US3171892A - Electronic apparatus for the observation of signals of biological origin - Google Patents

Description

March 2, 1965 Filed June 27,

PANTLE J. O. ELECTRONIC APPARATUS FOR THE OBSERVATION OF' SIGNALS OF BIOLOGICAL ORIGIN 2 Sheets-Sheet 1 March 2, 1965 J. o. PANTLE 3,171,892

ELECTRONIC APPARATUS FOR THE OBSERVATION OF SIGNALS OF BIOLOGICAL ORIGIN Filed June 27, 1961 2 Sheets-Sheet 2 United States Patent O 3,171,892 ELECTRONIC APPARATUS FOR THE OBSERVA- TION OF SIGNAIJS F BIOLOGICAL RIGIN Jorge Oitvani Pantle, 624 I. B. Blanco St., Montevideo, Uruguay Filed June 27, 196i, Ser. No. 120,045 Claims. (Cl. 179-1) This invention relates to an apparatus for the observation of signals of biological origin and more particularly to a device which enables to discriminate a certain type of signal with respect to other signals which appear simultaneously and try to confuse the observer.

In medical diagnosis it is of frequent practice to use as a source of data, certain manifestations such as acoustical, mechanical or electrical phenomena, bound to physiological functions of the human or animal organism.

When these manifestations are of such intensity or duration that they prevail over the background biological activity the observer usually does not iind any diiculty in establishing his diagnosis. On the other hand, when the desired signal is superimposed over a high background activity which tends tomake diiicult or even entirely prevent the task of collecting information, the observer will be faced with a difficult problem which he may not be able to solve. It also happens in many cases that the background biological activity has `a much higher intensity than the signal the diagnostician is interested in, in which case it is altogether impossible to arrive at any conclusion leading to a valid diagnosis.

One of the most typical examples where the above mentioned diculties are met is in the case of the continuous detection of fetal heart rate before and during labor. In this application, the signal whose frequency must be known for the diagnosis is made up of the fetal cardio complexes but these are usually of lower intensity than the maternal cardiac complexes which are also picked up at the same electrodes or microphones where the former ones appear.

The procedures or devices which were available up to now t-o the medical profession were unable to present them any valid data about the fetal heart rate because they could not distinguish between fetal and maternal cardio complexes or the otherwise high biological background activity made it impossible to recognize the fetal complex.

For these reasons, one object of this invention is to provide an apparatus which discriminates a certain desired signal from among a number of undesired signals the intensity of which may be higher than that or" the desired signal.

Another object of this invention is to offer the observer the possibility to monitor the fetal heart rate regardless of the interference that may be presented by the maternal cardiac signals.

Another object of this invention is to provide means for the instantaneous and continuous analysis of the electroencephalogram.

Another object of this invention is to provide an apparatus for distinguishing in an electroencephalogram certain waves or complexes which otherwise could not be done because of the presence of other interfering signals.

Another object of this invention is to provide an apparatus according to the above description for discrimination of the desired signal by means of easily adjusted manual controls.

Another object of this invention is to provide an apparatus as so far indicated, which discriminates biological signals of any nature on the basis of the length of the generated pulses.

ICC

Another object of this invention is to provide an apparatus according to the characteristics already indicated, which excludes all undesirable pulses.

In accordance with this invention, an apparatus is provided for the observation of biological signals. Said apparatus includes transducing means for converting said biologica-l signals into electrical signals; transmission means for said electrical signals including output means; and display means connected to said output means. Discriminating means are included in the transmission means for said electrical signals, responsive to the duration of said electrical signals.

In order to facilitate the comprehension of this invention some preferred embodiments will now be described in relationship to the accompanying drawings by way of example.

