WO2015000312A1 - 自动体外除颤仪及其前端测量系统和测量方法 - Google Patents

自动体外除颤仪及其前端测量系统和测量方法 Download PDF

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Publication number
WO2015000312A1
WO2015000312A1 PCT/CN2014/074066 CN2014074066W WO2015000312A1 WO 2015000312 A1 WO2015000312 A1 WO 2015000312A1 CN 2014074066 W CN2014074066 W CN 2014074066W WO 2015000312 A1 WO2015000312 A1 WO 2015000312A1
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Prior art keywords
sampling
signal
digital
channel
impedance
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PCT/CN2014/074066
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English (en)
French (fr)
Inventor
王启
陈大兵
申宁
李传林
岑建
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Shenzhen Mindray Bio Medical Electronics Co Ltd
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Shenzhen Mindray Bio Medical Electronics Co Ltd
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Priority to EP14819571.2A priority Critical patent/EP3017844B1/en
Publication of WO2015000312A1 publication Critical patent/WO2015000312A1/zh
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
    • A61N1/39—Heart defibrillators
    • A61N1/3904—External heart defibrillators [EHD]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/30—Input circuits therefor
    • A61B5/307—Input circuits therefor specially adapted for particular uses
    • A61B5/308—Input circuits therefor specially adapted for particular uses for electrocardiography [ECG]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
    • A61N1/39—Heart defibrillators
    • A61N1/3925—Monitoring; Protecting

