemic blood flow outlet and the flow rate of blood through the cardioplegia flow outlet may be controlled independently from one another by controlling the first valve and the second valve.

The EBC device may comprise a base. The base may support one or more of the reservoir, pumping chamber or buffer chamber, where present. The base may be located on a second side of the EBC device that is opposed to first side.

The outlet of the buffer chamber may comprise a control valve. The inlet of the reservoir may comprise a control valve. Typically, the flow of blood through the EBC device is controlled by the control valve in the outlet of the buffer chamber and/or the control valve in the inlet of the reservoir. Accordingly, the flow of blood into or out of the EBC device may be independent of the pressure applied to the reservoir, the pumping chamber or the buffer chamber. The control valve of the inlet of the reservoir or the control valve of the outlet of the buffer chamber may allow the flow rate of blood through the control valve to be controlled. The control valve of the inlet of the reservoir or the control valve of the outlet of the buffer chamber may be controlled by a feedback loop to ensure that the flow rate of blood into the EBC device is maintained, or that the flow rate of blood out of the EBC device is maintained.

Prior to use, the EBC device may be primed. Priming of the EBC device may ensure that blood is retained in the or each chamber of the EBC device before the EBC device is connected to a patient.

In a third aspect there is presented an EBC system comprising an inlet, an outlet, a first EBC component according to the first aspect and a second EBC component according to the first aspect, wherein the inlet of the EBC system is fluidly connected to the inlet of both the first EBC component and the second EBC component, and the outlet of the EBC system is fluidly connected to the outlet of both the first EBC component and the second EBC component, wherein the first EBC component and the second EBC component are configured such that the first stage of operation of the first EBC component occurs during the second stage of operation of the second EBC component and the second stage of operation of the first EBC component occurs during the first stage of operation of the second EBC component.

During use the inlet is typically in fluid communication with the circulatory system (e.g. the vena cava) of a patient such that blood is drawn from the patient into the EBC system. During use the outlet may be in fluid communication with the circulatory system (e.g. the aorta) of a patient such that blood is driven into the patient from the EBC system. During use the outlet may be in fluid communication with an oxygenator and the oxygenator may be in fluid communication with the circulatory system of the patient such that blood is driven through the oxygenator from the EBC system to the circulatory system (e.g. the aorta) of the patient.

The SC system may comprise a first valve that allows or prevents flow of blood to the first EBC component from the inlet and a second valve that allows or prevents the flow of blood to the second EBC component from the inlet. During use, the first valve may be open and allow the flow of blood to the first EBC component from the inlet during the first stage of the first EBC component operation and the second valve may be closed to prevent the flow of blood to the second EBC component from the inlet during the second stage of the second EBC component operation. Alternatively, the first valve may be closed to prevent the flow of blood to the first EBC component from the inlet during the second stage of the first EBC component operation and the second valve may be open to allow the flow of blood to the second EBC component from the inlet during the first stage of the second EBC component operation.

The EBC system may comprise a third valve that allows or prevents the flow of blood from the first EBC component to the outlet and a fourth valve that allows or prevents the flow of blood from the second EBC component to the outlet. During use the third valve may be open and allow the flow of blood from the first EBC device to the outlet during the second stage of the first EBC component operation and the fourth valve may be closed to prevent the flow of blood from the second EBC component to the outlet during the first stage of the second EBC component operation. Alternatively, the third valve may be closed to prevent the flow of blood from the first EBC component to the outlet during the first stage of the first EBC component operation and the fourth valve may be open to allow the flow of blood from the second EBC component to the outlet during the second stage of the second EBC component operation.

Typically, during use the first valve and the fourth valve are open and the second valve and the third valve are closed, or the first valve and the fourth valve are closed and the second valve and the third valve are open. Accordingly, blood is either allowed to flow into the first EBC component and out of the second EBC component, or blood is allowed to flow out of the first EBC component and into the second EBC component.

The inlet of the EBC system may comprise a valve. The valve may be a unidirectional valve such that blood may flow into the EBC system via the inlet and blood may not flow out of the EBC system via the inlet.

The inlet of the EBC system may comprise a control valve. The control valve may control the flow rate of blood into the EBC system.

The outlet of the EBC system may comprise a valve. The valve may be a unidirectional valve such that blood may flow out of the EBC system via the outlet and blood may not flow into the EBC system via the outlet.

The outlet of the EBC system may comprise a control valve. The control valve may control the flow rate of blood out of the EBC system.

Accordingly, during use blood received into the inlet of the EBC system is alternatively drawn into the first EBC component and the second EBC component. Blood pumped by the EBC system that is pumped out of the EBC system comes from the first EBC component and the second EBC component alternatively.

The EBC system may comprise an aspirator. The aspirator may be connected to the first EBC component and the second EBC component. The EBC system may comprise a fifth valve that allows or prevents the flow of blood from the aspirator to the first EBC component. The EBC system may comprise a sixth valve that allows or prevents the flow of blood from the aspirator to the second EBC component. The fifth valve may be open to allow the flow of blood from the aspirator to the first EBC component when the first valve is open to allow the flow of blood from the inlet to the first EBC component. The sixth valve may be open to allow the flow of blood from the aspirator to the second EBC component when the second valve is open to allow the flow of blood from the inlet to the second EBC component. Accordingly, negative pressure is applied adjacent to an end of the aspirator such that blood may be sucked up into the aspirator to the first EBC component or the second EBC component.

