MXPA97008380A - Non-invasive fetal probe that has mechanical and electric properties improves - Google Patents

Abstract

A non-invasive fetal probe having improved adhesion and electrical isolation, and which is fixed to the presenting part of a fetus to detect at least one fetal parameter during labor and delivery, in one embodiment in the present invention, The electrical isolation of the fetal probe includes a non-conductive element used in combination with various conductive assemblies made from gel formulations that are polymerized to form a fetal sensor, the non-conductive element, in addition to providing physical separation, also improves the separation between the fetal and maternal sensory elements of the fetal probe, noninvasive fetal probes are provided that have low profile designs and that help to diminish the tendency to detach from the fetal probes, caused by forces generated in the probe at the head of the fetus, the cervix of the mother or amb

Description

NON-INVASIVE FETAL PROBE THAT HAS IMPROVED MECHANICAL AND ELECTRICAL PROPERTIES RELATED REQUESTS This is a continuation in part of co-pending application Serial No. 08 / 487,806 filed on July 7 1995, which is a continuation in part of the application Serial No. 08 / 222,729 filed on April 4, 1994, now patent of E.U.A. No. 5,474,065.

FIELD OF THE INVENTION The present invention relates to fetal monitoring probes and, more particularly, to a noninvasive fetal probe that attaches biomedical sensors to the skin of a fetus during labor and delivery.

BACKGROUND OF THE INVENTION During labor and delivery, the welfare of the fetus must be carefully monitored. The procedure to monitor the fetus allows the doctor to assess the health of the fetus, detect fetal tension and provide adequate treatment. Internal (or direct) and external devices are used as well as methods to monitor and record fetal parameters such as heart rate, gas composition in the blood, and pH levels during labor and delivery. Brief and typical internal and external techniques are briefly noted, and are described in greater detail in the background section of U.S. Patent No. 5,474,065.

A. External Methods - Fetal Heart Rate Various forms of external methods can be used to monitor the fetus's heart rhythm. For example, an external method includes the use of ultrasound. Another external method includes the use of a sound source, which includes placing a microphone, capable of detecting sound waves generated by the heart of the fetus, on the abdomen of the mother. The abdominal wall electrocardiograph is a type of nerve. External analysis of fetal heart rhythm All external measures to measure fetal heart rhythm have an important advantage: they are not invasive, therefore, these methods largely avoid adverse effects on the mother or the fetus. The recording of the fetal heart rate using an external moni- toring method is not as good as that achieved by direct methods.This is a major limitation of external monitoring methods.As a general rule, it is necessary to restrict the movements of The mother during the external monitoring methods to reduce external signals and interference and obtain accurate traces.The movement of the artifact is so common with external techniques that make it virtually impossible to obtain readable traces unless data processing is used. Valuable information about the variability in heart rate can be lost through such processing.

B. Direct methods-fetal heart rhythm In the direct monitoring of the fetal heart rhythm, an electrode is placed directly on the presenting part of the fetus. Typically, the electrode is a spiral wire or hook that penetrates (is inserted directly) into the epidermis of the fetus and holds the fetal probe in position. The main advantage of a direct monitoring system of this kind is that the electrode detects the cardiac electrical signal of the fetus without the interference that occurs when the signal is detected through other means such as the mother's abdomen. The cardiac electrical signal of the fetus is an accurate signal, allowing an accurate determination of the fetus' heart rate and any variation in that rhythm. In addition, during direct monitoring of the fetus's heart rate, maternal movement is less restricted without compromising tracking. The limitation in this direct method of monitoring the fetal heart rate is that it is a invasive technique, exposing the mother and the fetus to the potential for injury, infection or both. The lesion may be in the form of trauma (such as haemorrhage at the fixation site) to the skin, face, or other parts of the fetus. In addition, mvasora fixation can threaten the life of the fetus by exposing it to the fluids of the maternal body that contain infectious components. Venereal diseases and viruses such as Acquired Inmune-deficiency Syndrome (AIDS) and hepatitis B can be transferred directly to the fetus. Furthermore, the wire or sharp hook exposes the patient (the mother) and the doctor to a potential injury.

