DE2109179B2 - DEVICE FOR DETECTING SHAPED PULSES OF A PULSE TRAIN - Google Patents

Description

das Fjr ^ uen ^ raterf (16) * ftlr the ¹ Ereeu ^

two $ t ^

So the frequency component range, which essentially includes: only, for non-changed (normal) pulses; comprises characteristic frequencies, and that i | enn energy determiners (IiB, 0) energy comparison fields (18) for comparing the; Energy content of the sifted out pulse levels | Yt4 U3) with each other and a sweat discriminator (20) assigned! Jjiiid, usury threshold discriminator (20) generates an output signal, e.g. to trigger an alarm, \ 30 if the energy difference exceeds a specified limit value;

2. device; according to claim 1, characterized in that for the determination of extrasystoles in the electrocardiogram the frequency filter (15) for generating the first pulse train / l / i) to frequencies in the range of 3 Hz and the frequency filter (16) for generating the second pulse train ( Ui) is tuned to frequencies in the range of 35 Hz,

3. Apparatus according to claim 1 or 2, characterized in that at least one (16) of the two frequency filter means, for. B. a compensator (17) or an adjustable voltage divider,

* ypr or downstream are used to compensate for the ^^ ngiSlciilA ^ icb 7 or S, thereby ^ • ä ^^ llpllllaer ^ Em evaluation ^ l ^^ n ^ mZeirl ^ rduct gMi ^ OTsSf ^ piSene; a same-

jffWm ^ lie EkÖ-Pulse, a ncnicraiiuiu »» Jng Λ ^ λ V. "" ■ -> ■■ ι ■ -r- Bandfflteii (2 ^, iläsiauf for QRS complexes significant frequencies are matched as well as an R-period discruninatbr (25) contains.

10 Device according to claim 3 and 9, with an adjustment amplifier adjustable by means of an integration amplifier, (characterized in that the integration amplifier (30) each time it occurs a voltage signal at the output of the R-wave discriminator (25) is preferably blocked for its duration.

11 Device according to claim 6 and 9, characterized by a reset controlled by the output signals of the R-wave discriminator (25)

icreis {34 35. 36) for the NuUpunktstellung the low-pass voltage (19) in each case immediately after the supply of its output signals (U ₄ ) to the downstream threshold discriminator (20).

The invention relates to a device for

vo, or downstream are fürdenA «oer ggen ^ n ^^ SSSS ^^ SSt differing ^ attenuation of the pulse train / U ₁ ) 45 ^^, Srdifenm, with at least two

Frequency filters, the two separate pulse trains with frequencies from the original pulse train from two different frequency component ranges of the

U,! _! - i ^ rC.l.fili. «. oiirfciohAn HIiH with PltlPItl

through the filters (15,16).

4. Apparatus naoh claim 3, characterized in that the center (17) on a Durchschhittspultyp are adjustable. . «Biwuu« ».». »- · ———.

5> Device according to iiinem of claims 4, 50 original: sieve pulse train, and with one marked by the fact that the frequency filters contain the energy content of the (15,16) an analog computer (18) connected downstream is determined for the seventh Pülsfölgen the formation of the difference between the amplitude devices of the type mentioned are valuable

.. "· ..._ ^ -: __. I ^ v /> ii. \ Aids in connection with the diagnosis,

utid ^J "· ——...__

metering device (19), e.g. B. low pass, for the sliding Summation of the analog computer output signal during one preferably the duration of one Normal pulse corresponding time duration is connected downstream.

