GB2195808A

GB2195808A - Model for simulating a medical procedure

Info

Publication number: GB2195808A
Application number: GB08720557A
Authority: GB
Inventors: Andrew Philip Daykin; Raymond John Bacon
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-09-16
Filing date: 1987-09-01
Publication date: 1988-04-13
Anticipated expiration: 2007-09-01
Also published as: GB8622257D0; GB2195808B; GB8720557D0

Abstract

A similator for procedures involving the insertion, into the living body, of a needle comprises a housing provided with an entry port 15 by way of which an epidural injection needle 16 may be advanced towards a passage 69 in a barrier member 57, which simulates bone surrounding an epidural space to be sought by the needle tip. The needle 16, in so advancing, encounters variable impedance means 21 simulating ligament tissue and comprising friction pads 33 and 35, the loading on the latter being adjustable. The barrier member 57 is presettable within certain ranges of displacement both transversely and in the fore and aft direction to simulate variations encountered in the living body. Simulation of attainment by the needle of the epidural space is signaled by contact with a piston 25. A sensor 27 disposed behind the piston 25, when contacted by the piston, emits an alarm, should the needle 16 be advanced excessively. <IMAGE>

Description

SPECIFICATION Teaching aids This invention relates to teaching aids. More particularly the invention is concerned with simulators for surgical procedures involving the insertion of a needle into the living body.

A particular and important case of such procedures is the simulation of the insertion of an injection needle to an epidural space.

Epidural injection is a method of producing anaesthesia and analgesia in surgical and obstetric procedures. The practice of the method demands a considerable expertise. The necessary skill, conventially, is gained in practicing upon patients. This necessarily involves some degree of risk and the present invention seeks to provide a teaching aid, a simulator, whereby a knowledge of the conditions, and variations therein, encountered in practicing on a diversity of patients, may be gained "offline".

According to the invention in its broadest sense, a simulator for surgical procedures involving the insertion, into the living body, of a needle, comprises a frame part; a needle entry position defined in the said frame part; and, spatially defined in the frame part, in the line of advance of a needle from the needle entry position, a series of elements possessing characteristics simulating substantially the tactilely recognisable characteristics of a series of body regions encountered during penetration of a needle to a target position within the living body.

The teaching aid may include a needle retained in the frame at the needle entry position.

An element of the said series may comprise impedance means operative when, in use, the needle is advanced from the said needle entry position, to provide an increasing impedance to the said advance.

The said impedance means may comprise friction pad means.

The simulator may be provided with position sensitive means responsive to a predetermined position being reached by the needle during its penetration, and operable to cause emission of a signal when the position has been reached.

The simulator may be provided with alarm means operable to emit an alarm signal whenever the needle has progressed beyond a notional target position corresponding to the position of the epidural space in the living body.

The alarm means may be operable by activation of a sensor by the needle during its advance beyond the notional target position.

These and other features of a simulator for surgical procedures involving the insertion, into the living body, of a needle, in accordance with the invention are hereinafter described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a diagrammatic side elevation of a simulator for such insertion; Figure 2 shows, diagrammatically, a section on the line Il-Il of Figure 1; Figure 3 shows a section on line Ill-Ill of Figure 4; and Figure 4 is a plan view of the simulator.

With reference to the drawings, the simulator 10 illustrated thereby comprises a reference frame part in the form of a housing 13.

The housing 13 defines a needle entry position in the form of a port 15 within which is retained an epidural injection needle 16. Specifically, the needle 16 comprises a Tuohy needle with Macintosh Wings modified as hereinafter described.

The housing 13 is in two parts 17, 19, respectively. The part 17 is in the form of a vertical tower; and the housing part 19 extends rearwardly from the part 17. The housing 13 has a clamp 12 by which it may be secured to a stable structure.

Within the housing part 17 there are impedance means 21 (Figure 2). Within the housing part 19 there are barrier means 23 (Figure 3) and first and second sensors 25, 27, respectively.