C. Non-invasive direct methods Several techniques have been described that attempt to obtain the benefits of direct fetal monitoring, avoiding the risks related to the invasive penetration of the fetal epidermis. The analysis of gas in fetal blood during labor has been used to determine the health of the fetus. Blood gas analysis is typically carried out in a clinical laboratory, on blood drawn from the fetus during labor (clearly an invasive technique). Alternatively, O ane et al., "Non-invasive continuous fetal transcutaneous 2 and PCO2 momtoring during labor," Journal Perinatal Medicine, 17 (6), 399 (1989), describes the monitoring of continuous transient fetal PO2 and PCO2 and does not invasive during labor. Okane and others used a commercially available device: the Micro Gas 7640 probe available from Kontron I Corporation of Everett, Massachusetts. This probe is attached to the head of the fetus using a suction ring connected to a vacuum pump that maintains a negative pressure of 200-300 mrn Hg. The sensor is large and requires cervical dilation of 4 c or more before insertion is possible. The large size of the sensor and the need to apply continuous suction, through an attached vacuum line, are obstacles to the use of the sensor .. The glue attachment of a transcutaneous? C? 2 electrode for fetal on- described by S. Schrnidt, "Glue fixation of the tcPc? 2 electrode for fetal rnomtoring" Journal Per natal Medicine, 15 (4), 377 (1987). Fixing with glue to a fetus is difficult to achieve. It requires sufficient dilatation and careful preparation of the placement site. The electrode commonly comes off during use and may need to be reapplied. In addition, trauma to the skin is possible during the removal of a sensor fixed with glue. Similarly, pressure sensitive adhesives such as those used for self-adhesive bandages are hydrophobic and do not adhere to moist surfaces such as the skin of the fetus. Another non-invasive technique to detect the ECG of the fetus during labor is described by N. Randall et al., "Detection of the Fetal ECG Dupng Labor by an Intrauterine Test," Journal Biomedicme, (10), 159 (England 1988 ), and in the US patent No. 5,025,787 issued to Sutherland et al. The article and patent disclose an intrauterine pressure catheter equipped with stainless steel tips that fuse a multi-pin electrode. The intrauterine probe is inserted through the vagina into the uterine cavity. The sensors are kept in contact with the fetus (but do not adhere to it) by the pressure between the uterus and the fetus. The electronic signal that comes from the sensors is processed to obtain an ECG of the fetus. The presence of arnniotic fluid attenuates the signal coming from the sensors. The article points out the difficulties to obtain precise results due to problems with the positioning of the tips of the electrode in a precise way. Moreover, a degree of isolation of the electrode is required for optimum detection of fetal signals. The international patent publication No. 10 92/04864 (which claims priority of United Kingdom patent applications No. 90-20983 and No. 90-25758 by Vander Merwe), discloses a fetal probe with a rigid suction cap of approximately 1.5 to 2 crn. diameter. The probe incorporates a sensor * of the fetal heart rate. A negative pressure is created in the rigid lid, by the action of a removable piston pump, to keep the probe on the skin of the fetus. The pump is released after a valve in the lid is closed. The rigid structure of the suction cover and the loss of negative pressure between the skin of the fetus and the suction cover allow the probe to be easily detached during use. The patent of E.U.A. No. 5,184,619 issued to Austin, describes an intrauterine pressure and fetal heart rate sensor that is inserted between a fetus and the uterine wall after the rupture of the membranes. The tubular device uses ECG electrodes, as well as a pressure transducer to detect the fetal heart rate and intrauterine pressure, respectively. The cardiac rhythm of the fetus is detected through the immune fluid. U.S. Patent No. 5,345,935 issued to Hsch describes a noninvasive medical probe that includes a suction cup of elastic walls having a peripheral septum to be applied to a patient's skin. The suction cup is connected to a pump that creates a vacuum inside the cup to adhere the cup to the surface of the patient's skin. Two mastering electrodes are provided, one in centrally and the o-t r * o adjacent externally to the cup, which can be used to monitor a fetus's heart rhythm. The patent of E.U.A. No. 5,474,065 issued to Meathrel et al., Which was issued from the patent application of E.U.A. Serial No. 07 / 222,729, provides a noninvasive fetal probe that overcomes the disadvantages of external devices; of direct and invasive devices and direct and non-invasive devices used to measure fetal parameters during labor and delivery. The probe includes a conductive hydrogel that adheres to both wet and dry surfaces and that is configured either in the form of a suction cup, or is coated on the inside surface of the shell of a suction cup. The combination of both the suction cup shape, which sustains the probe in the fetus and the hydrogel material, which allows an increased adhesion in the humid environment, makes it possible for the probe to be placed safely in the fetus during labor and delivery. In this way, the fetal probe is fixed securely to the part of the fetus in a non-invasive way to ensure its fixation without risk of injury to the fetus, the mother or the clinical staff. As a result, the probe is capable of transmitting an undated and clear signal that represents the fetal parameter that is being reactivated. The non-invasive fetal probes shown in the '065 patent may include various configurations of carrier armor to achieve physical or mechanical separation between the maternal fluids and the hydrogel. Figures 8A, 8B and 8C show three examples of variations in the configuration of the wall 50 of the shell 34. Although the different shell configurations described in the '065 patent help physically isolate the hydrogel from external fluids, ba or certain conditions (e.g., in exceptionally humid environments) the maternal and fetal sensory elements of the fetal probe can make electrical contact. This contact could interfere with the detection of an accurate fetal signal (ie, the differential signal obtained between the maternal (reference) electrode and the fetal electrode) despite the physical separation provided by the shell configurations described.