Patent Description:
Cannulae are well known and widely employed in the medical arts. Cannulae can be used to remove fluids from a biological system, such as removing blood from a vein or artery, or to introduce fluids into a biological system, such as providing saline, drugs, gases or other substances to a body.

In some cases, the cannula is merely a tube through which material may flow, but in other cases the cannula can be a more complex device allowing the affixing of the biological system to the cannula on a permanent or semi-permanent basis. Such affixing is performed to inhibit unintended disconnections of the biological system from the cannula due to movement of the biological system with respect to the cannula and/or due to pressure differences between a working fluid shared between the biological system and the medical device, etc. The prior art contemplates various surgical devices for insertion into an arterial or venous vessel. <CIT> describes a system and a method for providing sealable access to a viscus region or a hollow organ, the system comprising a tissue stabilizer to provide a stable work area. A puncture hole is formed through the tissue using a puncture device and a sealing device is inserted through the puncture hole and inflated to engage the interior tissue and create a seal.

To date, in all but the simplest cases (wherein the cannula may be retained in place via adhesive tape or similar techniques), affixing a cannula to a biological system has required surgical skills to be employed. Typically, the cannuta is affixed to the biological system by a surgeon or medical technician who sutures the cannula to the biological system. Such procedures require the person performing them to have a high level of skill and often require long periods of time to perform the suturing, specialized equipment and/or a suitable environment to successfully perform the necessary joining.

In some cases, the biological system to which the cannula is to be attached can be especially challenging with which to achieve a desired connection. For example ,in extracorporeal perfusion of lungs the pulmonary vein and/or a portion of the left atrium of the heart must be connected to a perfusion device via a cannula. Generally, the amount of the pulmonary vein or atrium available to be used to receive the stitches is quite limited and the pulmonary vein or atrium is exceedingly difficult to handle, being very slippery and with little, if any, rigidity. Thus, it takes a great deal of professional skill and time to suture a cannula to such biological systems.

It is desired to have a cannula which can be affixed to biological systems, including challenging biological systems such as pulmonary veins and/or heart atria, without requiring the levels of professional skill and time required for prior art cannulae. Further, it is desired to have such a cannula which can inhibit unintended disconnections of the cannula from the biological system due to relative movement there between or other factors.

It is an object of the present invention to provide a novel cannula for interfacing a medical device to a biological system which obviates or mitigates at least one disadvantage of the prior art, as defined in claim <NUM>. Advantageous embodiments are subject of the dependent claims.

According to a first aspect of the present invention, there is provided a cannula for connecting a medical device to a biological system comprising: a body having a first region and a second region, the first region including a main port for a working fluid and a vacuum port and the second region having a working fluid port in fluid communication with the main port and a tissue engagement portion, the tissue engagement portion comprising a groove about the exterior of the body and encircling the working fluid port, the groove including at least one vacuum outlet in fluid communication with the vacuum port.

Preferably, the groove includes a plurality of vacuum ports in fluid communication with the vacuum port. Also preferably, the second region further includes stand offs adjacent the working fluid port to inhibit direct contact between the working fluid port and a biological system to which the cannula is connected which might otherwise obstruct the flow of working fluid.

According to another aspect of the present invention, there is provided a cannula kit to connect a medical device to a biological system, the kit comprising: a body having a first region and a second region, the first region including a main port for a working fluid and a vacuum port and the second region having a working fluid port in fluid communication with the main port and a tissue engagement portion, the tissue engagement portion comprising a groove about the exterior of the body and encircling the working fluid port, the groove including at least one vacuum outlet in fluid communication with the vacuum port; and an affixment device to encircle tissue of a biological system at the tissue engagement portion and to maintain the tissue engaged therewith.

Preferably, the affixment device is a silk surgical suture, a resilient O-ring or a cable tie.

The present invention provides a novel cannula for connecting a medical device to a biological system. The cannula includes a tissue engagement portion, preferably in the form of an annulus, to which a vacuum is applied through the cannula to attract and hold tissue of the biological system in an initial connection while an affixment device is applied to complete the connection. The affixment device can be a wide variety of devices to establish a connection between the biological system and the cannula at the tissue engagement portion, including a silk surgical tie, a cable tie, a resilient member, such as a medical O-ring, etc. In addition to a working fluid conduit, comprising a main port, a working fluid passage and a working fluid port, and a port to apply the vacuum, the cannula can include a sensor port to allow sensing pressure or other characteristics of the working fluid at a point closely adjacent to the connection between the cannula and the biological system.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:.

