Field of the invention

The invention relates to a device for removing air from an extracorporeal blood circulation circuit, particularly a disposable device that can be adapted to the morphology of any type of extracorporeal circuit.

Background art

Devices have been long known and used for removing air accidentally contained in or introduced into extracorporeal blood circulation circuits, during cardiopulmonary bypass surgery and cardio-respiratory assistance in heart patients.

The presence of air in these disposable extracorporeal circuits is known to be totally undesired, as it might cause air embolism in patients, and eventually threaten their vital functions and survival.

For this purpose, a basic circuit, which is known for instance from

WO2005/065741 or EP 1 557186 comprises a line for venous blood drainage from the patient, along which a venous filter or reservoir is mounted for containing venous blood and from which any air is first removed.

A suction pump is provided downstream from the venous reservoir, for applying a negative pressure to the venous line and facilitate motion of blood from the patient and along the entire circuit.

An oxygenator is mounted downstream from the pump, where blood is enriched with oxygen and cleared from excess carbon dioxide, and downstream from this oxygenator, before final reintroduction of oxygenated blood into the patient through an arterial line, blood passes through an arterial filter, for filtering off any minor bubble of residual air.

Both the venous reservoir and the arterial filter have apertures for evacuating the removed and accumulated air and, according to the two above documents, devices are also provided for detecting volumes of air retained, accumulated or passing through the venous filter or reservoir.

These detector devices are typically connected with valves mounted on the evacuation apertures, and can be automatically controlled to open when the volumes of air to be removed reach predetermined values or to close once air has escaped to the atmosphere to restore the tightness of extracorporeal circuits.

A parallel bypass line may be also provided between the patient and the venous reservoir, with a suction pump and a downstream cardiotomy reservoir mounted therealong, which reservoir is in turn connected to a line for connection to the venous reservoir.

In order to minimize any risk of accidental ingress of air into the extracorporeal circuits, variants have been provided concerning both standard components of a circuit and their position therealong.

For example, the venous reservoir has been removed and replaced by an arterial filter which receives both the venous blood drainage line from the patient and the connection line between the cardiotomy reservoir and the venous filter.

A further drawback of these disposable extracorporeal lines is that they have to be filled before use.

Such filling step is carried out by first introducing carbon dioxide into the tubing that forms the extracorporeal circuit, to wholly saturate the atmosphere with this gas, which is known to be more soluble than air and then by a so-called "priming" procedure, which consists in progressively filling the extracorporeal circuit and the components mounted thereon, with a blood-biocompatible liquid solution typically known as "saline" or "priming solution" or simply "priming".

Such "priming" is carried out while closing both the access port for patient venous blood drainage, e.g. by a Klemmer forceps or equivalent device, and the arterial blood reintroduction access.

Only when the entire circuit has been saturated with the saline and properly debubbled in any component, the two access ports are reopened and blood starts to flow from the patient, under the negative pressure generated by the suction pump, and to circulate in the circuit in mixture with the saline which partially dilutes it.

These extracorporeal circuits are mainly used in machines known as "heart-lung machines", for treatment of patients that suffered serious heart damages, such as infarction; extracorporeal circuits do not have highly practical or quick startup, because they both have to be prepared long in advance, and their use has to be scheduled, which reduces in certain cases the possibility of saving patients' lives or affecting the integrity of some of their vital functions.

The prior art suffers from certain drawbacks.

A first drawback consists in that prior art extracorporeal circuits include a multitude of tubes for connection of the various components, each of which is formed individually and in that one or more supports have to be provided for proper arrangement of all the components, and for fixation of both components and the tubes that connect them.

While this multitude of tubes are made of plastic and hence are highly flexible, they still have a considerable overall size and their length and the loops they form to connect the various components often hinder the movements of the surgical staff during the procedure on the patient, which procedure has to be as quick as possible, as mentioned above, due to the nature of the disturbance; therefore niches may be formed in these tubes where air stagnates and is later susceptible of flowing in and out of the circuit, following the blood flows in the circuit.

A second drawback consists in that, in order to fill the entire extracorporeal circuit and prime all the tubes and components for steady- state operation, the patient's blood to be treated has to be diluted with the priming solution, and this step may cause serious hemodynamic decompensation, which may be dangerous for the safety of patients subjected to such extracorporeal support.

The venous filter and the arterial filter, with the associated tubes that connect them to the inlet and outlet of the extracorporeal circuits are among the components that most influence the quantity of blood to be withdrawn from the patient.

