WO1999051153A2

WO1999051153A2 - A cannula of changeable length and shape

Info

Publication number: WO1999051153A2
Application number: PCT/BG1999/000007
Authority: WO
Inventors: Alexander R. Stefanow; Ivan R. Stefanow
Original assignee: Stefanow Alexander R; Stefanow Ivan R
Priority date: 1998-04-02
Filing date: 1999-04-01
Publication date: 1999-10-14
Also published as: EP1006900A2; JP2002500546A; AU3020499A; WO1999051153A3; BG102367A

Abstract

The invention is a cannula (2) of changeable length and shape, which can be used in medical practice and other activities, which require the penetration of different devices into a medium, vulnerable to mechanical intervention and/or is without well-shaped confining walls. It is created by turning the end section of a flexible tube (1) in such a way that the external part turns out to be concentrically located around the initial interior tube. The external part acquires the properties of a solid cannula. Hardening immediately after the point of transition by means of freezing the liquid contained in it or by means of vacuuming hollow channels filled with small particles, or by means of swelling the toroids contained in it, or by means of unfolding rings of solid elements, or by means of meshing profile elements included in its walls.

Description

A CANNULA OF CHANGEABLE LENGTH AND SHAPE

Sphere of Technics

The invention refers to a cannula of changeable length and shape, which can be used in medical application during the penetration of various devices, e.g. endoscopes, into the living systems as well as other activities, which necessitate the penetration into a medium, vulnerable to mechanical intervention and/or is without well-shaped confining walls.

State of Art

There are tubes, tubular elements (1-7) and devices., e.g. endoscopes, including tubes and tubular elements (8, 9), which are characterised by the fact that after penetrating into the body along the existing lumens - oesophagus, blood vessels, etc. - they ensure some protection from mechanical traumas to the surrounding tissues during the operation of the devices.

A disadvantage of the existing tubes, tubular elements and devices containing tubes and tubular elements is the fact that during their penetration into the living system as well as during their removal, they cause considerable traumas due to the friction between their outside surface and the medium of penetration and particularly to the side pressure exerted by the sections where there are curves.

The patent /13/ proposes a new principle of action of a three-dimensional controllable cannula according to which the leading instrument is placed in a lumen of the cannula itself. The lumen is formed during the penetration into the body without having to use ready natural ways and operates on the principle of snail horns - protruding and retracting. The patent, however, does not propose a construction working on this principle, neither the moving force which will open and close the cannula.

The aim of the invention is to create a cannula- of changeable length and shape, which is to penetrate the living system not only through existing orifices and which is to reduce to a minimum the traumas to the surrounding medium e.g. the human body. The task is solved by a device in which the cannula is formed at entering the working medium only through lengthening, which enters the working medium only through lengthening the front end, which takes the turns in any direction only through growing in the same direction and which is taken out of the surrounding medium only through shortening of the front end, keeping static all the time in respect to the medium and keeping stable its shape.

Technical Character of the Invention

A flexible elastic tube has been created, including components by which it can be reversibly hardened and which is partly turned so that two concentrically located tubes are formed. In the place of the turning there is a transition from the interior toward the exterior tube, which after its hardening acquires the properties of a solid cannula. The interior tube I and this cannula 2 have walls passing from on into the other and the interior wall of the interior tube becomes the exterior wall of the cannula 2 and respectively the exterior wall of the interior tube becomes the interior wall of the cannula. The elongation of the cannula 2 is realised through skidding the interior tube in the direction of the place of its transition into the cannula. On the contrary the shortening of the cannula is realised through skidding its interior tube in the opposite direction.