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides an improved noninvasive fetal probe that adheres biornédic sensors to the skin of a fetus during labor. The invention includes electrical and mechanical improvements to provide improved adhesion and electrical isolation of noninvasive fetal probes. In one embodiment of the present invention, the electrical isolation of fetal probes includes a non-conductive element used in combination with various conductive assemblies made from gel formulations that are polimerized to form a fetal sensory area. It is the incorporation of the non-conductive element * which, in addition to providing a physical separation, also improves the electrical separation between the maternal and fetal sensory elements of the fetal probe. In another embodiment of the present invention, fetal probes having ba or profile designs are provided. These designs help to diminish the tendency of the fetal probes to detach, caused by the forces generated on the probe by the head of the fetus, the cervix of the mother or both. This makes it possible for the noninvasive probe to be securely attached to the fetus during labor and delivery. Accordingly, important aspects of the present invention are the electrical and physical isolation of the maternal and fetal sensing elements. Another aspect of the present invention is to improve the signal separation by increasing the path between the maternal and fetal sensor elements. An additional aspect is the use of a low profile design that allows a more secure fixation of the probe during labor due to the decreased risk of detachment caused by the fetal and cervical forces. It should be understood that both the foregoing general description and the following detailed description are exemplary, and do not restrict the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is better understood from the following detailed description when read in connection with the accompanying drawings, in which: Figure 1A is a cross section of a noninvasive fetal probe having a shell coated with a non-conductive coating and a gel, constructed in accordance with the present invention with a fetal brush type sensor; Figure IB is a cross section of the non-invasive fetal probe shown in Figure 1A placed in a fetus; Figure 2 is a cross section of a non-invasive fetal probe having a shell coated with a gel, constructed in accordance with the present invention with a fet-disk sensor; Figure 3 is a plan view of the fetal disk sensor most or in Figure 2; Figure 4A is a plan view of a maternal disc sensor; Figure 4B is a plan view of an alternative maternal disc sensor; Figure 5 is a cross section of the non-invasive fetal probe having a rim with a non-conductive coating; Figure 6A is an exploded view of the flange of the non-invasive fetal probe shown in Figure 5; Figure 6B is an exploded view of a modified flange design incorporating a rubber brush; Figure 6C is an exploded view of the design shown in Figure 6B with additional coatings; Figure 6D shows an exploded view of an elongated flange embodiment; Figure 6E shows an exploded view of an elongated shell modality; Figure 6F shows an exploded view of an extended rib embodiment; Figure 6G shows an exploded view of an alternative extended rib mode; Figure 6H shows an exploded view of a non-conductive rib mode; Figure 7 is a cross-sectional view of a further embodiment of a non-mouvenous fetal probe having a shell coated with a gei, a ridge and air spaces between the rim and the gel; Figure 8 is a cross section of a noninvasive fetal probe that has an air gap as shown in Figure 7, but with a more elongated and deeper shell; Figures 9-11 are cross sections of noninvasive fetal probes having a conductive gel with non-conductive hydrogel adhesive coatings; Figure 12 is a bottom view of the non-moving fetal probes of Figures 9-11; Figure 13 shows another embodiment of the non-invasive fetal probe having a gel structure in the form of a bellows; Figure 14 is a cross section of a non-invasive fetal probe having a shell coated with a gel having a fetal sensor in a loop arrangement; Figure 15 is a cross section of the noninvasive fetal probe of Figure 14 with an additional adhesion promoting surface on the gel; Figure 16 is a cross-section of a non-invasive fetal probe having a shell coated with a gel having a fetal sensor of conductive mesh or conductive wool; Figure 17 is a cross section of the noninvasive fetal probe of Figure 16 with an additional adhesion promoting surface on the gel; Figure 18 is a cross-section of a noninvasive fetal probe having a shell coated with a gel having a fetal strand sensor in a fan; Figure 19 is a cross section of the non-invasive fetal probe of Figure 18 with an additional adhesion promoting surface on the gel; Figure 20 is a partial cross section of a further embodiment of a noninvasive fetal probe having low profile electrode wires; Figure 21 is a partial cross section of a further embodiment of a noninvasive fetal probe having ba or profile electrode wires; - Figure 22 is a top view of the noninvasive fetal probe shown in Figure 21; Figure 23 is a partial transverse section of a further embodiment of a noninvasive fetal probe having low profile electrode wires; and Figures 24A, 24B and 24C show cross-sectional, perspective and top views, respectively, of an alternative fetal spring contact design.

