Double Spiral Electrode For Intra-cavity Attachment

Abstract

An electrode device is configured for mounting at or within parts of the human body, especially for obtaining ECG signals from a fetus. The electrode device includes two spiral pointed catcher elements displaced by 180.degree. which are mounted in an insulating carrier. A counter electrode in the form of a tubular metal guiding element surrounds the carrier and protects the vagina and the fetus when the pointed catcher elements are introduced. A cannula may be provided at the electrode device so that liquid medicine or an electrolyte can be supplied to the fetus simultaneously with measuring ECG signals. The electrode device is introduced into the vagina by means of a guiding element.

Description

BACKGROUND OF THE INVENTION

This application relates generally to an apparatus for obtaining measuring signals at or in parts of the human body, for example in cavities of the human body.

It is well known to take physiological measurements such as an electrocardiogram from an unborn child by using a needle electrode on which a second opposite polarity or counter electrode is mounted. Since a wrong positioning of the needle electrode can lead to substantial injuries of the fetus, the adjustment of said electrode has to be effected visibly. Thus, it is necessary to use an endoscope which, for the use in combination with a needle electrode, has an inclined top which permits the needle electrode to be positioned tangentially at the body part of the fetus. The needle electrode is mounted by means of a special pincers having gripping elements formed like a stork's bill. Such an electrode is rather complicated and does not exclude the possibility of substantially injuring the fetus.

It is also well known to obtain physiological signals using a so-called clip electrode working according to the principle of the suture clip. The counter electrode of the clip electrode is mounted on the insulating envelope of the signal lead. Practical use of this type of electrode has shown that it can be used only a few times before its prongs break. Furthermore, after being mounted in place, the electrode is not rigidly positioned at the fetus, and can pivot around an axis defined by the points of fixation. This can lead to the result that the counter electrode may touch the fetus, so that both the clip and counter electrodes have equal potentials and no measuring result can be obtained. A further disadvantage of this type of electrode arrangement is that its removal from a fetus is not easy and often causes substantial injury thereto. Also, this type of electrode has to be positioned visibly, which requires a relatively free entry to the desired point of location because of the size of the electrode. Often this special requirement cannot be met and the electrode is thus not usable.

Finally, it is well known to use an electrode in the form of a spiral shaped gripping device or catcher having two needle-like ends which are displaced by 180.degree.. This catcher electrode is positioned at the desired point of fixation on the fetus and is then affixed thereto by a short turn. The counter electrode is separate from the catcher electrode and has its own signal lead. The counter electrode is simply introduced into the same cavity of the body in which the catcher electrode is also present. As a result both electrodes do not have a defined relative position to each other, and the measuring result may be adversely affected. This is especially true if during the measurement the child or the mother is moving. The introduction of the catcher electrode is done manually or by means of a tampon holder. However, such a tampon holder is constructed for a different purpose and does not have the necessary stability to ascertain a precise mounting of the electrode. Also, the catcher electrode can cause injuries when being introduced as there is no exact guidance therefore, and such electrodes cannot be introduced into deep cavities of the body.

SUMMARY OF THE INVENTION

The present invention in one embodiment comprises a spiral catcher electrode having two pointed ends displaced from each other by 180.degree.. The catcher electrode is contained in a carrier formed of insulating material, and is connected to an electrical signal lead. In or at the carrier there is a metal member being outwardly accessible and being usable as a second opposite polarity or counter electrode. The carrier is mounted at one end of a rod-like guiding element or tube. The metal member used as the counter electrode can extend beyond the carrier. The carrier can comprise grooves or projections which coact with the guiding element and can be detachably mounted on the guiding element.

In another embodiment of the invention, the carrier carries at least one tube or cannula. One end of the cannula is disposed on the side of the front face of the carrier and is pointed, while the other end is connected to a liquid line. The cannula can centrally project from the front face of the carrier between the spiral arms of the catcher electrode. Alternatively, the cannula may be formed from at least one of the arms of the catcher electrode.