A cannula in accordance with an embodiment of the present invention is indicated generally at <NUM> in <FIG>. As described in more detail below, cannula <NUM> comprises a body <NUM> having a first region <NUM> comprising one or more ports for connecting to a medical device and a second region <NUM> for connection to a biological system.

Body <NUM> can be fabricated from a variety of materials, including any one of, or any combination of, engineering nylon or other plastic materials, stainless steel, aluminum, etc. and can be fabricated by injection molding, investment casting, 3D printing or via any number of other techniques as will be apparent to those of skill in the art. The primary limitations on the manufacture of body <NUM> are that it can be manufactured in a medically sterile manner, or that it can be suitably sterilized subsequent to manufacture. In a presently preferred embodiment, cannula <NUM> is manufactured by 3D printing from a suitable plastic material compliant with ISO <NUM>, for biocompatibility, and which is suitable for sterilization via Gamma or EtO sterilization processes and is a "single use" device which is disposed of after it has been used.

In the embodiment of <FIG>, cannula <NUM> includes three ports to which a medical device and/or device subsystems can be attached. Specifically, cannula <NUM> includes a vacuum port <NUM>, a sensing port <NUM> and a main port <NUM>.

Main port <NUM> serves as the working fluid (e.g. - perfusion fluid, blood, plasma, etc) connection of cannula <NUM> to the medical device. Vacuum port <NUM> allows a medical vacuum to be supplied to cannula <NUM>, as described in more detail below, and sensing port <NUM> provides access for the sensing of the pressure and/or other characteristics of the working fluid moving through manifold port <NUM> into, or out of, the biological system to which cannula <NUM> is affixed. Such other characteristics can include temperature, pH, dissolved gasses, etc..

Second region <NUM> of cannula <NUM> includes a tissue engagement portion <NUM> which, in this embodiment, is an annular groove, or indented portion of reduced diameter relative to the adjacent portions of second region <NUM>, formed in body <NUM>. In other embodiments, tissue engagement portion <NUM> can include a textured or barbed surface instead of, or in addition to, the groove shown in the Figures. In still other embodiments, the groove and surface features (such as textures or barbs) can be omitted from tissue engagement portion <NUM>. As shown in the Figures, tissue engagement portion <NUM> includes a plurality of vacuum outlets <NUM> each of which is in fluid communication with vacuum port <NUM> via vacuum passages <NUM> that are formed through body <NUM>. In the illustrated embodiment, cannula <NUM> includes six vacuum outlets <NUM> but, as will be apparent to those of skill in the art, more or fewer vacuum outlets can be provided in cannula <NUM> as desired and/or required for specific applications.

Second region <NUM> further includes a working fluid port <NUM> which is connected to main port <NUM> by a working fluid passage <NUM>. As can be seen in the Figures, tissue retention annulus <NUM> surrounds working fluid port <NUM>. The combination of main port <NUM>, working fluid passage <NUM> and working fluid port <NUM> forms a conduit allowing working fluid to be transferred between the medical device and the biological system through cannula <NUM>. The conduit formed by main port <NUM>, working fluid passage <NUM> and working fluid port <NUM> can include a chamber adjacent to working fluid port <NUM> that has a greater cross-sectional area (perpendicular to the direction of fluid flow) than the remainder of the conduit. An example of such a chamber is shown in <FIG>, in the form of a conical expansion of the conduit approaching working fluid port <NUM>. The chamber need not be conical in other embodiments.

Sensing port <NUM> is connected, via a sensing passage <NUM>, to a sample port <NUM> which, preferably, is located immediately adjacent to working fluid port <NUM>, to allow for the accurate sensing of the pressure, or other characteristics, of the working fluid as close to the connected biological system as possible.

While, in the illustrated embodiment, body <NUM> is shown as having a cylindrical shape, the present invention is not so limited and it is contemplated that other shapes can be employed to better complement some biological systems, if desired. For example, it is contemplated that body <NUM> can be fabricated with an oval or elliptical cross section presented to the biological system to be connected with, or with other shapes that may advantageously engage particular biological systems as will occur to those of skill in the art. Body <NUM> can have a variety of other cross-sectional shapes, including irregular shapes. In general, the shape of body <NUM> can be selected based on the shape of the biological system and medical devices to be connected by cannula <NUM>.

It is also contemplated that body <NUM> can include a second working fluid port (not shown) which can be used as a sampling port to provide a small amount of working fluid to a technician, or sensor, for testing of various characteristics of interest, or to allow the introduction of drugs or other materials into the working fluid and connected biological system.

