WO1995004494A1

WO1995004494A1 - An amnioscope

Info

Publication number: WO1995004494A1
Application number: PCT/AU1994/000444
Authority: WO
Inventors: Kevin Albert Barham
Original assignee: Kevin Albert Barham
Priority date: 1993-08-04
Filing date: 1994-08-04
Publication date: 1995-02-16

Abstract

An amnioscope (1) to permit visual access to an amniosphere of a lower uterine segment of a female patient. The amnioscope (1) includes a main elongate outer tube (2) having an operative end (6) adapted for insertion into the cervix to provide access to the amniosphere. Guide means are disposed within the tube (2) to receive and locate an endoscopic telescope (5) closely adjacent the operative end (6) of the main tube (2), thereby permitting transcervical inspection of the amniosphere.

Description

Title: AN AMNIOSCOPE

FIELD OF THE INVENTION

The present invention relates generally to amnioscopy, and more particularly to an endoscope for late pregnancy examination.

BACKGROUND OF THE INVENTION

Broadly speaking, amnioscopy involves the use of a tapered hollow tube, or "amnioscope", to permit visual inspection of the amniotic fluid contained in the "amniosphere" of the lower uterine segment for abnormalities. It has been found that any green discolouration in this region is indicative of faecal pollution from the fetus. The material normally responsible for such discolouration is called meconium, the presence of which staining the amniotic fluid is generally regarded as adding to the risk of fetal hypoxia. If this is detected in late pregnancy, most clinicians would terminate the pregnancy, either by induction of labour or caesarean section, depending upon the circumstances. Accurate inspection of the amniotic fluid and reliable interpretation and diagnosis is of great importance, because of the potential risk to the fetus.

In the past, however, the use of amnioscopy for reliable evaluation of the condition of the amniotic fluid has been severely limited, primarily because of the subjective nature of the observations which have hitherto been made with the naked eye, and also because of the inability to make accurate and meaningful records of those observations for subsequent reference and comparison.

It is therefore an object of the present invention to provide an improved amnioscope which overcomes or substantially ameliorates at least some of the deficiencies of the prior art.

DISCLOSURE OF THE INVENTION

Accordingly, the invention provides an amnioscope to permit visual access to the amniosphere of the lower uterine polar zone of a female patient, said amnioscope including a main elongate outer tube having an operative end adapted for insertion into the cervix to provide access to the amniosphere, and guide means disposed within the tube to receive and locate an endoscopic telescope closely adjacent the operative end of the main tube, thereby permitting transcervical inspection of the amniosphere.

The term "amniosphere" as herein used includes the decidua, fetal membranes, amniotic fluid, and presenting part of the fetus (where visible) .

The endoscopic telescope preferably incorporates means for generating an image representative of the amniosphere for remote display. The imaging means is preferably a miniature video camera or charge-coupled device (C.C.D.) adapted to transmit the image to a remote screen and/or suitable video recording apparatus.

Preferably, the guide means comprises a first inner guide tube extending generally axially within the main tube, to guide the endoscopic telescope toward the operative end of the main tube. The amnioscope preferably also includes a second inner guide tube extending generally parallel to and axially displaced from the first, to permit the simultaneous introduction of an endoscopic instrument and thereby enable intrauterine procedures to be performed within the field of view of the endoscopic telescope.

The inner guide tubes are preferably disposed to terminate marginally within the surrounding outer tube, thereby preventing inadvertent contact with and possible damage to the amniotic membranes. The inner guide tubes advantageously terminate between 0 to 10 mm, and preferably around 5 mm, from the remote end of the outer tube.

Preferably also, the amnioscope includes locating means disposed to locate the inner guide tubes in predetermined relative relationship within the main outer tube.

The locating means preferably includes a pair of longitudinally spaced apart spacing rings fixed to and extending generally around both guide tubes, the external diameters of the spacing rings corresponding approximately to the internal diameter of the outer tube at respective positions along the length thereof. This arrangement provides for positive radial location for the guide tubes. The outer tube preferably tapers inwardly toward its operative end in a generally frusto-conical configuration.

In the preferred embodiment, the inner guide tubes and associated spacing rings are fixedly interconnected to form a discrete sub-assembly adapted to be releasably retained in position within the main outer tube by means of a bayonet fitting. The sub-assembly incorporating the inner guide tubes is preferably interchangeable with an obturator incorporating a dome shaped head adapted to protrude beyond the operative end of the outer tube, to facilitate initial insertion of the amnioscope into the cervical canal.