7. Device according to one of claims 1 to 6, characterized by a front on the pulse signal path or pulse indicator (23 to 27) connected behind one of the two frequency filters (15, 16), the a voltage signal each time a pulse occurs generated which by a delay means, e.g. B. monostable flip-flop (26), so delay in time Methods. A first method is that in each case the amplitude of a QRS complex is one

ECG pulse train measured and possibly also the time is determined during which the measured amplitude exceeds a predetermined amplitude limit value. Such a method assumes that the failed QRS complexes are consistently

have larger amplitudes than normal. However, since this is not always the case, this is it Measurement method relatively uncertain. Another method is the QA duration

BestigunLj) the measurement certainty with such a method hl ^ g1 ^ dji§ei, depends on how exactly the individual t values can be measured. Since the jpes electrocardiogram ^ j ^^^ it is relatively difficult to find the zero points that are always correct. That Finding ^ the * sought zero crossings is also also made difficult by the fact that an electrocardiogram Variety ypn - for the actual measurement unin ^ eressanteitK - lvfull passages with one drjtten ^ le & ode ^ will each.die von einerii QRS-Kom-ρΐεκ enclosed area, determined this method seoJLyorauCidaß diejyqn a runaway QRS-Comp «i £ ej> Utete ^ Curve area is always larger than that of a normal QRS ^ complex. However, there are too often; overran QRS complexes that do not have this property -exhibit. With two other methods, ^ i ^ iils ^ die] (amplitude of the QR ^ complexes and in addition either the QA time or the area enclosed by the QRS complexes is determined Such combination methods have the disadvantage compared to the partial methods that the technical The effort is correspondingly large and measurement errors are still relatively frequent. Finally is still a method known in which the R-R interval in a Large number of individual time segments and the permissible amplitude value for each time segment is detected. The division of the interval can can also be adapted to a slow change in the mean value of the heart rate. To Devices working with such a method also give only inadequate measurement results, because the shape criteria used for each time segment are simply chosen.

The object of the invention is to provide a device for detecting shape-changed pulses of a pulse train indicate what the disadvantages of the after above-mentioned methods does not have working devices, d. H. which clearly identify of shape-changed pulses, especially of width-enlarged ones Extrasystoles, guaranteed

The task is specifically carried out with a device of the initially mentioned type according to the invention achieved in that the frequency filter for generating the first pulse train is matched to such a frequency component range of the original pulse train that both for non-shape-changed (normal) and for fonnyerähderae Pulse characteristic frequencies includes the frequency filter for the generation of the second pulse train, however, only on such a frequency component range that is essentially only for Unchanged (normal) pulses include characteristic frequencies, and that the energy meter Energy comparison means for comparing the energy contents of the two filtered pulse trains with one another and a threshold discriminator are assigned, which threshold discriminator has an output signal, z. B. to trigger an alarm, generated when the energy difference exceeds a specified limit

The invention is based on the knowledge that shape-changed pulses of a pulse train have a different energy frequency spectrum than normal pulses of the same train. For example, the proportion of high frequencies in broadly expanded extrasystoles in an electrocardiogram is much lower than in normal QRS complexes. By evaluating z. B. high and low frequency components of the pulse train can then be determined, oh wide-spread extrasystoles or only normal QRS complexes are present. A device of the type mentioned is already known from US Pat. No. 317 i 406. However, this US Pat. Connection of the EKG to the individual filters by switch) is broken down into individual energy frequency bands. These individual frequency bands are recorded one after the other on the paper strip of a recorder. By optically comparing the individual bands with the entire ECG, based on the examining doctor's practical experience, conclusions can be drawn about the possible presence of shape-changed pulses in the ECG. In the present invention, although the identification of shape-changed pulses, as in the subject of US Pat. No. 3,171,406, is done by evaluating the energy-frequency spectrum of the pulse sequence to be examined; In contrast to the subject of the US-PS, however, the subject of the present invention does not subdivide the entire pulse sequence into individual successive energy-frequency bands and the identification is not done by comparing the individual successive bands with the entire energy-frequency spectrum of the pulse sequence. In the subject matter of the present invention, a total of only two pulse trains with the properties listed above are specifically filtered out of the original pulse train and the energy content especially of these two trains is compared with one another. In contrast to the US patent, the comparison of the energy content is not done purely optically on the paper strip of a pen, but automatically by an electronic comparison device and thus independent of the experience of the examining doctor. The device according to the present invention also shows the presence of shape-changed pulses automatically and immediately while the EKG is being taken from the patient (alarm signal), while in US Pat Pulse sequence, based on the recording can be determined. The automatic identification of shape-changed pulses achieved with the present subject matter of the invention thus prevents, to a high degree, misdiagnoses which, in conventional devices, cannot be eliminated with certainty due to the optical identification based on experience and due to the large number of partial spectra to be evaluated.

