US 3273559 A
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H. L. EVANS Sept. 20, 1966 METHOD AND APPARATUS FOR MONITORING THE APPROACH OF BIRTH Filed Aug. 28, 1965 R Z 0 8% M J 4 %06 R W %IIMMMT$ k i m z "KL M M T:
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United States Patent 3,273,559 METHOD AND APPARATUS FOR MONITORING THE APPROACH OF BIRTH Henry Lee Evans, Ann Arbor, Micln, assignor to Conductron Corporation, Ann Arbor, Mich, a corporation of Delaware Filed Aug. 28, 1963, Ser. No. 305,149 7 Claims. (Cl. 128-2) This invention relates to a monitoring device and has more particularly to do with a device for monitoring the dilatation of the female cervix during labor and just prior to the actual birth of an infant. The device is so arranged that it eliminates the necessity for the attending physician making personal manual examination of the dilatation from time to time. Thus, it assists materially in contributing to the comfort of the mother during the final hours of labor and also provides a continuous indication of dilatation which assists in the avoidance of complications associated with precipitous birth that may occur during the time between the examinations by the physiclan.
It is common practice in the treatment of expectant mothers to judge the time of birth by the so-called expan sion or dilatation of the cervix and the present invention relates to a measuring means which can, without discomfort to the patient, be observed in a suitable instrument near the patient.
It is a further object to provide a means for suitably mounting monitoring devices which requires a minimum of equipment and discomfort to the patient.
Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claims.
Drawings accompany the disclosure and the various views thereof may be briefly described as:
FIGURE 1 illustrates a circuit diagram in block form showing the various elements of the apparatus.
FIGURE 2 illustrates the monitoring elements.
FIGURE 3 is a view showing the manner in which the monitoring elements are mounted on the lips of the cervix.
FIGURE 4 is a sectional view of the mounting clip taken on line 4-4 of FIGURE 5.
FIGURE 5 is a sectional view -of a mounting clip taken on line 5-5 of FIGURE 4.
In the female anatomy, the uterus or womb positioned above the vaginal cavity has a lower half or neck portion which is called the cervix. This is the area of the opening of the womb; and, during pregnancy, as child birth approaches, this opening gradually enlarges or dilates and the degree of dilatation is indicative of the descent of the child toward the cervical opening. The womb opening has lip portions referred to at and 12 in FIG- URE 3 in spaced relation, and on these lip portions are mounted expansion clips 14 and 16 having bifurcate gripping portions 18 pivoted at 20 with actuating handle portions 22 which are provided with re-entrant curved portions 24 to permit gripping and handling by forceps shown diagrammatically at 26. The bifurcate gripping portions 18 are provided with small projections in the form of teeth 28 to insure a firm location on the lip of the cervix. The nature of this portion of the body is such that these clips may be applied without discomfort to the patient.
A suitable coil spring 30 serves to hold the portions 18 in gripping relation and these parts are all made of a corrosion resistant material such as stainless steel which can be suitably sterilized. A small open-ended cylinder 32 is supported by apertured ears 34 on a transverse pivot pin 36 which serves as a pivot for the opposed portions of the clips 14 and and also as a location for the spring 30. The cylinder 32 is provided to carry the monitoring devices which form a part of the indicator circuit. These devices can consist of cylindrically shaped capsules 40 and 42 as shown in FIGURE 2. One capsule 40 can carry what is called a ferrite load and the dimension of this capsule can be approximately .5 centimeter in diameter and 1.5 centimeters in length. This ferrite load can be in the nature of a small cylinder of ferrite material in sintered form, for example, which has the properties of ferrite required in the circuit to be described, i.e., a high permeability or high Q rating. The capsule 42 can contain a miniaturized Hartley oscillator using a transistor as the active element with a coaxial output lead wire 44, this capsule being approximately .5 centimeter in diameter and 2 centimeters in length.
The tuned LC tank circuit of the oscillator is the heart of the device because it is in effect the measuring element and it includes an air-wound inductance in capsule 42 and the high permeability or high Q ferrite core in capsule 40. The combined inductance of the air core plus the ferrite determines, in conjunction with a fixed capacitor in the tank circuit, the frequency of oscillation of the Hartley oscillator circuit.
The ferrite 49 is attached by clip 14 to one of the cervical lips 10 and the air core 42 is attached by clip 16 to the other lip 12 as shown in FIGURE 3, the two units being initially adjacent and in close proximity with one another in the normal undilated condition of the cervix. As the two units are separated by dilatation, the inductance of the combination will decrease, and the frequency of oscillation will increase. The change of frequency in the output signal of the oscillator can be readily determined as a function of the known displacement of the two units and a separation indicator can be coupled to the oscillator output by suitable circuitry as described hereinafter to visually indicate the progress of the dilatation. The co-axial cable 44 will connect the active unit 42 inside the mother with the external telemetering equipment but it will be seen that only the slender coaxial cable 44 need extend through the Vagina and that there is no electrical wiring connection whatsoever between the two elements 40 and 42.