It is further preferred that the amnioscope includes effacement measuring means to provide a quantitative indication of the degree of effacement of the cervix.

In the preferred embodiment, the effacement measuring means comprises a fixed guide channel extending longitudinally along the outer surface of the main tube, a connecting rod slidably disposed within the guide channel, a reference head disposed on the remote end of the connecting rod to abut and thereby define a reference position for the outer surface of the cervix, and indicia disposed on the proximal end of the connecting rod to provide an indication of the distance between the reference head and the operative end of the main tube, that distance corresponding to the degree of effacement of the cervix.

Preferably, resilient bias means are provided to urge the connecting rod toward a zero position wherein the reference head is substantially flush with the remote end of the main tube. Abutment means are preferably also provided to prevent axial excursion of the connecting rod and reference head beyond the operative end of the main tube.

Advantageously, the reference head of the effacement measuring assembly also provides a vaginal marker for abdominal ultrasound assessment.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 is partially cut-away side elevation showing an amnioscope in accordance with the invention;

Figure 2 is a side elevation showing an internal sub-assembly of the amnioscope of Figure 1 incorporating two inner guide tubes and associated spacing rings according to the invention;

Figure 3 is an end elevation of the sub-assembly taken along line 3-3 of Figure 2;

Figure 4 is a cross-sectional view taken along line 4-4 of Figure 3 showing the proximal end of the sub-assembly;

Figure 5 is a sectional view taken along line 5-5 of Figure 2 ;

Figure 6 is a side elevation showing the principal components of the effacement meter of the amnioscope of Figure 1;

Figure 7 is a series of enlarged cross sectional views showing various elements of the effacement meter of Figure 6; and

Figure 8 is a diagrammatic cut-away side elevation of the amnioscope in position adjacent the amniosphere, also showing the cervix, forewaters, and fetal head.

PREFERRED EMBODIMENT OF THE INVENTION

Referring firstly to Figures 1 to 5, wherein corresponding features are denoted by corresponding reference numerals, the invention provides an amnioscope 1 including an open ended main outer tube 2, and guide means in the form of a first inner guide tube 3 extending generally axially within the main outer tube. The first guide tube is disposed to guide an endoscopic telescope 5 incorporating a miniature video camera toward the operative end 6 of the amnioscope. The proximal end of the guide tube is fitted with a nylon insert 7, adapted nestingly to receive and locate the corresponding end of the telescope assembly 5.

A second inner guide tube 10 extends generally parallel to and is axially displaced from the first, to permit the simultaneous introduction of an endoscopic instrument such as endoscopic forceps (not shown) , as described in more detail below.

The amnioscope further includes longitudinally spaced apart spacing rings 12 and 13 fixed to and extending generally around the respective guide tubes 3 and 10. As best seen in Figure 1, the external diameters of the spacing rings 12 and 13 correspond approximately to the internal diameter of the tapered outer tube 2 at respective positions along the length thereof. The combined external diameters of the inner guide tubes 3 and 10 corresponds approximately to the internal diameter of the main tube 2 adjacent its operative end 6, to provide additional radial support for the guide tubes within the apparatus.

As best seen in Figures 2 to 5, the inner guide tubes and associated spacing rings are fixedly interconnected by welding, brazing or other suitable means to form a discrete sub-assembly 15, adapted to be releasably retained in position within the main outer tube by a first bayonet fitting. The bayonet fitting comprises a lug or prong 16 extending radially from the proximal spacing ring of sub-assembly 15 to releasably engage a complementary slot 17 formed in the proximal end of the outer tube. As best seen in Figure 8, the slot 17 incorporates a circumferential branch adapted to receive the lug 16 and thereby locate the sub-assembly 15 in a manner similar to a conventional bayonet fitting. The slot also incorporates an adjoining longitudinal branch 18, adapted alternatively to locate a proximal fibre-optic light to permit monocular visualisation of the amniosphere of the lower uterine zone. This in turn facilitates accurate positioning of the amnioscope prior to any video endoscopic procedures.

As best seen in Figure 1, the inner guide tubes 3 and 10 terminate around 5 mm from the remote end of the surrounding outer tube. Additionally, the endoscopic telescope is located axially by the nylon insert 7 on the proximal end of the first guide tube 3 so as not to protrude significantly beyond the remote end of the guide tube. This configuration prevents inadvertent contact with and possible damage to the delicate amniotic membranes during the examination procedure.

