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|United States Patent
May 25, 1971
FETAL SCALP ELECTRODE UNIT
An electrode or lead unit for monitoring fetal heartbeat is disclosed which
includes, in the illustrated embodiment, three electrical leads having
jack connector ends to be plugged into female terminal sockets of an
electrocardiogram-type recording device or audio visual or other sensing
device. One of these is a ground lead electrically connected directly to
an elongated, sleevelike plastic grounding sheath which internally
receives the other two positive and negative electrode leads. One of the
latter terminates externally of an inner end of a terminal shield of the
sheath, being formed as a small pointed and barbed, relatively rigid and
nonbendable penetrating electrode element, a single element similar to a
fishhook, which is lightly embedded in the scalp or another skin area of
the fetus during the monitoring period. The other of the positive and
negative electrodes is in encircling relation to a shank part of the
penetrating element. The relationship of components is such that the
sheath unit make continuous grounding contact with the vaginal mucosa, so
as to afford a clear tracing on the recording device throughout the period
La Croix; George E. (Bloomfield Hills, MI) |
April 1, 1968|
|Current U.S. Class:
|Current International Class:
||A61B 5/0428 (20060101); A61B 5/0402 (20060101); A61B 5/0448 (20060101); A61b 005/04 ()|
|Field of Search:
128/2.06,2.1,(Digest),303.1,303.13,330,353,361,362,404,407,408,409,410,418 43/17.1 339/Inquired
U.S. Patent Documents
Kamm; William E.
1. An electrode unit for fetal monitoring or like application, comprising an electrically conductive electrode lead having means at one end thereof to transmit a signal to a recording or
related means, said lead being provided at its opposite end with a reversely reentrant, sharpened and barbed formation to embed in a skin area of a fetus, a second electrode lead generally paralleling said first lead and also provided with means at an
end thereof to transmit a signal to said recording means, and a sheath encircling said leads and exposing said opposite end of said first-named lead.
2. The unit of claim 1, in which the opposite end of said second lead encircles a shank portion of the reentrant formation of the first lead.
3. The unit of claim 1, in which the opposite end of said second lead encircles a shank portion of the reentrant formation of the first lead, said sheath being electrically conductive in nature and having means electrically connecting the same
as a ground component of said unit in relation to said recording means.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The improved scalp electrode or lead unit of the invention has application in the monitoring, during labor and also during delivery, of the fetal electrocardiogram, performed ordinarily, though not necessarily only, in a hospital maternity
section or ward. The institutional use will be more usual because more than one monitoring of plural deliveries may be obtained using a single recording device, to which the electrical connectors of the electrode unit are selectively and removably
plugged. Thus, a single nursing attendant or the physician may observe plural developments from a single monitor station located within or outside the view of a number of delivery beds.
2. Description of the Prior Art
There currently exist only four varieties of electrode capable of detecting the EKG. of the fetus in utero by direct application of the electrode to the presenting part of the fetus. Each of these is a tripolar lead consisting of a
two-conductor electrode unit, a positive conductor connecting to a modified Michelle skin clip and the negative electrode being located 1 to 11/2 cm. distal to the skin clip, and consisting of a coil of silver or silver-nickle alloy wound about the
first wire. One variety has a third lead located 11/2 cm. distal to the negative lead which serves as the ground. The other varieties employ a separate ground wire attached to the maternal thigh or ankle. The terminal pins or jacks of the electrode
leads vary according to the type of recording device used.
The printed literature, which represents the most pertinent art of which I am aware relating to the field of application of monitoring electrode units, includes an article by Dr. Edward H. Hon (Yale Journal of Biology and Medicine, Vol. 32, No.
5, page 397, Apr. 1960), describing the use of a double prong-type electrode encased in a plastic tubing. This method was discarded in favor of the use of the Michelle skin clip. Another article by Drs. Richard W. Stander et al. (Journal of the
American College of Obstetricians and Gynecologists, Vol. 22, No. 3, page 265, Sept. 1963), describes a method utilizing Michelle skin clips.