Cable 44 will carry direct current to the transistor and serve as the output lead to transmit the oscillator frequency to the counting device. The co-axial cable offers the advantage of a noise shielded signal path and small size, for example, 2 mms. diameter. It can be covered with an insert material, such as, for example, rayolin NF, which is stable from negative 55 to degrees centigrade, and thus lends itself to easy sterilization.
The output of the oscillator is fed to a waveshaping circuit to generate well-defined zero crossings of the output frequency, and this signal will in turn drive a monostable multivibrator. The output pulse amplitude will be constant, and the duration of the pulse less than the highest expected frequency. If the average value of the train of pulses is determined, it is found to be proportional to the input frequency, and this average value can be displayed on a meter calibrated to indicate displacement.
In FIGURE 1, the ferrite load 40' is shown in spaced relation to the Hartley oscillator 42 which is connected by the coaxial cable 44 to a waveshaper 46 having a suitable direct current supply. The waveshaper is connected to the monostable multivibrator 48 and this is connected to a separation indicator 50 of a visual nature, such as a needle or a dial.
The units used internally of the patient are preferably mechanically stabilized by encapsulation in irradiated polyolefin which can be heat shrunk to provide maximum holding of the elements without any volatile glues or solvents. The units will then be dip coated in a heat curable latex compound to provide a smooth closed cell surface that can be easily modified to expose the holding attachments and still provide a sealed capsule that can be sterilized prior to insertion. The co-axial cable cover also bonds well to latex and as previously indicated, can be sterilized. The output cable 44 may have a convenient quick disconnect plug at a suitable location exterior to the patient so that she may disconnect it from the indicator mechanism and move about if necessary.
What is claimed is:
1. A system for indicating the approach of childbirth in a female mammal comprising an electrical circuit including first and second elements physically and mechanically independent of each other adapted for insertion in the vaginal cavity of the female and co-operable electrically with each other to control a measurable parameter of said circuit as a function of the proximity of said elements to each other, means associated with said elements adapted to removably attach said first element to one lip of the cervical opening of the female and said second element to the other lip with no physical or mechanical association between the elements, and telemetering means located externally of the female and coupled to said electrical circuit for translating varia- :ions in said parameter into a signal for indicating the spacing of said cervical lips from each other.
2. A method for monitoring the imminent approach of :hildbirth in a female mammal comprising the steps of attaching a magnetically permeable element to one lip 3f the cervical opening of the female, attaching an in- :luctor element to the other lip of said opening, said elernents being physically and mechanically independent of each other, passing an electrical current through said inductor to generate a magnetic field encompassing said :lement in all positions of said lips, and translating :hanges in the inductance of said inductor caused by changes in the proximity of said element to said inductor into an electrical signal indicative of the spacing of said lips from each other.
3. A method for monitoring the imminent approach of childbirth in a female mammal which comprises the steps of associating, with the spaced lips of the cervix, first and second elements of an electrical inductance :ircuit co-operable with each other but physically detached from each other to control a measurable param- :ter of said circuit as a function of the proximity of said elements to each other and coupling in said circuit a telemetering means located externally of the body for translating variations in said parameter into a signal for indicating the spacing of said cervical lips.
4. An apparatus for indicating the approach of childbirth in a female mammal which comprises resiliently expandable clamping means for attachment to the opposed cervical lips of the female, means on said clamping means remotely operable manually to permit attachment and detachment, first and second elements adapted for insertion into the vaginal cavity carried respectively by said clamping means and physically independent of each other, an electrical circuit incorporating said elements to create a measurable parameter as a function of the proximity of said elements to one another, and telemetering means located externally of the female and coupled to said electrical circuit for translating variations in said parameter into a signal for indicating the spacing of said cervical lips from each other.
5. A device as defined in claim 4 in which only one of said elements is physically connected in said circuit.
6. A device as defined in claim 4 in which each of said elements is encapsulated in a waterproof, relatively inert material to permit sterilization.
'7. A device as defined in claim 4 in which said clamping means each comprise jaw-like members pivoted to each other, spring means to bias said members toward each other, and opposed extensions on said members to permit manipulation thereof to a proper clamping position.
References Cited by the Examiner UNITED STATES PATENTS 2,239,330 4/1941 Lorand 128-2 2,652,825 9/1953 Rauh 128Z 2,831,478 4/1958 Uddenberg 1282 2,824,220 2/1960 Von Micsky l28361 FOREIGN PATENTS 17,220 9/1900 Great Britain.
RICHARD A. GAUDET, Primary Examiner.
LOUIS R. PRINCE, Examiner.
S. BRODER, Assistant Examiner.