Foetal Blood Sampling Endoscope

Abstract

A medical instrument comprises two tubes arranged to define an annular space therebetween for application of suction to adhere the same to a body part while an associated instrument is housed within or passed through the inner tube. This finds particular application to endoscopes, especially amniscopes for foetal blood sampling, with one of the tubes being shorter than and preferably outside the longer main tube at its distal end, with a third tube of smaller order of cross-section passing back along the main tube towards its proximal end.

Description

This invention concerns medical instruments and has been developed initially in connection with foetal blood sampling. While the invention has application to medical instruments for other purposes, as will be seen from the terminal discussion hereinafter, it is convenient to consider the invention first in the light of its original derivation.

Foetal blood sampling is extensively employed, but normally only on cervices of about two fingers upwards dilated. Conventionally, such sampling involves passing an endoscope, fitted with an obturator, per vagina and, after removal of the obturator, visualizing the presenting part through the cervix with the aid of proximal lighting system clipped on the proximal end of the endoscope. The field is swabbed as dry as possible with long swab holders, and a jelly is applied to induce a large drop of blood to form when an incision is subsequently made by advancing a lance. The lance is then withdrawn and heparinized glass capillary tube is advanced to collect a sample from the drop of blood.

This technique is associated with difficulty in that it is assumed that no foetal movement occurs to change the field and that no contamination of the drop of blood occurs. In fact, the endoscope is normally pressed firmly on to the presenting part in an attempt to reduce the disadvantageous factors just mentioned, but this in itself is undesirable in leading to engorgement of the field and consequential error in pH readings. In practice, the movements of the fetal parts and the fact that the procedure is carried out at a distant vision cause some difficulty in obtaining a sample with any ease and, even then, the results so obtained may not be completely reliable.

An object of the present invention is to reduce the above disadvantages and, to this end, provides in a more general aspect, a medical instrument comprising two tubes arranged in generally coaxial manner to define an annular space therebetween, the inner tube serving to house therein or afford access therethrough for an associated instrument, and said space being open at one end and adapted at the other end for application of suction thereto.

In a more particular aspect, such as for use in the above discussed application of foetal blood sampling, the invention provides a medical instrument comprising a main tube having at its distal end a second tube of shorter length than the main tube, the two tubes defining an annular space therebetween which is open at its distal end, and a third tube communicating at one end with said space and leading at its other end towards the proximal end of the main tube, said third tube having small transverse dimensions relative to the other two tubes.

This more particular instrument will normally be used with a capillary tube for the purposes of collecting blood or other liquid samples. This capillary tube preferably passes from the proximal end and externally of the main tube, and through a passageway provided in the annular space, to communicate with an aperture in the inner wall of such space, so that the "cylindrical" space defined by such wall is unobstructed. For the same reason, namely, avoidance of unnecessary obstruction within the main tube, the annular space is preferably defined with the main tube innermost.

For use in foetal blood sampling or like operation, the presently proposed instrument is preferably provided with or adapted for use with a lance using protected disposable blades, the proximal end of the main tube being conveniently slotted so that the lance handle may project generally radially from the tube while the body of the lance passes along the tube.

Also, such an instrument preferably comprises, or is adapted to detachably receive, a distal field illuminating and/or viewing system.

In order that the present invention may be more clearly understood, the same will now be more fully described by way of example, with reference to the single FIGURE of the accompanying drawing which schematically illustrates one embodiment of the invention in longitudinal section.

The illustrated embodiment is an instrument designed for the above discussed application of foetal blood sampling. This instrument comprises a main tube 1 at one end, the distal end, where a second tube 2 is mounted externally therearound to define an annular space 3. The distal end of the space 3 is open, and the "proximal" end of the space 3 is closed by a wall 4 which in fact supports the tube 2 in its spaced relation from the main tube 1.

The wall 4 is apertured at 5 for communication with the space 3 of the interior of a third tube 6 sealably secured to the periphery of aperture 5. The tube 6 passes along the main tube towards the proximal end, in which region tube 6 is inclined away from the main tube and terminates in a bulbous end portion 7 or equivalent formation or fitting for connection to a flexible suction line and associated evacuation pump.