As shown in Figure 2, the impedance means 21 comprise two friction pad arrangements, 33, 35, respectively, disposed one behind the other in the line of advance of the needle 16 into the simulator 10. The impedance means 21 comprises in addition to the friction pads 33, 35, strong vertical rods 37, 39, respectively, which are received in linear bearings 41, 43, respectively, supported by a cross member 45 between the fore and aft walls of the housing part 17. The friction pads 33, 35, have recesses respectively to receive the lower ends of the rods 37, 39.

The friction pads 33, 35 possess characteristics simulating substantially the tactilely recognisable characteristics of a series of body regions (ligament tissue) encountered during penetration of the needle 16 to a notional target position within the living body.

The rod 39 has, at its upper end, an axial blind bore to receive the lower end of a vertical spindle 47 rotatable within the bore.

The spindle 47 projects through an aperture in the roof of the housing part 17 and, at an intermediate position, through an internally threaded sleeve 49 held against rotation and provided with a collar 51. The spindle 47 has an external thread which engages a complementary internal thread of the sleeve 49. Between the collar 51 and a shoulder 53 of the rod 39 there is a compression spring 54. The spindle 39 is rotatable by means of a knurled knob 55. Rotation of the knob 55 in the appropriate direction moves the sleeve 49 down.

This resuits in compression of the spring 54, which in turn causes downward movement of the rod 39, with the result that the load transmitted to the driction pad 31 by the rod 39 may be varied for the purposes of increasing or decreasing impedance to needle advance, i.e. simulating variations in resistance to needle penetration of ligament tissue.

It will be apparent that the frictional resistance experienced in advancing the needle 16 across the pads 33, 35, increases with needle forward displacement; the variable nature of the resistance of the pad 35 means moreover that the rates of increase in resistance to needle advance are, in general, different.

With reference to Figures 2 and 3, the barrier means 23 within the housing part 19 simulates the bone surrounding the epidural space, the said space being the aforementioned target position. The barrier means 23 comprises a barrier member 57 adjustable as to position by movement in a threaded spindle 59 which extends through an internally threaded upstanding portion 61 of the member 57.

One end of the spindle 59 is received in an aperture in the rear wall of the housing part 17, the said aperture being such that the spindle 59 is permitted a certain amount of lateral movement with respect to the housing part 17. The other end of the spindle 59 extends through a transverse slot 62 in the rear wall of the housing part 19. A sleeve 63 around the free end of the spindle 59 is in sliding contact with the transverse edges of the slot 62. A clamping disc 65 is screwed on to the sleeve 63 and can be tightened to releasably secure the sleeve in the slot 62. A knob 67 is secured to the end of the spindle 59.

The barrier means 23 simulates, as previously mentioned, the bone surrounding the epidural space. The barrier member 57 of the means 23 is movable 50 mm in the fore and aft direction and in the transverse direction by 30 mm. These displacements represent the ranges of variation which may be encountered in the living body. The setting of the barrier member 57, in the use of the teaching aid, is effected by the instructor as, indeed, is the setting of the friction at the friction pad 35.

As may be seen, the transverse setting of the member 57 is by movement of the disc 65; whilst the fore and aft movement of the member is by rotation of the knob 67.

The barrier member 57 has a central passage 69. Whilst contact with the barrier member blocks further advance of the needle 16, if the line of advance of the needle is correct, having regard to the variability in position of the barrier member, the needle will enter the passage 69. The passage is such that the needle may be offset with respect to the centre of the barrier member 57 by no more than 5 mm otherwise the advance of the needle is blocked.

Within the passage 69 there is a metal piston constituting the sensor 25. The piston 25 is normally biassed to a position 10 mm from the entrance to the passage. The piston is included in an electrical circuit to a solenoid valve 73, the circuit also including a small metal collar 75 which provides a sliding electrical connection to the epiduraJ needle 16.

The collar 75 also prevents complete removal of the needle 16 from the entry port 15 without impeding transverse angular displacement of the needle in seeking the passage 69.

The epidural needle 16 is advanced 10 mm into the passage from the passage entrance before contact is made between the needle tip and the head of the piston 25. As a result of this contact an electric circuit to the solenoid valve 73 is completed.

The bore of the Tuohy needle 16 is terminated shortly beyond the Macintosh Wings and is accessed by a small connector 77 on the needle hub. The needle 16 has an extension in the form of a solid bar made of electrically conductive material and is of two diameters at respective positions along the extension.