In the drawings:

FIGURE l is a block diagram of a preferred embodiment of the apparatus according to the present invention;

FIGURE 2 shows some of the waveforms which can be found in the apparatus schematically shown in FIG- URE l;

FIGURE 3 is a block diagram of a system for the discrimination of pulses as a function of their duration according to this invention;

FIGURE 4 shows the pulses which can be found at several points of the system of FIGURE 3 FIGURE 5 is likewise a block diagram of a system for the discrimination of pulses as a function of their duration, in accordance with this invention;

FIGURE 6 shows the waveforms corresponding to FIGURE 5;

FIGURE 7 is a block diagram of another system which has the same function as that of FIGURE 5;

FIGURE 8 shows the waveforms corresponding to the system of FIGURE 7;

FIGURE 9 is the block diagram o-f a system belonging to that part of the apparatus which eliminates undesirable pulses that occur in between desired pulses; and

FIGURE l0 shows the waveforms that correspond to the diagram of FIGURE 9.

With reference to FIGURE l; a selector switch 1 may select any pair from a plurality of input lines 2 each of which is connected to an individual pickup device. These pickup devices may be of an acoustic nature such as microphones adhered to different parts of the body or simple electrodes meant to pick up electrical signals on the organism. For instance, if it concerns taking the fetal heart rate, these electrodes may be placed in bands around the mothers abdomen. Each electrode is connected to the switch by means of conductors 2 permitting thereby to make the selection of the most adequate signal.

The signals (FIG. 2) that are captured, being mainly of very low intensity are fed to a low level amplifier 4 which amplifies them up to the proper level to drive the subsequent stages.

After being amplified in amplifier 4, the signals of waveshape 3 are fed to squaring stage 5 which includes transforming means that shape them into square waves. This process is carried out by well known methods commonly used in electronic enginering such as vacuum tube or transistor circuits saturated beyond a prefixed threshold level which can be set by external controls by the operator. It is also possible in this stage to set a minimum threshold level to exclude lower intensity signals which accordingly are not transformed into square waves, obtaining thereby a cleaner background by eliminating those signals which bear no relation with the desired signal and whose presence may only create undesirable responses at the subsequent stages of the machine. At the output of the squaring stage waveforms as shown at 6 of FIG- URE 2, will be found, where only those peaks have been transformed into square Waves which correspond to the fetal and maternal R waves and also someV strong interferences. The difference between these signals is here mainly expressed by their length. s

The output of the squaringstage is connected to duration discriminating stage 8 which discriminates these signals according to their duration. This discriminating stage eliminate-s all those pulses (see 6'), the duration of which is either shorter or longer than the preadjusted limit set by the operator, so that theoutput of this stage Waveshapes like 9 (FIGURE 2) will be found, which contain the desired pulses plus a few interfering signals of closely similar duration 10.

Waveshape 9 of the output of the duration discriminating stage S is fed to an inhibiting stage 11 which is so built thatV it rejects all signals which occur within a predetermined time interval immediately succeeding any signal received. In this way, by choosing the proper period for this time interval, it is possible to prevent Ithat inter-l tering -signals be transmitted between desired signals 7. Thus at last at the output of stage V11, a signal 12 will be obtained that includes only the desired pulses 12 separated from any disturbing interference.

The output of the inhibiting stage 11 is connected to display devices 13 which contain representing means for electrical signals which for this invention are to be interpreted as comprising any means `'whereby it is pos-r sible -to make sensorial manifestations of thesesignals,

such as an oscilloscope, a recording oscillograph, a pulse ratemeter, a frequency meter, a loudspeaker, an ear? phone, a warning light, a recorded tape or any other memory device for-on-line or olf-line reproduction."

By way of example, certain preferred embodiments will now be described as to the components which areV generically shown in the block diagram of FIGURE 1.

Supposing it is desired to record only those pulses the duration of which is shorter than a certain limit set by the operator, for the duration discriminating stage S, the layout shown in FIGURE 3 vcan be used, to which correspond the waveshapes shown in FIGURE 4.V The leading edge 14 of square'wave 15 delivered by stageS,

edge will produce a pulse 30 at the output of the gating vcircuit 28, in coincidence with itself.