The US-PS 33 44 233 already describes a device for the investigation of Signals by means of two filters and energy comparison. However, this device is only used for examination of human language in the sense of recording and displaying sound phenomena separated by depth and high sound frequency components. Accordingly, the filters are only a low-pass filter a high pass, the low pass all sound frequency components below the cutoff frequency of!, 2 kHz and the high-pass filter lets through all sound frequency components above 1.2 kHz for further processing. the The energy content of these broad, non-overlapping frequency bands are then compared with one another

IO

and give a measure of the relative difference in energy at high and low speech frequencies.

As already indicated several times, the present subject matter of the invention is in contrast for this purpose, however, a device for detecting shape-changed pulses especially in the electrocardiogram of a patient. The frequency filters are two bandpass filters, one of which is only open such a narrow frequency component range of the original EKG pulse train is matched that Frequencies characteristic of both non-shape-changed (normal) and shape-changed pulses (z. B. approx. 3 Hz), while the second frequency filter however, is only tuned to such a frequency component range that is essentially only for not Shape-changed (normal) pulses, characteristic frequencies (e.g. approx. 35 Hz) include the energy comparison means According to the present invention, only the energy content of these are then used for comparison filtered frequency bands. Furthermore, the energy comparison means a threshold discriminator associated with an output signal, e.g. B. to trigger a Alarms generated when the energy difference exceeds a set limit. Alarm devices are related to devices Acquisition and processing of EKG pulse sequences in particular is also already provided by US Pat. No. 33 52 300 already known Here, however, the alarm is only triggered if the duration of a number of consecutive R waves in the ECG have a preset value This means that the alarm is not given if z. B. width-extended pulses in the EKG occur, but only when the heart rate is a critical value for the patient exceeds In the device according to US-PS 33 52 300 so there are differences in the type of Alarm triggering (different tasks). Fundamental differences arise accordingly but also in structure, since the device according to US-PS 33 52 300 neither frequency filters nor energy detectors with structure and mode of operation of the type according to the invention

Further advantages of the invention emerge from the following description of an exemplary embodiment based on the drawing in conjunction with the subclaims.

F i g. 1 shows a normal EKG complex. The complex can be divided into three parts, namely a first part related to the atrial activity of the heart, which in the diagram shows a wave ^ ₀

35

40 curves 7 and 8 according to FIG. 3. The spectrum of curve 7 is represented by the course of curve 9 and the spectrum of curve 8 by the course of curve 10. As can be seen, the spectra of the two curves 7 and 8 according to FIG. 3 have considerable differences. These differences can be used as a criterion for identifying failed pulses. If, for example, two appropriately matched filters are used to filter out two frequency bands 11 and 12 selected as shown in FIG low, but relatively high in the presence of failed complexes. By compensating for the different attenuation of the pulse train by the filter, it can even be achieved that the energy difference in normal QRS complexes becomes zero, so that an energy difference occurs only in the case of failed QRS complexes. The energy difference that occurs in each case can be measured. If it exceeds a predetermined limit value, an alarm signal is generated

5 shows the basic circuit diagram of a device according to the invention operating according to such a criterion. According to Fig. 5, the EKG signal i / recorded by EKG electrodes on the patient's body (not shown) is fed to a preamplifier 13 (differential amplifier) a tape filter 16 upstream equalization amplifier 17 existing measuring unit adapted the bandpass filter 15 has a center frequency of about 5 Ha, the band filter 16 has a center frequency of about 35 Hz. the compensation amplifier 17 serves to compensate for the different attenuation of the ECG signal u \ in the two Filter branches.