The distal end portion of the main tube defining the annular space 3 is also provided with an aperture 8 which is associated with a further aperture 9 in the wall 4 to define a path for a capillary tube 10 therebetween. This path may simply provide a channel for tube 10 by boring the aperture 8 and 9 in alignment at a suitable angle, whereby tube 10 can be passed along the channel without undue difficulty while not being a loose fit. Alternatively, the path may be defined by tubing or like structure between the apertures 8 and 9 whereby the path for tube 10 is wholly separated from the annular space 3. In either event, the tube 10 is preferably of plastics material, such as polyethylene, and this is useful in connection with passage through a channel as first described to achieve an effective seal for the annular space vis-a-vis apertures 8 and 9.

The capillary tube 10 passes from the apertures towards the proximal end of the main tube, where it is supported by passage through a short length of larger tube 11 secured to the main tube, and then turns away from the main tube and terminates.

The main tube is provided with a longitudinal slot 12 extending part way along the tube from its proximal end. This slot, as mentioned earlier, facilitates the use of an associated lance. A preferred form of lance is indicated at 13 with the main body of the lance extending along the main tube interior, while having a handle 14 extending generally radially from the main tube through slot 11.

Also shown passing down the main tube interior is an associated distal field illuminating and viewing system 15, such as a McCarthy telescope.

In use of the illustrated instrument, the distal end is passed to the presenting part in the manner of an endoscope in the currently more usual technique. An obturator, preferably of expandable form can be used if desired, but trials with the invention have shown this to be unnecessary in normal circumstances. No immediate cleaning of the presenting part is essential, although this will still usually be done. When the instrument is suitably located relative to the presenting part, suction, for example up to about 14-16 p.s.i., is applied to the space 3 by way of tube 6 to "adhere" the instrument to the presenting part. The presenting part is then cleansed with swabs passed down the main tube, much as before, but without the prospect of subsequent contamination during the following sampling.

The lance is then partly inserted in the main tube, and after this the telescope is inserted to give a clear, stationary view. The lance can then be inserted further with its blade positioned to make an incision just above the blood exit aperture 8. After incision, the lance is retracted to give a clear field again and the blood is visualized as it forms a drop. The blood sample is collected from the drop by way of the capillary tube 10, a swab is held to the presenting part until haemostasis is obtained, and the instrument and associated parts withdrawn in generally the reverse procedure of that for insertion, the instrument proper being withdrawn last after releasing the suction grip.

This technique clearly represents an improvement on that first discussed above. There will be no relative movement between the presenting part and the distal end of the instrument, no risk of contamination in the area of the sample, and no significant error induced by application of pressure to the presenting part.

Also, the instrument can be made of sufficiently small diameter to permit sampling with cervices of less than two fingers dilated.

For example, one embodiment conforming to the illustrated form has been made with a main tube 1 internal diameter of one-half inch and wall thickness of one thirty-second inch, annular space 3 radial dimension of three thirty-seconds inch, and tube 2 wall thickness one thirty-second inch, giving an overall external diameter of three-fourth inch at the distal end. The suction line tube 6 in such embodiment of 1/8-inch external diameter to avoid extending radially beyond the tube 2, and the capillary tube 10 was of sufficiently small external diameter to pass through a tube 11 made of the same material as tube 6. For interest, the overall length of the instrument was 12 inches a McCarthy telescope of 5/32-inch diameter was used, and the associated lance had a main body stem of 1/16-inch rod and a handle of 1/8-inch rod.

The illustrated embodiment is, as noted in the introductory discussion of the invention, made to afford an unobstructed space within the distal end of the main tube. However, the annular space 3 could be defined by locating the tube 2 within the main tube 1 if required. Also, while reference has been made to various tubes, an instrument according to the invention need not be of tubular form in the more usually precise sense of cylindrical. The instrument may conveniently be of slightly convergent form towards its distal end, as shown in the drawing, in the manner of an endoscope. Indeed the invention contemplates the provision of what can be termed a suction annulus at the distal end of an otherwise conventional endoscope. Also with such convergence, an associated illuminating and visualizing system may be conveniently located along the inner face of the instrument main passageway, the system being chosen or designed to illuminate and visualize the instrument mouth when so positioned. Other systems, such as the McCarthy telescope, may be inclined in a divergent sense relative to the instrument axis, as in fact shown in the drawing, to make best use of their optical paths. Whatever the system, it need not be permanently connected with the main instrument, but can be detachably coupled by way of clips or passed through an auxiliary tube connected to the main tube, say. Where a visualizing system is not used, a simple illumination device can be clipped or clamped at the proximal end of the main tube.