DETAILED DESCRIPTION OF THE INVENTION / / Referring now to the drawing, in which like reference numbers refer to like elements throughout the description, Figures 1A, IB, 2, 5, and 7-23 illustrate a fetal probe non-invasive 10 constructed in accordance with the present invention. It is emphasized that the reference numbers in this application correspond to like elements having the same reference numbers in the figures of the U.S. Patent No. 5,474,065. As used throughout the description and the claims, the words "carried by" define the structural relationship between specified elements that are established by fixing the elements with one another by direct or indirect means. It was also emphasized that, according to common practice, the different elements of the drawing are not to scale. On the contrary, the width, length and thickness of the different elements are expanded or reduced arbitrarily for reasons of clarity. The fetal probe 10 is inserted through the birth canal and is attached to the presenting part (typically the head) of the fetus 100 as shown in Figure IB. The fetus 100 can have hair 102. Because it is "non-invasive", the fetal probe 10 does not penetrate the skin of the fetus. Once placed, the fetal probe 10 can continuously detect, depending on the sensors incorporated in the fetal probe 10, fetal parameters such as heart rate, composition of the gas in the blood, temperature and pH levels during labor and delivery. delivery. These fetal parameters are received by the monitor 80 as shown in Fig. 1A. Other types of sensors and test equipment or combinations of sensors and test equipment can be incorporated into the fetal probe 10.

I. Non-Invasive Fetal Probes That Have Improved Electrical and Physical Properties An important aspect of the present invention is the improved electrical and mechanical separation of the fetal and maternal sensors. Shown in Figures 1, 2 and 5-19, noninvasive fetal probes having a polymer shell 34, preferably made of a thermoplastic polymer, coated with a gel 30 which is preferably a hydrogel having conductive and / or adhesive properties . The gel 30 may also be covered with an insulating barrier 21 to improve the electrical isolation of the fetal sensor from electrical signals in the maternal environment. The insulating barrier 21 also provides improved electrical isolation between the fetal sensor 11 or 12 and the maternal sensor 16 or 17.

A. Noninvasive Fetal Probes Having Polymer Cores Returning to Figures 1-8, fetal probe 10 has a fetal brush sensor 11 or fetal disk sensor 12 with a fetal connector 14 positioned. A maternal sensor 17 and an maternal connector 18 may also be provided. Fetal sensors 11 or 12 and the maternal sensor 17 are electrodes, a fetal connector 14 and a maternal connector 18 are conductors, when the fetal probe 10 is a probe for measuring the fetal heart rate.

