WO2015063497A1

WO2015063497A1 - Trocar and cannula

Info

Publication number: WO2015063497A1
Application number: PCT/GB2014/053237
Authority: WO
Inventors: Dr Iain DAVIES
Original assignee: Davies Dr Iain
Priority date: 2013-10-31
Filing date: 2014-10-30
Publication date: 2015-05-07
Also published as: GB201319259D0

Abstract

The invention provides a trocar and cannula device (1) comprising: a cannula (3) comprising an axial passage and a distal end suitable for insertion into tissue; a cannula housing (5) which holds a proximal end of the cannula (3); a trocar (11) engageable with the axial passage of the cannula; and a trocar housing (9) which holds a proximal end of the trocar (11), wherein the trocar housing (9) is axially moveable relative to the cannula housing (5). The diameter of the axial passage of the cannula (3) is capable of expanding from an unexpanded state to an expanded state, thereby permitting increased fluid flow. The trocar (11) is arranged to force the axial passage of the cannula (3) into the expanded state by the action of axial movement of the trocar (11) through the axial passage of the cannula. It may be that the trocar (11) is arranged to force the axial passage of the cannula (3) into the expanded state when the trocar (11) is withdrawn through the axial passage of cannula (3) away from the distal end of cannula.

Description

TROCAR AND CANNULA

This invention relates to an improved trocar and cannula device, and the use of the trocar and cannula device.

Background to the invention

Trocar and cannula devices are generally used for delivery or removal of fluid from the body of a patient, for example, in order to access the blood stream in the veins and arteries. Trocar and cannula devices may also be used for insertion into body cavities in order to provide a passage from the cavity, for example in treatments requiring drainage of the chest.

In general, the trocar is an elongate surgical instrument that can be located inside a cannula and can be used to help pierce the skin and the wall of a cavity or canal in the body, e.g. to aspirate fluids or to instill a medication or other fluid. The trocar is removed, and the cannula is left in place. Thus, as is well known in the art, a trocar is a surgical instrument used with a cannula (and optionally together with an insertion needle) to puncture a body cavity for fluid aspiration, fluid delivery, or the like.

For blood access, the trocar and cannula are pierced through the skin and other tissues of a patient and the cannula is guided into position in a vein or artery. The trocar is then withdrawn from the cannula to allow the flow of blood such that blood samples may be taken.

A similar process is undertaken if the cannula is to be used to provide fluid, e.g. medication. Once the trocar is withdrawn the flow of the fluid though the cannula can occur and thus the medication or other fluid can be delivered into the vein or artery via the cannula. A large diameter cannula is preferred in order to achieve a greater amount of fluid flow through the cannula when giving fluid treatments. However, insertion of a cannula is always painful for the patient and it is traumatic for the tissue. A cannula can be difficult to insert, requiring skilled medical staff. The pain suffered by the patient and the difficulty of insertion by the operator exist in a linear relationship with the diameter of the cannula. The insertion process also needs to be relatively simple and quick in emergencies.

Therefore, there is a need for improved trocar and cannula devices, and a need for improving the usability and tolerability of wider trocar and cannula devices.

Description of the invention

According to a first aspect of the invention, there is provided a trocar and cannula device comprising:

-a cannula comprising an axial passage and a distal end suitable for insertion into tissue; -a cannula housing which holds a proximal end of the cannula;

-a trocar engageable with the axial passage of the cannula; and

-a trocar housing which holds a proximal end of the trocar, wherein the trocar housing is axially moveable relative to the cannula housing;

wherein the diameter of the axial passage of the cannula is capable of expanding from an unexpanded state to an expanded state, thereby permitting increased fluid flow, and

wherein the trocar is arranged to force the axial passage of the cannula into the expanded state by the action of axial movement of the trocar through the axial passage of the cannula. The trocar and cannula device of the invention advantageously provides a thin cannula that is easy to insert into tissue, thereby causing less pain and trauma to the patient. The cannula can also provide sufficient flow volume by expanding after insertion of the cannula into the tissue. The device of the present invention is capable of providing these beneficial properties during the insertion process, with a quick and simple mechanism of action.

The cannula may be substantially elongate, extending from a proximal end to a distal end.

The trocar may be substantially elongate, extending from a proximal end to a distal end.

In one preferred embodiment, at least part of the trocar is capable of expanding in diameter, wherein the expanded diameter of at least part of the trocar is substantially similar to the diameter of the axial passage of the cannula in its expanded state.

In one preferred embodiment, the trocar is arranged to force the axial passage of the cannula into the expanded state when the trocar is withdrawn through the axial passage of cannula away from the distal end of cannula. In one preferred embodiment, the trocar comprises an expansion section capable of expanding to a diameter that is greater than the diameter of the axial passage of the cannula in its unexpanded state.

Thus, in the present invention, the expansion of the cannula is preferably due to expanding the trocar once it is within the cannula. In one preferred embodiment the expansion of the cannula is due to drawing the trocar back out of the cannula. In one preferred embodiment the trocar and cannula are arranged such that the trocar can be located within the axial passage of the cannula, the trocar can then be expanded once it is within the cannula and the trocar can then be drawn back out of the cannula to cause expansion of the cannula.

Prior products that cause expansion of a cannula, sleeve or tube or other similar component do so by pushing an element such as a dilator into that component. For example, EP 2179762 discloses a stretchable-diameter inserter for hemodynamic studies. The device has an inserter tube, a hemostatic valve, a side line including a faucet, and two dilatators: a first dilatator having a smaller cross-section and a second dilatator having a larger cross-section. During a surgical procedure the inserter is arranged into the vessel by a standard operation. If the inserter needs to be used with an enlarged diameter, then a suitable dilatator is pushed into and engaged with the inserter.

US 6,338,730 describes cannulas for surgical and medical use which expand along their entire lengths. The cannulas, in an unexpanded condition and with a small diameter, are inserted through tissue. The cannulas are then expanded radially outwardly.

EP 1702575 relates to an access system which can be percutaneously introduced in a narrow diameter configuration and, which after introduction, can expanded to accommodate passage of larger diameter surgical instruments therethrough.