An additional drawback is that each junction between the components and the tubes or between tubes are potential accidental air ingress points: in systems with active venous drainage caused by the negative pressure maintained in the extracorporeal circuit, if junctions are not perfectly tight, air will be sucked in through any fissure created by such imperfect junctions.

A further drawback is that, in prior art extracorporeal circuits, the arterial filter and the venous filter, if any, are primed by introducing the saline from an aperture located in the upper area, typically coinciding with the inlet of the device, and by discharging it through an aperture located in the lower area, typically coinciding with the outlet.

This process involves the requirement of shaking the filters after priming, for instance by turning them upside down, for mechanically removing any air bubbles retained between loops of the filtering body.

In a different technique, the circuit and the filters are filled in an opposite direction, i.e. by introducing the saline through the lower outlet of a filter, namely the arterial filter, and causing it to flow in the extracorporeal circuit from bottom to top, and to exit through the upper inlet, thereby automatically pushing any air bubbles towards the latter.

Nevertheless, such filling process requires a special bypass line between the inlet and outlet, which is primarily used for this filling task.

Disclosure of the invention

It is an object of the present invention to improve the prior art.

Another object of the invention is to provide a device for removing air from an extracorporeal blood circulation circuit, that is particularly compact, and affords a significant reduction of priming volumes.

Yet another object of the invention is to provide a device for removing air from an extracorporeal blood circulation circuit, that significantly reduces the number of connection tubes between the components of the extracorporeal circuit.

In one aspect, the invention relates to a device for removing air from an extracorporeal blood circulation circuit as defined in claim 1 .

Therefore, the invention provides the following advantages:

- it avoids the need for any handling of the arterial filter and the venous filter to remove any air bubbles trapped in the loops of the filters, by providing retrograde filling, to ensure perfect performance of this step and removal of any air therein;

- it considerably reduces the number and length of the tubes that connect the components of the extracorporeal circuit;

- it reduces the volumes of saline and hence blood for priming the circuit before use, to minimize the risk of sudden and dangerous pressure drops in the vascular system of the patient;

- it constantly monitors the volumes of air separated from the blood and removes them, when these are close to values that may affect proper operation of the device and safety of the patient;

- it affords substantially complete removal of air from blood flowing in the extracorporeal circuit;

- it facilitates motion of blood in the extracorporeal circuit, while reducing or adapting the number of pumps required for maintaining a substantially constant flow along the tubes and the components through which it circulates;

- it orients certain parts of the device in directions that are favorable for the functional position of the tubes in space, and minimizes the required length and avoids undesired throttling;

- if required, it connects a pump directly to the body of the device for removing air from the extracorporeal blood circulation circuit, thereby further reducing both the overall size and the number of connecting tubes to be filled and, as a result, the overall volume of the extracorporeal circuit.

Brief description of the drawings

Further features and advantages of the invention will be more readily apparent upon reading of the detailed description of a preferred non exclusive embodiment of a device for removing air from an extracorporeal blood circulation circuit, which is shown as a not limiting example in the annexed drawings, in which:

FIG. 1 is a schematic view of an extracorporeal blood circulation circuit which incorporates a device for removing air from blood in an extracorporeal circuit according to the invention ;

FIG. 2 is a general schematic view of an embodiment of the device of the invention ;

FIG. 3 is a longitudinal sectional view of the device of the invention, as taken along a plane I l l-I l l of Fig. 2;

FIG. 4 is a longitudinal sectional view of the device of the invention, as taken along a plane IV-IV of Fig. 2;

FIG. 5 is a partially broken away view of a second embodiment of the device of the invention, as taken along a first viewing angle;

FIG. 6 is a partially broken away view of a second embodiment of the device of the invention, as taken along a second viewing angle, perpendicular to the first viewing angle of Fig. 5;

FIG. 7 is a schematic view of an extracorporeal blood circulation circuit which incorporates a second embodiment of the device for removing air from an extracorporeal blood circulation circuit according to the invention ;

FIG. 8 is a partially broken away view of a third possible embodiment of the device of the invention ;

FIG. 9 is a schematic view of an extracorporeal blood circulation circuit which incorporates a device for removing air from blood in an extracorporeal circuit according to a possible alternative embodiment of the invention.

Detailed description of one preferred embodiment

Referring to Fig. 1 , numeral 1 designates a patient having a venous line 2 and an arterial line 3 connected thereto, and numeral 1 00 generally designates an extracorporeal circuit for filtering and oxygenating the blood of the patient 1 , e.g. during cardiopulmonary bypass procedures.