The maternal sensor 17 can be positioned on the upper surface of the probe 10 or can extend down the sides of the probe 10, as long as the maternal sensor 17 does not make contact with the fetus to which the probe 10 is attached. The gel 30 provides the base at which the fetal sensor 11, 12 and the maternal sensor 17 are fixed and secured to the fetal probe 10 with the fetal presentation part 100. The cuirass 34 can be formed by a number of procedures understood by those skilled in the art, including molding. The dimensions suitable for the shell 34 are a total height of approximately 6.2 nm and a diameter of approximately 15 nm. By using cuirass 34, gel 30 and fetal sensor 11, 12 can be isolated from external fluids. Figures 6D and 6E show two variations in the configuration of the wall 50 of the shell 34. Figure 6D shows a flange 52, which is a radiating extension into the wall 50 in a plane that is approximately at an angle of 30 cm. degrees to the outer wall surface 48 of the shell 34. A flange extension 53 is provided which maximizes the electrical and physical separation between the fetal and maternal sensing elements. The angle of the flange 52 can be adjusted (for example, to angles between 15 and 60 degrees) to achieve a desired gripping force. The rim 52 has a side surface 54; a horizontal and lower surface 44 and an upper surface 56. Figure 6G shows the rib extension 51, which is an radiative extension outwardly of the wall 50 in a plane that is approximately 30 degrees away from the wall surface. outer 48 of the shell 34. The angle of the rib extension 51 can be adjusted (by * example at angles of between 15 and 60 degrees) to achieve a desired gripping force. Figure 6F shows a modality having both a rib extension 51 and a flange extension 53 used in combination, which provide an electrical and physical separation between the fetal and maternal sensing elements better than that provided by any single extension. Figure 6E shows a "straight" internal wall surface 36, without deviations or additions, completely parallel to the outer wall surface 48 of the wall 50 of the shell 34. An exterior wall extension * 49 is provided that maximizes the electrical and physical separation between the fetal and maternal sensory elements. As mentioned above, increasing the spacing of the fetal and maternal sensors, the flange extension 53 of FIG. 6D, the outer wall extension 49 of FIG. 6E and the rib extension 51 of FIG. 6G, when used alone or in combination, e.g., as in FIG. 6F, they help isolate the fetal sensor thereby allowing a monitor 80, such as that shown in FIG. 1A, to more easily isolate the fetal heart rate from the maternal signals. . The extension of flange 53, the extension of outer wall 49 and the extension of rib 51 further ensure electrical isolation of the fetal and maternal sensors by forming a seal between gel 30 and external fluids. As shown in Figure 2, this increased spacing can be provided by limiting the amount of gel 30 so that it does not fully extend to the edge of rim 52 of polymer shell 34 that serves to isolate * y 30 from the maternal-sensor 17. Various thermoplastic resins are preferred materials for forming shell 34. Exemplary materials include Pellethane® resin (a polytetramethylene glycol ether resin available from the Dow Chemical Company, such as Pellethane® 2363), Pebax® resin (an amide resin of polyether block available from Atochem, Inc, such as Pebax "2533), PVCs, polyurethanes and polyethylenes, each of these materials offer different combinations of characteristics important for the fabrication and operation of fetal probe 10. Some of these characteristics are the ease of molding, resistance, adhesion to gel compositions, hardness, water absorption, biocornpatibility, price and signal isolation. The isolation of the fetal electrode from the maternal electrode can also be further improved by providing additional insulation which can be in the form of insulating barriers, non-conductive coatings, rubber brushes and air spaces which will be described later and which can be used alone, in combination with one another. with another and in conjunction with the extension of flange 53 or the extension of outer wall 49 or extension of rib 51. In Figures 1A and IB an insulating barrier 21 is shown which is disposed between the shell 34 and the gei 30. The figures 5 and 6A show a non-conductive coating 29 disposed on the lower surface 44 of the flange 52. Figures BB and 6C show a rubber brush 22 disposed on the lower surface * 44 of the flange 52, which has grooves 23 that can employ specially coated coatings. selected such as an absorbent coating 24; a non-conductive adhesive coating 25; or both, as shown, for example, in Figure 6C. Figures 7 and 8 show an air space 33 provided between the rim 52 and the gel 30. In another embodiment, a nonconducting rib 31 is shown in Figure 6H which helps isolate the fetal sensor 11 from the maternal environment. The non-conductive rib 31 may be a non-conductive coating, preferably a non-conductive hydrogel adhesive coating. The nonconductive rib 31 also helps to place the fetal probe 10 into a fetus that has a particularly large amount of hair. This is achieved by the ability of the non-conductive rib 31 to wrap the fetal hair and, if a hydrogel adhesive is employed, due to its wet adhesive properties. This non-conductive rib 31 is particularly useful when the wall 50 of the shell 34 has no flange, rib or other flange-like surface present to be placed against the display surface of the fetus. To further increase the physical separation between maternal and fetal environments, a noninvasive fetal probe is provided as shown in Figure 8. This fetal probe 10 modality has a longer and deeper cuff 34 in addition to an air space 33 This tapered design provides an increased path between, and therefore an improved electrical separation of, the fetal sensor 11 and the maternal sensor 17. The tapered design also has the advantage of providing a fetal probe 10 having a sufficiently small diameter. as to be easily applied when starting labor. For example, a V-shaped concave cup with a diameter of 15 to 20 m or that can be collapsed within a dispenser or guide tube of this diameter or less is preferred. Such a size allows the application of the fetal probe 10 when cervical dilation is 1 cm less.