The first EBC component may comprise an oxygenator. The second EBC component may comprise an oxygenator. The first EBC component may comprise an oxygenator and the second EBC component may comprise an oxygenator. The or each oxygenator may be connected to a pressurised source of oxygen or a gas comprising oxygen such that oxygen or a gas comprising oxygen is driven through the oxygenator during use through blood retained within the first EBC component and the second EBC component to thereby oxygenate or partially oxygenate that blood.

In embodiments comprising an aspirator and a pressurised source of oxygen or a gas comprising oxygen, the aspirator may comprise a concentric or parallel channel to direct a flow of oxygen or a gas comprising oxygen. In embodiments comprising an aspirator and a pressurised source of carbon dioxide or a gas comprising carbon dioxide, the aspirator may comprise a concentric or parallel channel to direct a flow of carbon dioxide or a gas comprising dioxide.

The use of an EBC system according to the present aspect may allow a continuous flow of blood to be pumped. The first EBC component and/or the second EBC component may comprise a first pumping chamber and a second pumping chamber respectively. Blood from the inlet of the EBC system may be drawn directly into the first pumping chamber and the second pumping chamber. Alternatively, the first EBC component and/or the second EBC component may further comprise a first reservoir and a second reservoir respectively, and blood from the inlet of the EBC system may be drawn into the first reservoir or the second reservoir.

In embodiments where the first EBC component comprises a first drive unit as described in the first aspect and the second EBC component comprises a second drive unit as described in the first aspect, the first drive unit and the second drive unit may be operated in a coordinated fashion. For example, when the first drive unit is operating in a first mode where a negative pressure is applied to the pumping chamber of the first EBC component, the second drive unit may be operating in a second mode where positive pressure is applied to the pumping chamber of the second EBC component. Wien the first drive unit is operating in a second mode where a positive pressure is applied to the pumping chamber of the first EBC component, the second drive unit may be operating in a first mode where a negative pressure is applied to the pumping chamber of the second EBC component. The timing of cycling between the first mode and the second mode for the first drive unit may be directly coordinated to the timing of the cycling between the first mode and the second mode of the second drive unit. For example, the first drive unit may be cycled at the same time as the second drive unit is cycled. Alternatively, there may be a delay between cycling of the first drive unit and cycling of the second drive unit.

In embodiments where the first EBC component comprises a first pumping chamber and the second EBC component comprises a second pumping chamber, the first pumping chamber may surround or partially surround the second pumping chamber. The second pumping chamber may surround or partially surround the first pumping chamber. The second pumping chamber and the first pumping chamber may share a common wall. The EBC system may comprise a buffer chamber. The blood driven from the first pumping chamber in the second stage of operation may be driven into the buffer chamber. The blood driven from the second pumping chamber in the second stage of operation may be driven into the buffer chamber. The first pumping chamber and the second pumping chamber may surround the buffer chamber. For example, the first pumping chamber may partially surround a portion of the buffer chamber and the second pumping chamber may partially surround another portion of the buffer chamber. Alternatively, the first pumping chamber may at least partially surround the buffer chamber and the second pumping chamber may at least partially surround the first pumping chamber.

According to a fourth aspect there is provided a method of use of an EBC system according to the second aspect, the method comprising the steps: 1) priming the EBC system such that blood is retained within the first EBC component; 2) driving blood from the first EBC component to the outlet and drawing blood into the second EBC component from the inlet; 3) driving blood from the second EBC component to the outlet and drawing blood into the first EBC component from the inlet; 4) repeating steps 2) and 3).

Accordingly, blood is continuously drawn into the EBC system via the inlet and blood is continuously driven out of the EBC system via the outlet.

Brief Description of the Figures

Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the accompanying drawings.

Figure 1 is a schematic side view of an embodiment of an EBC component according to the disclosure; Figure 2 is a schematic side view of an embodiment of an EBC device according to the disclosure; Figure 3 is a flow chart showing an example priming process for an EBC device according to

the disclosure;

Figure 4 is a schematic side view of an embodiment of an EBC device according to the disclosure where the reservoir and pumping chamber are arranged concentrically around the buffer chamber; Figure 5 is a schematic side view of an embodiment of an EBC device according to the disclosure where the reservoir and the pumping chamber comprise an oxygenator; Figure 6 is a schematic side view of an embodiment of an EBC device according to the disclosure where the reservoir and pumping chamber comprise an oxygenator and are arranged concentrically around the buffer chamber; Figure 7 is a schematic view of an EBC system comprising two EBC devices according to the

disclosure and a separate oxygenator;

Figure 8 is a schematic view of an EBC system comprising two EBC devices with integral oxygenators and an external oxygenator; Figure 9 is a flow chart showing an example process of operation of an example EBC system; Figure 10 is a side schematic of an EBC system comprising a first EBC device and a second EBC device arranged concentrically around a common buffer chamber.

Figure 11 is a schematic side view of an embodiment of an EBC component according to the disclosure; and Figure 12 is a schematic side view of a drive unit according to an embodiment according to

the disclosure.