Numeral 4 designates a device for removing air from the extracorporeal circuit 1 00, which comprises a body 1 04 with a first housing chamber 1 06 and a second housing chamber 1 05 defined therein, which receive respective filters, namely a venous filtering element 20 that forms a venous filter 6 with the first housing chamber, and an arterial filtering element 21 that forms an arterial filter 5 with the second housing chamber 1 05.

As shown in the figure, the two housing chambers 1 05 and 1 06 are coaxially mounted one above the other, as shown herein without limitation with the first housing chamber 1 06 below the second housing chamber 1 05.

Respective upper areas 31 and 39 of the latter, defined as first accumulation compartment and second accumulation compartment respectively, are designed to accumulate any air removed from blood as it flows through the extracorporeal circuit 1 00.

The first accumulation compartment 31 is equipped with a central coaxial vent conduit 32 with a tap 208 (or an equivalent valve means known to the skilled person) at its outward end, which opens and closes the vent conduit 32 and is connected with a vent line or tube 1 6 opening into a collecting element 24 which is maintained at a negative pressure whose absolute value is lower than the absolute value of the negative pressure in the venous filter 6 and is obtained, as shown below, by the action of a pump 7 mounted downstream from the venous filter 6.

The terms "line" and "tube" will be interchangeably used below, as they are coincident for the purposes of implementation.

Furthermore, the term "negative pressure" will be generally intended as a pressure whose absolute value is lower than atmospheric pressure.

The collecting element 24 also receives a line 14 which connects it to the second area 39, through a tap 1 3 (or an equivalent shut-off member), for opening or closing the line 14.

As shown in Fig. 1 , a line 22 extends from the tap 1 3 for directly connecting the line 14 with the venous line 2.

A passage 305 is formed in the middle of the arterial filter 5, and allows the conduit 32 to extend all along it and project out of the upper wall 306 of the arterial filter 5.

Both the filter 20 and the filter 21 are retained in their respective housing chambers by means of respective end elements 40 and 50, generally known as "pottings", which hold them fixed therein.

As shown in Fig. 1 , in the most complete embodiment of the device 4 of the invention, the above mentioned pump 7 is mounted to the base of the venous filter 6, and is thus integral with the body 1 04. Nevertheless the skilled person will understand that the pump 7 may also be separate from the body 1 04, as described below, and alternatively mounted separate therefrom to a line 9, as shown by broken lines, that connects the venous filter 6 with an integral assembly comprising a heat exchanger 1 0 for heating blood to the normal body temperature and an oxygenator 1 1 .

A connection line 1 2 extends from the latter, for connecting the exchanger/oxygenator assembly 1 1 /1 2 to an inlet 30 for accessing the second housing chamber 1 05 and the arterial filter 5.

A level sensor 8 is also designed to be mounted to the venous filter 6 for detecting the air volumes collected in the conduit 32 and in the underlying first accumulation compartment, and may be connected to an electronic control system, which is designed to control the opening of the tap 208, or to an alarm device.

A line 26 is also provided in the extracorporeal circuit 1 00, and extends from a container unit 27, typically a bag, that contains saline to be used for priming the extracorporeal circuit 1 00.

The line 26 opens into the line 9 through a tap 1 8 (or another known valve device), which is designed to control its opening or closing operation.

Fig. 1 also shows that the two venous 2 and arterial 3 lines may be interconnected by a connecting line 60, whose junctions with the venous 2 and arterial 3 lines will be regulated by corresponding taps 61 and 62 or Klemmer forceps or equivalent valve members, to facilitate priming of the extracorporeal circuit 100.

Referring to Fig. 2, which shows the device 4 in an embodiment that has no pump 7, the body 1 04 appears to be divided into two coaxial half- bodies having a common longitudinal axis "A", which are arranged one above the other, the lower one being referenced 304 and the upper one 404.

The two half-bodies 304 and 404 are assembled in such an arrangement as to be able to rotate relative to each other.

Referring to Figures 3 and 4, the lower half-body 304 appears to have a first upper annular portion 306 designed to be constrained in a known manner, e.g. by interlocking arrangement or welding, to a mating lower annular counter-portion 406, which integrally extends from the upper half body 404.

The base of the conduit 32, referenced 1 32, is trapped therein, with an interposed annular seal 1 33 that surrounds the outer surface of the base 1 32 and ensures its sealing action against the inner surface of the annular counter-portion 406.

As shown in Figures 2 and 3, an inlet port 31 0 for the blood drained from the patient 1 is formed in the lower half-body 304, which port has a connection for the venous line 2, whereas an outlet port 41 0 for the filtered and oxygenated blood to be reintroduced into the patient 1 through the arterial line 3 is formed in the upper half-body 404.

