GB2060891A - Electronic obstetric device - Google Patents

Abstract

An electronic obstetric device for evaluating the course of parturition is provided with a foetal heart rate detector 1 and a uterine contraction detector 2. Means 3, 3c, 3f, 3d are provided to convert signals from said detector to a wave form representation. A comparator 4 (also Fig. 1) evaluates components of each of said wave forms to ascertain the parameters thereof and activates an alarm when one (or both) of the signals depart by more than a predetermined amount from a predetermined fixed value. By comparing the said components against a basal value which is manually adjusted by an obstetrician, said obstetrician may acurately review the components of foetal heart rate and those of uterine contraction and may also evaluate their inter-relation. <IMAGE>

Description

SPECIFICATION Electronic obstetric device The present invention relates to an electronic obstetric device for evaluating the course of parturition which device is provided with a foetal heart rate detector, a uterine contraction detector, means for the conversion of signals from said detector to a wave form representation, and means for evaluating components of each of said wave forms to ascertain the parameters thereof.

In conventional devices for the supervision of delivery, related patterns of heart rate and uterine contractions cannot be monitored.

Such devices can only generate an alarm signal when foetal heart rate increases or decreases extraordinarily. The method of the present invention removes the defects above by comparing said components against a basal value which is manually adjustable by an obstetrician, whereby said obstetrician may review the components of foetal heart beats, those of uterine contraction, individually and interdependently, thereby providing an increased warning of foetal distress.

According to one aspect of the invention therefore, there is provided an obstetric device comprising a foetal heart rate detector, a uterine contraction detector, means for the conversion of signals from said detectors to a wave form representation, and including means for evaluating components of each said wave form to ascertain the parameters thereof.

According to a second aspect of the invention, there is provided a diagnostic method which comprises monitoring a signal from a foetal heart rate detector, monitoring a signal from a uterine contraction detector, converting said signals to a wave form representation, and evaluating components of each said wave form to ascertain the parameters thereof.

According to a third aspect of the present invention, there is provided a comparator circuit which comprises means for monitoring a signal from a foetal heart rate detector, means for monitoring a signal from a uterine contraction detector, means for converting said signals to a wave form representation, and means for evaluating the components of each said wave form and measuring the parameters thereof.

A preferred embodiment of the invention will now be described by way of illustration only with reference to Figs. 1 to 3 of the accompanying drawings.

Figure 4 shows a prior art device in diagramatic form.

Figure 1 is a block diagram showing the combination of a data treatment circuit in accordance with this invention, Figures 2 and 3 are related diagrams showing foetal heart rate signals and uterine contraction signals taken during parturition as a function of the time and showing the relevant wave form and other elements and Fig. 4 is a basic diagram of a conventional obstetric device for supervising parturition.

Fig. 4 indicates the basic construction of a known delivery monitoring device. In said Fig.

a heart rate detector is adapted for retention on the abdomen of a pregnant woman during parturition. A detector for uterine contractions 2 is similarly retainable. Signals generated by both these devices are fed to a recorder unit 3.

A comparator 4 comprises a circuit for detecting the basic data for diagnosis by the doctor. The input terminals of the comparator 4 are connected respectively to the output terminal 3a (heart rate signals) and output terminals 3 b (the uterine contraction) .

The outputs 3 e and 3 f are connected respectively to stylii responsive to signals gener ated in said recorder unit 3, which give a visual trace on paper reel 3c, driven by a motor 3d in the usual geared fashion.

The conventional comparator 4 mentioned above receives both the heart rate and the uterine contraction signals and utilizes these to generate an alarm signal when either or both of these individual signals depart by more than a predetermined amount from given fixed values.

To further refine this information an embod iment shown in Fig. 1 provides a data treat ment section shown generally at 4 comprised of an analog-digital transformer 4a, a data memory section 4b, a parameter calculator 4c, a parameter comparator section 4d, a parameter variable determination section 4e, a score calculation section 4f, a weight variable determination section 4g, a total score com parator section 4h, a total score variable determination section 4iand an alarm signal indication section 4j.