The skidding of the interior tube 1 is effected by pushing or pulling several guiding bands 8, longitudinally attached to its interior wall and included in a groove 7 along the length of the device, e.g. the endoscope 5, for, whose penetration into the surrounding medium the cannula is constructed. The bands 8 can impart their movement along the entire length of the interior tube 1 under the impact of the operator, applying the necessary force at the beginning of the interior tube outside the medium. In which the cannula 2 penetrates and the endoscope 5 inserted in it. The bands 8 have enough flexibility to follow the bending at the point of transition from the interior tube 1 into the cannula 2. The turns are obtained by advanced pushing of the bands from the outside of the turn and delayed pushing of the same bands from the inside of the turn in the condition of cannula elongation. The sections from the bands 8, passing into the composition of the cannula 2 after leaving along the guiding grooves 7 become static together with the newly built section of the cannula, immediately after the point of transitions Description of Drawings

The cannula 2 is static in respect to the surrounding medium with the exception of its end section, which is created at the point of transition of the interior tube 1 into the cannula 2 and thus the friction in this medium is eliminated, both in the cannula itself and of the endoscope 5 inserted in it. The cannula unlike the interior tube 1, has a stable shape, i.e. it is relatively hard, that is why in the turns, it and the endoscope inserted in it don't press the surrounding medium laterally.

Consequently, the cannula described above, does not traumatise the surrounding medium either by longitudinal friction, or by lateral pressure, except in the place and at the moment of elongation, respectively shortening at the end of this cannula.

Examples of Execution

Example 1. A cannula 2, of changeable length and shape, chown in fig. 1 and 2, concentrically including a soft tube 1 built of double walls, between which is located a substance 3 in molten state and the same substance in solid state 4, with welting temperature several degrees higher than the temperature of the surrounding medium. In which the cannula penetrates. Motive bands 8 located along the length of the interior wall of the interior tube and respectively along the exterior side of the cannula. They are included in the grooves 7 of the endoscope 5, which grooves end at the periphery of the endoscope head 6. The endoscope moves forward or backward at the rate of elongation or respectively of shortening of the cannula. The function of the endoscope head, which covers the section of the cannula, is to facilitate the transition of the interior tube into the cannula and vice versa and to reduce to a minimum the traumas to the surrounding medium during the penetration of the growing end of the cannula in it.

The elongation of the cannula is effected by skidding the interior flexible tube between the endoscope and the cannula in the direction of the growing end of the cannula, the turning of the soft tube under the endoscope head under the impact of the motive bands, which at this point move apart and turn the direction of their movement at 180 D and turning this section into the end section of the cannula. The softness of the interior tube is maintained by continuous heating of the melt, included in it through the heaters 9, built in the surface layer or the endoscope and in the inside wall of its head. The hardening of the end section of the cannula is effected through crystallisation of the melt and its transformation into a solid substance because of the heat liberation from the melt into the surrounding medium. When the cannula is shortened, the endoscope moves towards the cannula exit, its head presses the pain of transition, the surface layers of the crystallised substance melt, the respective section of the cannula softens and its transition into the end section of the interior tube becomes possible. This transition is accompanied by pulling the motive bands in the direction of the cannula exit and skidding the interior tube in the direction of this exit.

Example 2. A cannula, shown in fig. 3, similar to that described in Example 1, in which the melt and the crystallised substance are located in toroidal channels 12, included in the mass of the interior tube and respectively the cannula. lying, on a plane perpendicular to the axis of the internal tube of the cannula.

The advantage of this cannula is the facilitated movement at the point of transition and the circumstance that during the formation of the turns, the melt in pushed from the internal side of the turn towards its external side and crystallises in this state, fixing the state of the turn at the highest degree.

Example 3. A cannula, similar to those described in Example 1 and 2, in which the hardening of the cannula is achieved by crystallisation of a minimal quantity of melt, wetting a mass of small slippery solid particles, e.g. microscopic plastic granules. The hardening of the entire mass is achieved through crystallisation of the melt wetting the solid particles.

The advantage of this cannula is that the amount of the crystallising melt is less as compared with the quantity of the total mass, which passes from a liquid into a solid state, that is why less heat energy and respectively less time are necessary both for the hardening and the softening of the mass.

Example 4. A cannula, shown in fig. 4, similar to that described in Example 1, in which the hardening of the cannula is achieved as a result of vacuuming the space between the two walls of the tube, filled with small slippery solid particles, e.g. plastic granules 10. At the point of transition is situated a pressing washer 11, linked with the endoscope head, which facilitates the separation of the vacuumed space between the double wall of the cannula from the space between the double wall of the internal tube, in which the pressure is normal. When the endoscope goes backwards the end section of the cannula comes over the pressing washer 11, and the pressure in it immediately becomes equal to the normal, liquidity of the mass of solid particles is restored and this makes possible the reverse transition of the end section of the cannula into the end section of the interior tube.