WO 00/02616 discloses methods for implanting articles, such articles for drug delivery, in solid tissue. The method uses a radially expandable sleeve, which is expandable from a narrow diameter configuration to a large diameter configuration providing a non-collapsible lumen. An assembly of a sleeve with a needle is introduced to a target site beneath a patient's skin. After reaching the target site, the needle is drawn out. After fully withdrawing the needle, a cannula/dilator assembly is introduced through the inner lumen of the expandable sleeve. The dilator can be then drawn out, leaving the cannula in place within the radially expanded sleeve. Therefore there is not an arrangement in these documents where a trocar is arranged to force the axial passage of the cannula into the expanded state when the trocar is withdrawn through the axial passage of cannula away from the distal end of cannula, or an arrangement where a trocar comprises an expansion section capable of expanding to a diameter that is greater than the diameter of the axial passage of the cannula in its unexpanded state.

Having the expansion caused by the trocar makes the claimed product more efficient to make and to use. No extra piece of equipment is required to be made, provided and sterilised; only the trocar and cannula are needed which would conventionally be used to get the cannula into position. No extra steps are therefore needed in terms of providing and using an extra component. Therefore the process can be carried out quickly and effectively. This is clearly vital in emergency situations, but indeed in all clinical situations the patient and clinician will benefit from a swift procedure.

Having the trocar arranged to force the axial passage of the cannula into the expanded state when the trocar is withdrawn through the axial passage of cannula away from the distal end of cannula also makes the process more efficient. No extra steps are needed. The trocar would need to be withdrawn in a conventional process so as to allow fluid to flow via the cannula. The benefit of the present invention is that the cannula is widened during that same withdrawal step, meaning that greater fluid flow is subsequently possible through said cannula. Therefore because no further steps are required the process can be carried out quickly and effectively. This speed is clearly vital in emergency situations, but indeed in all clinical situations the patient and clinician will benefit from a swift procedure.

In general, it will be appreciated that it is more straightforward to insert a cannula having a smaller diameter. Insertion of a cannula is always painful for the patient and it is traumatic for the tissue. A cannula can be difficult to insert, requiring skilled medical staff. The pain suffered by the patient and the difficulty of insertion by the operator exist in a linear relationship with the diameter of the cannula. However, a large diameter cannula is preferred in order to achieve a greater amount of fluid flow through the cannula when giving fluid treatments. In particular, in emergency situations providing sufficient quantity of a fluid treatment quickly can be vital, or taking sufficient quantity of a blood sample can be vital. The present invention has the benefit of allowing a smaller diameter of cannula to be inserted, making that insertion step more straightforward and less painful, but for a larger size of cannula diameter to actually be used in order to provide fluid or take fluid samples. This is achieved by a product that does not have extra components, such as a separate dilator, meaning that it is simpler to make, sterilise and use. Further, the product can be used in a manner that does not require additional steps, because the expansion of the cannula can be caused by withdrawal of the trocar, which is a step that would be undertaken anyway before samples were taken via the cannula or fluids provided through the cannula. In the present invention the trocar and cannula device may be for intravenous (IV) access. The trocar and cannula device may be for drainage; for example, the trocar and cannula device may be for drainage of the chest of a patient.

The trocar and cannula device may further comprise a grip housing positioned between the cannula housing and the trocar housing. The grip housing may be movable relative to the trocar housing and/or the cannula housing. The trocar may be slidably disposed within an axial passage of the grip housing. The grip housing may further comprise a grip handle. The grip handle may extend laterally from the grip housing. The grip housing may interlock with the cannula housing. The trocar housing may be capable of locking into position relative to grip housing. The trocar housing and grip housing may have at least two lock positions. One lock position may comprise a pre-engaged position where the trocar housing has not been moved towards the grip housing, and the trocar has not been engaged through the axial passage of the cannula. A second lock position may compromise an engaged position where the trocar housing has been moved towards the grip housing, and the trocar has been engaged through the axial passage of the cannula. The grip housing and the trocar housing may comprise a latch mechanism in order to lock them into a fixed position relative to each other. The latch mechanism may be a tongue and groove mechanism. The grip housing may comprise one or more tongues and/or one or more grooves, which are arranged to interlock with opposing tongues and/or grooves on the trocar housing. The tongue and grooves may extend circumferentially in the trocar housing and/or grip housing. The trocar housing may comprise a push button suitable for a user to push the trocar housing towards the cannula housing. The push button may be an integral surface of the proximal end of the trocar housing.

In one embodiment of the invention, the trocar and cannula device may further comprise an insertion needle disposed within the axial passage of the cannula. The insertion needle may be axially moveable relative to the cannula. The insertion needle may be smaller in diameter than the diameter of the trocar.

The trocar may be arranged to force the axial passage of the cannula into the expanded state when the trocar is pushed through the axial passage of cannula towards the distal end of the cannula. In another embodiment, the trocar may be arranged to force the axial passage of the cannula into the expanded state when the trocar is pulled/withdrawn through the axial passage of cannula away from the distal end of the cannula. At least part of the trocar may be greater in diameter than the diameter of the axial passage of the cannula in its unexpanded state. At least part of the trocar may be substantially similar in diameter as the axial passage of the cannula in its expanded state.

The trocar may be arranged to be withdrawn from the axial passage of the cannula by movement of the trocar housing away from the cannula housing. The insertion needle may be arranged to be withdrawn from the axial passage of the cannula together with the trocar. In one embodiment, the trocar may comprise a pip (i.e. a wider section) located adjacent to the distal end of the trocar. The pip may provide any shape of bulge or protrusion. It may be a curved shape or it may be a non-curved (angular) shape. The pip may, in one embodiment, comprise a substantially oval-shape or substantially rectangle-shape in a longitudinal cross-section. The pip may be directly adjacent to the distal end of the trocar or it may be a small distance from the distal end of the trocar, e.g. it may be located 2mm or less from the distal end of the trocar, such as 1mm or less or 0.5mm or less or 0.3mm or less. The pip of the trocar may be positioned at the distal end of the cannula when the trocar and cannula device is in a pre-engaged position (where the trocar extends all the way through the axial passage of the trocar). The pip may be larger in diameter than the axial passage of the cannula in its unexpanded state.

