Abstract:
A fetal electrode sleeve and wire interconnect system for transmitting signals indicative of fetal heart rate from a fetus inside a mother through a cable to a monitor external to the mother. The system includes a holder having a fetal spiral electrode on one end and a maternal reference electrode on its opposite end. A safety cap has a retention groove, a grip, a tip with a recessed end opposite the grip, and a conductive sleeve. The conductive sleeve has a first end enclosed by the grip, a second end enclosed by the tip, and an intermediate exposed portion enclosed by neither the grip nor the tip. A twisted wire strand including a pair of insulated wires each having a first end and a second end, the first ends of the wires respectively connected to the fetal electrode and the maternal reference electrode, the second end of one wire attached to the first end of the conductive sleeve and the other wire being disposed inside the conductive sleeve, extending beyond the second end of the conductive sleeve, and terminating at its second end as a bare and exposed wire at the recessed end of the tip so that the second end of the wire is protected. A housing receives the safety cap and facilitates electrical connection between the wires and the cable.

Description:
TECHNICAL FIELD 
     The present invention relates generally to systems used to monitor the health of a fetus during labor and deliver and, more particularly, to an interconnection arrangement for safely monitoring fetal heart rate. The arrangement electrically interconnects a remote fetal monitor with bipolar fetal electrodes. 
     BACKGROUND OF THE INVENTION 
     It is desirable to monitor the biological functions (such as heart rate) of a fetus continuously during labor and delivery in order to detect fetal distress. Devices which are external to the mother&#39;s body are insufficiently sensitive. In the case of heart rate signals, such devices do not adequately isolate the fetal and maternal heartbeats. Consequently, devices which attach directly to the fetus during labor are used. U.S. Pat. No. Re. 28,990, issued to Hon et al., discloses a fetal spiral electrode assembly historically used to monitor fetal heart rate during birth. 
     The conventional fetal spiral electrode assembly includes a curved guide tube of adjustable shape for insertion of the fetal spiral electrode through the mother&#39;s cervix and into contact with the fetus during labor. A nonconductive plastic tip or holder is slidably received in the guide tube. A sharp, pointed, fetal spiral electrode is mounted on the forward end of the holder for contacting the fetal epidermis. 
     A reference (maternal) electrode in the form of a flat fin or plate is electrically isolated from the fetal electrode and located on the rear end of the holder. A flexible, hollow drive tube with a cutout on its forward end fits inside the guide tube and engages the holder. The drive tube has a diameter smaller than the diameter of the guide tube. The cutout of the drive tube engages the reference electrode in the holder to impart translation and rotation to the holder and, hence, to the fetal spiral electrode. A handle on the opposite end of the drive tube allows the user to push, pull, and rotate the drive tube within the guide tube. A forward-twisting force is applied to the drive tube to affix the fetal spiral electrode in the fetal epidermis. 
     The two electrodes are connected to separate wires which are threaded through the common center of the drive and guide tubes until they ultimately exit at the rear end of the drive tube. The wires connected to the electrodes are twisted about each other so that any induced voltages caused by external electromagnetic interference will be the same in each and therefore will not adversely affect the measurement of the galvanic potential difference between the electrodes. After the fetal spiral electrode is secured to the fetal epidermis, the drive tube and guide tube are removed by pulling the tubes longitudinally over the wires and away from the mother. Removal of the drive and guide tubes leaves the electrodes, the holder, and the wires in place inside the mother. The bare, uninsulated ends of the wires are then connected, via an intermediate support or leg plate, to a fetal monitor. 
     To use the fetal spiral electrode product, the shape of the guide tube is adjusted and the guide tube is inserted through the mother&#39;s cervix and into contact with the fetus. Once the guide tube contacts the fetus (and is held against the fetus using one of the user&#39;s hands), the drive tube is advanced (using the second hand) until the fetal spiral electrode contacts the fetus. While pressure is maintained against the fetus by the guide tube and drive tube, the drive tube is rotated, using the second hand and the handle, until the fetal spiral electrode is secured to the fetal epidermis. Typically, one full revolution suffices to secure the fetal spiral electrode. Then the drive tube and guide tube are removed by sliding them over the electrode wires. 