B. Noninvasive Fetal Probes with Non-Conducting Ribs In an alternative embodiment, the non-invasive fetal probes according to the present invention can have gel 30 with a non-conductive rib 31. In FIGS. 9-11, fetal probes 10 are shown having gel 30 which can be a conductive hydrogel, with a nonconductive rib 31 around the perimeter. The non-conductive rib 31 may be a non-conductive coating, preferably a non-conductive hydrogel adhesive coating, which helps to electrically isolate the fetal sensor 11, 12 from electrical signals in the maternal environment. The nonconductive rib 31 also helps to place the fetal probe 10 into a fetus that has a particularly large amount of hair. This is achieved by the ability of the non-conductive rib 31 to wrap fetal hair and, if a hydrogel adhesive is employed, through its wet adhesion properties. This non-conductive rib 31 is particularly useful for isolating the fetal sensor 11, 12 from the maternal environment when a flange, rib or other flange-like surface is not present to be placed against the presentation surface of the fetus. Although Figures 9 and 10 show the nonconductive rib 31 extending only partially upwardly from the fetal fixation surface, the nonconductive rib is not limited to this region but may extend further toward the maternal sensor 17 as shown in FIG. Figure 11. Figure 12 shows a bottom view of the fetal fixation surface of the probes 10 shown in Figures 9-11. In a further embodiment, a noninvasive probe 10 is provided having a shell extension configuration shown in Figure 13, which also maximizes the separation between the maternal and fetal arnbifent.es. In this embodiment, the gel 30 has a bellows configuration with a cuirass 34 and a cuirass extension 37 located around the perimeter of the fetal fixation surface that supports a 99 non-conductive adhesive 35 which can be a hydrogei material. As shown in Figures 9-13, fetal probe 10 is covered with a shell 34 and, in the embodiment shown in Figure 13, an additional shell extension 37 which prevents gel 30 from contacting the maternal environment for help * electrically isolate the fetal sensor from electrical signals in the maternal environment. The shell 34 and the shell extension 37 also provide electrical insulation between the fetal sensor 11, 12 and the maternal sensor * 17.

II. Noninvasive fetal probes that have low profile designs In a further modality, a noninvasive fetal probe is provided that has low profile designs as shown in Figures 20-23. During the design of a fetal probe, the fixation force that holds the fetal probe 10 in place over a fetus must be taken into account. This clamping force should be sufficient to keep the fetal probe 10 in place during labor, which could require fix times of ten hours or more. During labor, a fetal probe is subjected to tilting forces that are generated by the movement of the fetus' head, the mother's cervix, or both. The low profile designs according to the present invention help to diminish * the tendency to detach from the fetal probes caused by these fetal and cervical forces generated on the probe. This makes it possible for the noninvasive probe to be securely attached to the fetus during labor and birth. The fetal probe designs shown in Figs. 20-23 achieve these low profiles by reducing the total height of the probe 10 either by forming the fetal connector wire 14 and the maternal connector wire 18 to include a substantially perpendicular curvature (Fig. 20) or connecting these wires to the probe 10 in a radial direction (figures 21 and 23). Where probe 10 incorporates cuirass 34, the radial fixation of the fetal connector wire 14 can be achieved by means of a fetal circumferential sensor 13 shown in FIGS. 21 and 22. The maternal sensor 16 of FIGS. 21 and 22 is preferably a steel band that is connected to the maternal connector. 18. In still another embodiment, a fetal probe having a low profile having substantially uniform fetal and maternal electrodes is provided. A preferred embodiment, shown attached to the fetus 100 in Figure 23, is a fetal probe 10 having a maternal sensor 17 and a fetal sensor 12 both of which are flat discs and are separated by an insulating layer 19. Preferably, the insulating layer 19 extends over fetal sensor 12 to improve separation of maternal sensor 17. ' III. Probe for Fetal Heart Rate A specific application of fetal probe 10 will be described to better illustrate * the advantages of fetal probe 10. Fetal probe 10 can be used to monitor the fetal heart rate without penetrating the epidermis of the fetus. At least four criteria affect the quality of the signal of the rhythmless fetal heart rate: (1) the symmetry between the fetal and maternal (reference) electrodes, (2) the maximum separation between the fetal and reference sensors, (3) the maximum surface contact area to keep the impedance to the minimum and (4) the stabilized connections. The application of fetal probe 10 to monitor the fetus' heart rhythm satisfies these criteria well. In this application, a fetal sensor detects the electrical signal of the transcutaneous fetal heart rate. To do this, the fetal sensor must be kept in contact with the presenting part of a fetus, either directly or through the gel 30. Preferably the gel 30 is a conductive hydrogel in the case where electrical contact between the fetus and the fetal sensor is indirectly established through the gel 30 as shown, for example, in Figures 1A, IB, 2, 5, 7, 8, 9-11 and 13. In cases where the fetal sensor makes contact directly with the fetus, the gel 30 may optionally include a conductive material such as to improve the electrical contact and the transmission of the electrical fetal signals. The fetal sensorial ism must provide a sufficiently large surface area and be electrically conductive to detect the electrical signal of the heart rhythm. fetal. The present invention includes several types of fetal sensors that illustrate but do not limit the types that may be employed. Previously, a fetal brush sensor 11 (shown in FIGS. 1A, IB, 5, 7-11 and 13) and a fetal disk sensor 12 (shown in FIGS. 2, 3 and 23) were mentioned. A suitable material for the construction of the fetal brush sensor 11 is a carbon fiber wire. Carbon wires are lightweight, flexible and radiolucent (ie *, are partially or completely transparent to X-rays). Moreover, they provide good electrical conductivity and do not react with gel components or saline solutions. A suitable carbon wire can be obtained from the Minnesota Uire and Cable Company in St. Paul, Minnesota, and can replace the stainless steel in the formation of the fetal sensor 11. The fetal brush sensors 11 can also be formed from steel wire multi-strand stainless steel, such as a steel wire coated with Teflon® sold by Cooner Uire in Chatsworth, California. Such a wire is very thin and light in weight, and therefore adds little handle to the fetal probe 10. When used to form the fetal brush sensor 11, the Teflon® cover is removed to expose the stainless steel wire. The exposed wires are subsequently scattered to form a brush. Alternatively insulating cover materials for the wire other than Teflon® can also be used. The circumferential fetal sensor 13 can be formed from conductive wire (e.g., stainless steel) that does not react with gel components or saline solutions. The conductive wire used typically has an insulating cover 15 that protects the wire portion of the circumferential fetal sensor 13 extending out of the shell 34 of the maternal environment. See figures 21 and 22. The insulating cover 15 is stripped to expose the wire portion of the circumferential fetal sensor 13 on the inside of the shell 34 so that it can make contact with the conductive gel 30. The fetal disk sensor 12 in this Application may be the silver-silver chloride sensor commonly used in ECG monitoring electrodes. Additional fetal sensors are also provided which are useful in the present invention, namely, a loop arrangement 6 (Figures 14-15), a fiber or conductive maya wool "(figures 16-17), and a conductive" fan-strand "configuration 8 (figures 18 and 19). The materials used for these different fetal sensors must be conductive and non-reactive with gel components or saline solutions. Moreover, the materials incorporated in the fetal sensors must also not react with the fetal tissue or in the fetal environment (eg, with the vernix or rneconium). Although no attempt is made to be limited to any particular selection of materials, exemplary materials particularly useful for the fetal sensors of the present invention are carbon, stainless steel, silver, gold, silver-silver chloride and combinations thereof.