In another embodiment, at least part of the trocar may be capable of expanding in diameter, wherein the expanded diameter of at least part of the trocar may be substantially similar to the diameter of the axial passage of the cannula in its expanded state (e.g. they may be the same, or may be within 20% of each other or within 10% of each other). The trocar may comprise an expansion section capable of expanding to a diameter that is greater than the diameter of the axial passage of the cannula in its unexpanded state. Suitable materials for this section include non-porous, medically implantable, physiologically inert materials, and/or any other commercially available material that is able to be stretched/expanded but that can still maintain its rigidity, ensuring an essentially stretched/expanded yet semi-rigid surface. Examples include plastic material, silicone material and nitrile material.

The expansion section may comprise a deformable wall, wherein the deformation may cause the diameter of the expansion section to increase, for example, by forming a pip (i.e. a wider section) in the trocar. The pip may provide any shape of bulge or protrusion. It may be a curved shape or it may be a non-curved (angular) shape. The deformable wall may comprise a series of axially extending slits, which are circumferentially distributed around the expansion section of the trocar. The expansion section may comprise a hinge, wherein the hinge may allow deformation of the expansion section, thereby increasing the diameter of the expansion section. The expansion section may comprise a deformable collar section. The deformable collar section may, in one embodiment, comprise silicone. The deformable collar section may, however, comprise any surgically acceptable material that is capable of deforming/bending.

In one embodiment, the trocar and cannula device may further comprise a trocar connector. The trocar connector may be a rod disposed inside an axial passage of the trocar. The trocar connector may be anchored to the trocar at a position between the distal end of the trocar and the expansion section. The trocar connector may be arranged to hold the distal end of the trocar in position, whilst the proximate end of the trocar is axially moved towards the distal end, thereby forcing the expansion section to expand in diameter.

The trocar and cannula device may further comprise an anchor tube connected to the trocar connector and arranged to hold the trocar connector in position. The trocar may be slidably disposed within the anchor tube. The anchor tube may be fixed to the grip housing. The trocar connector and anchor tube may be capable of being withdrawn from the axial passage of the cannula together with the trocar, for example by the movement of the grip housing away from the cannula housing.

The widest part of the trocar may, in one embodiment, be about 1.5mm wide or more. The widest part of the trocar may, in one embodiment, be from about 1.5mm to about 3mm. The widest part of the trocar may, for example, be about 2mm in diameter. Such diameters may be useful when, for example, the invention is used for IV access. However, larger diameters may also be used, such as from about 3mm to about 10mm or more; for example when the invention is used in a drain, such as a chest drain. The trocar may be substantially uniform in diameter along its length. Alternatively, the trocar may be tapered, and/or may comprise a pip (a wider section). In an embodiment where the trocar comprises an expansion section, the trocar may, for example, be from about 0.5mm to about 2.5mm or more in diameter, e.g. from about 0.5mm to about 2mm, or from about 0.6mm to about 1mm, such as about 0.8mm in diameter, in its unexpanded state. In one such embodiment the trocar may be from about 0.7mm to about 2.1mm in diameter in its unexpanded state. In the embodiments where the trocar comprises an expansion section, the expansion section of the trocar may, for example, be from about 0.7mm to about 5mm or more in diameter, e.g. from about 0.8mm to about 4mm, or from about 1mm to about 3mm, such as about 2mm in diameter, in its expanded state. In one such embodiment, the expansion section of the trocar may be from about 1.5mm to about 3mm in diameter in its expanded state. In general, the expansion section of the trocar may have a diameter in the expanded state of greater than 0.7mm, or greater than 1mm or greater than 1.5mm. In some embodiments the expansion section of the trocar has a diameter in the expanded state that is greater than 3mm, or greater than 4mm or greater than 5mm, or even greater than 8mm or greater than 10mm. These larger diameters may, for example, apply when the invention is used in a drain, such as a chest drain.

The axial passage of the cannula may be from about 0.5mm to about 3mm or more in its unexpanded state, e.g. from about 0.7mm to about 2.5mm or from about 0.7mm to about 2.1mm. The axial passage of the cannula may, for example, be about 0.8mm in diameter in its unexpanded state.

The axial passage of the cannula may be at least about 0.7mm, or at least about 1mm, or at least about 1.5mm, or at least about 2mm, in its expanded state (such as about 3mm or more, or 4mm or more, or 5mm or more). It may even be about 8mm or more in its expanded state; in one embodiment, the axial passage of the cannula may be about 10mm or more in diameter in its unexpanded state. This may, for example, apply when the cannula is used as chest drain. The axial passage of the cannula may be expandable from an unexpanded diameter of about 0.7mm to about 1mm to an expanded diameter of about 3mm to about 3.5mm. Alternatively, the axial passage of the cannula may be expandable from an unexpanded diameter of about 0.6mm to about 0.8mm to an expanded diameter of about 2mm to about 2.5mm. In one embodiment the axial passage of the cannula may be expandable from an unexpanded diameter of about 0.7mm to an expanded diameter of about 2mm, for example when used for IV access.

The axial passage of the cannula may be expandable from an unexpanded diameter of about 1mm to about 2mm to an expanded diameter of about 5mm to about 8mm. Alternatively, the axial passage of the cannula may be expandable from an unexpanded diameter of about 1.5mm to about 2.5mm to an expanded diameter of about 8mm to about 10mm. In one embodiment the axial passage of the cannula may be expandable from an unexpanded diameter of about 2mm to an expanded diameter of about 10mm, for example when used for a drain, such as a chest drain.