     U.S. Pat. No. 5,680,859 issued to Urion et al. is an improvement over the device disclosed in the &#39;990 patent. Manual connection of the uninsulated ends of the wires is cumbersome and risks shorting the wires. If shorted, the wires cannot transmit correct signals from the fetal and reference electrodes. Accordingly, the &#39;859 patent adds a connector to the wire ends of the fetal spiral electrode assembly disclosed in the &#39;990 patent. 
     FIG. 6 is a side view of the fetal spiral electrode system  110  disclosed by Urion et al. Electrode system  110  includes a sharp, pointed fetal spiral electrode  120  for contacting the fetal epidermis; a reference (maternal) electrode  122  in the form of a flat fin or plate which is electrically isolated from fetal spiral electrode  120 ; a holder  124 ; and two electrode wires  126   a  and  126   b.    
     Holder  124  is an electrically insulating plastic and is adapted to be slidably received inside an introducer  140 . Fetal spiral electrode  120  is mounted on the forward end of holder  124 . Reference electrode  122  is attached to the rearward end of holder  124 . 
     A drive rod  130  is slidably received in introducer  140 . Drive rod  130  has a clutch  128  at its forward end. Clutch  128  engages reference electrode  122  in holder  124  to impart translation and rotation to holder  124  and, hence, to fetal spiral electrode  120 . A handle  150  on the opposite end of drive rod  130  allows the user to push, pull, and rotate drive rod  130 . Drive rod  130 , clutch  128 , and handle  150  are integrally molded together. 
     Electrode wires  126   a  and  126   b  are separately coupled to respective electrodes  120  and  122 . Electrode wire  126   a  (typically green in color) connected to fetal spiral electrode  120  and electrode wire  126   b  (typically red) connected to reference electrode  122  form a twisted wire strand  118  which extends from electrodes  120  and  122  along the entire length of drive rod  130  and handle  150 . A retainer  166  is provided near the end of handle  150  opposite drive rod  130 . Retainer  166  locks wire strand  118  in a fixed position. The ends of wires  126   a  and  126   b  opposite holder  124  terminate in a male connector  132 . 
     Turning to FIG. 7, wires  126   a  and  126   b  (which are typically about 450 mm or 18 inches in length) are provided with an untwisted length  116  along a short distance (25-50 mm or 1-2 inches) of wire strand  118 . Untwisted length  116  allows the clinician to separate wires  126   a  and  126   b  without cutting them. The individual wires  126   a  and  126   b  are separately connected to first and second terminal (or ring) contacts  134  and  136  in connector  132 . Contacts  134  and  136  are electrically and physically separated by a spacer  138 . Connector  132  has a forward tapered tip  142  which plugs into a longitudinal passage in the end of handle  150  (connector  132  is shown plugged into the passage in FIG.  6 ). 
     Connector  132  is designed to be inserted into a support or leg plate  170  which is affixed to the mother (typically to the thigh). Support plate  170  is connected, via a cable  176 , to a monitor  178 . Upon insertion of connector  132  into the opening of support plate  170 , ring contacts  134 ,  136  on connector  132  click into physical and electrical contact with two corresponding barrel contacts in support plate  170 . Moreover, tip  142  of connector  132  abuts a wall in support plate  170  to prevent over-insertion of connector  132 . 
     Support plate  170  carries its own ground electrode  180 . Insertion of connector  132  in support plate  170  connects electrodes  120  and  122  to monitor  178 . Consequently, three electrical circuit paths are created upon interconnection of connector  132  of fetal spiral electrode system  110  and support plate  170 : (1) fetal electrode  120  to green wire  126   a  to terminal  134  to a first barrel contact to a first output terminal to monitor  178 ; (b) reference electrode  122  to red wire  126   b  to terminal  136  to a second barrel contact to a second output terminal to monitor  178 ; and (c) ground electrode  180  to a third output terminal to monitor  178 . 
     Connector  132  has a grip  144  with an ergonomically designed shape to permit the user to grasp it easily and to ensure a proper, sealed connection of connector  132  to support plate  170 . Grip  144  also acts as a strain relief element through which twisted wire strand  118  enters connector  132 . The diameter of connector  132  changes, at a shoulder  146 , from a smaller diameter plug  148  to larger diameter grip  144 . The length of smaller diameter plug  148  is selected to correspond to the length by which connector  132  must be inserted fully into support plate  170  to assure optimal signal quality. Thus, connector  132  permits a visual indication of full attachment of connector  132  to support plate  170 . 
