SU1680071A1 - Device for time selection of cardiac signals - Google Patents

Abstract

A device for the temporary selection of cardio signals is related to medical technology. The purpose of the invention is to improve the noise immunity and reliability of the results. The device comprises a selector 1, a key 2 and a driver 3 of the output signal, as well as voltage converters 8 and 14 - duration. A multistage resistor divider 5 voltage, a switching circuit B, an addition circuit 7, a subtraction circuit 13, an AND circuit 11, an OR circuit 12, an interference intensity analyzer 9, and the relationship between them are additionally introduced into the device, which allows adaptively changing the ratio analysis interval and guard interval, depending on the intensity of the noise accompanying the removal of the cardio signal, ie with increasing intensity of interference, increase the guard interval and decrease the analysis interval, and vice versa, and thereby increase the noise immunity and measurement accuracy. 1 hp ff, 3 ill. (Ls

Description

about

00 Oh

about

Xi

The invention relates to medical technology, and more specifically to devices for analyzing electrocardiograms, and can be used in rhythm-based cardiac analyzers.

The purpose of the invention is to improve the noise immunity and reliability of the results.

FIG. 1 shows a block diagram of a device for temporal selection of cardiovascular signals; in fig. 2 is a block diagram of the interference intensity analyzer; in fig. 3 - timing charts of signals, explaining the operation of the device.

The device contains serially connected amplitude selector 1 of R-teeth, key 2, output signal generator 3, serially connected transducer 4 cardiointerval-voltage, multi-stage resistive divider 5, switching circuit 6, addition circuit 7, first voltage-duration converter 8 ( guard interval generator) interference intensity analyzer 9, serially connected trigger 10, AND 11, OR circuit 12, serially connected subtraction circuit 13 and the second voltage-for transducer 14 efficiency (shaper analysis interval), the key 2 output is connected to the signal input of the converter 4 cardiointerval voltage, the first input of the trigger O, the second input of the OR circuit 12, the output of the amplitude selector 1 of the R-teeth is connected to the first input of the analyzer 9 interference intensity and the second input of the AND 11 circuit, the output of the OR 12 circuit is connected to the control input of the first voltage-duration converter 8, and the output of the converter 4 cardiointerval-voltage is connected to the first inputs of the addition circuit 7 and the subtraction circuit 13 , the first output of the noise intensity analyzer 9 is connected to the control input of the switching circuit 6, the second output of the noise intensity analyzer 9 is connected to the control input of the switch 2, and the output of the trigger 10 is connected to the control input of the cardiointerval-voltage converter, the output of the switching circuit 6 connected to the second input of the subtracting circuit 13, while the output of the first voltage-duration converter 8 is connected to the control input of the second voltage-duration converter 14, the output of which is connected to the second trigger input 10.

The analyzer 9 intensity of interference contains a serially connected circuit And 15, the counter 16 and the decoder 17 and

connected in series are a standby multivibrator 18, a trigger 19, and an AND circuit 20, the first output of the AND circuit 15 is the first input of the interference intensity analyzer 9, the input of the standby multivibrator 18, the second input of the AND circuit 20 and the second input of the AND circuit 15 are interconnected and the second input of the noise intensity analyzer 9, the output of the standby multivibrator 18 is connected to the control input of the counter 16, and the set of all output bits of the decoder 17 is the first output of the noise intensity analyzer 9 corresponding to the output the bit of the decoder 17 is connected to the signal input of the trigger 19, and the output of the circuit 20 is the second output of the analyzer 9 of the interference intensity.

A device for temporal selection of cardio signals operates as follows.

The registered cardio signal in the considered measurement cycle is fed to the input of the amplitude selector 1 of R-waves, the output of which, if the signal exceeds a certain threshold, forms a pulse of standard amplitude and duration (Fig. 3, plot Ui). This pulse, the passage through the switch 2, is fed to the signal input of the converter 4 of the cardiointerval-voltage. On the leading edge of the voltage pulse Ui, a constant voltage corresponding to the recorded cardio-interval (Fig. 3. Plot JJ4) is generated at the output of the output signal generator 3, and the next cardiointerval-voltage conversion cycle starts at its trailing edge. At the same time, the pulse from the output of switch 2, the passage through the circuit OR 12, is fed to the control input of the first voltage-duration converter 8. On the falling edge of this pulse at the output of the voltage-duration converter 8, a pulse is formed with a duration proportional to the voltage at its signal input (Fig. 3, plot Us). The duration of this pulse, in the absence of interference, is 0.8 ... 0, 9, the duration of the recorded cardiointerval. The specific value of the duration is determined depending on the physiological characteristics of the group of subjects.