The diameter of the axial passage of the cannula may be expandable by at least about 20%. The diameter of the axial passage of the cannula may be expandable by at least about 50%, or by at least about 80%. The diameter of the axial passage of the cannula may be expandable by at least about 100%. The diameter of the axial passage of the cannula may be expandable by at least about 100%, 110% 120%, 130%, 140% or 150%. The diameter of the axial passage of the cannula may be expandable by from about 30% to about 150%. The diameter of the axial passage of the cannula may be expandable by at least about 200%, at least about 300%, at least about 400% or at least about 500%. The amount of expansion of the diameter of the axial passage may depend upon the material composition of the cannula section and the increase in diameter of the trocar. The amount of expansion of the diameter of the axial passage may be selected depending on the intended end use of the invention.

The axial passage of the cannula in its expanded state may be substantially uniform in diameter along its length.

The cannula may comprise any surgically acceptable material. The cannula may comprise stretchable/expandable material in conjunction with other surgically appropriate materials of fixed dimensions. The cannula may comprise non-porous, medically implantable, and physiologically inert material. The cannula may comprise plastic material. The cannula may comprise silicone material. The cannula may comprise nitrile material.

The cannula may comprise at least one fold extending axially along the cannula in its unexpanded state. The fold may be arranged to unfold to allow the cannula to expand to the expanded state. The cannula may comprise at least two folds extending axially along the cannula in its unexpanded state. Alternatively, the cannula may comprise at least three, four or five folds extending axially along the cannula in its unexpanded state. The cannula may comprise two folds. The cannula may comprise four folds. The cannula may be arranged to expand in diameter by an unfolding of the folds in the cannula.

The cannula may comprise at least one split axially extending along the length of the cannula. One side of the split cannula may overlap with the opposing side of the split cannula, for example in the unexpanded state. The split cannula may allow the cannula to form a rolled structure. The cannula may comprise a flexible barrier membrane traversing the split in the cannula, thereby preventing leakage of fluid from the split. The flexible barrier may comprise any surgically acceptable material. The flexible barrier may comprise non-porous, medically implantable, and physiologically inert material. The flexible barrier may comprise plastic material. The flexible barrier may comprise rubber or latex material. The flexible barrier may comprise silicone material.

The axial passage of the cannula may be arranged to be held in its expanded state by the pressure of fluid passing through the axial passage. In an embodiment of the cannula comprising at least one split, the cannula may further comprise a latch mechanism to hold the cannula in its expanded state. The latch mechanism may comprise a tongue and groove running along the length of the cannula adjacent to the edges of the split. The trocar and cannula device may comprise a flashback chamber, for example, for visualising blood flow or water vapour into the trocar and cannula device. The flashback chamber may comprise a translucent material or window. The flashback chamber may comprise a translucent window in any of the cannula, cannula housing, trocar and/or trocar housing. The flashback chamber may comprise a translucent window in the trocar housing, such as a distal portion of the trocar housing.

Advantageously the flashback chamber would provide the operator a visual confirmation of blood flow to confirm successful vascular access. In the case of a chest drain, the flashback chamber would advantageously allow visualisation of fog/water vapour from hot air, indicating the insertion into the chest cavity.

The cannula housing may comprise a valve. The valve may be arranged to control the flow of fluid through the cannula. According to another aspect of the invention there is provided a method of use of the trocar and cannula device as defined above, wherein the device comprises an insertion needle, the method comprising the steps of: -inserting the insertion needle and cannula into the tissue of a patient;

-pushing the trocar housing towards the cannula housing, which pushes the trocar through the axial passage of the cannula, wherein the trocar causes the expansion of the diameter of the axial passage of the cannula;

- withdrawing the insertion needle and trocar from the cannula together.

According to a further aspect of the invention there is provided a method of use of the trocar and cannula device as defined above, the method comprising the steps of:

-inserting the trocar and cannula into the tissue of a patient;

-pushing the trocar housing towards the cannula housing, which causes at least part of the trocar to expand in diameter;

-withdrawing the trocar from the axial passage of the cannula, wherein the trocar causes the expansion of the diameter of the axial passage of the cannula. The trocar may be withdrawn from the axial passage of the cannula by moving the trocar housing in a direction away from the cannula housing.

The method may also comprise use of the trocar and cannula device with a grip housing, whereby the trocar housing is pushed towards the cannula housing and the grip housing after the insertion of the cannula into the tissue of the patient. The grip housing and trocar housing may be pushed together and interlocked in position.

The grip housing may be moved in a direction away from the cannula housing during withdrawal of the trocar from the axial passage of the cannula. The method may comprise the use of the trocar and cannula device for drainage from a patient, such as chest drainage. The method may comprise the use of the trocar and cannula device for intravenous (IV) access, for example for fluid delivery and/or fluid removal from a patient. The patient may be a human (and in this regard may be an adult or may be a child), but may alternatively be an animal, for example a household pet (such as a cat or dog) or a farm animal (such as a horse).

The skilled person will understand that optional features of one embodiment or aspect of the invention may be applicable, where appropriate, to other embodiments or aspects of the invention.

Description of the Drawings and Examples

Embodiments of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings.

Figure 1 is a cross-sectional diagram of a trocar and cannula device according to the invention:

Figure 1A shows a pre-engaged position of the trocar

Figure IB shows an engaged/depressed position of the trocar

Figure 1C shows a withdrawn position with the insertion needle and trocar withdrawn from the cannula;

Figure 2 illustrates the trocar and cannula device according to Figure 1 in use:

Figure 2 A shows the device in use wherein the trocar is being pushed through the cannula by the user in order to enlarge the diameter of the cannula Figure 2B shows the trocar locked into an engaged/depressed button position;

Figure 3 is an enlarged view of the cannula as shown in Figure 1 :

Figure 3A shows the cannula in an unexpanded state with the trocar only partially engaged

Figure 3B shows the cannula in an expanded state, with the trocar fully engaged;

Figure 4 is a cross-sectional diagram of an alternative trocar and cannula device according to the invention:

Figure 4A shows a pre-engaged position of the trocar

Figure 4B shows an engaged/depressed position of the trocar

Figure 4C shows a withdrawn position with the trocar withdrawn from the cannula;

