COMBINATION SPIRAL EKG ELECTRODE AND PH PROBE

Abstract: A combined spiral EKG electrode and pH probe for use in monitoring a fetus during labor is described. The combined probe includes a spiral wound needle which acts as an EKG electrode and also houses a fiber optic pH probe. Optical fibers and wires from the needle as well as from a reference electrode on the probe assembly are passed back through the cervix and vagina of a woman in order to provide simultaneous information as to both EKG and pH of the fetus during labor.

Description: The present invention is an electrode for use in fetal monitoring. In particular, the invention relates to an electrode for use in continuously measuring both EKG signals and hydrogen ion concentration (pH) of a fetus during birth. Heretofore, a variety of electrode structures and applicators have been described for use in inserting a bipolar electrode structure through the vagina and cervix of a woman in labor and attaching it to the epidermis of a fetus. Such electrode structures are designed to be operatively connected to an amplifier and a cardiotachometer for recording the fetal electrocardiogram and heart rate during labor and delivery. The pH value of blood is related largely to the carbon dioxide and acid concentration in the blood. For many years it has been recognized that the pH value of the blood (or tissue) of a fetus during delivery may provide an early indication of fetal distress, since increased carbon dioxide, with or without fixed acid concentration (manifested by decreasing pH values), may mean that the fetus is receiving insufficient oxygen. That can be an indication of compression of the umbilical cord, which could result in restricted oxygen supply and permanent brain damage. Heretofore, various pH electrodes have been developed for the purpose of continuously monitoring the pH values of the fetus. Typically, pH values were measured using two electrochemical half cells with the potentials across the half cells connected in opposition, so as to cancel one another. NTIS, No. PB 82-970453 (1982), Springfield, VA, USA, describes a fiber optic pH probe for tissue measurements incorporated into a small rigid needle. As noted, the monitoring of the electrocardiograph and the pH of a fetus are both desirable. Accordingly, a number of different types of electrodes have heretofore been developed to monitor either EKG or the pH. Unfortunately, in view of the manner in which such electrodes are applied to the scalp of the fetus, i.e., through the vagina and cervix of a woman in labor, it has not heretofore been possible to attach more than one electrode to the scalp of a fetus at any given time. Therefore, it would be highly desirable to have a combined pH and EKG electrode. In accordance with the present invention a combined EKG electrode and pH probe comprises a hollow, electrically conductive spiral needle which houses a fiber optic pH probe. The combined unit serves to electrically measure EKG while optically measuring the pH of the fetus. In the Drawing: FIG. 1 is a side view of the combined pH and EKG probe of the present invention: FIG. 2 is a bottom view of the probe of FIG. 1: FIG. 3 is a cross-sectional side view of the probe of FIG. 1: FIG. 4 is an exploded view of the preferred embodiment of the end of the needle used in the present invention: and FIG. 5 is an alternative embodiment for use with the end of the needle. Referring generally to FIGS. 1 - 3, the preferred embodiment of the combined pH and EKG probe 10 of the present invention is shown. The probe 10 is comprised of a base assembly 12 which is made of a soft material such as a silicone plastic. Molded into the plastic base 12 is a hollow, electrically conductive, spiral wound needle 14. The needle 14 is used both as the EKG electrode and also as a housing for the fiber optic probe. The needle 14 extends out of the broad portion 16 of the base assembly 12. The broad portion 16 of the base assembly 12 is somewhat concave and has raised bumps 18 formed thereon. The base assembly 12 tapers from the broad portion 16 to the top 20 which is substantially squared in shape (when viewed from the end) in order that a square tube (not shown) can be used as an applicator for inserting the electrode 10 into scalp of the fetus through the vagina and cervix of a woman in labor. A pair of wires 22, 24 are electrically connected to the hollow, spiral wound needle 14 and to a reference electrode 26 formed at the top 20 of the plastic base assembly 12. The hollow needle 14 extends through the side 28 of the base assembly 12 in order to permit optical fibers 30, 32 to pass down through a tube 34 into the end of the needle 14. Referring now to FIG. 4, the end of the needle 14 comes to a point 36. Near the point 36 of the needle 14 is a window 38 formed in the needle 14 in order to allow body fluids from the scalp of the fetus to enter into the area containing the fiber optic probe 40 and ion permeable membrane envelope. These items operate in a manner more fully described in U. S. Patent No. 4,200,110 entitled FIBER OPTIC PH PROBE which issued to J.I. Peterson, et al. on April 29, 1980. Referring to FIG. 5, an alternative embodiment for the end of the needle is shown. In the alternative embodiment there is a spiral opening 42 cut adjacent the end 44 of the needle 14 to permit body fluids from the scalp of the fetus to enter the ion permeable membrane of the fiber optic pH probe. The purpose of the squared off top end 20 of the plastic assembly 12 is to permit the use of an elongated tube (not shown), which is typically constructed of plastic, which also has a squared off end to be used as an insertion tool for applying the probe 10 through the vagina and cervix of a woman in labor and into the scalp of a fetus. The present probe 10 provides for simultaneous monitoring of both pH and EKG of a fetus during labor without requiring that more than one probe be inserted into the scalp of the fetus. Thus, the benefits derived from both EKG monitoring and from pH monitoring are simultaneously available.

Claims: A combined EKG electrode and pH probe for simultaneous electrical and chemical monitoring of a fetus, comprising: a base assembly (12); a single, spiral shaped hollow electrically conductive needle (14)used as an EKG electrode and, which extends from said base assembly (12) for electrical monitoring of a fetus; a reference electrode (26) on said base assembly (12); and a fiber-optic pH probe (30, 32) which extends through said hollow needle (14). The probe of Claim 1, wherein said base assembly (12) is substantially wider than the diameter of said needle (14). The probe of Claim 1 or 2, wherein the tip of said fiberoptic probe (30, 32) is within the portion of said needle (14) adjacent to the tip (36) thereof. The probe of Claim 3, wherein said needle (14) includes an opening (38) adjacent to the tip (36) thereof which permits fluid from the fetal scalp to contact said fiberoptic probe (30, 32). The probe of Claim 3 or 4, wherein the top of said base assembly (12) has a substantially square shape so as to conveniently receive an insertion tool having the same shape, for ease of insertion of said probe into the scalp of a fetus through the vagina and cervix of a woman in labor. The probe of any of Claims 1 to 5, wherein said base assembly (12) is made of a plastic material. The probe of any of Claims 4 to 6, wherein said opening (38) in said needle (14) is substantially rectangular. The probe of any of Claims 4 to 6, wherein said opening (38) in said needle (14) is a spiral shaped opening. The probe of any of Claims 3 to 8 further comprising means for sending both electrical signals, from said EKG probe, and light signals, from said fiber optic pH probe, to sensing means external to the woman.

Inventors: HOCHBERG, HOWARD MARTIN, SCHMALZBACH, EDWIN LEWIS, ZIEDONIS, JANIS GUNARS
Applicants: ABBOTT LABORATORIES
Application year: 1983
Main classification: A61B5
IPC codes: A61B5