     Connector  132  solves the problem of manual connection of the uninsulated ends of the electrode wires. But the connector  132  with its exposed first and second terminal (or ring) contacts  134  and  136  does not prevent entirely the risk of accidental electrocution of patients by having an exposed contact engage a hazardous voltage. Such prevention is not only desirable, it is now mandated by the U.S. government and by international standards. 
     The “Performance Standard for Electrode Lead Wires and Patient Cables” of the Code of Federal Regulations, Chapter 21, Part 898, states that, beginning on May 9, 2000, all fetal scalp electrodes and associated cable systems must comply with the standard. In summary, this performance standard is designed to prevent accidental electrocution of patients by precluding an exposed lead or contact that might come into contact with a hazardous voltage. Consequently, leads and contacts must be constructed to prevent accidental patient contact with hazardous voltages and, after May 9, 2000, unprotected electrode lead wires and cables cannot be manufactured, distributed, or sold in the United States. Existing leads and contacts on fetal spiral electrode products currently sold in the United States market are non-compliant because the leads and contacts are exposed. Specifically, the current fetal spiral electrode designs have either two bare wires or exposed contacts that could potentially come into contact with an electrical source when not connected to the support or leg plate. 
     If a lead or contact may be placed on a conductive surface or inserted into an electrical socket, hazardous voltages could occur. Alternatively, if a user can run a finger over the lead or contact and can touch metal, the lead is considered non-compliant under the governmental standard. For a lead or contact to comply with the standard, it must preclude contact with hazardous voltages and pass specific tests. 
     There are approximately 45,000 fetal monitors in the United States and approximately three million fetal spiral electrodes are used per year. The deficiencies of the conventional devices and the market demand show that a tremendous need exists for an improved fetal spiral electrode interconnect system that functions to electrically and mechanically connect the conventional twisted wire pair with the cable to the remote fetal monitor. To overcome the shortcomings of conventional fetal spiral electrode systems, an integrated fetal electrode sleeve and wire system is provided. The principal object of the present invention is to provide an improved system that is fully compliant with governmental performance standards. An important related object is to provide a system that reduces safety risks, especially the risk of inadvertent connection to an electrical source. Another object is to provide a system that provides both safe and reliable tracing of fetal heart rate to help caregivers deliver the best patient care. 
     SUMMARY OF THE INVENTION 
     To achieve these and other objects, and in view of its purposes, the present invention provides a fetal electrode sleeve and wire interconnect system for monitoring signals indicative of fetal heart rate from a fetus inside a mother during labor and delivery. The system comprises a cable having a maternal lead, a fetal lead, and a ground lead. A holder has a fetal spiral electrode on one end and a maternal reference electrode on its opposite end. The system also comprises a ground electrode secured to the mother, particularly to the leg of the mother, preferably using an adhesive. A safety cap has a retention groove, a grip, a tip opposite the grip with a shroud defining both a safety cap terminus and an end recessed relative to the terminus, and a conductive sleeve. The grip of the safety cap has a plurality of cutouts disposed opposite the tip, the cutouts providing strain relief to and increasing the flexibility of the safety cap and being adapted to facilitate handling of the safety cap by the user. The conductive sleeve includes a first end enclosed by the grip, a second end enclosed by the tip, and an intermediate exposed portion enclosed by neither the grip nor the tip. A twisted wire strand is formed by a pair of insulated wires each having a first end and a second end, the first ends of the wires respectively connected to the fetal electrode and the maternal reference electrode, the second end of one wire attached to the first end of the conductive sleeve and the other wire being disposed inside the conductive sleeve, extending beyond the second end of the conductive sleeve, and terminating at its second end as a bare and exposed wire at the recessed end of the tip so that the second end of the wire is protected within the shroud. 