The sub-assembly 15 is interchangeable with an obturator 20 incorporating a dome shaped head 21 adapted to protrude beyond the operative end of the outer tube. This facilitates initial insertion of the amnioscope, as described more fully below.

As best seen in Figures 7 and 8, the apparatus preferably also includes an effacement measuring apparatus 25 to provide a quantitative indication of the degree of effacement of the cervix. The measuring apparatus includes a fixed guide channel 26 extending longitudinally along the outer surface of the main tube, and a connecting rod 27 slidably disposed within the channel. An ectocervical reference head 28 is supported on the remote end 29 of the connecting rod, to abut and thereby define a reference position for the outer surface of the cervix. The proximal end of the connecting rod incorporates indicia in the form of linear scale 30, to provide an indication of the distance "A" between the reference head 28 and the operative end 6 of the main tube.

The connecting rod 27 also extends slidably through a support housing 35, which is releasably engageable in coaxial alignment with the guide channel 26 by means of a second bayonet fitting 36 or other suitable locating means. The housing 35 contains resilient bias means in the form of a compression spring 37 extending between an end cap 38 threaded to the proximal end of the housing and an annular bush 39 secured to the connecting rod. The spring 37 thereby urges the connecting rod toward a zero position, wherein the reference head 28 is substantially flush with the remote end 6 of the main amnioscopic tube.

A grub screw 40 extends slidably through a longitudinal slot formed in the top of the housing 35, through a correspondingly threaded radial bore formed in the annular bush 39, and into abutting engagement with the connecting rod. Thus, the grub screw adjustably locates the bush in a preselected relative axial position on the connecting rod. In this way, the position of maximum displacement of the reference head, which corresponds to the point at which the bush 39 abuts corresponding shoulder 42 within the housing, can be adjusted by loosening grub screw 40, sliding - li ¬ the annular bush to the desired position on the connecting rod, and retightening the grub screw.

As best seen in Figure 7, the reference head 28 is defined by an arm 45 pivotally mounted to the remote end of the connecting rod. The pivotal arm 45 is resiliently biased toward an upstanding orientation generally normal to the connecting rod by tension spring 47 and an intermediate connecting linkage 48 disposed within remote cavity 50. By folding the arm 45 of the reference head downwardly into axial alignment with the connecting rod against the bias force of the spring 47, the connecting rod 27, reference head 28, and housing 35 can be withdrawn from the supporting guide channel 26 together as a second discrete sub-assembly 51.

Turning now to describe briefly the operation of the device, the effacement measuring sub-assembly 51 is first positioned within the guide channel 26 and secured by engagement of the associated bayonet fitting 36. The connecting rod is then calibrated by releasing grub screw 40 and positioning bush 41, such that the reference head is biased toward a zero position substantially flush with the remote end of the main tube by the spring 37, and prevented from axial excursion beyond that position by bush 39 abutting corresponding annular shoulder 42.

The obturator 20 is then inserted into the main tube, such that the domed head 21 protrudes beyond the operative end 6 thereof. The instrument is then inserted through the cervical canal and advanced into the uterus in the conventional manner. With the outer tube in position, the obturator 20 is removed.

If desired, a proximal fibre-optic light can then be installed. This light is conveniently located in position by the longitudinal branch 18 of the slot 17 formed in the outer tube. The proximal fibre-optic light permits direct monocular visualisation of the amniosphere of the lower uterine zone, which may be useful in facilitating accurate positioning of the amnioscope, prior to commencement of any video endoscopic procedures. With the amnioscope thereby appropriately positioned, the fibre-optic light is also removed. It should be appreciated, however, that this aspect of the procedure is optional and subject to the particular circumstances and the nature of the procedure.

The sub-assembly 15 incorporating the inner guide tubes 3 and 10 is then engaged in place of the obturator and/or the proximal fibre-optic light and locked into position by engaging lug or prong 16 with the circumferential branch of slot 17. The endoscopic telescope 5 incorporating a miniature video camera and in-built illumination is then passed through the central inner guide tube 3 such that the lens is positioned closely adjacent the operative end of the main tube 2, close to the amniotic sack. The telescope is prevented from protruding beyond the guide tube by annular shoulder 55 which axially abuts the complementary nylon insert 7 fitted to the proximal end of the guide tube.