As shown in Figure 3, the port 31 0 opens into the first accumulation area 31 , whereas the outlet 41 0 opens into a filtered blood collection area defined between the base 1 32 of the conduit 32 and the lower portion of the second housing chamber 1 05, referenced 49.

The lower area of the half-body 304 has an outlet port 37 formed therein, for the venous blood filtered by the venous filtering element 20, which port has a standard connector for the connecting line 9 for connection to the integral exchanger/oxygenator assembly 1 1 /1 2.

In addition to the inlet 30, a pair of vent ports 1 7 and 1 7A are also provided in the upper half-body 404, namely in the upper portion thereof, which ports both have standard connecting mouths for respective vent lines 14' and 14 (Fig. 1 ) and both communicate with the second accumulation compartment 39.

The difference between these two vent ports is that the vent port 1 7 is controlled by a gas permeable membrane 52 mounted at the base of the vent port itself, while the vent port 1 7A is completely free and connected via the vent line 14 to the collecting element 24 maintained under negative pressure.

Figures 5 and 6 show an embodiment of the device 4 which incorporates the pump 7 at the lower base, whereas all the components of the device 4 are equal to and designated by the same numerals as those of Figures 2, 3, 4.

It shall be noted that the pump 7 is enclosed in a box-like enclosure 307 which is associated as an extension of the lower half-body 304 and is coupled thereto along a connection line 308 which, if required, may consist of two annular elements 309 and 31 1 tightly joined together in such a manner as to be able to rotate relative to each other.

Fig. 7 shows a second embodiment of the body 1 04, here referenced 504, which only differs from the above described embodiment in that the two venous 6 and arterial 5 filters are arranged side-by-side, although still in a common housing body, i.e. the body 504.

The other unchanged components of the extracorporeal circuit 1 00 are designated in Fig. 7 with the same numerals.

Referring to Figure 8, in which the same numerals have been maintained for the parts equal to the previous embodiments, it may be appreciated that a possible further embodiment of the device for removing air from the extracorporeal circuit 1 00 has the two housing chambers 1 05 and 1 06 in coaxial relation and arranged one inside the other in the container body 1 04, whose base is also connected to the enclosure 307 for the pump 7 which hence forms a one-piece assembly with the body 104, like in the embodiment of Figures 5 and 6.

In the embodiment of Figure 8, the first chamber 106 appears to be placed within the second chamber 1 05 which, as a result, exteriorly surrounds it; nevertheless the skilled person will easily appreciate that the positions of the two chambers 105 and 1 06 are interchangeable without affecting the operation of the inventive device, as long as the latter is properly connected with the two venous 2 and arterial 3 lines.

As compared with the above described embodiments, the conduit 32 appears to be designed to be connected to the second accumulation compartment 39 via a connecting conduit 500 with a valve member 50, e.g. a tap, mounted thereto, for opening or closing such connection.

It shall be further noted that the bottom of the first housing chamber 1 05 is connected to the enclosure 307 for the pump 7 through a connecting port, referenced 37'.

Also, it shall be noted that, like in the above described embodiments, the venous 20 and arterial 21 filtering elements and their respective end elements 40 and 50 are held in their proper filtering position by means of an inner frame, 51 0 and 520 respectively, which have apertures at the two venous 20 and arterial 21 filtering elements for allowing the passage of venous and arterial blood flows to the latter.

The operation of the device for removing air from an extracorporeal blood circulation circuit is as follows: the venous line 2 and the arterial line 3 are connected to the patient 1 .

This is followed by a priming step, in which the whole extracorporeal circuit 1 00 is filled with saline.

This priming step is carried out by controlling the two taps 61 and 62 or equivalent Klemmer forceps, to cause the two venous 2 and arterial 3 lines connected to the patient 1 to be closed while the line 60 that connects them is opened.

Thus, the patient 1 is temporarily isolated from the extracorporeal circuit 1 00 until completion of the priming step.

Then, the tap 1 8 is opened and the saline contained in the container unit 27, typically a bag, falls by gravity into the extracorporeal circuit 1 00 and fills all the lines, the pump 7, the venous 6 and arterial 5 filters, the exchanger

1 0, the oxygenator 1 1 .

The filling level moves from bottom to top, i.e. in a retrograde direction relative to the normal direction of blood flows in the device, according to the arrangement as shown in Fig. 1 , whereby any air in the lines and components of the extracorporeal circuit 1 00 is automatically removed through the vent line 14' formed in the upper area of the half-body 404 of the arterial filter 5 which, excluding the container unit 27, is the highest point of the whole extracorporeal circuit 1 00.