     The housing of the fetal electrode sleeve and wire interconnect system has an aperture receiving the safety cap, without restriction relative to the orientation of the safety cap, and an opening receiving the cable. A retaining element engages the retention groove in the safety cap upon insertion of the safety cap in the aperture of the housing and releasably holds the safety cap in the housing. A snap is connected to the ground electrode and attached to the ground lead of the cable. The housing rotates without restriction relative to the ground electrode. A guide of the housing at least partially encircles the snap and includes an alignment channel receiving and aligning the tip of the safety cap upon insertion of the safety cap into the housing. An axial contact element is aligned in the channel of the guide and attached to the maternal lead of the cable, the axial contact element axially engaging the tip of the safety cap and contacting the bare and exposed wire upon insertion of the safety cap into the housing. The housing also has a radial contact element including at least one finger, the finger radially engaging the intermediate exposed portion of the conductive sleeve of the safety cap upon insertion of the safety cap into the housing thereby electrically contacting the conductive sleeve, the radial contact element also being attached to the fetal lead of the cable. Finally, the housing may have a rubber O-ring positioned in the aperture of the housing and through which the safety cap is inserted into the housing, the ring wiping the safety cap upon insertion. 
     The fetal electrode sleeve and wire interconnect system also comprises a monitor connected to the cable. A drive mechanism imparts rotation and translation to the holder to secure attachment of the fetal spiral electrode to the fetus. An introducer is disposed around at least a portion of the drive mechanism and can be comfortably inserted through the cervix of the mother. The holder is slidably and rotatably disposed in the introducer. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention is best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures: 
     FIG. 1 is a perspective view of the safety cap in accordance with the present invention; 
     FIG. 2 is a top perspective view of the bottom half of the housing, with engaged components, according to the present invention; 
     FIG. 3 is a top view of the housing and engaged components illustrated in FIG. 2; 
     FIG. 4 is a detailed, perspective view of the radial contact element according to the present invention; 
     FIG. 5 is a perspective, exploded view highlighting the individual components of the sleeve and wire system of the subject invention; 
     FIG. 6 is a side view of a conventional fetal spiral electrode system; and 
     FIG. 7 is a perspective view of the connector of the conventional fetal spiral electrode system, illustrating that component in combination with several conventional elements. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawing, in which like reference numbers refer to like elements throughout, FIG. 1 is a perspective view of a safety cap  10  having three, main components: a grip segment  12 , a tip segment  14 , and a conductive sleeve  16  extending axially (or longitudinally) through the centers of grip segment  12  and tip segment  14 . Conductive sleeve  16  is typically about 1.5 mm in diameter and made of a gold-plated brass tube. As shown in dashed lines in FIG. 1, conductive sleeve  16  has a first end enclosed by grip segment  12 , extends partially (about halfway as shown) into tip segment  14 , and has a second end enclosed by tip segment  14 . 
     The insulated wire  6  of the twisted wire pair that engages the fetal spiral electrode  120  (see FIG. 6) is attached (e.g., welded) to the end of conductive sleeve  16  within grip segment  12 . Grip segment  12  and tip segment  14  are preferably molded around conductive sleeve  16  while leaving an exposed portion  18  of conductive sleeve  16 . Exposed portion  18  is enclosed by neither grip segment  12  nor tip segment  14 . A retention groove or detent  20  is provided in safety cap  10 . Retention groove  20  may be provided in grip segment  12 , as shown, or in tip segment  14  of safety cap  10 . A series of cutouts  22  (six are shown in FIG. 1) are formed in the end of grip segment  12  opposite tip segment  14  to provide strain relief, increase flexibility, and facilitate the grip of the user. 
     The end  24  of tip segment  14  opposite grip segment  12  is recessed, creating a shroud that defines both a terminus for safety cap  10  and an end recessed relative to that terminus. The insulated wire  8  of the twisted wire pair that engages the maternal electrode  122  (see FIG. 6) travels through conductive sleeve  16  and terminates, without any separate connector component, as a bare and exposed wire in recessed end  24 . More specifically, wire  8  extends beyond the second end of conductive sleeve  16  and terminates at its second end (opposite the first end which is attached to maternal electrode  122 ) as a bare and exposed wire at the recessed end  24  of tip segment  14  so that the second end of wire  8  is protected within the shroud. Therefore, conductive sleeve  16  is the only contact or terminal engaged by wires  6 ,  8 , and only wire  6  is electrically and mechanically connected to conductive sleeve  16 . Recessed end  24  assures that safety cap  10  meets safety regulations by preventing inadvertent and undesired contact with wire  8 . Because both wires  6 ,  8  are encapsulated within single molded plastic safety cap  10 , safety cap  10  avoids exposed electrode wires or contacts. 