Y A modication of this lat-ter system which from the flexibility operating viewpoint results in an improvement over the previous system, inasmuch it does not force the of which is set by the operator and it represents the lower gating limit. The same leadingw edge 14 also triggers simultaneously Va second monostable multivibrator 31 which delivers a square wave pulse 32v the` duration of which, as set by the operator, represents the upper gating limit. Gating circuit 33 has three inputs which are connected to the -squaring output of the squaring stage 5 and to the loutputs of first and second monostable'mul-tivibrators 29 and 31respectively, and it is so built that it be turned on by the lagging edge 34 of lower limit control pulse 30 and turned off by the lagging edge 35 of the upper limit control pulse 32. Furthermore, the gating circuit will respond to the lagging edge 19 of pulse 15, but only when this edge occurs during the ltime the gate is on, that is between the lagging edge 34 of lower limit control pulse 30 and the lagging edge 35 .of -the upper limit control pulse 32. Accordingly, 'if pulse 15 is of the correct duration, its lagging edge 19 will produce a pulse 20fat the output of gating circuit 33, in coincidence Vwith itself.

Within` the structure of this invention, as shown in FIGURE l, a suitable inhibition stage 11 for the transmission channel has been provided Vwhich constitutes triggers monostable multivibrator 16 which delivers a gating pulse 17 the duration of which is set by lthe operator. Said pulse 17 controls gatel 18 which will only operate while .this pulse is present.v Gate 18 is KVso designed thatv it will operatewith the lagging edge 19 of the desired pulse 15v but only if this lagging edge occurs during the time the gating pulse 17 is on. Accordingly, if pulse 15 has the correct duration, its lagging edge will produce another pulse Z0, preferably of square shape, at the output of gate 18, incoincidence with itself.

In order to extend the range-f of time discrimination, it is possibleito adopt another system which will discriminate at the duration discriminating stage 8 against signals Ithe duration of which is either longer or shorter than the desired signal. be constructed in accordance with the layout shown Vin FGURES 5 and'6. s

Leading edge 14 of pulse 15'coming from the squaring stage 5, triggers a monostable multivibrator 23 which delivers a square wave pulse 24 the duration of which is set `by the operator and' it represents the lower gating limit. Lagging edge 25 of this pulse24 triggers kmonov stable multivibrator `26', which `delivers another square Wave pulse'27, theduration of which is also set by the operator, and when itis added -to the duration of the preceding pulse 24, their sum represents the upper gating limit. Y A

Square wave pulse 27 controls gating circuit 28 which is operating only while pulse 27 is on- The gating circuit is so constructed that it responds -to the lagging edge 19 of pulse 1S but only when this lagging edge 19 occursY For this purpose stage 8 can an adequate ilter to be used in cases where periodicity or quasi-periodicity of the phenomena exists, in order to block the channel lduring the intervals where no or small probabilities may be present as to the generation of valid signals. The purpose of this Istage 11 is to avoid the transmission of signals which in spite of their being very much like the desired signal inl amplitude and duration, may not be considered valid on account of when they occur.

AV possible layoutfor stage 11 will now be described with reference to FIGURES 9 and 10.

The output of the duration discriminating stage 8 is connected to.. monostable multivibrator 36 which is triggered by the lagging edge 37 of pulse 2t) emerging from the discriminating stage 8, and produces a square wave pulse 38 disabling gating circuit 39 which is so built as to produce an output pulse when triggered by the leading edge 39v of pulse 20 Ibut only in theabsence of square wave pulse 38. Under these conditions, pulses 39 appear in response to the leading edges 39' of a following pulse only when the following pulse 20 occurs after a time limit longer than the length of pulse 38 immediately succeeding the previous pulse 20. In this way no output pulse will be produced during the blocking period in response to any input signal.

l claim: A

1. Electronic apparatus for use in investigating biological activity such as the fetal heartbeat superimposed upon extraneous backgroundrbiological activityincluding the maternal heartbeat :wherein the biological activity is represented substantially by signals in the form of at least two yintermingledy series of pulses ofdifferent periodicity and with each series having a different distinctive pulse width, lcompris-ing in combination, transducer meansffor generating electricalsignals corresponding to said two intermingled series of pulses, mean for -shaping the pulses into a sequence of square waves of a duration corre-` sponding to the durationof pulses in saidl signals, pulse duration discriminating means coupled lto-said shaping means to select only those pulses of a predetermined duration from said sequences of pulses to form a moditied series of pulses, inhibiting means coupled for receiving the modified series occurring within a predetermined time interval following a previous signal to thereby produce an output sequence of signals representative of one of said two intermingled series of pulses to the exclusion of the extraneous background activity.