The advantage of the described cannula is the high speed of transition from liquid into solid state of the mass, filling the space between the double walls of the tubes.

Example 5. A cannula, shown in fig. 5, similar to that described in Example 2, in which the toroidal channels 12 included in the interior tube and the cannula and lying on a plane perpendicular to their axis, represent hollow, multichamber toroids equipped with valves 13, for each chamber separately. The valves are situated on the external side of the interior tube and respectively the internal side of the cannula, i.e. they are facing the space between the two tubes. This space is divided into two parts internal and external - by a flexible tube 14, dividing the space between the two tubes and ending at the point of transition with a slide 15. The values open as a result of pressing the slide 15 at the point of transition. In the space between the tube 14 and the cannula overpressure is maintained, whereas in the space between the tube 14 and the interior tube underpressure "vacuum" is maintained. During the movement of the endoscope forward and respectively transition of the and section of the interior tube into the section of the cannula, through the valves 13 the chambers of the topmost toroid are filled with air, causing in this way the hardening of the respective end section of the cannula. After passing the slide 15 the valves are closed and the air remains closed in them. During a turn formation the chambers from the external side of the turn are able to swell to a higher degree than the chambers from the internal side of the turn. Thus the toroids, remaining unevenly swollen, in the different chambers, fix the turn condition. When the endoscope is taken cut, the chambers of the topmost toroid open again because the valves are pressed to the slide and after passing into the internal space between the endoscope and the interior tube, because of the vacuum they quickly get empty and cause the softening, of the respective tube section 1.

The advantages of the described cannula are the quick transition from soft into hard and from hard into soft state of the tubes around the point of transition and the stable fixing of the formed turns. Example 6. A cannula, shown in figures 6 and 7, similar to that described in Example 2, in which instead with toroidal channels the hardening of the cannula 2 is achieved by rings 16, attached to the internal wall of the interior tube and respectively the internal wall of the cannula, lying on a plane, perpendicular to their axis. The rings are reversibly collapsible in such a way that in a folded state their diameter coincides with the diameter of the interior tube, while in an unfolded state it coincides with the diameter of the cannula. The reversible folding achieved by the elements 17 of the ring, linked with each other as well as with the segments 18 of the ring by hinges 19, attached perpendicularly to the ring plane. The elements 17 are attached to the side walls of the segments 18 in recesses, restraining the movement of the elements 17 in such a way that in a folded state they form a sharp angle, and in an unfolded state - an obtuse angle, bigger than 1801:, whereas the hinges between the elements 17 are located at a radius a little bigger than the radius at which the hinges between the elements 17 and the segments 18 are located. In this position the unfolded state of the ring 16 is stable which means that a spontaneous folding at an even external pressing is not possible. The rings are linked with the interior tube and the cannula through the washers which can rotate freely at the pint of transition. The motive bands 8 are attached to the hinges between the elements 17.

The advantage of this cannula is the safety of the reversible transition from folded into unfolded state of the mechanical system.

Example 7. A cannula, shown in fig. 8, similar to that described in Example 1, in which the hardening of the cannula is caused by the meshing of profile bodies 21 and 22 to each other in the interior between the two walls of the cannula. In the concrete example, shown in fig. 8, these are longitudinal bands with indented cross section of the contact surfaces, lying freely in beds, larger than them, in such a way that the concave end of the band 21 from one side gets in the concave end of the opposite band 22. The pressing of the bands to each other, their meshing and the hardening of the cannula is the result of the elastic deformation of the cannula walls at the transition of the interior into the cannula. The best result is obtained when the internal wall of the interior tube and the internal wall of the cannula are in a state close to equilibrium. In this case the external wall of the cannula, which is obtained at the transition of the internal wall of the interior tube, turns out to have a considerably larger circumference, that is why it is stretched and consequently strained, and it presses the bands under it. In the interior tube, the external wall almost does not change its circumference and remains in a state, close to equilibrium, i.e. not strained, while the interior wall is in such an equilibrium that the opposite bands are apart and unmeshed. The combination of these two states makes the cannula hard and the interior tube soft.