Figure 5 illustrates the use of the trocar and cannula device shown in Figure 4, together with an enlarged view of the distal end of the trocar as shown in Figure 4:

Figure 5A shows the expansion section of the trocar in an unexpanded state in the pre-engaged position before depression of the button on the trocar housing

Figure 5B shows the expansion section of the trocar in an expanded state after the trocar housing button is depressed;

Figure 6 is a cross-sectional diagram showing the cannula and trocar connector of the trocar and cannula device of Figure 4 in more detail:

Figure 6A shows the expansion section of the trocar in the unexpanded state

Figure 6B shows the expansion section of the trocar in the expanded state; Figure 7 is a cross-sectional diagram of a further alternative trocar and cannula device with an alternative trocar comprising a pip shaped distal end:

Figure 7A shows the device in the pre-engaged position where the trocar is fully engaged through the cannula

Figure 7B shows the device where the trocar is partially withdrawn through the axial passage of the cannula, causing partial expansion of the diameter of the cannula

Figure 7C shows the device with the trocar substantially withdrawn from the cannula, where the cannula is fully expanded in diameter along its length;

Figure 8 is a perspective view of the trocar and cannula device of Figure 7;

Figure 9 illustrates a cannula expansion mechanism in cross-section;

Figure 10 illustrates an alternative cannula expansion mechanism in cross-section;

Figure 11 illustrates the alternative cannula expansion mechanism of Figure 10 in use as the trocar is withdrawn;

Figure 12 illustrates an alternative cannula expansion mechanism where the cannula is split along its length in order to form a rolled up tube with overlapping edges;

Figure 13 is a cross-sectional view of the cannula expansion mechanism of Figure 12 as it is expanded by the trocar in use;

Figure 14 is an alternative cross-sectional view of the cannula expansion mechanism of Figure 12; Figure 15 illustrates another cannula expansion mechanism according to the mechanism of Figure 12, with an additional flexible membrane to prevent leakage;

Figure 16 shows the split of the cannula of Figure 15 in an open state demonstrating the anti-leak membrane;

Figure 17 illustrates another cannula expansion mechanism comprising folds in the cannula; and

Figure 18 illustrates the cannula expansion mechanism of Figure 17, together with the appropriate trocar pip for effecting the expansion:

Figure 18A shows the cannula with a single folded section

Figure 18B shows the cannula with two folded sections

Figure 18C shows the cannula with four folded sections.

Example 1 - a trocar and cannula device

With reference to figure 1A, the trocar and cannula device 1 is in a pre-engaged/pre-use position. The trocar and cannula device 1 has a cannula 3 attached at the proximal end into a cannula housing 5. The cannula 3 is a plastic tube having an axial passage therethrough, which is intended for the passage of fluid, such as blood.

The cannula housing 5 is substantially cone shaped having an axial passage extending therethrough. The cannula housing 5 holds and partially surrounds the proximal end of the cannula 3. The cannula housing 5 interlocks with a grip housing 7. The grip housing 7 is a substantially tubular section having an axial passage extending therethrough. A trocar 11 extends through the axial passage of the grip housing 7. The grip housing 7 has a grip 8 extending radially from the grip housing 8, which is suitable for holding by a user's finger. A trocar housing 9 is slidably engaged and interlocked with the grip housing 7. The trocar housing 9 is a substantially tubular shape with an open distal end and a closed proximal end. The trocar housing 9 includes a button 15 at the closed proximal end, which is suitable for a user to push. The trocar 1 1 is fixed to the trocar housing 9 by the proximal end of the trocar 11. In this pre-engaged position, the trocar 11 extends through the axial passage of the grip housing 7 and the axial passage of the cannula housing 5, such that the distal end of the trocar 11 is partially engaged within an axial passage of the cannula 3 at the proximal end of the cannula 3.

The grip housing 7 and the trocar housing 9 are interlocked by tongue and groove surfaces 41, 43, 45, 47, which allow them to lock into a pre-engaged position (button not depressed, according to figure 1A) or an engaged position (button depressed according to figure IB). The grip housing 7 includes a circumferential groove 47, which interlocks with a circumferential tongue 45 of the trocar housing 9. The trocar housing has a circumferential groove 43, which interlocks with a circumferential tongue 41 of the grip housing 7. The trocar housing 9 and the grip housing 7 are slidably engaged between the two positions.

The trocar and cannula device 1 further includes an insertion needle 13 extending from the cannula housing 5 and disposed within the axial passage of the cannula 3 when the trocar and cannula device 1 is in the pre-engaged position. The distal end of the insertion needle 13 extends out of the distal end of the cannula 3 when the trocar and cannula device 1 is in the pre-engaged position. The insertion needle 13 is a hollow metal tube with a pointed distal end intended to pierce through tissue.

The axial passage of the cannula 3 has two diameters depending on the cannula being in an unexpanded state or an expanded state. The first smaller diameter is about 0.8mm in the cannula's unexpanded state (shown in figure 1A), and the second larger diameter is about 2mm in the expanded state (shown in figures IB and 1C).

The insertion needle 13 is about 0.8 mm in diameter, which is substantially similar in diameter to the axial passage of the cannula 3 in its unexpanded state.

The trocar 11 is 2mm in diameter, which is greater than the diameter of the axial passage of the cannula 3 in its unexpanded state, and substantially similar to the axial passage of the cannula 3 in its expanded state. In use, the diameter of the trocar 11 determines the diameter of the axial passage of the cannula 3.

In the pre-engaged state of the trocar and cannula device 1, the distal end of the trocar 11 is partially engaged within the axial passage of the proximal end of the cannula 3 (as shown in figure 1A). Therefore, the cannula 3 is partially expanded into its expanded state in the proximal region where the trocar 11 engages. The distal portion of the cannula 3 that is not engaged by the trocar 11 remains in the unexpanded state, having a lesser diameter.