One advantage of the novel apparatus is that it allows a safe and simple mounting of the measuring head even with a moving fetus. The removal of the measuring head does not endanger the fetus. As the piercing of the catcher electrode causes only small injuries, the danger of infection is decreased. Finally, the measuring head is fixedly mounted at the point of fixation during the measurement and the two electrodes maintain their relative position to each other even with movement of the fetus. With these conditions accurate measuring signals are obtained.

An advantage of the improved apparatus including the cannula is that it is possible to supply to the location under test an electrolytically conductive liquid in order to improve the measuring results. Furthermore, it is possible to medically treat the fetus or mother by injecting medicine through the cannula. Also, liquid may be extracted from the cavity by help of the cannula.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are partial sectional views of the measuring head and associated guide member in two different embodiments of the present invention.

FIG. 3 is a cross-sectional view of the measuring head shown in FIG. 2 and rotated 90.degree..

FIGS. 4-9 are a cross-sectional and outline views of different embodiments of the measuring head of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment illustrated in cross section in FIG. 1 comprises a gripping or catcher electrode 10 which is built such that its two free pointed ends are displaced by 180.degree. relative to each other in a plane which is normal to the longitudinal extension of the apparatus. This catcher electrode is surrounded by an electrically insulating material in the form of a carrier 11 in such a manner that its ends project resiliently from this material. The carrier 11 has the shape of a cylinder and comprises at its lower end a cylinder-like extension 11' of smaller diameter. A second, counter electrode is formed from a metal ring 12 mounted on the carrier 11. The catcher electrode 10 and the metal ring 12 constitute the two electrodes of the measuring head. Accordingly, the catcher electrode is connected with an electrical lead 13 and the ring 12 is connected with an electrical lead 14. The carrier 11 is by means of extension 11' mounted on a rod-like guiding element in the form of a guiding tube 15 which at its lower end is provided with a knurled portion 16 in order to simplify its handling. The two leads 13, 14 are passed through the guiding tube and are connected to the input receptacles of an electronic measuring and processing apparatus, not shown.

The illustrated guiding tube can be made of metal or of a suitable plastic material. If the tube is formed of plastic material it can have a certain flexibility which permits that the apparatus can be used in curved cavities of the body.

In FIGS. 2 and 3 there is illustrated another embodiment of the novel apparatus, in which the catcher electrode 10 is mounted in a carrier 18 which simultaneously surrounds a pin-like counter electrode 19 such that the ends of electrode 19 project slightly from carrier 18. Electrodes 10, 19 are connected to the electrical leads 13, 14 respectively. The carrier 18 is mounted on a guiding tube 20 which is split at its upper end so that the conical and resilient tube parts 20' thus formed surround the carrier 18. With this arrangement, the pin-like counter electrode 19 is held in the slits between the tube parts. Another tube 21 is slidably mounted on the guiding tube 20. When displaced upwardly, the tube 21 pushes against the conical tube parts 20' and thus fixes the counter electrode 19 rigidly in the slits of the guiding tube 20. For the purpose of simple handling, the guiding tube 20 has a knurled gripping portion 17 at its lower end. The tube 21 is also provided with a similar gripping portion 22 at its lower end in order to simplify the actuation of the tube assembly. Thus, by displacing the tube 21 in one or the other direction relative to guiding tube 20, the carrier 18 can be securely clamped in place or unclamped so as to be detached from the guide tube. Because of the length of the tubes, tube 21 does, from a practical point of view, represent a remote actuation of the clamping. It can be actuated within or outside of the body cavity. As shown in FIG. 2, it can be a further advantage to mount a tubular sleeve 23 with rounded edges at its front face on the tube 21 such that the sleeve 23 can only be displaced on the tube 21 by exerting a certain force. Before the introduction of the apparatus into the body cavity, this tubular sleeve is moved into the represented position in which it surrounds the pointed ends of the catcher electrode 10 for the purpose of protection. Upon touching the point of adjustment, the tubular sleeve displaces backwards and thus releases the action of the catcher electrode 10. During the introduction of the apparatus, the body cavity is protected against injury from the catcher electrode by means of the tubular sleeve 23.