As the profile band 21 and 22 lie freely in their beds in the interior of the interior tube, during the formation of turns they are able to retire toward the longer places of transition on the external side of the turn and toward the shorter places of transition on the internal side of the turn. After the point of transition, this state is fixed in the bard cannula, fixing the shape of the cannula as well with the same turn. The best result is obtained when the profile bands can be bent but are extensible and besides, the contact surface of the opposite profile bands have a high coefficient of friction.

The advantage of the described cannula is the smoothness of the external walls of the cannula and the interior tube and the safety of transition from the soft tube into the hard cannula and vice versa.

Example 8. A cannula, shown in figures 9 and 10, similar to those described in Examples 2 and 5, in which the hollow toroids, lying on a plane perpendicular to the axes of the cannula and the interior tube are multichambered, but do not contain valves, i.e. they are quite closed and contain a liquid 23 with a temperature of boiling higher than the temperature of the surrounding medium of the cannula. The end of a light-conducting fibre 25 reaches the interior of each separate chamber 24. The fibres 25 lie along the entire length of the respective chamber up to the beginning of the interior tube, from where at command light is fed differentially to the separate fibres. The additional fibres 26, reaching, the surface of the internal side and the cannula between the toroids receive the light being reflected from the internal surface of the endoscope head, having reached that place through the fibres 27. In this way the fibres 26 play the part of indicators, registering when the respective toroids reach the point of transition and signalling that light is to be fed to the fibres 25. This light causes the evaporation of the liquid 23 and the swelling and hardening of the chambers 24. When the cannula grows in a straight line, light is fed into all the chambers of the toroid, having reached the point of transition and it o

acquires the regular shape of a toroid. When the cannula grows in a curved line light is fed only toward the chambers on the external side of the turn and they swell and harden, while the others remain shrunk. Thus a cannula is formed with an unspecified folded shape and a stable state of the walls, both in the straight sections and in the sections with turns. When the cannula is shortened, the light reaching the chambers 24 in the toroid at the point of transition is switched off consecutively. The substance in them becomes liquid again, the chambers shrink and soften and this allow the end section of the cannula to become the end section of the interior tube.