It is anticipated and understood that the different fetal sensors are interchangeable with, and can be incorporated either in place of, or in combination with, any of the fetal sensors of the noninvasive probes described (the probes themselves are merely exemplary of the present invention). Unless otherwise specified, hereinafter the term "fetal sensor" refers collectively to the fetal brush 11, the fetal disk 12, the fetal circumferential sensor 13, the loop arrangement 6, the "wool" or fiber mesh conductive 7 and the "fan-strand" conductive configurations 8. The fetal sensors shown in Figures 14, 16 and 18 are shown partially embedded in, and partially exiting the gel 30 to provide direct contact, and thus improving the conductivity, between the fetal * sensor and the fetal tissue when the fetal probe is fixed to the fetal presentation part. When the partially embedded fetal sensors of Figures 14, 16 and 18 are used to establish direct contact with a fetus, the fetal sensors may also be covered with an adhesion promoter layer 5 as shown in Figures 15, 17 and 19 The adhesion promoter layer 5 may include a lubricious jelly (e.g., jelly K-YR) or a conductive medium (e.g., a conductive migrating hydrogel) that can flow around the hair to improve adhesion. In the case of the conductive migrating hydrogel, the additional advantage of a lower impedance in the skin interface -sensor. Additional means are also provided to increase * Maternal and fetal differential signals. This is achieved by the spring contact 58 shown in Fig. 24A, which is partially embedded in the gel 30 and provides direct contact and thus improved conductivity between the fetal sensor and the fetal tissue when the fetal probe is fixed to the presentation part of the fetus. The spring contact 58 is shown in perspective in Figure 24B and in a top view in Figure 24C. In this application, the fetal connector 14 is an isolated lead wire that is suitable for conducting the electrical signals from the fetal sensor to a monitor signal processing unit without being susceptible to interference from the maternal and respiratory environment. maternal sensor. The fetal connector 14 passes through the shell 34 within the gel 30 and the maternal sensor 16 or 17 and is finally connected (perhaps through other wires and electrical connections) to a fetal heart rate monitor 80 shown in FIG. Figure 1A. The environment in which the fetal probe 10 is used, namely within the uterus, requires the isolation of the bioro wire. The connection between the fetal connector 14 and the fetal sensor 12 is embedded in the gel 30. The fetal sensors of the present invention can be completely embedded in the gel 30 (as shown in FIGS. 1A, IB, 2, 5, 7-11 and 13), partially embedded in, or positions on, the surface of the gel 30 (as shown in FIGS. 14, 16 and 18) or otherwise portrayed by the gel 30. In case Fetal sensors are not completely embedded in the gel 30, if an adhesion promotion layer 5 is used, the fetal sensors of the present invention can also be either partially (FIGS. 15 and 19) or fully (FIG. 17) embedded in FIG. the adhesion promotion layer 5. In either case, the fetal sensor connector 14 and the maternal sensor connector 18 connect the fetal and maternal sensors, respectively, to an external monitor 80. In this application, the maternal sensors 16 and 17 should provide enough surface area They are large and electrically conductive to detect the electrical signal of the maternal heart rate and other electrical or muscular activity. In addition, maternal sensors 16 and 17 must be inert to the chemical reaction with fluids and biological tissues. The carbon fiber or stainless steel multi-fiber wires described above for use as the sensor-fetal 11, they can also be used for the maternal sensor 16. Alternatively, the maternal sensor 16 can be an electrically conductive material such as a thin metal (e.g., silver, aluminum or stainless steel) or a metallized film ( e.g., aluminum-coated polyester) covering the upper surface of the insulating barrier 21. Other non-metallic films and coatings and the conductive conductor may also be used, such as conductive carbon and conductive graphite. The maternal sensor 16 (figures 21 and 22) and the maternal sensor 17 (figures 1, 2, 4, 5, 7-11, 13-20 and 23) can be a band, washer, wire loop or plate that is adapt in the upper part of, or otherwise carried by the shell 34 or the insulating layer 19. In an exemplary embodiment, as shown in Figures 4 A and 4B, the stainless steel disc 17 may have approximately 3.5 a 4.0 mm wide (preferably 3.7 inrn) and 5.0 to 5.5 rnrn diameter (preferably 5.4 mm) and may contain an elongated hole 9 (Figure 4B) to facilitate the passage of fetal connector 14 through the ism. The maternal connector 18 is a lead wire which may be a sheathed multi-wire wire connected to the maternal sensor 17 to communicate received electrical signals. The maternal connector 18 may be fixed perpendicular * a (FIG. 4A) or in the plane of the maternal sensor 17. Typically, the mains connector wire (s) 18 is or is fixed to the maternal sensor 17 by an electrical spot welding operation. . The maternal sensors 16 and 17 mainly detect the maternal electrical environment while the fetal sensors 11, 12 and 13 mainly detect the fetal electrical environment on the surface of the fetus. However, the signal received by each sensor has a component signal smaller than 11 it comes from the other environment (that is, the fetal sensor detects signals that come from the maternal environment while the maternal sensor detects signals that come from the fetus). Using the signal detected by the maternal sensors 16 and 17 as a reference signal, any maternal heart signals and other muscle or electrical signals passing through the fetus can and are detected by the fetal sensor can be electronically filtered on the fetal monitor 80 to provide a differential signal that is an accurate measurement of the fetus's heart rate. This is achieved by isolating the R waves of the fetus from the dormant signals. The noninvasive fetal probe 10 has two wires 14, L8 - similar to conventional fetal scalp electrodes - for the fetal sensor and the maternal sensor. Both the fetal wires 14 and the maternal wires 18 can be replaced by a connection system that does not have wires, such as a radio transmission system, to communicate information coming from the fetal sensor and the maternal sensors 16 or 17 to the monitor 80. A radio system may require * support hardware and is understood by those skilled in the art. Referring again to the insulating barrier 21 (Figures 1A, IB and 2) and 'to the non-conductive coating 29 (Figures 5 and 6A), these elements serve to maintain electrical isolation between the fetal and maternal sensors. Pebax, a polyethylene block amide, is a type of J2 insulating material that can be incorporated to serve this purpose. Other similar materials that have sufficiently high dielectric properties can also be adequate. The insulating barrier 21 and the non-conductive coating 29 must be flexible so as not to impede the flexibility of the gel 30. With respect to the non-conductive coating 29 (FIGS. 5 and 6A), the non-conductive adhesive 35 (FIG. 13), and the promoter layer of adhesion 5 (figures 15, 17 and 19), because these elements make contact with the fetus, preferably incorporate adhesive materials that are conformable and that are used in sufficient amounts and thickness as to wrap the fetal hair and other irregularities of surface, as well as to promote the fixation to a fetus that has a large amount of hair. In addition to promoting attachment to fetal tissue, the adhesive materials used should be capable of improving * the electrical isolation of the fetal probe from the maternal environment. An adhesive with wet bonding capabilities is particularly preferred. The selection of gel compositions and production techniques useful in the present invention is within the scope of those skilled in the art, showing examples, but not limited to, the hydrogels of the U.S.A. No. 5,474,065. The hydrogel compositions described in that patent can be molded or formed to provide almost any desired size and shape. The gel 30 can be formed by placing the gel composition in a mold in a desired manner and then polyepting the gel members in the mold. Alternatively, probes in the form of a suction cup can be prepared by spin casting, similar to the method used to prepare soft contact lenses. Although conductive gels are preferred for building gel 30 to improve or establish electrical contact between the fetal sensor and the fetal presentation part, it is recognized that gel 30 does not need to be a conductive material in cases where the sensor fetal establish direct contact with the fetus. Although illustrated and described herein with reference to certain specific embodiments, the present invention is not, however, designed to be limited to the details shown. It is understood that the different embodiments are merely illustrative of the present invention and that the different features can be used alone or in conjunction with each other in any combination as will be readily recognized by those skilled in the art. It is also recognized that various modifications can be made to the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention. For exampleAlthough the fetal probe 10 of the present invention has been described in detail for the attachment of non-invasive fetal heart rate sensors, the fetal probe 10 can also be used for other sensors such as blood gas analyzers and oxirnetpa sensors. In such a case, fetal connector 14 and maternal connector 18 can constitute optical fibers instead of lead wires.