With the output of the video camera connected to a suitable video screen, the amniotic fluid can then be examined for green discolouration. By moving the instrument slowly along its longitudinal axis, deeper layers of amniotic fluid can be inspected. Any meconium flakes can be recognised when the fluid is put into motion by quickly moving the instrument back and forth a few millimetres, in accordance with conventional techniques. The video image from the camera can also be transmitted to suitable video recording apparatus, for subsequent comparison with a reference colour chart, or analysis by specialist practitioners. It will be appreciated that this aspect of the invention thereby permits more objective and recordable visual evaluation of the condition of the amniotic fluid. Further after completion of the inspection of the amniotic fluid, the amnioscope is directed towards the face of the fetus, previously located by ultrasoundography, and the gross body movement and heart rate of the fetus in response to photostimulation noted synchronously with the ultrasoundography and cardio topography. These are synchronised also with the video endoscopy. In this regard, it has been found that the mature healthy fetus is photokinetic, whereas the obtunded fetus tends to be photostatic.

The second guide tube 10 permits the simultaneous introduction of an endoscopic instrument, such as endoscopic forceps (not shown) . This enables a range of key procedures such as:

(1) Video stripping of membranes from the decidua to activate labour;

(2) Video amniotomy to induce labour; and

(3) Video decidual cytology or biopsy to assess the prostagladin status of the decidual micro-environment; to be performed within the field of view of the endoscopic camera. The image of such procedures can then be magnified and viewed simultaneously by a surgical team on the remote screen. It will be appreciated that because the inner guide tubes are maintained in fixed relative relationship, a stable image of the endoscopic instrument is maintained, despite any movement of the amnioscope as a whole.

With the apparatus in position in the cervical canal, as best seen in Figure 8, the ectocervical reference head 28 of the effacement measuring assembly abuts the outer surface of the cervix. The reading "A" on the linear scale 30 thereby corresponds approximately to the wall thickness "A" of the cervix, which corresponds to the degree of effacement.

This in turn provides an indication of the degree of difficulty of induction of labour, and whether or not prostoglandins may be required to induce labour. The current practice of measuring effacement is generally carried out by digital palpation, which is open to subjective inaccuracy. Consequently, this aspect of the invention also represents a significant advancement over the prior art.

Thus, the invention permits a particularly effective examination in late pregnancy of the amniotic fluid of the forewaters, provides access, to the membranes around the forewaters and the decidua of the lower uterine segment, and finally provides a means of fetal photostimulation. It also permits direct measurement the dilation and effacement of the cervix. Accordingly, the invention represents significant advance over the prior art.

Although the invention has been described with reference to a specific example, it will be appreciated that the invention may be embodied in many other forms.

Claims

CLAIMS : -

1. An amnioscope to permit visual access to an amniosphere of a lower uterine polar zone of a female patient, said amnioscope including a main elongate outer tube having an operative end adapted for insertion into the cervix to provide access to the amniosphere, and guide means disposed within the main tube to receive and locate an endoscopic telescope closely adjacent the operative end of the main tube, thereby permitting transcervical inspection of the amniosphere.

2. An amnioscope according to claim 1, further including an endoscopic telescope adapted to be positioned closely adjacent the operative end of the main tube by said guide means.

3. An amnioscope according to claim 2, wherein said endoscopic telescope incorporates imaging means adapted to generate an image representative of said amniosphere for remote display.

4. An amnioscope according to claim 3, wherein said imaging means includes a miniature video camera adapted to transmit said image to a video recording apparatus.

5. An amnioscope according to any one of the preceding claims, wherein said guide means includes a first inner guide tube extending generally axially within the main tube, to guide the endoscopic telescope toward the operative end of the main tube.

6. An amnioscope according to claim 5, further including a second inner guide tube extending generally parallel to and axially displaced from the first inner guide tube, to permit the simultaneous introduction of an endoscopic instrument through the cervix to the amniosphere, thereby enabling intrauterine procedures to be performed within a field of view of said endoscopic telescope.

7. An amnioscope according to claim 6, wherein said first and second inner guide tubes are disposed to terminate marginally within the surrounding main outer tube, thereby preventing inadvertent contact with and possible damage to amniotic membranes.

8. An amnioscope according to claim 7, wherein said first and second inner guide tubes terminate internally at a position disposed between 0 mm and around 10 mm from the remote end of the outer guide tube.