<FIG> shows a representative example of the connection of cannula <NUM> to a pulmonary vein <NUM> and to a vacuum supply <NUM>, a working fluid reservoir <NUM> and a pressure sensor feedline <NUM>. <FIG> depicts a method <NUM> of connecting the cannula <NUM> to a pulmonary vein or other biological system, and will also be referred to in the discussion below.

To make the connection of <FIG> between the cannula <NUM> and the pulmonary vein <NUM>, vacuum supply <NUM> is connected to vacuum port <NUM> at block <NUM> of method <NUM>. At this point, working fluid reservoir <NUM> and/or pressure sensor feedline <NUM> can also be connected, or either or both of these can optionally be connected after the cannula <NUM> has been connected to the pulmonary vein <NUM>. In the illustrated embodiment, the connection to sensing port <NUM> is shown as being a Luer connector, but any suitable means of making a connection can be employed as desired.

Following the connection of vacuum supply <NUM> to vacuum port <NUM>, at block <NUM> of method <NUM>, the operator, who will typically only need to be a medical technician with moderate skills, then draws the pulmonary vein <NUM> up over second region <NUM> (more specifically, over tissue engagement portion <NUM>) until pulmonary vein tissue completely covers tissue engagement portion <NUM>. With biological tissue covering each vacuum outlet <NUM> of tissue engagement portion <NUM>, the performance of method <NUM> proceeds to block <NUM>, at which a vacuum is applied to vacuum port <NUM> via vacuum supply <NUM> (that is, a vacuum pump or other apparatus connected to vacuum supply <NUM> is switched on). That vacuum is, in turn, applied to vacuum outlets <NUM> via vacuum passages <NUM>. As will be apparent to those of skill in the art, as the tissue of pulmonary vein <NUM> overlies each vacuum outlet <NUM>, the vacuum supplied to the respective outlet <NUM> will suction the pulmonary vein tissue onto tissue engagement portion <NUM> and will assist in maintaining the tissue in place, in an initial connection, until a final connection is made to affix the tissue as described below.

In many cases, the supplied vacuum will provide an added benefit in that the technician or other medical professional making the connection of cannula <NUM> to the pulmonary vein <NUM>, or other biological system, will hear an audible noise caused by the vacuum drawing atmosphere through vacuum outlets <NUM>. As biological tissue engages and obstructs each vacuum outlet <NUM>, the volume of the audible noise will decrease correspondingly, until the noise terminates when the pulmonary, or other biological, tissue has engaged and obstructed all of vacuum outlets <NUM>. When this happens, the medical technician will know that a good initial connection has been achieved. If the vacuum noise does not terminate, the technician will know that they have failed to make a good initial connection and to further manipulate pulmonary vein <NUM> until the noise terminates indicating that such a good initial connection has been obtained.

Once a good initial connection has been obtained, with some portion of the tissue of pulmonary vein, or other biological system, covering tissue engagement portion <NUM>, at block <NUM> of method <NUM> an affixment device <NUM> can be employed by the operator to complete the connection. The affixment device <NUM> encircles the biological tissue engaging the tissue engagement portion <NUM> and is tightened to further compress the biological tissue into tissue engagement portion <NUM>, thus completing the affixation of the biological tissue to cannula <NUM>. Once the affixment device <NUM> is properly in place the supply of vacuum to vacuum port <NUM> can be removed, if desired (block <NUM> of method <NUM>). Removal of the vacuum can be achieved by switching off the vacuum-generating apparatus (e.g. a vacuum pump) connected to vacuum supply <NUM>, or by disconnecting vacuum supply <NUM> from vacuum port <NUM>.

In some embodiments, if the vacuum is sufficiently strong, the application of affixment device <NUM> may be omitted. In other embodiments, the order of at least some of the above steps may be changed. For example, in some embodiments block <NUM> (application of the vacuum) may be performed before block <NUM> (placement of biological tissue over tissue engagement portion).

In the illustrated embodiment of <FIG>, affixment device <NUM> is a silk surgical suture that is tied around tissue engagement portion <NUM>. Affixment device <NUM> can also be nylon, cotton, or the like, or any suitable combination thereof. The proper use of such an affixment device is well within the skills of a medical technician, and is much less difficult to perform than the prior art technique of suturing the biological system to the cannula, which typically required advanced surgical skills.