     FIG. 2 is a top perspective view and FIG. 3 is a top view illustrating the reusable housing  30 , and specifically the bottom half  32  of housing  30 , of the subject invention. Housing  30  is teardrop shaped to facilitate handling, especially when the user holds housing  30  while inserting safety cap  10  into housing  30 . The top half  34  of housing  30  is shown in FIG.  5 . Top half  34  and bottom half  32  of housing  30  have respective pins and holes to create a snap-fit connection forming the entire housing  30  upon engagement. 
     Housing  30  defines an aperture  36  in which are disposed one or more rings  38 . Safety cap  10  can be inserted into aperture  36  and through rings  38  without regard to or restrictions relative to orientation. During insertion, rings  38  function to wipe safety cap  10  free of debris, moisture, and other undesirable contaminants. Rings  38  also function as a partial stop, upon engagement with groove  20  in safety cap  10 , releasably holding safety cap  10  in housing  30 . 
     In a preferred embodiment, two rings  38  are provided. The first ring  38  is a rubber O-ring that performs the wiping function. The second ring  38  performs the retention function upon engagement with groove  20 . Elements alternative to the second ring  38  might also perform the retention function, such as a C-shaped clamp, a tilted circular spring, or a spring-loaded clamp—each designed to engage groove  20  in safety cap  10  and releasably hold safety cap  10  in housing  30 . 
     As shown in FIG. 2, retention groove  20  is provided on grip segment  12  of safety cap  10 . Accordingly, the retention element is positioned near aperture  36  of housing  30 . Retention groove  20  could also be provided on tip segment  14  of safety cap  10 . In that case, the retention element would have to be positioned further away from aperture  36 , into housing  30 . 
     Housing  30  also defines an opening  42  which may, but need not, be disposed opposite aperture  36 . The trunk cable  40  connected to the remote fetal monitor  178  (see FIG. 7) can be inserted into opening  42 . Trunk cable  40  typically has three, separate wires  44 ,  46 ,  48 , and may also be shielded. Central ground wire  48  is connected to a snap  50  affixed to bottom half  32  of housing  30 . Snap  50  engages a ground electrode  54  (see FIG. 5) located on the underside of bottom half  32  opposite snap  50 . Ground electrode  54  is held in position, typically against a mother&#39;s leg. Ground electrode  54  can also be positioned against a mother&#39;s abdomen. For convenience, housing  30  may be attached to the patient via adhesive placed on one side of ground electrode  54 , rendering ground electrode  54  a self-adhesive ground electrode and avoiding the need for a separate leg plate strap. Preferably, ground electrode  54  has a large surface area to assure adherence to the patient. Snap  50  is sized to allow a variety of alternate electrodes to be incorporated as ground electrode  54 . Although not required, a separate strap may be used to facilitate attachment of housing  30  to the patient (i.e., the mother). 
     Housing  30  is rotatable relative to ground electrode  54  in either the clockwise or counterclockwise direction. This rotation allows housing  30  to be oriented into any desired angular orientation. The rotatable connection helps to avoid inadvertent disconnection of safety cap  10  from housing  30  when, for instance, a patient or caregiver brushes against the twisted wire pair  6 ,  8 ; housing  30 ; or trunk cable  40 . 
     A nonconductive (molded) Y-shaped guide  60  is also provided in housing  30 . Guide  60  has a central column  62  and two branches  64 ,  66 . Branches  64 ,  66  engage and at least partially encircle snap  50 , thereby supporting housing  30  and protecting the electrical connection between snap  50  and ground wire  48 . An alignment channel  68  is provided in the end of guide  60 . Alignment channel may be a bore in guide  60 . At least the forward portion of tip segment  14  of safety cap  10  enters alignment channel  68  upon full insertion of safety cap  10  into housing  30 . Alignment channel  68  of guide  60  helps to prevent over-insertion of safety cap  10  in housing  30 . If retention groove  20  is provided on tip segment  14  of safety cap  10 , the retention element (e.g., second ring  38 ) may be disposed on central column  62  of guide  60 . 