An analog-digital transformer 4a abstracts the wave-form of both signals of heart rate and the uterine contraction every 0.5 seconds and transforms said wave-forms into digital signals corresponding to the peak values of said wave-form described hereinbelow, and outputs said signals to the data memory section 4b. The data memory section 4b memo rizes the series of corresponding digital signals input and at the same time, outputs, the digital signals sequentially.

The parameter calculation treatment section 4c has a digital calculation circuit to calculate the ''parameters of momentary treatment'' mentioned hereinbelow in detail and outputs the calculated values in digital signals to the next circuit 4d.

The final parameter judgement section 4d is provided with a comparative theory circuit for contrasting non-responding signals and re sponding signals which respond only to the hereinafter described momentary treatment parameters selected from the certain value (weight) signals inserted manually by the doctor into the calculation process.

The variable parameter determination section 4e and the score calculation section 4f respectively are also provided with digital calculation circuits.

The total score final judgement section 4h, also has a digital calculation circuit, receives a digital signal representative of the total score described hereinbelow and is capable of comparing said digital signal with a variable limit value. The variable determination section 4i is adapted to output said digital signal input by the doctor to the judgement section 4h mentioned above. The alarm signal indication section 4j is provided with the indication lamp and buzzer for the doctor.

In the construction of the data treatment section 4, the variable parameter determination section 4e, the weight variable determination section 4g input by the doctor, and the total score variable determination section 4i respectively, input digitalized expected values by the operation of digital switches. However, as such expected values are set manually each of the above various sections can become a means for obtaining analog values by other known means not shown in figure, for example, by transforming the constructions of operation into a potentiometer.

When the heart rate signal A (Fig. 2) and the signal B of uterine contraction (Fig. 3) are output to the analog-digital transformer 4a in Fig. 1 from the output terminal of the heart rate signal 3a and the output terminal of the uterine contraction signal 3b shown in Fig. 1, said 4a sends a representative digital signal to the data memory section 4b thus transforming the heart rate signal A and the uterine contraction signal B into a digital signal in abovementioned sequences. The signal B gives an output representative of a uterine contraction and time. Signal A is calculated from the heart pulse interval, and the heart pulse itself of the foetus. Said signals A and B are abstracted about every 0.5 seconds and the information on the variability of each waveform signal A and B can be accurately represented.In this case, the heart rate signal A responds within the range of 0-250BPM (beats per minute) and the uterine contraction signal B responds within the range of 10-100 mmHg to the analog electric pressure of about 0-1.25 volt. The series of digital signals representing various wave peak values (described hereinbelow) abstracted from the two signals A and B are retained and memorised in the data memory section 4b (Fig. 1). At the same time, a series of digital signals are transferred at sampling intervals of about 0.5 seconds to the parameter calcula- tion section 4c(Fig. 1), once said digital signals memorised in above 4b have been transferred they can be renewed by the arrival of a new series of waveform signals to be memorised.

Accordingly, as the series of digital signals mentioned above are set series by series from the data memory 4b they can be utilized individually for calculation at the parameter calculation section 4c. Thus, the various parameters necessary for judging the heart pulse signal A and the uterine contraction signal B (Fig. 1 and Fig. 3) can be calculated.

A doctor can also insert standard values into the system to take account of any physiological evaluation of a patient by operating a switch installed on the weight variable determination input 4g (Fig. 1). The standard value is inserted as a digital signal (hereinafter called the parameter of periodical treatment), and these are continuously fed as a pulse to the score calculation section 4f(Fig. 1).

During the measurement of uterine contractions various final judgement signals are sent to said 4f from the parameter final judgement section 4d(Fig. 1). The inter-relationships of these and their calculation methods are described in the following accompanying examples as shown in Fig. 2 and Fig. 3. For example in Fig. 2 and Fig. 3, supposing the lines a and a' indicate the most frequent level which the heart pulse signal A and the uterine contraction signal B appears in six minutes.