2. Apparatus as dened in claim 1 wherein the pulse discriminating means includes adjustable means `for selecting said duration; and .the inhibiting means includes adjustable means for selecting the duration of said time interval.

3. Apparatus as dened in claim 2 wherein said discriminating means comprises a monostable multivibrator coupled to receive pulses from said pulse shaping means, and a gating circuit coupled to pass pulses responsive to the coincident input of said sequence of square waves and the output of said multivibrator.

4. Apparatus as dened in claim 2 wherein said discriminating means comprises a rst monostable multivibrator coupled to receive pulses from said pulse shaping means, a second monostable multivibrator coupled to receive output signals from the rst monostable multivibrator, and a gating circuit coupled to pass pulses responsive to the coincident input of said `sequence of square waves and the output of said second multivibrator.

5. Apparatus as defined in claim 2 wherein said inhibiting means comprises a monostable multivibrator coupled to generate square waves responsive to trigger pulses in the modied :series of pulses from the pulse duration discriminating means and a gating circuit coupled for inhibiting pulses in said modified series responsive to output square waves from the multivibrator.

References Cited in the le of this patent UNITED STATES PATENTS 2,522,551 Williams Sept. 19, 1950 2,552,013 Orpkin May 8, 1951 2,575,910 Mathes Nov, 20, 1951 2,985,828 Mason May 23, 1961 3,020,483 Losee Feb. 6, 1962 FOREIGN PATENTS 1,242,669 France Aug. 22, 1960

Claims (1)

1. ELECTRONIC APPARATUS FOR USE IN INVESTIGATING BIOLOGICAL ACTIVITY SUCH AS THE FETAL HEARTBEAT SUPERIMPOSED UPON EXTRANEOUS BACKGROUND BIOLOGICAL ACTIVITY INCLUDING THE MATERNAL HEARTBEAT WHEREIN THE BIOLOGICAL ACTIVITY IS REPRESENTED SUBSTANTIALLY BY SIGNALS IN THE FORM OF AT LEAST TWO INTERMINGLED SERIES OF PULSES OF DIFFERENT PERIODICITY AND WITH EACH SERIES OF PULSES OF DIFFERENT DISTINCTIVE PULSE WIDTH, COMPRISING IN COMBINATION, TRANSDUCER MEANS FOR GENERATING ELECTRICAL SIGNALS CORRESPONDING TO SAID TWO INTERMINGLED SERIES OF PULSES, MEANS FOR SHAPING THE PULSES INTO A SEQUENCE OF SQUARE WAVES OF A DURATION CORRESPONDING TO THE DURATION OF PULSES IN SAID SIGNALS, PULSE DURATION DISCRIMINATING MEANS COUPLED TO SAID SHAPING MEANS TO SELECT ONLY THOSE PULSES OF A PREDETERMINED DURATION FROM SAID SEQUENCES OF PULSES TO FORM A MODIFIED SERIES OF PULSES, INHIBITING MEANS COUPLED FOR RECEIVING THE MODIFIED SERIES OCCURRING WITHIN A PREDETERMINED TIME INTERVAL FOLLOWING A PREVIOUS SIGNAL TO THEREBY PRODUCE AN OUTPUT SEQUENCE OF SIGNALS REPRESENTATIVE OF ONE OF SAID TWO INTERMINGLED SERIES OF PULSES TO THE EXCLUSION OF THE EXTRANEOUS BACKGROUND ACTIVITY.

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