     A conductive axial contact element  70  is also provided in housing  30 . Axial contact element  70  is connected on one end to maternal wire  46  of trunk cable  40  and, as shown in the example illustrated in the drawing, may be a spring-loaded probe or “pogo pin.” On its end opposite wire  46 , the probe may have a sharp point  72 . The probe is hollow and encases a spring (not shown) which biases sharp point  72  outward from the hollow probe. Axial contact element  70  is aligned with alignment channel  68  of guide  60  so that, when tip segment  14  of safety cap  10  enters alignment channel  68  upon full insertion of safety cap  10  into housing  30 , the end (e.g., sharp point  72 ) of axial contact element (e.g., pogo pin)  70  axially enters recessed end  24  of tip segment  14  and makes electrical contact with the bare and exposed end of wire  8 , which engages the maternal electrode, of the twisted wire pair. Thus, alignment channel  68  of guide  60  assures proper alignment between axial contact element  70  and wire  8  disposed in tip segment  14 . 
     Finally, a conductive radial contact element  80  is provided in housing  30 . As shown in the example illustrated in FIG. 4, radial contact element  80  may be a cantilever beam  80 . The cantilever beam has a central body  82  from which extends longitudinally a head  84  and from which extend transversely two flanges  86 ,  88 . Head  84  is connected to fetal wire  44  of trunk cable  40 . Also extending from body  82  are a pair of arms  90 ,  92 , each of which ends in a flexible, V-shaped finger  94 ,  96 , respectively. A hole  98  is provided in each flange  86 ,  88  to receive a fastening member  102  (e.g., a screw, bolt, or the like) securing the cantilever beam to housing  30 . A hole  100  in body  82  engages a projection  104  on guide  60  to help align the cantilever beam with respect to guide  60  within housing  30 . 
     Recessed end  24  of tip segment  14  of safety cap  10  engages and separates flexible fingers  94 ,  96  of radial contact element  80  as safety cap  10  is inserted into housing  30 . When safety cap  10  is fully inserted in housing  30 , ring  38  engages groove  20  on safety cap  10  and the end of axial contact element  70  engages wire  8  disposed in tip segment  14 . Substantially simultaneously, fingers  94 ,  96  of radial contact element  80  radially clamp onto exposed portion  18  of conductive sleeve  16 , to which wire  6  of the twisted wire pair is attached. The engagement between fingers  94 ,  96  and conductive sleeve  16  may be sufficiently strong to further releasably secure safety cap  10  in housing  30  and help to prevent over-insertion of safety cap  10  in housing  30 . Moreover, audible and tactile indications are provided to the user when safety cap  10  is properly engaged in housing  30 . FIGS. 2 and 3 illustrate safety cap  10  as fully inserted into housing  30 . 
     Upon full insertion of safety cap  10  into housing  30 , three separate electrical paths are created. The first path is from (a) ground electrode  54  located on the underside of bottom half  32  of housing  30  opposite snap  50  and held in position against a mother&#39;s leg, to (b) snap  50  engaging ground electrode  54 , to (c) ground wire  48  connected to snap  50 , and to (d) remote monitor  178  through trunk cable  40 . The second path is from (a) fetal spiral electrode  120  (see FIG. 6) affixed to the fetus, to (b) wire  6  of the twisted wire pair that engages fetal spiral electrode  120 , to (c) conductive sleeve  16  disposed within grip segment  12  and to which wire  6  is attached, to (d) radial contact element  80  which radially clamps onto exposed portion  18  of conductive sleeve  16 , to (e) fetal wire  44  connected to radial contact element  80 , and to (f) remote monitor  178  through trunk cable  40 . The third path is from (a) maternal reference electrode  122  (see FIG. 6) proximate fetal spiral electrode  120  inside the mother, to (b) wire  8  of the twisted wire pair that engages maternal reference electrode  122 , to (c) the end of axial contact element  70  which axially engages wire  8 , to (d) maternal wire  46  connected to axial contact element  70 , and to (e) remote monitor  178  through trunk cable  40 . 