Detailed Description

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

Example 1

With reference to Figure 1, an extracorporeal blood circulation (EBC) component 1 comprises a pumping chamber 2, a pneumatic drive 4, an inlet 6, an outlet 8, a first pressure sensor 10 and a second sensor 12. The pneumatic drive 4 comprises a pressure inlet 14 and a vacuum inlet 16. The inlet 6 comprises a valve 18 and the outlet comprises a valve 20.

During use blood is drawn into the pumping chamber 2 through the inlet 6 when a negative gauge pressure is applied to the pumping chamber 2 through the vacuum inlet 16 of the pneumatic drive 4 in a first stage of operation, and blood is driven out of the outlet 8 of the pumping chamber 2 when positive gauge pressure is applied to the pumping chamber 2 through the pressure inlet 14 of the pneumatic drive 4.

The SC component 1 is typically incorporated into an EBC device to provide the blood pumping functionality of that EBC device.

Example 2

With reference to Figure 2 an extracorporeal blood circulation (EBC) device 22 comprises a first chamber 24 (acting as a reservoir), a second chamber 26 (acting as a pumping chamber), and a third chamber 28 (acting as a buffer chamber). The first chamber 24 comprises a Vina cava pathway 30 (acting as an inlet), an outlet 32, a first sensor 34 and a second sensor 36. The vina cava pathway inlet 30 comprises a control valve 38. The outlet 32 comprises a unidirectional valve 40. The vina cava pathway inlet 30 connects the EBC device 22 to the circulatory system of a patient during use.

The first chamber 24 is fitted with a manually adjustable valve 42, which is connected to an aspirator 44 to allow pericardial suction from the surgical wound area directly into the first chamber 24 via a filter 46. This enables pericardial suction without having to use a separate pump-driven suction system as typically used in the existing CPB machines.

The first chamber 24 is a blood reservoir and is maintained at slightly negative gauge pressure, -4.8 kPa (-0.7 PSI), via a vacuum regulator valve 48, and receives deoxygenated blood from the Vina cava pathway inlet 30 through a control valve 38, which helps ensure the level of blood within the first chamber 24 stays within a set range defined by an upper limit and a lower limit.

The negative gauge pressure in the first chamber 24 is such that it satisfies the suction requirement to overcome hydrostatic head pressure in the aspirator 44 and is maintained within limits to keep the venal pressure constant with the valve 38.

The unidirectional valve 40 only allows blood-flow out of the first chamber 24 when the pressure differential across the valve 40 is positive.

The second chamber 26 comprises an inlet 50, an outlet 52, a gas inlet control assembly block 54 (acting as a pneumatic drive), a third sensor 56 and a fourth sensor 58. The outlet comprises a valve 60. The second chamber 26 provides the first-stage (suction) to draw blood into the second chamber and second-stage pneumatic driving force to enable blood circulation. The gas inlet control assembly block 54 comprises a gas inlet 62 and a vacuum inlet 64.

Alternating negative and positive pneumatic pressure is applied to the second chamber 26 in cycles via gas inlet control assembly block 54 to enable extracorporeal blood circulation. During the application of negative gauge pressure (which is set appropriately at a more negative value than that in the first chamber 24, (e.g. -13.8 kPa (-2PSI)) the second chamber 26 starts to fill via the inlet via the valve 40.

Once the second chamber 26 is filled to a predetermined level, it is pressurised (e.g. 34.5 kPa (5PSI)) by the gas inlet control assembly block 54 driving gas into the second chamber 26. This causes the blood to flow out of the second chamber 26 via the outlet 52 and valve 60 into the third chamber 28, which may also be fitted with an inlet blood filter 70.

The third chamber 28 comprises an inlet 68, an inlet blood filter 70, a pressure regulator 72, a fifth sensor 74, a sixth sensor 76, an outlet 78, a control valve 80 and a unidirectional valve 82.

The third chamber 28 facilitates the final output aortic blood flow using positive pneumatic pressure. It also acts as a flow buffer during the time of second chamber 26 blood intake cycle.

The pressure regulator 72 is a control valve to keep the pneumatic pressure of set magnitude close to the maximum positive gauge pressure applied to the second chamber 26, but with automatic regulation within a set maximum/minimum limits to accommodate for changes in demands, if required.

Third chamber 28 also serves as a stabilising reservoir, allowing additional settling provision for removing any microbubbles and acting as a bubble trap. The pressure within the third chamber 28 is maintained at a level enough to keep the head pressure requirement to meet the necessary flow compliance.

Example 3

In an alternative example, with reference to Figure 5, the first chamber 24 comprises a first oxygenator 84, with microscopic holes to allow oxygen or medical air to enter the first chamber 24 via a control valve 86. The control valve 86 controls the gas flow into the first chamber 24 in response to monitored variables such as; chamber pressure, oxygen and carbon dioxide levels in the aortic discharge outlet 78. The first chamber 24 can provide a degree of pre-oxygenation and CO2 removal using the oxygenator 84.

The second chamber 26 comprises a second oxygenator 88, with microscopic holes to allow oxygen or medical air to enter the second chamber 26 via a control valve 90.