In use, the cannula 3 in its unexpanded, lesser diameter, state (see figure 1A) is guided into the tissue by the insertion needle 13. The button 15 is depressed (see figure IB) by the user using the grip 8 as leverage, whereby the grip housing 7 and the trocar housing are slidably locked closer together. This action drives the trocar 11 through the axial passage of the cannula 3 and over the insertion needle 13, which causes expansion of the diameter of the axial passage of the cannula 3. Both the grip housing 7 and the trocar housing 9 are withdrawn away from the cannula housing 5 (see figure 1C), which causes withdrawal of the trocar 11 and the insertion needle 13 from the axial passage of the cannula 3, thereby permitting fluid flow through the expanded cannula 3. Figure 2A illustrates the action of the user, who uses the button 15 and grip 8 to push the trocar 1 1 through the cannula, such that the cannula 3 is changed from an unexpanded state (figure 2A) to an expanded state (figure 2B). In the engaged state of the trocar and cannula device 1, the distal end of the trocar 11 is fully engaged within the axial passage of the cannula 3 (as shown in figure IB). Therefore, the cannula 3 is expanded into its expanded, larger diameter, state along its entire length.

Figure 1C shows the trocar and cannula device 1 in a withdrawn position. Such a position is where the cannula 3 has been successfully inserted into the tissue and the insertion needle 13 and trocar 11 are disengaged from the axial passage of the cannula 3. The grip housing 7 and trocar housing 9 remain locked together in the engaged position. The cannula housing 5 is separated from the grip housing 7. The cannula 3 is in an expanded, larger diameter, state along its length. Figure 3 A shows the cannula 3 and insertion needle 13, with the trocar 11 partially engaged within the axial passage of the cannula. In this position, the diameter Dl of the insertion needle 13 and the axial passage of the cannula 3 is substantially similar at about 0.8mm. The diameter D2 of the trocar 11 is 2mm, which forces the diameter of the axial passage of the cannula 3 to expand to an equal diameter D2 in the region that the trocar 11 engages the cannula 3. Figure 3B shows the trocar 11 fully engaged through the full length of the cannula 3, causing the cannula 3 to be in an extended diameter state throughout its length.

Example 2 - a trocar and cannula device With reference to figure 4 a cross-section of an alternative trocar and cannula device 2 is provided. With reference to figure 4A, the trocar and cannula device 2 is in a pre-engaged/pre-use position. The trocar and cannula device 2 has a cannula 3 attached at the proximal end into a cannula housing 5. The cannula 3 is a plastic tube having an axial passage therethrough, which is intended for the passage of fluid, such as blood.

The cannula housing 5 is substantially cone shaped having an axial passage extending therethrough. The cannula housing 5 holds and partially surrounds the proximal end of the cannula 3. The cannula housing 5 interlocks with a grip housing 7. The grip housing 7 is a substantially tubular section having an axial passage extending therethrough. A trocar 111 extends through the axial passage of the grip housing 7. The grip housing 7 has a grip 8 extending radially from the grip housing 7, which is suitable for holding by a user's finger. A trocar housing 9 is slidably engaged and interlocked with the grip housing 7. The trocar housing 9 is a substantially tubular shape with an open distal end and a closed proximal end. The trocar housing 9 includes a button 15 at the closed end, which is suitable for a user to push. The trocar 111 is fixed to the trocar housing 9 by the proximal end of the trocar 111. In this pre-engaged position, the trocar 111 extends through the axial passage of the grip housing 7 and the axial passage of the cannula housing 5, such that the distal end of the trocar 11 is fully engaged through the whole length of an axial passage of the cannula 3.

The grip housing 7 and the trocar housing 9 are interlocked by tongue and groove surfaces 41, 43, 45, 47, which allow them to lock into a pre-engaged position (button not depressed, according to figure 4 A) or an engaged position (button depressed according to figure 4B). The grip housing 7 includes a circumferential groove 47, which interlocks with a circumferential tongue 45 of the trocar housing 9. The trocar housing has a circumferential groove 43, which interlocks with a circumferential tongue 41 of the grip housing 7. The trocar housing 9 and the grip housing 7 are slidably engaged between the two positions.

The trocar 111 is a metal tube having a pointed distal end suitable for insertion into tissue. The proximal end of the trocar 111 is fixed to the trocar housing 9. The trocar is 0.8mm in diameter, which is substantially equal to the diameter of the axial passage of the cannula 3 in its unexpanded state. The trocar 111 has an expansion section 19 near to the distal end. The expansion section 19 has a plurality of laser cut slits 21 circumferentially arranged around the trocar 111 and extending in an axial direction along the trocar 1 11 (see figure 5). The slits 21 of the expansion section 19 cause a weakening in the structure of the expansion section 19 of the trocar such that it is capable of deforming and bulging under pressure. In an unexpanded state, the trocar 111 expansion section 19 is not deformed and is the same diameter as the rest of the trocar 111. In an expanded state, the expansion section 19 is deformed such that it forms a bulge in the trocar 111 (see figure 5B), whereby the diameter of the bulge in the expansion section 19 is greater than the rest of the trocar 111. The diameter of the bulge in the expansion section 19 is greater than the diameter of the axial passage of the cannula 3 in the cannula's unexpanded state.

The trocar and cannula device 2 further includes a connector 17 and an anchor tube 18, which in use effect the deformation of the expansion section 19 of the trocar 111 (shown in more detail in figure 6). The connector is a plastic or silicone rod disposed within the distal end of the trocar 111. The connector 17 is anchored at the distal end to the trocar 111 at a position between the distal end of the trocar 1 11 and the expansion section 19 of the trocar 111 (see 1 19 in figure 6A). The connector 17 is further anchored at the opposing end to the anchor tube 18. The anchor tube 18 is a metal tube fixed to the grip housing 7 and extending axially through the cannula housing 5. The trocar 111 extends through the length of the anchor tube 18. The trocar 111 is capable of sliding through the anchor tube 18.