This last discussion, with its reference to an otherwise conventional endoscope, has already indicated the more general application of the invention. This involves the provision of a suction annulus whereby an instrument can be readily, and comfortably, adhered to a patient to facilitate sampling or other procedures without adversely changing the conditions for such procedures. Foetal blood or like sampling with an endoscope type instrument clearly represent one suitable application for the invention, and instead of an endoscope having a suction annulus permanently connected thereto, a detachable annular suction system can be provided for coupling internally with a conventional converging amnioscope while allowing passage of an associated lance, etc., through the annulus. Another, somewhat different application may be to E.C.G. and E.E.G. electrodes. It is sometimes required that electrodes be attached to a patient for a long period (some hours) and this can give rise to difficulty in terms of satisfactory securement and patient discomfort. Use of an electrode assembly mounted in a suction annulus may go some way to reducing these difficulties.

Claims

I claim:

1. An endoscope for foetal blood sampling, comprising:

a main first tube which is open at both ends and is conically shaped to provide an unobstructed smoothly convergent interior from one end, the proximal end, to the other, distal end;

a suction head second tube significantly shorter than but having slightly greater diameter than said first tube, coaxially disposed around the distal end region of said first tube to define therewith a generally cylindrical annular space therebetween, the respective distal ends of said first and second tubes being substantially coplanar and a wall connecting the proximal end of said second tube to the exterior of said first tube to close said annular space at its proximal end, said space being of small radial thickness relative to the internal diameter of said first tube at its distal end;

a suction-applying third tube of significantly smaller diameter than said first and second tubes, similar length to said first tube, connected to extend longitudinally along the exterior of said first tube, connected at its distal end with the proximal end of said second tube to communicate with said annular space without extending radially beyond the exterior of said second tube at such communicating connection, and having means at its proximal end for connecting said annular space with a vacuum source;

a lance of similar length to but significantly smaller diameter than said first tube disposed within and longitudinally along the interior of said first tube, and freely translatable axially with respect to said first tube so that the end of said lance may be moved beyond said first tube to puncture a foetus held across the distal end of said first tube by suction applied to said annular space; and

a sample-extracting fourth tube of smaller diameter than any of said first, second and third tubes, of similar length to said first tube, and disposed to extend longitudinally along said first tube to terminate at the distal end of the interior thereof to draw off a foetal blood sample from said puncture.

2. An endoscope according to claim 1 wherein said second tube is substantially cylindrical and is connected with said first tube by an annular proximal end wall with which said third tube is connected to communicate with said annular space.

3. An endoscope according to claim 1 wherein said first tube is longitudinally slotted part way therealong from its proximal end, and said lance has a handle projecting radially from its proximal end, which handle is received in said slot to pass therethrough to the exterior of said first tube while allowing translation of said lance.

4. An endoscope according to claim 1 comprising an elongate distal field illuminating means disposed to extend longitudinally along the interior of said first tube.

5. An endoscope for foetal blood sampling, comprising:

a long main first tube which is open at both ends and conically shaped to provide an unobstructed smoothly convergent interior from one end, the proximal end, to the other, distal end where the internal diameter is about one-half inch;

a suction head second tube of cylindrical form significantly shorter than but having slightly greater internal diameter than the external diameter of said first tube at its distal end and coaxially disposed around such end, the respective distal ends of said first and second tubes being substantially coplanar, so that said first and second tubes define a generally cylindrical annular space therebetween of about 3/32-inch radial thickness;

an annular end wall connecting the proximal end of said second tube to the exterior of said first tube to close the proximal end of said annular space;

a suction-applying third tube of similar order of length to said first tube connected to extend longitudinally along and in engagement with the exterior of said first tube, and having an external diameter not greater than the radial thickness of said end wall, said third tube being connected at its distal end with said end wall to communicate with said annular space, and having means at its proximal end for connecting said annular space with a vacuum source;

means adapted for puncturing a foetus held across the distal end of said first tube by suction applied to said annular space; and means for extracting a foetal blood sample from said puncture.