LITERATURE

1. Author's certificate CCCP SU 1477371A1 (11.05.86)

2. Author's certificate CCCP SU 1480806A1 (06.07.87)

3. Author's certificate CCCP SU 1819566A1 (17.04.91)

4. Author's certificate CCCP SU 1099949A1 (25.02.82)

5. Author's certificate CCCP SU 1819567A1 (28.06.91)

6. Patent USA 5643174 (01.07.97)

7. Patent USA 5620408 (15.04.97)

8. Author's certificate CCCP 925310 (15.01.79)

9. Patent PF RU 2022518 Cl (13.02.91)

10. Patent USA 5558665 (24.09.96)

11. Patent USA 5448989 (12.04.95)

12. Patent USA 5645520 (08.07.97)

13. Swedish patent 9604792-3

Fig. 5 - CROSS SECTION

5. Endoscope

6. Endoscope Head

12. Toroid channels

13. Valves

14. Flexible tube

15. Slide

Fig. 6 - CROSS SECTION

5. Endoscope

6. Endoscope head

16. Rings

Fig. 7 - CROSS SECTION

1. Interior wall

2. Cannula

3. Endoscope 8. Motive band

17. Element for unfolding the ring

18. Segment of the ring

19. Linking hinge

20. Linking washer

Fig. 8 - CROSS SECTION

1. Interior tube

2. Cannula

3. Endoscope 8. Motive band

21 and 22. Profile bands

Fig. 9 - LONGITUDINAL SECΗON

5. Endoscope

6, Endoscope head

23. Evaporable substance

24. Chambers

25. Light conducting fibre to the chamber

26. Light conducting fibre - indicator Description of the attached figures

Fig. 1 - LONGITUDINAL SECTION

1. Interior tube

2. Cannula

3. Melt

4. Hardened substance

5. Endoscope

6. Endoscope head

Fig. 2 - CROSS SECTION 1. Interior tube 2 . Cannula

3. Melt

4. Hardened substance

5. Endoscope

7. Groove of the motive band

8. Motive band

9. Heaters

Fig. 3 - LONGITUDINAL SECTION

1. Interior tube

2. Cannula

3. Melt

4. Hardened substance

5. Endoscope

6. Endoscope head 12 Toroid channels

Fig. 4 - LONGITUDINAL SECΗON

1. Interior tube

2. Cannula

5. Endoscope

6. Endoscope head

10. Plastic granules

11. Pressing washer 29. Light conducting fibre - illuminator Fig. 10 - CROSS SECΗON

1. Interior wall

2. Cannula

3. Endoscope 12. Toroid

24. Chamber.

25. Light conducting fibre to the chamber

Claims

Patent claims

1/ A cannula 2 of changeable length and shape, which is obtained from a flexible tube 1, which is partly turned so that 2 concentrically located tubes are formed, passing from one into another at a point where the cannula change its length together with its shape and characterised by the fact that the tube walls contain components, which at the point of transition from the interior tube into the cannula cause a stable but reversible hardening whereas it acquires the rigidness of a real cannula, having the length and shape acquired during the transition.

2/ A cannula, according to Claim 1, characterised by the fact that the interior tube and the cannula are built up of double walls, between which there is a substance, which has melting temperature higher than the temperature of the surrounding medium of the cannula that is why it is in solid aggregate state 4 in the cannula, whereas in the interior tube it is maintained as a melt 3 through heating with heaters 9, which are located in the surface layer of the endoscope 5, which is to be protected by the cannula.

3/ A cannula 2 according to Claim 2, characterised by the fact that the substance imparting solidity to the cannula is in the form of a melt in the interior tube and is contained in toroid channels 12, located on a plane, which is perpendicular to the axis of the interior tube and the cannula.

4/ A cannula 2, according to Claims 2 and 3, characterised by the fact that the mass imparting solidity to the cannula consists of solid particles 10, wetted by a substance with melting temperature higher than the temperature of the surrounding medium.

5/ A cannula 2, according to Claim 1, characterised by the fact that the cannula hardness as a result of vacuuming the space between the double walls, which are filled with small solid particles 10.

6/ A cannula 2, according to Claims 1 and 3, characterised by the fact that the hollow toroids 12 are empty and are divided into several chambers, equipped with valves 13 for each separate chamber, which open while skidding past the slide, lying at the internal side of the transition between the interior tube and the cannula and this slide is attached to the upper end of the flexible tube 14, which is concentrically situated between the interior tube and the cannula, and in the space of the cannula and the flexible tube 14 there is overpressure, whereas in the space between the flexible tube 14 and the interior tube there is underpressure.

7/ A cannula, according to Claim 1, characterised by the fact that the interior tube and the cannula contain between their double walls profile bands 21 and 22, which can slide freely in the interior tube, longitudinally in their individual beds, corresponding to their shape, and which are pressed and meshed to each other in the cannula, ensuring the solidity of the cannula in this way, whereas in the interior tube they are apart from each other and in this way they provide the possibility for longitudinal sliding and the softness of the interior tube.

8/ A cannula, according to Claims 1, 3 and 6, characterised by the fact that the chambers 24 of the toroid 12 are completely closed and contain a substance 23 with melting temperature higher than the temperature of the surrounding medium in the cannula, and the end of a light conducting fibre 25 reaches each of the chambers, stretching from the chamber to the beginning of the interior tube, while another light conducting fibres 26 reach the surface of the interior tube and the cannula in such a way, that at the point of transition they face the internal surface of the endoscope head 6, whereas at the internal surface of the head lie light conducting fibre 27, along which light is continuously fed, and after the light reaches the light conducting fibres 26 between the toroids it is led to the beginning of the interior tube, at which it registers the reaching of the respective toroid to the transition point, at which the cannula is to grow in a straight line, light is sent to the chambers of this toroid 12, which causes the evaporation of the substance in them as well as their swelling and hardening, but when the cannula is to form a turn, light is sent to the chambers at the external side of the turn and they swell, light is not sent to the chambers at the internal side of the turn and these chambers remain shrunk.