The amplitude (the signal amplitude of heart pulse) b is shown in between the lowermost point of wave-form of said signal A and said line a, the delay time c is the distance from the uppermost point of wave-form of said signal B to the lowermost point of wave-form of heart pulse signal d indicates the recovery time which the wave-form of said signal A crosses the line a from the lowermost points, and e shows the time (the deceleration period) which the wave-form of said signal A crosses the line a descending and again crosses said line a ascending.

Further, f is the area occupied in the plane of the amplitude b by the wave-form of signal A within the period of deceleration e.

In such measuring patterns as mentioned above, the preceding amplitude b, the delayed time C, the recovery time d and the deceleration period e can respectively be calculated momentary data', (ie: momentary treatment parameters). On the other hand, abovementioned line a during the six minutes period and above mentioned fare called periodical treatment parameters which may be adjusted by the doctor in every six minutes from the starting point in the time of "to be calculated periodically". As a result the digital signal which shows the value of parameters a and f (Fig. 2 and Fig. 3) selected by the doctor, is sent continuously to the final judgement section 4dshown in Fig. 1.In this section 4d digital signal for each parameter b to e of said digital signals selected previously by the doctor is compared with the predetermined values therefor. Thus, the line a is positioned by the calculated values from the abovementioned momentary calculation point for each six minute period.

In other words, while monitoring a pregnant woman the totals of the line a and the area f in 4dare compared with the responding values selected by the doctor; the final judgement signal is transferred to the score calculating section 4f already mentioned above.

The relationship between a periodical parameter weighted by the doctor and the combined construction of the present invention is now clarified. In the parameter calculation section 4c, the most frequent appearance level (base line) a of the heart pulse signal A of the foetus during the measurement period is calculated. At the same time, the total area in every deceleration period e (a momentary treatment parameter) is calculated and a digital signal of this value is fed to the final judgement section 4d. Said 4dtransfers the final judgement signal, having finished the comparison, to the score calculating section 4f. The weight of the periodical treatment parameter selected by the doctor is compared in the score calculating section 4f in Fig. 1.

The "total score" acquired by adding such value to the weight of "the momentary treatment parameters" obtained from the 4c is supplied to said judgement section 4h in Fig.

1.

Thus, the final information is completed by addition of the total values together and by the integration of the corresponding weight in parallel in the section 4f. After the judgement of total score, 4h in Fig. 1 receives a digital signal of the total score sent from the score variable determination section 4i. "Thus the above mentioned total score sent from 4f" is compared with "said variable limit value of total score sent from said 4i".

When the detecting circuit detects a total score over said limit value in this 4h, an alarm signal is transferred to the alarm signal indication section 4j. The alarm signal may be a lamp and/or a buzzer which is actuated so that the doctor can obtain integrated information and a warning.

In Fig. 2 and Fig. 3 the relationship between the above mentioned data treatment section 4 (Fig. 1) and the periodical parameters may be considered as follows: if the established value b, is shown against the amplitude b of the heart pulse signal A, a signal b > b, is obtained (Fig. 2). The final judgement section 4d of that parameter (Fig.

1) outputs the final judgement signal calculated as described above toward the score calculation section 4f. If said b, is to be b2 larger than b the final signal is not passed from said 4d. Where the wave-form amplitude of heart pulse signal A, the deceleration period e (Fig. 2) and the delayed time c (Fig. 3) in the wave-form of the uterine contraction signal B, are respectively larger than the established values in the parameter b,, e, (Fig.

2) and C1 (Fig. 3) these final signals flow from 4d.

However, as the established value dt corresponding to the recovery time d shown in Fig.

3 is the greater, these final signals are acted on similarly to said d; if d is larger than d, and the parameters c and e are larger than the responding established value ct and et no final signal flows to the alarm. 4d outputs the final signals only when it calculates that a particular value has been exceeded.