The first and/or second oxygenator 84/88 provides a degree of pre-oxygenation. During the positive pressure cycle (corresponding to the second stage), oxygenation is switched on in the second chamber 26, the rate of which may be matched to maintain the required bloodoxygen/CO2 level. Pressure inside the second chamber 26 is regulated by 54.

Aspirator control valve 42 has two manually adjustable knobs: one to control the rate of aspiration and the other to optionally direct an amount of oxygen/medical air flow into the surgical wound area through the concentric casing 92 to form a cloud of oxygen, which can minimise bacterial infections and promote oxygenation of the blood sucked as blood travels down the aspirator tube 44 mixing with oxygen.

Therefore, in case of using integral oxygenation, both chambers (first chamber 24 and second chamber 26) provide oxygenation and removal of CO2.

During the negative gauge pressure cycle, oxygenation will continue; although not necessarily at the same rate as that during the positive gauge pressure cycle. The vacuum level is maintained dynamically by the gas inlet control assembly block 54 to keep the rate of fill in second chamber 26 appropriately.

A concentric arrangement of the first chamber 24, second chamber 26 and third chamber 28 is shown in Figure 6.

Priming stage An important starting procedure in the preparation of CPB for surgery is the system priming; usually with a priming solution or with blood, or a combination. It will be appreciated by the person skilled in the art that the volume required for priming of the system will depend upon the size and thereby total blood volume of the patient upon which the device is to be used.

In the present EBC device, the priming volume can be much smaller compared to the running volume. After initial priming (depending on the case requirements) the running volume is reached within a few pneumatic cycles because of the ability to control the venal reservoir intake and blood-flow out from the device independently using the control valves 38 & 80.

The following priming process is suitable for both Example 2 and Example 3.

With reference to Figure 3, first chamber 24 priming can be achieved simply by applying a negative gauge pressure of --4.8 kPa (-0.7PSI) to facilitate suction of priming fluid into the first chamber 24 to a required fill level. This level is then roughly maintained throughout the priming of the rest of the system by allowing more liquid to be sucked in until the priming cycle was completed.

The third chamber 28 is first exposed to atmospheric pressure and the servo-motor valve 72 is closed. Negative gauge pressure, e.g. -13.8 kPa (-2PSI) is then applied to the second chamber 26, which opens the check valve 40 passing liquid from the first chamber 24 to the second chamber 26. When the liquid level in second chamber 26 rises to a suitable level below its upper limit, positive gauge pressure is applied, e.g. 34.5 kPa (5PSI), which automatically closes the valve 40 while opening the valve 60. This passes liquid into the third chamber 28.

The valve 72 is kept opened until a sufficient amount of priming fluid is driven into the third chamber and then closed.

The volume of the third chamber 28 is greater than that of the second chamber 26 to ensure that the second chamber 24 output is fully accommodated during the pressure cycle with some space to spare. This residual space acts as a gas buffer and facilitate bubble trapping.

When the liquid level in the second chamber 26 drops to a lower limit, the pressure cycle reverses; sucking liquid into second chamber 26 as before. The process is continued until the full system is primed, at which point the venal and aortic servo-motor controlled valves 38 & 80 and the pressure regulator valve 72 are activated through their control circuitry in readiness for initiating extracorporeal circulation.

Description of extracorporeal circulation

Once the system is primed, alternating pressure cycles (e.g. -13.8 kPa & 34.5 kPa (-2PSI & 5PSI)) are applied to the second chamber 26 such that the blood is pumped via the aortic control valve 80. The flow rate can be controlled at a required rate mainly with control valves 38 & 80, e.g. 5Um typically.

In case of using integral oxygenation (Example 3), the blood will also get oxygenated. If integral oxygenation is not used, an external oxygenator is connected downstream following the aortic output 78.

Example 4

With reference to Figure 4, an EBC device is provided according to Example 2, or Example 3 where the individual chamber cavities are provided in one concentric design.

As can be seen from Figure 4, the chambers are arranged concentrically. Dimensions are so chosen to meet the required flow circulation and buffering capacity together with low blood-chamber surface contact area. Also, the priming volume required is to be kept to a minimum as an additional important consideration. Starting with a smaller priming volume, the blood volume within the chambers can be built up within a few pressure cycles to reach to the desired capacity.

Such optimisation strategies, while achieving the desired perfusion flow rate, are possible because there are many design parameters available, including system pressure differentials, Chamber liquid levels, pressure cycle frequency and system geometry.

In Figures 2 & 5, the locations of valves and connectors are shown in places appropriate for clarity and ease of understanding. However, in practice they will be placed in suitable locations for ease of construction and operation.

For example, Figure 4 shows the case where the concentric design is mounted on a hollow box 94 as a table-top design. In this case all control valves, e.g. 48, 38, 72, 54, 80; and control electronics are assembled with access to appropriate manual controls in the front face and tubular connections at the back. Interface connections to computer and display may be provided on any side of the base 94.

Unlike in the case of existing CPB machines with mechanical pumping systems, the total tubular length within the blood circulation circuit is very much reduced by this design, which is also an important advantage.

The chambers can be manufactured as a single disposable unit, just like the reservoirs, oxygenators etc. in the present CPB systems. All control valves, electronic hardware and base assembly, which will not come in contact with blood or any fluids will remain as reusable stationary components EBC system.