However, these procedures of the named experts require resort to a special applicator, a Kelly clamp or a uterine packing forcep which has been specially modified to enable a secure grip on the electrode structure of the device.
The electrode unit of Dr. Stander appears to be an improvement on the Hon unit, in point of a simplification of the connections to the recording device; however, it, too, is relatively bulky and requires special applicators, as mentioned above.
A later article by Dr. Hon describing a new applicator (Journal of Obstetrics and Gynecology, Vol. 30, No. 2, page 281, Aug. 1967), reveals this unit also to be rather bulky and to require a very special type of applicator structure, in the form
of what is essentially a long forcep with a spring attachment. Incidentally, the cost of the device is in the neighborhood of $60.00.
In general, the Michelle skin clip, as modified by Dr. Hon, requires the application of two skin electrodes to the scalp or presenting skin area of the fetus, utilizing the Michelle crimping or squeezing action, with a resultant quite deep
penetration and possible abrasion. Also, it is seen that the most practical devices available to the profession are relatively bulky. They also require the use of special applicators, endoscopes (a device similar to a sigmoidoscope) to facilitate
visualization, and also an additional ground wire to the maternal thigh or ankle, as well as a special adaptor or connector, all of which limitations render the devices unsuitable for clinical use, the reason being that the more complex a device is the
less it is suited for clinical purposes, as a practical matter.
SUMMARY OF THE INVENTION
As designed to overcome the drawbacks of generally similar monitoring electrode units known to the art, the size of the improved unit is such that a conventional surgical packing forcep, which is a fine elongated clamp, grasps the lower pole of
the plastic end shield which holds both the positive and negative electrodes. This means, then, that no special applicator is needed. Standard packing forceps, or Kelly or Allis clamps, are available at any hospital. Use of the improved electrode unit
may be introduced at virtually any stage of labor, unlike the other types, if the cervix is dilated only sufficiently to introduce the packing forcep.
The grounding technic is unique, in that in other devices a special ground lead often departed from contact with the vagina, so that electrical AC interference would result as recorded. With the continuous external shielding of the improvement,
including a third ground lead electrically connected to a portion of the shielding, contact is always had with the vaginal mucosa, giving clear tracings throughout the monitoring period. This is unique.
Three microconnectors for the positive, negative, and ground leads facilitate rapid connection and disconnection from the female connector sockets of the input cable to the recording device. Skin penetration and abrasion of the fetus are
minimal; a skin clip is not required, but a penetration of the epidermis is substituted, and the need for external grounding to the mother's thigh or ankle is eliminated, due to the presence of the external grounding sheath or shield of the improved
unit. Once the device is applied, in the manner to be described, to the fetal epidermis area, scalp or otherwise presented skin area, the entirety of the monitoring of the heartbeat may be carried out at a remote point.
BRIEF DESCRIPTION OF THE
FIG. 1 is a fragmentary perspective view illustrating the use by a physician of the improved monitoring electrode, with the assistance of a standard packing forcep;
FIG. 2 is an enlarged scale fragmentary view more clearly showing the application of the unit to the infant's scalp at a hooked, fishhooklike end electrode element of the device;
FIG. 3 is a perspective view of the electrode unit as a whole;
FIG. 4 is a fragmentary perspective view of a somewhat schematic nature, showing the basic electrode and sheath members of the improved unit, a covering shield being omitted.
DESCRIPTION OF A PREFERRED EMBODIMENT
The fetal heartbeat monitoring scalp electrode unit of the invention, generally designated by the reference numeral 10, essentially comprises, in a preferred form suitable for use in all types or conditions of monitoring, three elongated
electrode leads. However, for certain uses less than three may be employed. As herein shown, the conductors or leads are designated 12, 14 and 16, each individually insulated externally at 13 along a major portion of its effective length, and each
provided at its outer end with a suitable plug-in jack connector element 18, by which it is releasably connected to a female terminal socket of the cable of a conventional electrocardiogram recording instrument, (all not shown) or audiovisual or other
sensing device. The conductors or electrode leads may illustratively be of tinned copper wire.