It is also contemplated that a wide variety of other technologies can be employed as affixment device <NUM>. For example, a resilient medical (sterile) O-ring can be employed instead of the silk surgical suture, the O-ring being stretched over the biological tissue and tissue engagement portion <NUM> and then released to compress the biological tissue in place in tissue engagement portion <NUM> to achieve the desired connection. As another example, a so-called "cable tie" can be employed as affixment device <NUM> and medical versions of such cable ties are commonly available. It is also contemplated that a second affixment device (not shown) can also be employed above (more distal from tissue engagement portion <NUM>) tissue affixment device <NUM> to further secure the biological tissue if desired. In such a case, body <NUM> can include a second annular groove, or indented portion of reduced diameter (not shown) which the second affixment device can engage, but in such a case no vacuum outlets <NUM> would be provided in the second annular groove. In still further embodiments, a second annular groove as mentioned above can include a second set of vacuum outlets, also connected to vacuum port <NUM>.

As should now be apparent to those of skill in the art, the actual selection and configuration of affixment device <NUM> is not particularly limited and a wide variety of solutions will occur to those of skill in the art.

While in the above-described embodiment tissue engagement portion <NUM> is in the form of an annulus (e.g. - a groove in the cylindrical body <NUM>), the present invention is not so limited and tissue engagement portion <NUM> can be formed in a variety of other shapes, depending upon the biological system to which cannula <NUM> is to be attached and/or the cross sectional shape of body <NUM> presented to the biological system. For example, tissue engagement portion <NUM> can be formed as an ellipsoidal groove in body <NUM>, etc. As mentioned earlier, a variety of other shapes, including irregular shapes, can be employed for tissue engagement portion <NUM>.

<FIG> and <FIG> show another embodiment of a cannula, indicated generally at <NUM>, in accordance with the present invention and wherein like components to those of the embodiment of <FIG> discussed above, are indicated with like reference numerals.

As best seen in <FIG>, cannula <NUM> includes a set of stand offs in the form of upraised flutes <NUM> which operate to prevent the surface of cannula <NUM> surrounding working fluid port <NUM> from directly abutting the biological system to which cannula <NUM> is connected, to ensure that flow to and/or from working fluid port <NUM> is not restricted by such abutment.

While the illustrated embodiment includes flutes <NUM> which are formed with body <NUM>, it is contemplated that similar stand offs can be provided instead by providing one or more metal or plastic protrusions or legs, or by employing loops of metal or plastic to form a cage-like structure adjacent working fluid port <NUM> to inhibit direct abutment of working fluid port <NUM> with the biological system to which cannula <NUM> is connected.

<FIG> shows another embodiment of a cannula, indicated generally at <NUM>, in accordance with the present invention and wherein like components to those of the embodiment of <FIG> discussed above, are indicated with like reference numerals. In this embodiment, a solid state sensor <NUM> is included in body <NUM> in place of sensing port <NUM>, sensing passage <NUM> and sample port <NUM>. Solid state sensor <NUM> can be used to sense one or more characteristics of the working fluid, such as pressure, temperature, pH, dissolved gasses content, etc. Solid state sensor <NUM> can also include an acoustic sensor to detect the absence or present of the above-mentioned vacuum noise, as used as an indicator of the desired initial connection.

With some manufacturing techniques for cannula <NUM>, such as injection molding, or casting, solid state sensor <NUM> can be molded in place with its electrical leads <NUM> extending from region <NUM> of body <NUM>, while with other manufacturing techniques solid state sensor <NUM> can be affixed, by a suitable epoxy, etc., in an appropriate aperture provided for it, and its electrical leads <NUM>, in body <NUM>. In other embodiments, solid state sensor <NUM> can be a wireless sensor (e.g. powered by a battery and including wireless data transmission hardware); in such embodiments, leads <NUM> can be omitted. It is also contemplated that in some circumstances, the need for a sensor may not exist and sensing port <NUM>, and its associated sensing passage <NUM> and sample port <NUM> can be omitted altogether, as could solid state sensor <NUM>.

While in the embodiments and examples discussed above working fluid port <NUM>, working fluid passage <NUM> and main port <NUM> are arranged in a substantially straight configuration, it is contemplated that, in some circumstances, it may be desirable to have main port <NUM> at an angle to working fluid port <NUM>. For example, main port <NUM> can be located at a ninety degree angle with respect to working fluid port <NUM> and such a geometry, and a variety of others, can be achieved by configuring the shape and/or position of working fluid passage <NUM> as desired. Similarly, vacuum port <NUM> and/or sensing port <NUM> (if present) can be located in a variety of different arrangements as may be desired to accommodate different physical needs of connecting to a variety of biological systems.