As soon as the priming step is completed, with the circuit closed upon itself, the pump 7 is actuated for enough time to remove any stagnating air bubbles and level the temperature of the whole solution to a predetermined value.

Subsequently, the taps 61 and 62 (or equivalent Klemmer forceps) are controlled to open the connection with the patient 1 and shut off the connection between the two venous 2 and arterial 3 lines, which is temporarily established by opening the line 60, thereby allowing the venous blood to be drained into the extracorporeal circuit 1 00.

The tap 1 8 is also moved to the closed position, thereby isolating the container unit 27 from the rest of the extracorporeal circuit 1 00.

The pump 7 is actuated again and creates a negative pressure in the extracorporeal circuit 1 00, which causes the blood of the patient 1 to flow through the venous line 2 into the housing chamber 1 06 of the venous filter 6, via the inlet port 31 0 of the half-body 304.

The venous blood of the patient 1 is filtered by the venous filtering element 20 and the air separated from the venous blood is collected in the first accumulation area 31 of the first housing chamber 1 06 and the conduit 32, if any.

The volume of air collected in the first collection compartment 31 and the conduit 32 is detected by the level sensor 8 which triggers an alarm as soon as the volume of accumulated air reaches a high value, to warn an operator that he/she may operate by directly sucking in air from the accumulation zone, using the tap 208, or by automatically controlling the opening of the tap 208 to evacuate air into the collecting element 24, which is maintained, e.g. by means of an additional suction device external to the extracorporeal circuit 1 00 at a negative pressure having a more negative value than the maximum negative pressure value that can be generated in the extracorporeal circuit 1 00 by the pumping action of the pump 7, relative to atmospheric pressure.

The filtered venous blood flows out of the venous filter 6 through the outlet port 37 and is pushed by the pump 7 along the line 9, to reach the integral assembly composed of the exchanger 1 0 and the oxygenator 1 1 , in which it is heated to an appropriate temperature, as defined for the purposes of proper treatment, and is enriched with oxygen. Then, blood flows from the oxygenator 1 1 along the arterial line 1 2 and enters the arterial filter 5 through the inlet 30 formed in the half-body 404, thereby filling the second housing chamber 1 05.

The arterial blood is filtered by the arterial filtering element 21 and the air removed by filtering accumulates in the second accumulation compartment 39.

Then, air is evacuated outwards from this second accumulation compartment 39, through both vent ports 1 7 and 1 7A, the only difference being that airs flows out of the vent port 1 7 spontaneously, through the gas- permeable membrane 52, whereas through the vent port 1 7A it is conveyed into the collecting element 24 via the line 14.

By handling the tap 1 3, the air that passes through the vent port 1 7A may be also diverted towards the venous line 2, via the connecting line 22: thus, the air accumulated in the second accumulation compartment 39 may be conveyed and accumulated into the first accumulation compartment 31 and the conduit 32 and eliminated therefrom as described above.

The arterial blood that has been filtered by the arterial filtering element 21 is collected on the bottom of the second housing chamber 1 05, wherefrom it is perfused into the patient 1 again, after passing through the outlet port 410, via the arterial line 3.

In the embodiment of the device 4 for removing air from an extracorporeal circuit 1 00 as shown in Figures 2, 3, 4, the two half-bodies 304 and 404 are mounted in such an arrangement as to be able to rotate relative to each other, to facilitate the orientation of the ports 310, 41 0, 30 and 1 7A and the associated connecting lines between the patient 1 and the device 1 00.

As shown in Figures 1 and 7, the pump 7 may be enclosed in a compartment formed at the base of the half-body 304, and thereby form substantially one piece with the venous 6 and arterial 5 filters, or may be separated therefrom, as shown in Figures 1 and 7 by broken lines, without affecting the operation of the device 4 for removing air from the extracorporeal circuit 100. The operation of the second possible embodiment of the device 4 for removing air from the extracorporeal circuit 100 as shown in Fig. 7 is identical to the one described above, and to the one of the third embodiment as shown in Figure 8.

Nevertheless, in the latter case, it shall be noted that, if required, the first accumulation compartment 31 and the second accumulation compartment 39 may be connected by means of the connecting conduit 500 by opening the tap 501 or, conversely, may be left separate, by leaving the tap 501 in the closed position.

The invention has been found to fulfill the intended objects.

The invention so conceived is susceptible to changes and variants within the inventive concept.

Also, all the details may be replaced by other technical equivalent elements.

In practice, any material, shape and size may be used as needed, without departure from the scope as defined by the following claims.