The pulse from the output of the voltage-duration converter 8 is fed to the second input of the noise intensity analyzer 9, to the first input of which a signal is output from the amplitude selector 1 of the R-teeth. During the operation of this pulse, the signal from the second output of the analyzer 9 of the intensity of interference received at the control input of key 2 locks it, and in the analyzer 9 of the intensity of interference, the number of pulses 5 of which exceeds the pickup threshold of the amplitude selector 1 of the R-waves is counted.

Depending on the number of registered pulses, the corresponding line of the first output of the analyzer 9 10 of interference intensity appears, which is fed to the control input of the switching circuit 5. This signal is applied to the corresponding switch circuit 6 key, by means of which the output of the switching circuit 15 6 connects a part of the voltage from the output of the 4 cardioin, terval-voltage converter, corresponding to the number of pulses whose level exceeds the pickup threshold of the amplitude selector 1 R the teeth during the action of the pulse from the output of the former 8 of the guard interval, i.e. the number of interference pulses (Fig. 4. plot Ue).

The voltage from the output of the switching circuit 6 is fed to the second inputs of the addition circuit 7 and the subtracting circuit 13, the first inputs of which are supplied by the voltage from the output of the cardiointerval-4 converter 4. At the output of circuit 7 of addition 30, a voltage is formed, which is the sum of two voltages: a constant voltage proportional to the duration of the last recorded cardiointerval and a part of the same voltage 35 proportional to the intensity of the interference (Fig. 4, section U). Similarly, the voltage at the output of the subtracting circuit 13 is the difference of the same voltages (Fig. 4, plot 1) 1h). In accordance with this, the pulse duration from the output of the voltage-voltage converter 8 is increased by a certain amount proportional to the intensity of interference in the current analysis cycle (Fig. 4, plot Us), a 45 the pulse width at the output of the second voltage converter 14 the duration during which the presence of the R-wave is analyzed is reduced by the same amount (Fig. 4, plot (JA). By 50 this, in each measurement step, depending on the intensity of the interference, such a ratio is established between the duration of the protective The analysis interval minimizes the total detection error. This is achieved by selecting the nominal values of the elements of the multistage resistive divider 5. When the signal at the output of the converter 8 is voltage-duration, the key 2 is opened, and the voltage-duration converter 14 is started the output of which forms a pulse during which the next R-wave is expected. The duration of this pulse, subject to the absence of interference, is chosen to be 0.4 ... 0.3 times the duration of the previous cardiointerval.

The pulse from the output of the key 2 is fed to the signal input of the converter 4 cardiointerval-voltage. On the leading edge of this pulse, a constant voltage corresponding to the registered cardio-interval is formed at the output of the cardiointerval-voltage converter, and a new cardiointerval-voltage conversion cycle starts on its trailing edge.

At the same time, the same pulse, the passage through the circuit OR 12, is fed to the control input of the voltage-duration converter 8. The pulse generated at the output of the converter 8 voltage-duration, arrives at the second input of the analyzer 9 interference intensity, its leading edge dropping all the analyzer nodes to the initial state. For the duration of this pulse, the signal from the second output of the analyzer 9 of the interference intensity, which arrives at the control input of the key 2, blocks it.

Thus, the key 2 is open for a period of time determined by the leading edge of the pulse of the second imaging unit 14 of the analysis interval and the instant of occurrence of the R-wave of the cardio signal (Fig. 4, plot Lte).

The recorded pulses corresponding to the R-teeth of the cardio signal from the output of the key 2 are fed to the input of the imaging unit 3 of the output signal.