     Noteworthy are the orientations of the electrical contacts made with fetal electrode wire  6  and with maternal reference wire  8 . Wire  6  is connected to conductive sleeve  16 , and radial contact element (e.g., cantilever beam)  80  clamps radially (or in a perpendicular direction) onto exposed portion  18  of conductive sleeve  16 . In contrast, wire  8  engages axial contact element (e.g., pogo pin)  70  axially (or in a longitudinal direction). The two connections are also in separate planes, separated at least by the combined thickness of conductive sleeve  16  and the insulation around wire  8 . Thus, the connections of wires  6 ,  8  have optimum separation and orientation that function to prevent short circuits—especially in the surrounding environment of conductive fluid. 
     FIG. 5 is a perspective, exploded view highlighting the individual components of the sleeve and wire system  1  of the subject invention. A label  110  may be affixed to housing  30  to identify the device and to provide information helpful to the user. Sleeve and wire system  1  electrically and mechanically connects wires  6 ,  8  of the twisted wire pair with trunk cable  40  of remote fetal monitor  178 . Housing  30  protects such connection, especially from fluid contamination. 
     In using the sleeve and wire system  1  of the present invention, a caregiver inserts the forward end of curved guide tube or introducer  140  through the mother&#39;s vagina and cervix until the forward end of guide tube  140  makes contact with the fetal head or other portion of the fetus. Holding the forward end of guide tube  140  stationary, the caregiver then pushes the rear end of flexible drive rod or drive tube  130  forward until fetal spiral electrode  120  at the forward end of the wire  6  of the twisted wire pair makes contact with the fetal epidermis. The forward end of the other wire  8  attaches to spade-like maternal electrode  122  which is electrically isolated from fetal spiral electrode  120 . 
     The caregiver then rotates flexible drive tube  130  clockwise about one full turn while maintaining the forward end of guide tube  140  against the fetal head. This action will screw fetal spiral electrode  120  into the fetal epidermis. Thereafter, the caregiver grasps the outer ends of drive tube  130  and guide tube  140  and slides tubes  130 ,  140  as a unit off wires  6 ,  8  and safety cap  10 , leaving only bipolar electrodes  120 ,  122  and two twisted wires  6 ,  8  within the mother. The outside diameter of safety cap  10  is smaller than the inside diameter of drive tube  130  which, in turn, is smaller than the inside diameter of guide tube  140 . Thus, guide tube  140  and drive tube  130  may be pulled together over safety cap  10  and thereby removed from the twisted wire pair. 
     After removal of tubes  130 ,  140 , safety cap  10  is free and accessible for its insertion into housing  30 . Such insertion creates the three separate electrical paths discussed above and thereby connects the three electrodes (fetal  120 , maternal  122 , and ground  54 ) with remote monitor  178 . A galvanic potential difference may then be measured between bipolar electrodes  120 ,  122 . 
     Sleeve and wire system  1  of the subject invention offers ease of use. Drive tube  130  and guide tube  140  can be removed by the user in one step, saving time. No additional steps are required. Connection between wires  6 ,  8  and trunk cable  40  is fast and accomplished without regard to orientation. Safety cap  10  and housing  30  permit connection and re-connection of electrodes  120 ,  122  several times during labor. Sleeve and wire system  1  is and, more specifically, the connections between safety cap  10  and housing  30  and between trunk cable  40  and housing  30  are, sufficiently robust to withstand fluid contact (such as by splashing if not immersion) for a minimum of twelve hours. Sleeve and wire system  1  of the subject invention also offers reliability: excellent signal quality and signal acquisition throughout labor, resulting in accurate and consistent fetal heart rate tracings by monitor  178 . 
     Housing  30  provides a reliable electrical and mechanical interface between electrodes  120 ,  122  and monitor  178  throughout labor, resulting in accurate and consistent fetal heart rate tracings. Housing  30  has a relatively low profile and low weight. Housing  30  also has smooth and rounded edges. These features maximize patient comfort. 
     Other than monitor  178 , the components of sleeve and wire system  1  are sufficiently inexpensive to permit single use followed by disposal (i.e., the components are disposable). Caregivers may wish to clean and sterilize, then reuse, trunk cable  40 . If so, trunk cable  40  can be cleaned and disinfected after each use with hand soap, isopropyl alcohol, chlorine bleach (1:10 with water), or 2% glutaraldehyde solution. The cost of the components of sleeve and wire system  1  is further reduced because complex components, such as a printed circuit board, are not required. 
     Although illustrated and described above with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.