The lead 12, which is a grounding lead, is electrically connected conductively to conductive metal strands incorporated in an elongated external sheath 20, through the entire length of which the other two insulated electrode leads 14, 16 extend
in insulated relation to one another and sheath 20 as positive and negative conductors. A plastic sleeve 22 confines the leads 12, 14, 16 adjacent the jack ends thereof; and the sheath 20 maintains grounding contact at all times with the vaginal mucosa
to afford clear tracings at the recording device.
This includes the zone most remote from the plug-in jacks 18, i.e., opposite the zone at which the ground contact lead 12 is in contact with the conductive sheath 20; and there is a nonconductive tubular plastic shield 23 surrounding said remote
end of the sheath 20, the shield 23 being encircled by a constrictive coil portion of the lead 16, to be described.
Considering the electrode lead 14 as being a positive lead, for example, its end remote from its jack 18 is bared at 26 (FIG. 4), and has applied thereto, in electrically conducting contact therewith, a relatively rigid reentrant and arcuate,
pointed and barbed end at 28, accurately resembling a small size fishhook. This hook end may well be of tinned bronze, silver, or other conducting metal appropriately plated, as by silver chloride or gold. The hook is adapted to be lightly engaged
embeddingly with the scalp of the fetus, or some other exposed skin area; and the material of the barbed end, as exposed at 26, is of sufficient rigidity to manually permit and maintain the engagement during the period of use of unit 10.
Considering the last of the three electrode wires, or lead 16, as being a negative connector, its inner end is also exposed at 30, outwardly of shield 23, and formed in a coil 32 surrounding the shield 23 and shank of the fishhook element 28, as
shown in a schematic way in FIGS. 3 and 4. In practice the nearest end of coil 32 is approximately 11/2 cm. away from the end of hook portion 28, so as to prevent a skin penetration by the latter in excess of, say, 2--3 mm. Coil 32 of course has
electrical contact with the vaginal secretion. Actually, in the manner indicated in FIG. 3, the end of shield member 23, is cut on the bias at 34, its terminus projecting beyond fishhook electrode element 28.
In the use of the unit 10, the technic is to introduce the electrode, using a standard forcep 36 and the fingers for guidance. This can be done in bed without special positioning, preparation, etc. It is done as if one were doing a clean vaginal
examination, a procedure often done in bed. The perineum is washed off beforehand, the gloved fingers introduced into the vagina and then with a forward motion of the forcep the electrode is introduced until it is in apposition to the scalp. Pressing
against the scalp, the direction of force is reversed and the hook electrode element 28 is gently set into the scalp. All of this can be done by digital palpation only and does not require visualization by resort to special examination, endoscope, etc.
The fetal scalp electrode 10 may consist of less than three electrode leads as stated previously. As an example, a single wire lead having a small angle hook 28 on one end thereof forming a positive electrode may be utilized with the technique
described herein. The single wire and hook electrode may be used individually without an external shield or it may be combined with an external shield which is grounded. An electrode having a pair of wires (positive and negative) and hook 28 may be
used without an external shield. Such electrode may also be provided with an external shield which is grounded to form a tripolar lead as explained previously.
In general, the unit is simple, compact and inexpensive, as compared with related types of monitoring electrode units, and the technic of its application and use are much simplified. Its use is, as indicated above, not dependent upon resort to
special applicator means; it insures a continuous grounding at all times, without AC interference resulting from loss of ground; and its electrode leads are rapidly applied with ease to socket terminals of the usual input cable of the recording device.
Naturally, uses of the claimed unit in related fields, such as the signalling of electroencephalograms (EEG), electromyograms (EMG), combinations thereof, and the like are contemplated.
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