The axial passage of the cannula 3 has two diameters depending on the cannula being in an unexpanded state or an expanded state. The first smaller diameter is about 0.8mm in the cannula's unexpanded state (shown in figure 4A), and the second larger diameter is about 2mm in the expanded state (shown in figure 4C). The trocar 111 in its unexpanded state is about 0.8mm in diameter, which is substantially equal to the diameter of the axial passage of the cannula 3 in its unexpanded state. After expansion of the expansion section 19 into a bulge, the diameter of the bulge is about 2mm, which is substantially similar to the axial passage of the cannula 3 in its expanded state. In use, the diameter of the bulge in the trocar 111 determines the diameter of the axial passage of the cannula 3, when it is withdrawn therethrough.

In use, the cannula 3 in its unexpanded, lesser diameter, state (see figure 5A) is guided into the tissue by the trocar 111. The button 15 is depressed (see figure 5B) by the user using the grip 8 as leverage, whereby the grip housing 7 and the trocar housing are slidably locked closer together. This action forces the proximal end of the trocar 111 to move towards the distal end, whereby the distal end is anchored into position by the connector 17 and anchor tube 18. This action causes the deformation and bulging of the expansion section 19 of the trocar 111. The trocar housing 9 and grip housing 7 are withdrawn (see figure 4C), which causes the withdrawal of the trocar 111, anchor tube 18, and connector 17 through the axial passage of the cannula 3, which causes expansion of the diameter of the axial passage of the cannula 3.

Example 3 - trocar with a pip shaped distal end With reference to figure 7, an alternative trocar 211 and expansion mechanism is illustrated. In the pre-engaged position shown in figure 7A, the trocar 211 extends through the axial passage of the cannula 3. The trocar needle 211 has a pip shaped bulge 23 before the distal end which is positioned at the distal end of the cannula (see X of figure 7A). During the withdrawal of the trocar 211 (see figure 7B), the pip shaped bulge 23 forces expansion of the cannula whereby it stretches into an expanded state. The cannula 3 remains expanded along its length (see figure 7C). Figure 8 illustrates the alternative trocar and cannula device 201 in the pre-engaged position ready for insertion into tissue. Example 4 - cannula expansion mechanisms

With reference to figure 9, a cannula expansion mechanism is shown in a cross-section of the cannula 103. The cannula 103 comprises a series of ribs 25 extending axially along the cannula and circumferentially spaced. The ribs are separated by stretchable walls 27 which stretch and become thinner allowing the diameter of the cannula 103 to increase. The stretchable walls may, in one embodiment, be a deformable plastic, nitrile or silicone material. Suitable materials will be selected from non-porous, medically implantable, physiologically inert materials, and/or any other commercially available material that is able to be stretched between ribs but that can still maintain its rigidity, ensuring an essentially stretched yet semi-rigid surface.

With reference to figure 10, another cannula expansion mechanism is shown in a cross-section of the cannula 203. The cannula 203 comprises thicker 29 and thinner 31 wall sections which alternate circumferentially around the cannula 203. The thinner walls 29 are arranged to stretch thereby allowing the diameter D3 of the cannula 203 to increase. The stretchable walls may, in one embodiment, be a deformable plastic, nitrile or silicone material. Suitable materials will be selected from non-porous, medically implantable, physiologically inert materials, and/or any other commercially available material that is able to be stretched between ribs but that can still maintain its rigidity, ensuring an essentially stretched yet semi-rigid surface.

Figure 11 illustrates the cannula expansion where a trocar with a pip shaped distal end 23 is withdrawn through the cannula 203 to effect the expansion of the cannula 203 diameter. A further alternative expansion mechanism is shown in figures 12 to 14. In this embodiment, the cannula 303 has a split extending axially along the cannula 303 allowing it to be rolled into a tube. The edges of the split cannula overlap to form the cannula 303. Figure 13 shows the expansion of the cannula 303 as a trocar is withdrawn through the axial passage of the cannula 303. The diameter at position A is increased during the cannula 303 expansion. The diameter at position B remains the same. Figure 14 shows the expansion of the cannula 303 in cross-section, where pressure of the tissue and fluid on the cannula (see small arrows) helps to maintain the cannula 303 in the expanded state and a latch/flap 341 interlocks with the edge of the cannula 303 in order to prevent collapse of the cannula back to an unexpanded state.

Figures 15 and 16 show another cannula expansion mechanism where the cannula 403 has an axial split according to the cannula of figure 12. However, the cannula 403 further comprises a flexible membrane 451, which bridges/traverses the split in the cannula 403 in order to prevent fluid leakage.

A further cannula expansion mechanism is illustrated in figure 17. The cannula 503 is an extruded tube which is folded along the length of the cannula 503 in two opposing sections in order to form a smaller diameter in the unexpanded state. In order to expand the diameter of the cannula 503, the folds are opened as the trocar (not shown) is pulled through the cannula 503.

With reference to figure 18 the cannula 503, 603, 703 is provided with one, two and four folded sections. As the number of folded sections increase, the distance X of the height of the folded section is decreased, thereby causing less pressure on the surrounding tissue during use. Alternative pip shapes of the trocar can be provided depending on the number of folded sections in order to provide effective pressure on the cannula during expansion. For example, the pip shape 23 is oval in cross-section for cannulas 503, 603 having one or two folded sections (see figures 18A and 18B). For a cannula 703 having four folded sections, the pip shape 23 is rectangular in cross-section (see figure 18C) allowing pressure to be exerted on at least four sides of the cannula 703 during expansion.

Claims

1. A trocar and cannula device comprising:

-a trocar engageable with the axial passage of the cannula; and

wherein the trocar is arranged to force the axial passage of the cannula into the expanded state by the action of axial movement of the trocar through the axial passage of the cannula.

2. The trocar and cannula device according to claim 1, further comprising a grip housing positioned between the cannula housing and the trocar housing.

3. The trocar and cannula device according to claim 2, wherein the grip housing is movable relative to the trocar housing.

4. The trocar and cannula device according to claim 2 or claim 3, wherein the trocar is slidably disposed within an axial passage of the grip housing.

5. The trocar and cannula device according to any one of claims 2 to 4, wherein the trocar housing is capable of locking into position relative to grip housing.

6. The trocar and cannula device according to any one of claims 2 to 5, wherein the grip housing and the trocar housing comprise a latch mechanism in order to lock them into a fixed position relative to each other.