If during the pulse from the output of the protective interval generator 8, the number of pulses from the output of the amplitude selector 1 of the R-wave, which is greater than or equal to a certain threshold number, for example 4, arrives at the first input of the interference intensity analyzer 9, then after the end of the pulse from the output of the converter 8, the voltage-duration of the signal from the second output of the analyzer 9 interference intensity continues to hold the key 2 in the locked state. With the rising edge of the pulse from the output of the voltage-duration converter 8, the voltage-duration converter 14 is triggered, the output of which goes to the second input of the trigger 10. Since the number of interference pulses has exceeded the threshold level in the current analysis cycle, the analysis is not performed.

the key 2 is closed, and "during the signal at the second input of the trigger 10, its first input does not receive a pulse from the output of the key 2. The output signal of the voltage-to-voltage transducers 14, with its falling front, triggers the trigger 10 to the opposite state (Fig. 4, plot Uio). The signal from the trigger output 10 is fed to the control input of the converter 4 of the cardiointerval – voltage, fixing a voltage proportional to the last recorded cardiointerval at its output and to the first input of the I 11 circuit.

The next impulse from the output of the amplitude selector 1 R-teeth is fed to the second input of the circuit AND 11 and further, the passage through the circuit OR 12, goes to the control input of the converter 8, voltage-duration, start it. The impulse from the output of the voltage-duration converter 8 is fed to the second vhddd analyzer 9 of the interference intensity, dropping all the nodes of the battery into its initial state with its leading edge. The falling edge of the mmpus from the output of the voltage-to-voltage converter 8 is triggered by the voltage-duration converter 14, producing a pulse, during which the appearance of the R-wave is analyzed. The impulse corresponding to the R-wave from the output of the key 2 is fed to the signal input of the converter 4 cardiointerval-voltage. On the trailing edge of this pulse, the next voltage-duration conversion cycle begins, and the trigger 10 is reset.

Since the formation of a constant voltage at the output of the converter 4 cardiointerval-voltage is carried out along the leading edge of the voltage pulse Ui, the voltage at its output corresponds to the last recorded cardiointerval. If, in the current measurement cycle, the number of interference pulses exceeds a threshold level, then the analysis of the appearance of the R-wave is not performed, and the R-tooth is not recorded.

Thus, a device for temporal selection of cardio signals provides for the formation of a time interval for analyzing the presence of the R-wave of a cardio signal associated with the magnitude of the previous cardio interval and the level of intensity of the noise accompanying the cardio signal in the current measurement cycle. If the intensity of the interference exceeds a certain threshold level, then the output of the device is blocked and the signal in this cycle is not recorded, which increases the noise immunity and reliability of the results.

Claims (2)

1. A device for temporal selection of cardiosignals, containing a series-connected amplitude selector, a key, an output signal shaper, and the key output is also connected to a cardiointer-shaft-voltage converter and a trigger, as well as two voltage-duration converter, the output of the first of which is connected to the input of the second voltage-duration converter, characterized in that, in order to improve the noise immunity and reliability of the results, a multi-stage voltage divider, switching circuit, addition circuit, circuit I are additionally introduced into it , OR circuit, subtraction circuit, and intensity analyzer interferences, the cardio-shaft-voltage converter being connected via a multistage voltage divider connected in series, the switching circuit and the addition circuit are connected to the first input of the second voltage-duration converter, to the second input of which through a series-connected AND and OR circuit there is a trigger output connected also to the second input of the converter cardiointervap-voltage, the output of which is connected to the second input of the addition circuit and the first input of the subtraction circuit, with the third input of which is connected to the output of the switching circuit, and the output of the circuit The subtraction is connected to the second input of the first voltage-duration converter, the output of which is connected to the second trigger input, the output of the second voltage-duration converter is connected to the first input of the interference intensity analyzer, the second input of which is connected to the output of the amplitude selector and the second input of the And circuit, and the first output is connected to the second key input, the second output is connected to the second input of the switching circuit. 2. The device according to claim 1, characterized in that in the noise intensity analyzer, the first circuit AND has a serial connection, the counter and the decoder, as well as the sequentially connected waiting multivibrator, the trigger and the second circuit AND, the first input of the first circuit AND is the first input of the noise intensity analyzer and connected to the input of the standby multivibrator and the second input of the second AND circuit, the second input of the first And circuit is the second input of the noise intensity analyzer, the output of the standby multivibrator is connected to the control input ode counter the set of all output bits of the decoder is the first output of the interference intensity analyzer, the corresponding output bit of the decoder is connected to the trigger input of the trigger, and the output of the second AND circuit is the second output of the interference intensity analyzer.