_C1 °! ^s _< ^ ^us 8 ^to 8 ^ss « ^{lial U} * (low-frequency component of the EKG signal CA) of the filter 15 and the output signal U ₃ (high-frequency component of the EKG signal U _x ) of the mother 16 are fed to an analog computer 18, which the Difference U * -Uf between the amplitude squares of the filter output signals CJi and U ₃ forms (two summing elements for forming the sums U ₂ + U ₃ and U ₂ - U ₃ and a multiplier for multiplying the sums). The signal Uf- U ₃ * is mfiiieri · Dcr..Z _W ccC \ ieS above ■ hd tifaddT filter QÜVdraicn fU ^ i

present, a monostable flip-flop 29 connected downstream of the logic link 21 responds and generates an alarm. If a READ pulse is present, but the voltage signal at the output of the threshold discriminator is zero, a monostable multivibrator 28 connected downstream of the logic element 22 is triggered and the presence of a normal QRS system is displayed. The READ pulse is generated from the output signal U _{2 of} the band filter 15 after rectification in a rectifier arrangement 23, filtering in a low-pass filter 24, comparison in a comparator 25 and, after a time delay, in a monostable multivibrator 26 with a downstream control device 27 (time reference circuit)

The regulation of the compensation amplifier 17 in the sense of an adaptation of the two filter branches can take place automatically as a function of the output signal t / _{4 of} the low-pass filter 19 via an integration amplifier 30. The control of the compensation amplifier 17 is done in such a way that when QRS complexes representative of the patient occur, the signal i / 4 at the output of the low-pass filter 19 becomes zero. The control of the equalization amplifier 17 can also be carried out after switching over the switch 31 by hand via a resistance potentiometer 32.

To prevent during the seizure of a Pulse the measuring process is disturbed by a change in the balance of the two filter branches the integration amplifier 30 via its input HOLD during one of the duration of the QRS complex corresponding time blocked The blocking process is carried out by the comparator 25 of the time reference circuit initiated. The duration of a blocking is determined by the duration of a monostable flip-flop 33 generated pulse

In order to ensure the best possible summing properties of the low-pass filter 19, the low-pass filter 19 must have a have a low cut-off frequency. So with such a filter a summed QRS wave at high Heart rate does not interfere with the following QRS wave, a reset circuit is provided for the low-pass filter 19, the the output of the low-pass filter as a function of the output signal of the comparator 25 via the monostable Flip-flops 33 and 34, the controllers 33 and 36 and via the controller input RESET to zero potential switches after a QRS complex has been summed. It should be noted that the delay time of the The monostable multivibrator 26 is shorter than the sum of the delay times of the monostable multivibrator 33 and 34. The signal passed from the low-pass filter 19 to the threshold discriminator 20 can thus be read, before the aforementioned zeroing takes place

The average level matching amplifier 14 mentioned at the beginning can be selected automatically from the Output of the band filter 15 (depending on the signal i / 2) or after switching the switch 37 from Hand controlled via a resistance potentiometer 38.

F i g. 6 shows the course over time of the most important ones in the basic circuit diagram according to FIG. 5 occurring voltages. The voltage U \ (^ corresponds to the EKG signals occurring at the input of the preamplifier 13. The voltages U2 (t) or lh (t) result at the outputs of the band filters 15 or 16, the voltage i / ₄

1 }

(t) corresponds to the output signal - (IZ ₂ ² - U ₃ ² ) dt

τ J

¹ 0

of the low-pass filter 19. The voltage Us (t) corresponds to the alarm signal generated at the output of the monostable multivibrator 29 when a failed QRS complex occurs.

The invention is not limited to the embodiment described, it can be used within the framework of the following claims can be modified as required.

For this purpose 3 sheets of drawings

Claims (1)

_ Occurrence of ellehdiskriminators (20) 14 | ^ output signals ^ Β ^^ β ^^ ϊ ^ ¹ ^^ J ^ m ■■■ MäMmm ^^ ΪΡ ^ ϋ ^^ SRain signal * ® - ^^^^ S ^ raaBJ ^ töfr ^ u ^ gai ^ gnals »Fuögs ^ äi: (21); ünd only at ^ '^ ■' - ■ • '•' "" • ^ ■ ^ panriungssignals des