9. An amnioscope according to claim 8, wherein said first and second inner guide tubes terminate internally at a position disposed approximately 5 mm from the remote end of the outer guide tube.

10. An amnioscope according to any one of claims 1 to 9, further including locating means disposed positively to locate said guide means in predetermined relative relationship within the main outer tube.

11. An amnioscope according to claim 10 when dependent upon any one of claims 6 to 9, wherein said locating means is disposed to locate said first and second inner guide tubes in predetermined spacial relationship within the main outer tube.

12. An amnioscope according to claim 11, wherein said locating means includes a pair of longitudinally spaced apart spacing rings fixed to and extending generally around both said first and second guide tubes, said spacing rings having external diameters corresponding approximately to the internal diameter of the outer tube at respective positions along the length thereof, such that said spacing rings provide positive radial location for said first and second guide tubes within said main outer tube.

13. An amnioscope according to any one of the preceding claims, wherein said main outer tube is generally frusto-conical in shape, having side walls converging substantially uniformly toward said operative end, to facilitate insertion into the cervix.

14. An amnioscope according to any one of claims 6 to 13, wherein each of said first and second guide tubes is substantially cylindrical.

15. An amnioscope according to any one of claims 10 to 14, wherein said guide means and said locating means are interconnected to form a discrete sub-assembly adapted to be releasably retained in a predetermined position within the main outer tube.

16. An amnioscope according to claim 15, wherein said sub-assembly is adapted to be releasably retained in position within the main outer tube by means of a bayonet type fitting incorporating at least one locating prong on said sub-assembly, engageable with a complementary slot formed in the main outer tube.

17. An amnioscope according to claim 15 or claim 16, wherein said sub-assembly is selectively interchangeable with an obturator incorporating a generally dome shaped head adapted, in use, to protrude beyond the operative end of the outer tube, thereby facilitating initial insertion of the amnioscope into the cervical canal.

18. An amnioscope according to any one of the preceding claims, further including effacement measuring means to provide a quantitative indication of the degree of effacement of the cervix.

19. An amnioscope according to claim 18, wherein said effacement measuring means comprises a fixed guide channel extending longitudinally along the outer surface of the main tube, a connecting rod slidably disposed within the guide channel, a reference head disposed on the remote end of the connecting rod to abut and define a reference position for the outer surface of the cervix, and indicating means to provide an indication of the distance between the reference head and the operative end of the main tube, thereby to provide an indication of the degree of effacement of the cervix.

20. An amnioscope according to claim 19, wherein said indicating means includes indicia disposed on the proximal end of the connecting rod to provide a direct indication of the position of the rod relative to the guide channel.

21. An amnioscope according to claim 20, wherein said indicia are calibrated to provide a direct measure of the distance between the reference head and the operative end of the main tube.

22. An amnioscope according to any one of claims 19 to 21, further including resilient bias means disposed to urge the connecting rod forwardly toward a zero position wherein the reference head is substantially flush with the remote end of the outer tube.

23. An amnioscope according to claim 22, further including abutment means disposed to prevent axial excursion of the connecting rod and the reference head beyond the operative end of the main tube, corresponding to said zero position.

24. An amnioscope according to any one of claims 19 to 23, wherein said reference head is defined by an arm pivotally mounted to the remote end of the connecting rod, said arm being resiliently biased toward an upstanding orientation generally normal to the connecting rod, whereby rotation of said arm into coaxial alignment with said connecting rod against said bias force permits withdrawal of the connecting rod and reference head through the supporting guide channel as a second discrete sub-assembly.

25. An amnioscope according to claim 24, wherein said second effacement measuring sub-assembly is releasably positioned and secured relative to the guide channel by means of a second bayonet type fitting.

26. An amnioscope according to claim 24 or claim 25, wherein said effacement measuring means further includes a housing extending around a portion of the proximal end of the connecting rod, a bush slidably disposed within said housing and around said connecting rod, said bush being releasably engageable in preselected positions with said connecting rod by means of a grub screw, said grub screw extending outwardly through an elongate slot formed in the housing, said bias means comprising a spring disposed intermediate said bush and an end wall of said housing, to urge said bush toward a position of maximum forward axial displacement corresponding to abutment with a forward end wall of said housing, such that said zero position of said reference head can be selectively adjusted by manually altering the position of said bush relative to said connecting rod by means of said grub screw.

27. An amnioscope, substantially as hereinbefore described with reference to the accompanying drawings,