Claims (38)

1. NOVELTY OF THE INVENTION CLAIMS
2. L.- A noninvasive fetal probe adapted to be fixed to the presentation part of a fetus and monitor by
3. At least one fetal parameter during labor and delivery, said probe includes: a shell that has a non-conductive element; a gel coated on said shell forming a surface that secures the probe to a fetus that will be monitored, a fetal sensor carried by said gel and which detects at least one fetal parameter, said non-conductive element of said breastplate isolating said fetal sensor from the fluids in an environment surrounding the probe; a maternal sensor carried by said shell and which detects at least one maternal pair; and means for communicating to a monitor the fetal and maternal parameters detected by said fetal sensor and said maternal sensor, respectively. 2. A non-invasive fetal probe according to claim 1, wherein said non-conductive element is selected from the group consisting of a non-conductive rib, a flange, a wall extension, a rib extension and combinations thereof. 3. A non-invasive fetal probe according to claim 2, further comprising an insulating barrier disposed between said shell and said gel.
4. 4. A non-invasive fetal probe according to claim 2, wherein said shell is a polymer.
5. 5. - A non-invasive fetal probe according to claim 2, wherein said non-conductive element is a rim having a lateral surface, an upper surface and a lower surface, said probe further comprising an air space disposed between said upper surface of said flange and said surface formed by said gel.
6. 6. A non-invasive fetal probe according to claim 5, wherein said gel has a "V" shape.
7. 7. A non-invasive fetal probe according to claim 6, wherein said gel has a diameter of 10-20 inrn.
8. 8. A non-invasive fetal probe according to claim 2, wherein said non-conductive element is a wall extension extending from said shell beyond said surface formed by said gel.
9. 9. A non-invasive fetal probe according to claim 2, wherein said fetal sensor is selected from the group consisting of a brush sensor, a disc sensor, a loop arrangement, a conductive fiber wool, a conductive fiber mesh, a conductive fan strand and combinations thereof.
10. 10. A non-invasive fe / tal probe according to claim 9, wherein said fetal sensor comprises at least one material selected from the group consisting of carbon fibers, stainless steel, silver, gold, silver, silver chloride and combinations thereof.
11. 11. A non-invasive fetal probe according to claim 9, further comprising an adhesion promoter layer disposed on said fetal sensor.
12. 12 .-- A non-invasive fetal catheter in accordance with Claim 11, in said adhesion promoter layer comprises at least one material selected from the group consisting of a lubricating jelly, a conductive medium, a conductive migrating hydrogel and combinations thereof.
13. 13. A non-invasive fetal probe according to claim 2, wherein said communication means comprise a fetal connector that connects said fetal sensor to said monitor and a maternal connector that connects said maternal sensor to said monitor.
14. 14. A non-invasive fetal probe according to claim 13, wherein said fetal connector and said maternal connector extend in a radial direction from said shell and each comprises a substantially perpendicular curvature.
15. 15. A non-invasive fetal probe according to claim 13, wherein said fetal connector * and said maternal connector extend in a radial direction from said shell. t
16. 16.- A non-invasive fetal sona in accordance with claim 15, wherein said fetal connector is connected to said gel by means of a circumferential sensor fet.
17. 17. A non-invasive fetal probe according to claim 2, wherein said gel further comprises a partially embedded spring contact adapted to make direct contact with the fetus that will be inomaled after securing said gel to the presenting part.
18. 18. A non-invasive fetal probe according to claim 2, wherein said non-conductive rib is a conductive hydrogel adhesive coating.
19. 19.- A non-invasive fetal catheter adapted to be fixed to the presentation part of a fetus and monitor at least one fetal pair during the labor and delivery, said catheter compr-ende: a breastplate; a gel coated on said shell forming a surface that secures the probe to a fetus that will be impacted, said shell has an outer perimeter that forms a flange with a lateral surface, an upper surface- and a lower surface that isolates said gel from the fluids in an environment surrounding the probe; a fetal sensor carried by said gel and which detects at least one fetal parameter; and an insulating element disposed on said lower surface of said flange.
20. 20. A non-invasive fetal probe according to claim 19, wherein said insulating element is a non-conductive coating.
21. 21. A non-invasive fetal probe according to claim 19, wherein said insulating element is a go brush having grooves.
22. 22. A non-invasive fetal probe according to claim 21, further comprising at least one coating selected from the group consisting of an absorbent coating, a non-conductive adhesive coating and combinations thereof, disposed in said grooves.
23. 23.- A non-invasive fetal probe that is fixed to the part of presentation of a fetus and to monitor at least one fetal parameter during labor and delivery, this probe includes: a gel that forms a surface that ensures the probe to a fetus that will be monitored and that has an outer perimeter * with a non-conductive rib disposed thereon, a shell disposed on said gel; a fetal sensor carried by said gel and which detects at least one fetal pair; and means for communicating * the fetal parameter detected by said sensor from said sensor-to a monitor.
24. 24. A non-invasive fetal probe according to claim 23, wherein said non-conducting rib is a non-conductive hydrogel adhesive coating.
25. 25. A non-invasive fetal probe according to claim 23, wherein said gel is in the form of a bellows and said non-conductive rib is a non-conductive adhesive supported by a shell disposed on said outer perimeter of said gel.
26. 26.- A non-invasive fetal probe adapted to be fixed to the presentation part of a fetus and monitor at least one fetal parameter during labor and delivery, this probe includes: a substantially flat gel that carries a fetal sensor that detects at least one fetal parameter, said gel Lene a surface that secures the probe to a fetus that will be monitored; a substantially flat insulating layer disposed on said gel; a substantially flat maternal sensor carried by said insulating layer and which detects at least one maternal parameter; and means for communicating the fetal and maternal parameters comprising a fetal connector connecting said fetal sensor to said monitor and a maternal connector that connects said maternal sensor to said monitor, wherein said fetal connector and said maternal connector extend in a radial direction from said gel.
27. 27. A non-invasive fetal probe according to claim 1, wherein said gel is a conductive hydrogel.
28. 28. A non-invasive fetal probe according to claim 1, wherein said gel is an adhesive hydrogel.
29. 29. A non-invasive fetal probe according to claim 1, wherein said gel is a conductive adhesive hydrogel.
30. 30. A non-invasive fetal probe according to claim 19, wherein said gel is a conductive hydrogel.
31. 31. A non-invasive fetal probe according to claim 19, wherein said gel is an adhesive hydrogel.
32. 32. A non-invasive fetal probe according to claim 19, wherein said gel is a conductive adhesive hydrogel.
33. 33. A non-invasive fetal probe according to claim 23, wherein said gel is a conductive hydrogel.
34. 34. A non-invasive fetal probe according to claim 23, wherein said gel is an adhesive hydrogel.
35. 35.- A non-invasive fetal probe according to claim 23, wherein said gel is a conductive adhesive hydrogel.
36. 36. A non-invasive fetal probe according to claim 26, wherein said gel is a conductive hydrogel.
37. 37. A non-invasive fetal probe according to claim 26, wherein said gel is an adhesive hydrogel. /
38. 38.- A non-invasive fetal probe according to claim 26, wherein said gel is a conductive adhesive hydrogel.