A small flexible tube 79 extends between the connector 77 and the solenoid valve 73, which is battery operated. The battery, which is replaceable, is preferably housed within the apparatus. An on/off control switch is also provided.

When the electric circuit to the solenoid valve 73 is completed by contact of the needle 16 with the piston 25, the valve 73 is caused tb open, and allow the injection media to be vented to the exterior of the housing.

The injection media may comprise a liquid, e.g. saline, a gas, e.g. air, or a mixture of these media.

The housing 13 is, as already mentioned, in two parts 17, 19. The part 17 forms a vertical tower; the housing part 19 which is lower in height, has a window aperture 81 through which the instructor may witness the advance of the needle to the epidural space represented, in position, by the undeflected position of the piston 25. The window aperture 81 is disposed so that the needle 16 and its movement cannot be observed from the needle entry port 15.

The second sensor 27 is provided to develop a signal indicative of advance of the needle 16 an excessive distance through the notional epidural space and penetration of the dura, simulating a dural tap. The sensor 27 thus forms part of alarm means operable to emit an alarm signal whenever the needle 16 progresses beyond the target position referred to above. The sensor 27 is, in the embodiment, in the form of a microswitch fixed with respect to the barrier member 57 in the path of movement of the piston 25 under pressure from the needle 16. Upon contact between the piston and the microswitch, which occurs after a further 2 mm of movement of the needle 16 following its contact with the piston 25, an alarm buzzer (not shown) sounds to denote failure of the simulated injection process.

Whilst the invention has been described with reference to the accompanying drawings and certain generalisations asserted as to the nature and scope of the invention, the invention also embraces or comprises any novel subject matter or combination including novel subject matter as herein disclosed or contemplated.

Claims

1. A simulator for surgical procedures involving the insertion, into the living body, of a needle, the simulator comprising a frame part; a needle entry position defined in the said frame part; and, spatially defined in the frame part, in the line of advance of a needle from the needle entry position, a series of elements possessing characteristics simulating substantially the tactilely recognisable characteristics of a series of body regions encountered during penetration of a needle to a target position within the living body.

2. A simulator as claimed in Claim 1, which includes a needle retained in the said frame part at the needle entry position.

3. A simulator as claimed in any preceding claim, in which an element of the said series comprises impedance means operative when, in use, the needle is advanced from the said needle entry position, to provide an increasing impedance to the said advance.

4. A simulator as claimed in Claim 3, in which the said impedance means comprises friction pad means.

5. A simulator as claimed in Claim 4, in which the said friction pad means comprises a multiplicity of friction pads disposed one behind another in the direction of needle advance, and, associated with at least one friction pad, means for applying a variable load thereto thereby to permit variation in the friction between the said at least one pad and the needle during its-advance.

6. A simulator as claimed in any one of Claims 1 to 5, provided with position sensitive means responsive to a predetermined position being reached by the needle during its penetration, and operable-to cause emission of a signal when the position has been reached.

7. A simulator as claimed in Claim 6, in which the position sensitive means comprise an electrically conductive element included in an electric circuit to be closed by contact between the needle and the said conductive element.

8. A simulator as claimed in Claim 7, in which closure of the electrical circuit operates to vent injection media from the needle.

9. A simulator as claimed in any one of Claims 1 to 8, having alarm means operable to emit an alarm signal whenever the needle has progressed beyond a notional target position corresponding to the position of the epidural space in the living body.

10. A simulator as claimed in Claim 9, in which the said alarm means include a microswitch.

11. A simulator as claimed in Claim 9 or 10, in which the alarm means is operable by activation of a sensor by the needle during its advance beyond the notional target position.

12. A simulator as claimed in any preceding claim, in which the said frame part is a housing.

13. A simulator as claimed in Claim 12, in which the simulator housing has an aperture through which the advance of the needle may be observed.

14. A simulator as claimed in Claim 13, in which the simulator housing is such and the aperture is so disposed therein, that the needle and its movement cannot be observed from the needle entry position.

15. A simulator as claimed in any preceding claim, substantially as hereinbefore described with reference to the accompanying drawings.

16. A simulator substantially as hereinbefore described with reference to the accompanying drawings.