Also, in example of Fig. 2, the base line a is shown within the area between the upper limit a2 and the lower limit a,. The final judgement signal of this parameter is not output, but the cumulative value Ef of area f in the wave-form of heart pulse signal A is over the established cumulative value < ;f, of that parameter, thus the final judgement signal from 4d is sent to the score calculation section 4f(Fig. 1).

Thus, the supervision of only a specified parameter is possible by adjusting the variable determination section 4g so as to acquire a total score which is over "the maximum limit value" mentioned above in relation to the determination section 41. When the final judgement signal which corresponds only to a certain parameter is transferred alone to the score calculation section 4f in Fig. 1 of this invention that parameter can be monitored alone.

According to the invention a doctor can vary and participate in the evaluation of given parameters based on a consideration of the individual differences and additional diseases of a pregnant woman and can acquire automatically information with which to direct his diagnosis.

Claims (20)

1. An obstetric device comprising a foetal heart rate detector, a uterine contraction detector, means for the conversion of signals from said detectors to a wave form representation, and including means for evaluating components of each of said wave forms to ascertain parameters thereof.

2. A device according to claim 1 wherein said conversion means for signals is an analoged digital transformer.

3. A device according to either of claims 1 or 2 wherein said means for evaluating components comprises: comparator means for comparing said components against a predetermined basal value for said component.

4. A device according to claim 3 wherein said basal value is manually set.

5. A device according to either of claims 3 or 4 wherein the comparator means includes means for comparing a signal from the foetal heart detector with a signal from the uterine contraction detector to provide an integrated component.

6. A device according to any one of the preceding claims 2 to 5 wherein a signal from the transformer can be fed via a data memory store to a parameter calculator.

7. A device according to claim 6 wherein a signal representative of a calculated parameter can be fed to a parameter comparator and wherein said parameter comparator has a secondary variable input for adjustment of basal parameter values.

8. A device according to claim 7 wherein the values obtained from the parameter comparator are summed, weighted, compared with a threshold value and fed to an alarm if said threshold value is exceeded.

9. A device substantially as hereinbefore set forth with reference to, and as illustrated in, any one of Figs. 1 to 3 of the accompanying drawings.

10. A diagnostic method which comprises monitoring a signal from a foetal heart rate detector, monitoring a signal from a uterine contraction detector, converting said signals to a wave form representation, and evaluating components of each separate wave form to ascertain the parameters thereof.

A A method according to claim 10 wherein said wave form is converted to a digital form.

12. A method according to either of claims 10 or 11 which comprises providing a basal value for a component, comparing a wave form component therewith and providing an output only if said component differs from said basal value by more than a predetermined amount.

13. A method according to any one of claims 10 to 12 which comprises evaluating a relationship between the wave form generated by the foetal heart rate detector and a wave form generated by the uterine contraction detector, to provide a component representative of said relationship.

14. A method according to any one of claims 10 to 13 including audible and visual alarm means.

15. A method substantially as hereinbefore set forth as illustrated in and with reference to Figs. 1 to 3 of the accompanying drawings.

16. A comparator circuit which comprises: means for monitoring a signal from a foetal heart rate detector, means for monitoring a signal from a uterine detector, means for converting said signals to a wave form representation, and means for evaluating components of each said wave form and measuring the parameters thereof.

17. A circuit according to claim 16 including an analogue to digital transformer.

18. A circuit according to either of claims 16 or 17 including variable means for providing a basal value for a component, and means for comparing the actual value of said component with said basal value.

19. A circuit according to any one of claims 16 to 18 including means for evaluating a relationship between a wave form generated by the foetal heart rate detector and a wave form generated by the uterine detector, and means providing a component representative of said relationship.

20. A comparator circuit substantially as hereinbefore set forth with reference to and as illustrated in Figs. 1 to 4 of the accompanying drawings.