Blood flow measurement In existing CPB systems, blood flow is monitored by a variety of techniques, such as ultrasonic doppler or transit time, infra-red and sometimes electromagnetic methods. Although most of these can be positioned on a flow path section external to the blood flow, a main limitation is that they are indirect methods, requiring frequent calibration and are subject to significant variability.

In the Examples above, blood flow is measured using differential pressure between the pressure measured at the top of a chamber and at the bottom of the chamber using pressure sensors, e.g. 10, 12. The pressure at the top of the chamber is the pressure of gas in that location. The pressure at the bottom of the chamber is the sum of the gas pressure and the instantaneous hydrostatic pressure. Accordingly, a drop in liquid level per unit time directly relates to the output flow rate, which can be computed knowing the differential sensor output and the cross-sectional geometry of the chamber. If the internal geometry is uneven, this can be accommodated by first determining the relationship between level change with actual flow volume change as a function of liquid level within the chamber and using this in the computation of instantaneous flow rate.

In the Examples presented herein, the two sensors within a given chamber are of the same type. Before the EBC devices are used the operating characteristics (pressure vs output) are first established. These characteristics are typically represented by straight line graphs with differing offsets and gradient (gain). The gain and offset of one of the sensors is adjusted to very closely coincide with the other. This process has been found to overcome common mode and differential error characteristic of the pressure sensors to allow direct measurement of blood level and blood flow rate. The difference signal resulting from the characterised and adjusted sensors directly represents the liquid level. The derivative of the difference signal represents the flow rate of blood into or out of the chamber. Accordingly, eliminating the problems from both common mode and differential error characteristics of the pressure sensors allows accurate direct measurement of blood level and blood flow rate.

The described method has been found to provide superior results compared to existing methods of flow measurement in this or in similar applications as it is closer to an absolute measurement compared to indirect methods, such as ultrasonic or infra-red technology.

Example 5

With reference to Figure 7, an EBC system 100 comprises a first pumping chamber 102 (corresponding to a first EBC device) and a second pumping chamber 104 (corresponding to a second EBC device) connected to the extracorporeal circuit via a vena cava inlet 106 and an aorta outlet 108. The flow of blood from the inlet 106 to the first pumping chamber 102 is controlled by a first valve 110, and the flow of blood from the inlet 106 to the second pumping chamber 104 is controlled by a second valve 112. The flow of blood from the first pumping chamber 102 to the outlet 108 is controlled by a third valve 114 and the flow of blood from the second pumping chamber 104 to the outlet 108 is controlled by a fourth valve 116.

Figure 7 shows the EBC system where the first pumping chamber 102 is in the second stage of operation of an EBC device, and the second pumping chamber 104 is in the first stage of operation of an EBC device. Accordingly, Figure 7 shows the first valve 110 and the fourth valve 116 closed to prevent the flow of blood from the inlet 106 to the first pumping chamber 102, and to prevent the flow of blood from the second pumping chamber 104 to the outlet 108.

The second valve 112 and the third valve 114 are shown to be open to allow the flow of blood from the inlet 106 to the second pumping chamber 104 and the flow of blood from the first pumping chamber 102 to the outlet 108.

The EBC system comprises an aspirator 118 connected to the first pumping chamber 102 and the second pumping chamber 104 and the flow of blood from the aspirator 118 to the first pumping chamber 102 is controlled by a fifth valve 120 and to the second pumping chamber 104 is controlled by a sixth valve 122. The fifth valve 120 is open when the first pumping chamber 102 is in the first stage of operation and is closed when the first pumping chamber 102 is in the second stage of operation. The sixth valve 122 is open when the second pumping chamber 104 is in the first stage of operation and is closed when the second pumping chamber 104 is in the second stage of operation. The aspirator 118 comprises a control 124 to allow a user to control when the aspirator 118 is operated.

The EBC system further comprises an oxygenator 126, unidirectional valve 128 and a flow control valve 130 downstream of the first pumping chamber 102 and second pumping chamber 104. The EBC system further comprises a unidirectional valve 132 and a flow control valve 134 up stream of the first pumping chamber 102 and second pumping chamber 104.

A reversible pneumatic pressure differential is applied to the two reservoirs alternatively to enable circulation.

System priming Initially the first pumping chamber 102 is primed, e.g. with -0.5 to 1.6Liters of priming solution. Lower priming volumes may be used as required.

The second valve 112 and the third valve 114 are kept in the open position (and the first valve 110 and the fourth valve 116 & the Push-on closed). The fifth valve 120 and sixth valve 122 may be kept operating in synchronism with the first valve 110 and the second valve 112 respectively, but they are redundant during priming and until the hand-held control 124 is pressed when required during normal operation.

Then an appropriate pneumatic pressure differential Pi -P2 (in this case Pi>P2) is applied such that an aortic infusion rate (a blood flow rate out of the outlet of the EBC system 100) of approximately 5 Um (or a rate as determined by the user) is achieved, under the control of the control valve 130.

The second pumping chamber 104 then receives venal blood. This can be initially set at a rate somewhat higher than the infusion rate to enable a satisfactory build-up of reservoir blood volume by appropriate adjustment to P2 and the control valve 134 in the venal circuit, while ensuring P3 remains within the range of permissible venal blood pressure.