7. The trocar and cannula device according to any one of the preceding claims, wherein the trocar housing comprises a push button suitable for a user to push the trocar housing towards the cannula housing.

8. The trocar and cannula device according to claim 7, wherein the grip housing comprises a grip handle suitable for a user to grip during use of the push button.

9. The trocar and cannula device according to any one of the preceding claims further comprising an insertion needle disposed within the axial passage of the cannula.

10. The trocar and cannula device according to claim 9, wherein the insertion needle is axially moveable relative to the cannula.

11. The trocar and cannula device according to claim 9 or claim 10, wherein the insertion needle is smaller in diameter than the diameter of the trocar.

12. The trocar and cannula device according to any one of claims 9 to 11, wherein the insertion needle is arranged to be withdrawn from the axial passage of the cannula together with the trocar.

13. The trocar and cannula device according to any one of the preceding claims, wherein the trocar is arranged to force the axial passage of the cannula into the expanded state when the trocar is pushed through the axial passage of cannula towards the distal end of the cannula.

14. The trocar and cannula device according to any one of the preceding claims, wherein at least part of the trocar is greater in diameter than the diameter of the axial passage of the cannula in its unexpanded state.

15. The trocar and cannula device according to any one of the preceding claims, wherein at least part of the trocar is substantially similar in diameter as the axial passage of the cannula in its expanded state.

16. The trocar and cannula device according to any one of the preceding claims, wherein the trocar is arranged to be withdrawn from the axial passage of the cannula by movement of the trocar housing away from the cannula housing.

17. The trocar and cannula device according to any one of the preceding claims, wherein at least part of the trocar is capable of expanding in diameter, wherein the expanded diameter of at least part of the trocar is substantially similar to the diameter of the axial passage of the cannula in its expanded state.

18. The trocar and cannula device according to any one of the preceding claims, wherein the trocar is arranged to force the axial passage of the cannula into the expanded state when the trocar is withdrawn through the axial passage of cannula away from the distal end of cannula.

19. The trocar and cannula device according to any one of the preceding claims, wherein the trocar comprises an expansion section capable of expanding to a diameter that is greater than the diameter of the axial passage of the cannula in its unexpanded state.

20. The trocar and cannula device according to claim 19, wherein the expansion section comprises a deformable wall, wherein deformation of the wall is arranged to cause the diameter of the expansion section to increase.

21. The trocar and cannula device according to claim 19, wherein the expansion section comprises a hinge, wherein the hinge allows deformation of the expansion section thereby increasing the diameter of the expansion section.

22. The trocar and cannula device according to any one of claims 19 to 21, further comprising a trocar connector arranged to hold the distal end of the trocar in position, whilst the proximate end of the trocar is axially moved towards the distal end, thereby forcing the expansion section to expand in diameter.

23. The trocar and cannula device according to claim 22, further comprising an anchor tube connected to the trocar connector and arranged to hold the trocar connector in position.

24. The trocar and cannula device according to claim 23, wherein the trocar is slidably disposed within the anchor tube.

25. The trocar and cannula device according to claim 23 or claim 24, wherein the anchor tube is fixed to the grip housing.

26. The trocar and cannula device according to any one of claims 22 to 25, wherein the trocar connector is disposed inside an axial passage of the trocar.

27. The trocar and cannula device according to any one of claims 22 to 26, wherein the trocar connector is anchored to the trocar at a position between the distal end of the trocar and the expansion section.

28. The trocar and cannula device according to any one of claims 23 to 27, wherein the trocar connector and anchor tube are arranged to be withdrawn from the axial passage of the cannula together with the trocar.

29. The trocar and cannula device according to any one of the preceding claims, wherein the diameter of the axial passage of the cannula is expandable by at least 20%.

30. The trocar and cannula device according to any one of the preceding claims, wherein

- the axial passage of the cannula is expandable from an unexpanded diameter of about 0.6mm to about 0.8mm to an expanded diameter of about 2mm to about 3mm; or

- the axial passage of the cannula is expandable from an unexpanded diameter of about

1.5mm to about 2.5mm to an expanded diameter of about 8mm to about 10mm.

31. The trocar and cannula device according to any one of the preceding claims, wherein the axial passage of the cannula in its expanded state is substantially uniform in diameter along its length.

32. The trocar and cannula device according to any one of the preceding claims, wherein the axial passage of the cannula is arranged to be held in its expanded state by the pressure of fluid passing through the axial passage.

33. The trocar and cannula device according to any one of the preceding claims, wherein the cannula comprises stretchable material.

34. The trocar and cannula device according to any one of the preceding claims, wherein the cannula comprises at least one fold extending axially along the cannula in its unexpanded state.

35. The trocar and cannula device according to claim 34, wherein the cannula comprises at least two folds extending axially along the cannula in its unexpanded state.

36. The trocar and cannula device according to claim 34 or claim 35, wherein the cannula is arranged to expand in diameter by an unfolding of folds in the cannula.

37. The trocar and cannula device according to any one of the preceding claims, wherein the cannula comprises at least one split, the split axially extending along the length of the cannula, wherein one side of the split cannula overlaps the opposing side of the split cannula.

38. The trocar and cannula device according to claim 37, wherein the cannula comprises a flexible barrier membrane traversing the split in the cannula for preventing leakage of fluid from the split.

39. The trocar and cannula device according to any one of the preceding claims, further comprising a flashback chamber.

40. A method of use of a trocar and cannula device as defined in any one of claims 19 to 28, or as defined in any one of claims 29 to 39 as dependent on any one of claims 19 to 28, the method comprising the steps of

-inserting the insertion needle and cannula into the tissue of a patient;

-withdrawing the insertion needle and trocar from the cannula together.

41. A method of use of the trocar and cannula device as defined in any one of claims 1 to 39, the method comprising the steps of

-inserting the trocar and cannula into the tissue of a patient;

-withdrawing the trocar from the axial passage of the cannula, wherein the trocar causes the expansion of the diameter of the axial passage of the cannula.