In further embodiments, one or more of main port <NUM>, vacuum port <NUM> and sensing port <NUM> need not be located in first region <NUM>. Instead, as shown in <FIG>, in a further embodiment of a cannula, indicated generally at <NUM>, at least one of main port <NUM>, vacuum port <NUM> and sensing port <NUM> can be located to second region <NUM>. In particular, in the variation shown in <FIG>, vacuum port <NUM> is located within second region <NUM>. More generally, vacuum port <NUM>, sensing port <NUM> and main port <NUM> may be located anywhere on cannula <NUM> that does not interfere with the placement of biological tissue over tissue engagement portion <NUM>.

In still further embodiments of a cannula, as indicated generally at <NUM> in <FIG>, sample port <NUM> need not be located within working fluid passage <NUM> adjacent to working fluid port <NUM>. Instead, sample port <NUM> can be located adjacent to working fluid port <NUM> but outside working fluid passage <NUM>.

Cannulae in accordance with the present invention have been found to be particularly useful for extra-corporeal organ perfusion systems and, in particular, for extra-corporeal lung perfusion. In prior art extra-corporeal perfusion systems, a skilled surgeon was required to suture the pulmonary vein to the perfusion system cannula and such an operation often took twenty minutes or more. With the cannulae of the present invention, a surgeon can achieve a desired connection between the cannula and the pulmonary vein in a few minutes and, in fact, such a connection can be achieved by a less skilled medical technician in about the same time. Further, the connection obtained with the present invention is robust and can easily survive transportation of the organ, such as from a donor harvesting location to a transplant location.

However, cannulae in accordance with the present invention are not limited to use for extra-corporeal organ perfusion and can alternatively be used in a wide variety of situations wherein it is desired to obtain a reliable affixment of a cannula to a biological system without requiring advanced surgical skills and/or an undue amount of time to achieve the affixment. For example, in some embodiments a cannula as described herein can be employed for accurate measurement of pressures across the tympanic membrane of an ear (e.g. a human ear), by connecting the working fluid port <NUM> to the irregular external geometry of the ear.

Referring now to <FIG>, a method <NUM> of using a cannula as described herein is illustrated. At block <NUM>, the biological system (e.g. a lung being readied for transplantation) is prepared for cannula insertion. Preparation of the biological system may include, for example, cleaning or other manipulation of the tissue to be connected to the cannula. At block <NUM>, the cannula (e.g. any of cannulae <NUM>, <NUM>, <NUM>, <NUM> and <NUM> mentioned above, or any of the variations discussed herein) is removed from its sterile packaging. At block <NUM>, the cannula is attached to the prepared biological system, for example by performing method <NUM>.

Once the cannula is attached to the prepared biological system, at block <NUM> fluid flow into the biological system is initiated via main port <NUM> and working fluid port <NUM>. In some embodiments, where sensors are employed, sensing can also be initiated at block <NUM>, for example via sensing port <NUM> or sensor <NUM>. At block <NUM>, fluid flow (and sensing, if employed) is continued until the procedure is complete. Completion can include any one of, or any combination of, the completion of a treatment of the biological system, the completion of transport of the biological system to a transplant location, and the like.

When the procedure is complete, the performance of method <NUM> proceeds to block <NUM>. At block <NUM>, fluid flow to the biological system via the cannula is halted. If sensing was initiated at block <NUM>, such sensing is also halted at block <NUM>. At block <NUM>, the affixment device attaching the cannula to the biological system is removed. At block <NUM>, the cannula is disconnected from the biological system. The cannula can then be discarded, or resterilized for further use.

Claim 1:
A cannula (<NUM>) for connecting a medical device to a biological system, comprising:
a body (<NUM>) including a main port (<NUM>) for a working fluid, a working fluid port (<NUM>), and a conduit (<NUM>) extending through the body (<NUM>) between the working fluid port (<NUM>) and the main port (<NUM>), the conduit (<NUM>) configured to transfer the working fluid between the main port (<NUM>) and the biological system, via the working fluid port (<NUM>); the body (<NUM>) further including a tissue engagement portion (<NUM>) having an annular groove encircling the working fluid port (<NUM>) on an exterior of the body (<NUM>) between the main port (<NUM>) and the working fluid port (<NUM>); and
the body (<NUM>) further including a vacuum port (<NUM>), at least one vacuum outlet (<NUM>) included in the annular groove of the tissue engagement portion (<NUM>), and at least one vacuum passage (<NUM>) extending through the body (<NUM>) between the at least one vacuum outlet (<NUM>) and the vacuum port (<NUM>).