The process is then reversed with pressure differential applied in the opposite direction with first valve 110 and the fourth valve 116 opened.

This process may be repeated a couple of times until adequate reservoir blood volume (e.g. 3L) are available for circulation.

This operation is estimated to take about 90 seconds and may be carefully monitored by pressure and flow sensors under the control of dedicated software and hardware.

Steady-state operation During surgical procedures, the above reciprocal application of the pressure differentials is continued to maintain a steady blood-circulation of -5L/m, or at a rate as determined by the user.

The reservoir blood levels are constantly monitored and controlled in real-time by dedicated hardware and software. This is necessary since the human body has elasto-plastic behaviour for fluid retention and therefore the difference between the aortic and venal flow can have short-term fluctuations.

It is important to note that, since either of the pumping chambers while in the receiving mode can have negative gauge pressure with respect to atmosphere, the aspiration of blood from the surgical wounds (pericardial succession) can be achieved without any additional aspirator pumps as in the existing systems. Furthermore, other suction pumping requirements can also be integrated with separate control valves. The hand-held aspirator control 124 allows succession to be directed automatically to the receiving reservoir at any instant of time.

Blood oxygenation Blood oxygenation can be achieved in a number of ways. The schematic in Figure 7 shows an external blood oxygenator 126, which can be of any standard type in use, e.g. Extracorporeal Membrane Oxygenator (ECMO) by setting up the drive pressure required for a given type.

It is known that ECMO's have better performance compared to bubble oxygenators for prolonged operations, although, there is no conclusive evidence that for operations under 2 hrs, there is any difference in overall performance between the two types. It is also known that significant number of oxygenator failures happen; requiring emergency replacements during surgery, which is a very high-risk situation.

Example 6

The system of Example 5 can be modified to provide oxygenation of the blood. In this example, with reference to Figure 8, the first pumping chamber 102 comprises an oxygenator 136 and the second pumping chamber 104 comprises an oxygenator 138. The requirements for pneumatic drive pressure and oxygenation may be achieved at the same time by providing the necessary pressure drive by the bubbling oxygen within the pumping chambers 102 and 104.

The design of such a pumping chamber requires matching many parameters; such as flow rates, gas supply rate, reservoir height & capacity and partial pressures of 02 and 002, etc. within required tolerances.

Two of the main advantages of such an integral design would be (1) the reduction of cost of the disposable components of the CPB systems and (2) enhanced safety against oxygenator failures. The latter is due to the fact that a system with easily switchable facility for oxygenation may take over the full functionality in an emergency.

An example flow chart describing the operation process of the system of Example 6 is shown in Figure 9. The first valve 110, the second valve 112, the third valve 114, the fourth valve 116, the fifth valve 120 and the sixth valve 122 are represented as valves 1-6 respectively.

The first pumping chamber 102 and the second pumping chamber 104 are represented as Reservoir A and Reservoir B respectively.

The bubble oxygenator shown in Figure 8 has a curvature, which could be upward curvature or downward curvature. This is to promote a small convection pattern within the chamber due to differences in hydrodynamic drag and also reduce the possibility of the microscopic bubbles reaching the outlet. Figure 8, for example, shows the integral oxygenator assembled in the experimental prototype, which has a downward curvature.

In Figure 8, oxygenation is shown in two stages. The example shown is a point at which the first pumping chamber 102 is supplying blood into the aortic pathway, while the second pumping chamber 104 is receiving venal blood from the Vena cava.

Starting with the second pumping chamber 104, it can be seen that a controlled oxygen supply is provided to allow partial oxygenation of blood as it fills to a set level. S3 & 54 are two-way solenoid valves with one of the paths containing a variable restrictor (Rv) to provide oxygen at a different rate when the reservoir is in the receiving mode. During this period, S2 is opened to P2, which is maintained at a level below the atmospheric pressure (i.e. P2 is negative --13.8 kPa (--2P51)). This not only promotes the removal of CO2 from the blood, but also enables the aspirator circuit and the other suction pumping requirements to become active. When the reservoir is filled to a set level it is ready to switch over its function from the "receiver mode" to the "supply mode".

In the "supply mode" valves 1 -4 are appropriately switched over to enable oxygenated blood to be pumped into the aorta. At the same time the pneumatic solenoid of the reservoir is switched to Pi to apply the pneumatic pressure drive. This valve can then be closed until next stage of the sequence. Oxygen supply is switched to the bubble oxygenator via path 1 of Sa.

The rate of supply of oxygen (or an appropriate mixture of oxygen and medical air) is controlled such that it matches the requirements of blood flow rate (e.g. -51/m) and blood oxygenation level. These parameters may be monitored by software and provide the necessary control functions to maintain the desired set points.

When the supply reservoir is emptied to a set level, the above process is reversed and continues to reciprocate under the monitoring and control functions implemented in software with dedicated electronic hardware. While both chambers provide means of oxygenation and removal of carbon dioxide, the higher pressure in the drive chamber has the added advantage of increasing the efficiency of blood-oxygenation, and the lower negative pressure in the opposite chamber provides effective removal of carbon dioxide.