FIGS. 4 and 5 illustrate different measuring heads which can be mounted on a guiding element. The measuring head shown in FIG. 4 comprises the catcher electrode 10 and a counter electrode in the form of a metal ring 25 which is sleeve-like, inserted intothe carrier 26. Also, both electrodes are connected with respective electrical leads 13 and 14. At its lower end the carrier 26 comprises recesses 27 into which a complementarily formed guiding element can be engaged. In lieu of these recesses there can also be provided projections 28 which are schematically illustrated in FIG. 5, where a ring 30 positioned on the carrier forms the counter electrode for the catcher electrode 10.

Another embodiment of the measuring head is shown in FIG. 6. The carrier for the electrodes is not made unitary but is manufactured with a ring 31 of insulating material. The electrodes 10, 34 are mounted by means of an electrically insulating casting material to extend from opposite ends of the ring 31. In the illustrated embodiment, mounting plugs 35 serve for mounting the carrier on the guiding tube.

Although in the illustrated embodiments the guiding elements are always shown to be guiding tubes, it is also possible to replace the tubes by a compact guiding rod. In this case the electrical leads laterally extend from the carriers of the measuring heads and they can be located laterally along the guiding rod.

There can be provided still another ring measuring system, for example for pressure measurement, at or within the carrier of the measuring head. If only pressure is to be measured with this apparatus, the counter electrode is unnecessary and the catcher would serve merely as a mounting element. In the case where the measuring head carries both measuring head systems, measuring data for several parameters may be obtained simultaneously.

In FIG. 7 there is represented a measuring head, wherein the catcher electrode 10 is isolatedly mounted in a carrier 18 that simultaneously surrounds a pin-like counter electrode 19, the ends of which project slightly at both sides of the carrier. Electrodes 10, 19 are connected with electrical signal leads 13, 14, respectively. Furthermore, the carrier 18 carries a tube or cannula 36 having a pointed end which projects beyond the upper front face of the carrier 18. As shown, the cannula is centrally located between the arms of the catcher electrode 10. The rear end of the cannula is connected with a liquid line 37. When the measuring head is affixed to a fetus, for example, by a short turn, the tubing immerses into the fetus. If desired, the tubing can be mounted in the carrier in a manner such that its length projecting beyond the front face of the carrier is adjustable. This can be achieved, for example, by providing on the external portion of the cannula a screw-threaded portion which coacts with a corresponding internally threaded portion in the carrier.

The embodiment according to FIG. 8 is similar to that of FIG. 6. However, the catcher electrode 10 mounted in insulating material 32 consists of two parts 10a and 10c, of which the latter itself forms a cannula having one end embedded in the carrier in communication with a liquid pipe 37. Both catcher arms 10a, 10c are connected with each other and act as an electrode, which can coact with the caplike counter electrode 34. The outer shape of the carrier is determined by a sleeve 31 having two holding trunnions 35.

In FIG. 9 is illustrated another embodiment of a measuring head wherein both catcher arms 10c are formed as cannulas. They are embedded in an insulating mass 29 which is surrounded by a ring 30 that serves as a counter electrode. The two cannulas are electrically connected together to form one electrode. Each cannula is connected to a liquid pipe 37. The carrier 29 includes lateral extensions 28 which simplify its handling. In the illustrated embodiments, the liquid pipes are connected to the cannulas within the insulating mass; however, it is also possible to provide these connections outside of the carrier.

Claims

I claim:

1. A measuring head assembly for obtaining measuring signals from cavities of the human body comprising:

a spiral catcher electrode having two arms with pointed ends being displaced by 180.degree. relative to each other;

a carrier formed of an insulating material surrounding a portion of the catcher electrode;

an electrically conductive member extending from the carrier in a fixed spatial relation with the catcher electrode, the conductive member being operable as a counter electrode with the catcher electrode;

a pair of electrical signal leads connected respectively to the catcher electrode and the conductive member; and

a guiding tube having an end portion of a predetermined configuration for receiving and holding the carrier by engaging the conducting member extending from the carrier, thereby enabling the carrier to be detachably mounted in the guiding tube.

2. The apparatus of claim 1 including a cannula having a pointed end extending centrally from the carrier between the spiral arms of the catcher electrode.

3. The apparatus of claim 2 wherein the length of the pointed end extending from the carrier is adjustable.

4. The apparatus of claim 1 wherein at least one of the arms of the catcher electrode is a cannula.