The basic operation of the system topologies of Figure 7 & 8 may be summarised in the form of a state transition diagram, as in Figure 9, below. The flow chart is drawn to encompass Figure 8, since it is possible to easily identify the procedure of Figure 7 by leaving aside the operations that are only specific to Figure 8. A more elaborate design (not shown here) will use two mass-flow controllers for oxygen supply at the two different rates required.

It is noted that S3 & Rv can also be combined to form a single control valve.

For simplicity, please note that it is assumed that at the start all valves are in the closed position.

State diagram components are described in Table 1 below: Component Type Function Valves 1-6 Bidirectional, Non-contact with Selects appropriate circulation pathway (non-contact) flow (e.g. active clamps) Si -S4 Two-way solenoid with closed position when de-energised Provides pneumatic pressure (and oxygen as in Fig. 8) (Medical grade) START switch Binary "on-off', Latching type Process ON or OFF Signals "A-full", Binary signals obtained from Process reversal -reciprocity signals "B-full" level sensors in the reservoirs

Table 1

Example 7

With reference to Figure 10, the configuration of Example 5 and 6 in an alternative Example is implemented as a concentric design with parameters optimised to meet the design requirements with minimal blood-surface contact area. An EBC system 200 comprises a first EBC device 202, a second EBC device 204 and a common buffer chamber 206. The first EBC device 202 and a second EBC device 204 are arranged concentrically around the common buffer chamber 206. Blood flows from an inlet 208 to the first EBC device 202 and the second EBC device 204. Blood flows from the first EBC device 202 and the second EBC device 204 to the common buffer chamber 206, and blood flows from the common buffer chamber 206 to the outlet 210.

A common pneumatic drive 212 applies positive pressure to the first EBC device 202 or the second EBC device 204 during the second stage of operation of the first EBC device and the second EBC device. The common pneumatic drive 212 applies a negative pressure to the first EBC device 202 and the second EBC device 204 during the first stage of operation of the first EBC device 202 and the second EBC 204.

The EBC system 200 is supported on a base 214.

The EBC system 200 further comprises an aspirator 216 that allows blood to be drawn into the first EBC device 202 and the second EBC device 204 from an external wound, for example.

The first EBC device 202 comprises an oxygenator 218 in the pumping chamber of that device.

The second EBC device 204 comprises an oxygenator 220 in the pumping chamber of that device.

If the pressure changes were applied sufficiently fast, the common buffer chamber 206 can be omitted, in which case a gas diffuser may be installed inside each of the first EBC device 202 and the second EBC device 204 to avoid agitation. However, it is best to use the assembly with the common buffer chamber 206.

Vi & Vo are inlet and outlet control valves 222 and 224 as in the half bridge design. The pneumatic drive 212 reciprocally applies the pressure and vacuum to the first EBC device and the second EBC device, simultaneously. Oxygen flowing into the chambers are controlled by valves marked O. Note that in the case of Full-bridge configuration (Examples 5, 6 and 7), there is no separate venal reservoir as the venal blood is automatically directed towards the reservoir with negative pressure during reciprocal application of pneumatic pressure via venal control valve VI.

It is important to note that a desktop version of either configuration as above will have much less connecting tubular length compared to existing systems such as that with peristaltic pumps.

Example 8

With reference to Figures 11 and 12 an extracorporeal blood circulation (SC) component 301 comprises a pumping chamber 302, a pneumatic drive 304 (acting as a drive unit), an inlet 306, an outlet 308, a first pressure sensor 310 and a second sensor 312. The pneumatic drive 304 comprises a chamber 322 (acting as a drive chamber), a piston 324 (acting as a drive piston) and a pressure conduit 326 connecting the chamber 322 to the pumping chamber 302.

The piston 324 is configured to move back and forth along the chamber 322 in a cyclical nature. In a first mode the piston 324 moves along the chamber 322 to reduce the volume of the chamber 322 to thereby drive gas retained within the chamber 322 through the pressure conduit 326 into the pumping chamber 302 to apply a positive gauge pressure to the pumping chamber 304. In a second mode the piston 324 moves along the chamber 322 to increase the volume of the chamber 322 to thereby draw gas retained within the pumping chamber 302 into the chamber 322 to apply a negative gauge pressure to the pumping chamber 302.

During use blood is drawn into the pumping chamber 302 through the inlet 306 when a negative gauge pressure is applied to the pumping chamber 302 through the pressure conduit 326 of the pneumatic drive 304 in a first stage of operation, and blood is driven out of the outlet 308 of the pumping chamber 302 when positive gauge pressure is applied to the pumping chamber 302 through the pressure conduit 326 of the pneumatic drive 304.

In an alternative example the pneumatic drive 304 comprises a gas inlet. During the first stage of operation at least a portion of the gas drawn into the chamber is drawn from the gas inlet.

The gas inlet comprises a valve that allows gas to pass through the gas inlet to the chamber but does not allow gas to pass through the gas inlet from the chamber.

The pneumatic drive 304 comprises a gas outlet. During the second stage of operation at least a portion of the gas driven from the chamber is driven through the gas outlet. The gas outlet comprises a valve that allows gas to pass through the gas outlet from the chamber but does not allow gas to pass through the gas outlet to the chamber.

While there has been hereinbefore described approved embodiments of the present invention, it will be readily apparent that many and various changes and modifications in form, design, structure and arrangement of parts may be made for other embodiments without departing from the invention and it will be understood that all such changes and modifications are contemplated as embodiments for other EBC components and EBC systems as a part of the present invention as defined in the appended claims.

Claims

Claims 1. An extracorporeal blood circulation (EBC) component comprising a pumping chamber, the pumping chamber comprising: an inlet comprising an inlet valve; an outlet comprising an outlet valve; and a pneumatic drive configured to apply a positive pressure and a negative pressure to the pumping chamber, wherein, during use in a first stage the pneumatic drive applies a negative pressure to the pumping chamber to thereby draw blood into the pumping chamber via the inlet, and wherein in a second stage the pneumatic drive applies a positive pressure to the pumping chamber by driving a gas into the pumping chamber to thereby drive blood retained within the pumping chamber out of the outlet.
2. An EBC component according to claim 1, wherein the gas driven into the pumping chamber by the pneumatic drive comprises oxygen.
3. An EBC component according to claim 1 or claim 2, wherein gas driven into the second chamber during the second stage is in direct contact with the blood retained within the pumping chamber.
4. An EBC component according to any preceding claim, wherein the pumping chamber comprises an oxygenator.
5. An EBC component according to claim 4, wherein the oxygenator is located within the pumping chamber such that during use the oxygenator is submerged or substantially submerged beneath the blood retained within the pumping chamber during at least the first stage or the second stage.
6. An EBC component according to either of claims 4 or 5, wherein the oxygenator is connected to an oxygen gas source such that during use oxygen or a gas comprising oxygen is driven into the oxygenator and out into the blood retained within the pumping chamber.
7. An EBC component according to any one preceding claim, wherein the pumping chamber comprises at least one pressure sensor configured to detect the pressure within the pumping chamber.
8. An EBC component according to any preceding claim, wherein the pneumatic drive comprises a drive unit, the drive unit comprising a drive chamber and a drive piston, wherein movement of the drive piston within the drive chamber applies positive gauge pressure in a positive stroke and applies a negative gauge pressure in a negative stroke.
9. An EBC device comprising the EBC component according to any one preceding claim, a reservoir and a buffer chamber, the reservoir comprising a reservoir inlet comprising an inlet flow-control valve, a reservoir outlet, and a vacuum regulator configured to apply a negative pressure to the reservoir during use, wherein the reservoir outlet is fluidly connected to the inlet of the pumping chamber such that during the first stage blood is drawn into the pumping chamber from the reservoir through the reservoir outlet, the buffer chamber comprising: a buffer inlet; a buffer outlet comprising an outlet flow-control valve and a pressure regulator configured to apply a positive pressure to the buffer chamber during use, wherein the buffer inlet is fluidly connected to the outlet of the pumping chamber such that during the second stage blood is driven out of the pumping chamber to the buffer chamber through the buffer inlet of the buffer chamber.
10. An EBC device according to claim 9, wherein the reservoir comprises an oxygenator. 25
11. An EBC device according to claim 10, wherein the oxygenator is located within the reservoir such that during use the oxygenator is submerged or substantially submerged beneath blood retained within the reservoir during at least the first stage or second stage.
12. An EBC device according to any one of claims 9 toll comprising an aspirator.
13. An EBC device according to claim 12, wherein the aspirator comprises a gas outlet, and during use the gas outlet of the aspirator is configured to direct gas at a target area.
14. An EBC device according to any one of claims 9 to 13 comprising at least one pressure sensor configured to detect the pressure within the reservoir.
15. An EBC device according to any of claims 9 to 14, wherein the reservoir surrounds or substantially surrounds the pumping chamber.
16. An EBC device according to any of claims 9 to 15, wherein the reservoir inlet further comprises a unidirectional valve such that during use the unidirectional valve allows blood to flow into the reservoir through the inlet and prevents the flow of blood from the reservoir out of the inlet.
17. An EBC device according to any of claims 9 to 16, wherein the reservoir inlet further comprises a control valve.
18. An EBC device according to any one of claims 9 to 17, wherein the buffer outlet further comprises a unidirectional valve such that during use the unidirectional valve allows blood to flow out buffer chamber through the buffer outlet and prevents the flow of blood into the buffer chamber through the buffer outlet.
19. An EBC device according to any one of claims 9 to 18, wherein the buffer outlet comprises a control valve.
20. An EBC device according to any one of claims 9 to 19, wherein the buffer chamber comprises at least one pressure sensor.
21. An EBC device according to any one of claims 9 to 20, wherein the buffer chamber is surrounded by the pumping chamber, and wherein the pumping chamber is surrounded by the reservoir.
22. An EBC device according to claim 21, wherein the pumping chamber and reservoir are concentric about the buffer chamber.
23. An EBC system comprising an inlet, an outlet, a first EBC component according to any one of claims 1 to 8 and a second EBC component according to any one of claims 1 to 8, wherein the inlet of the EBC system is fluidly connected to the inlet of both the first EBC component and the second EBC component, and the outlet of the EBC system is fluidly connected to the outlet of both the first EBC component and the second EBC component, wherein the first EBC component and the second EBC component are configured such that the first stage of operation of the first EBC component occurs during the second stage of operation of the second EBC component and the second stage of operation of the first EBC component occurs during the first stage of operation of the second EBC component.