Definitions

  • the present application relates to a medically applied defibrillator, and more particularly to an automatic external defibrillator and a front end measuring system and measuring method thereof.
  • Automatic External Defibrillator (Automatic External Defibrillator, AED) is a widely used defibrillation device that is accepted by more and more people because of its simple operation and small size. In developed countries in Europe and America, AED is widely used in public places such as stations, airports, and schools.
  • the more commonly used defibrillation method is biphasic defibrillation.
  • the electrode sheet is first contacted with a suitable part of the patient's body (for example, the human body), and the AED treatment system needs to collect and analyze the treatment-related information to determine whether or not electric shock treatment is required. Specifically, it includes: 1. Measuring the impedance information of the electrode piece and the human body contact circuit, determining whether the electrode piece and the human body are in good contact, whether the patient has motion, etc. by detecting the body impedance, and serving as a reference for the subsequent biphasic electric shock defibrillation adjustment parameter. 2. Detecting whether the patient has a built-in pacemaker.
  • the Pace marker of the pacemaker is synchronously transmitted to the analysis algorithm. 3, through the treatment of the electrode sheet ( 2-lead II) Collecting the electrocardiogram of the human body (Electrocardiograph, ECG) Waveform data, combined with the above analysis of contact impedance, pacing (Pace) signal and ECG waveform data, can determine whether the patient is ready for defibrillation rhythm. If a defibrillation rhythm is detected, the charge and discharge device is activated to treat the patient. The detection performed before the start of the electric shock treatment of the patient by the charging and discharging device is generally called the front end measurement of the defibrillator. It can be seen that accurately measuring the signals of the body impedance, the pace mark, the ECG waveform data and the like is the successful defibrillation treatment. The essential.
  • the body impedance, Pace signal, and ECG waveform data have different requirements on the sampling rate and accuracy of the signal during detection and analysis.
  • Different sampling rates and accuracy require the use of AD converters with different sampling rates and sampling accuracy.
  • the sampling rate and accuracy are a pair of contradictory parameters, that is, the AD converter with high sampling rate has low precision; the AD converter with high precision has a low sampling rate. This allows the detection of body impedance, Pace signal and ECG waveform data to be measured in three separate channels to meet the required sampling rate and accuracy.
  • the AED front-end measurement system includes three measurement channels, namely an ECG measurement channel 13, a body impedance measurement channel 14, and a Pace pulse detection channel 15, and then three sampling data are respectively sent to the processor MCU.
  • the processor MCU calculates and analysis in 16 when the defibrillation rhythm is detected and the body impedance measurement is in the defibrillation range (the electrode pads are reliably connected to the human body).
  • the control start charging circuit 18 charges the energy storage device 17. After the charging is completed, the operator is prompted to discharge, and then the human body 10 is discharged through the discharge circuit 12 and the electrode sheet 11 to complete the treatment.
  • the body impedance measurement adopts the carrier driving method, that is, the small signal is applied to the human body, and the impedance of the human body can be obtained by performing the conditioning and A/D conversion on the carrier component obtained by dividing the body.
  • the Pace detection is implemented by a hardware comparator, which usually includes preamplifier, filtering (high pass, low pass, band pass), post stage amplification, and dual limit comparison.
  • the ECG sampling circuit is realized by AC coupling and two-stage amplification. It often includes input stage defibrillation protection and filtering, preamplification, high-pass filtering and post-amplification.
  • a front end measurement system for an automatic external defibrillator comprising:
  • a carrier driving circuit configured to amplify the generated alternating current signal, and output the processed two alternating current signals to the two electrode sheets;
  • the sampling circuit includes at least one sampling channel, wherein at least one sampling channel is a common sampling channel, and the shared sampling channel is a measurement channel shared by at least two different tested quantities, the measured quantity being a patient impedance, an ECG Any one of waveform data and a Pace pulse, the shared sampling channel comprising a differential amplifier and an analog to digital converter, two inputs of the differential amplifier being coupled to the two electrode pads, respectively, an output of the differential amplifier
  • An analog-to-digital converter is coupled to the analog-to-digital converter, wherein the input analog signal is sampled by a set sampling rate, converted into a digital signal, and outputted, and the sampling rate of the analog-to-digital converter is greater than or equal to the sharing The largest of the sampling rates required for at least two of the tested quantities corresponding to the sampling channel; and
  • a processor for generating an AC signal and outputting to a carrier driving circuit, the processor being coupled to the sampling circuit to control the sampling circuit and receive a digital sampling signal output by the sampling circuit for the shared sampling channel
  • the output digital sampling signal is divided into at least two paths, and signal extraction processing is performed according to the required sampling rate and accuracy requirements.
  • An automatic external defibrillator comprising a front end measurement system as described above.
  • a front end measurement method for an automatic external defibrillator includes:
  • Detecting signals on the two electrode sheets and performing data sampling During data sampling, at least two different tested quantities share one sampling channel, and the measured quantities are in patient impedance, ECG waveform data, and Pace pulses. Or a sampling rate of the shared sampling channel is greater than or equal to a maximum of sampling rates required by at least two tested quantities corresponding to the shared sampling channel; and
  • the digital sampling signal output by the shared sampling channel is received by the processor, the digital sampling signal is divided into at least two paths, and signal extraction processing is performed according to the required sampling rate and accuracy requirements.
  • the front end measurement system and the measurement method when sampling the original data, the analog-to-digital converter is oversampled, and then the oversampled signals are respectively set according to the set ratio in subsequent processing.
  • the sampling value is extracted, so that two or three of the three measurement channels of the patient impedance, the ECG signal and the Pace signal can be shared, thereby reducing the hardware in the sampling circuit and thereby reducing the hardware.
  • the device dispersion problem and node interference problem bring about the accuracy of the instrument measurement results.
  • Figure 1 is a schematic view showing the structure of a defibrillator
  • FIG. 2 is a schematic structural view of a front end measurement system of a defibrillator according to an embodiment
  • FIG. 3 is an equivalent circuit diagram of an electrode sheet and a human body contact according to an embodiment
  • FIG. 4 is a schematic diagram of signal extraction processing performed by a processor of an embodiment on sampled data
  • FIG. 5 is a specific equivalent circuit diagram of an electrode sheet of an embodiment in contact with a human body
  • FIG. 6 is a flow chart of a front end measurement method of an automatic external defibrillator according to an embodiment
  • FIG. 9 is a schematic structural view of a front end measurement system with a calibration circuit according to an embodiment.
  • the defibrillator is applied to the human body (i.e., the patient is a human) as an example. Those skilled in the art should understand that the defibrillator can also be applied to other animal patients.
  • Human body impedance measurement generally uses a measurement method in which an AC small signal is applied to the human body. Since the AC signal has certain requirements on the frequency of the signal, it cannot be too small. Clinically, if the frequency is large, the damage to the human body will be smaller. Considering the actual system implementation and data processing, an AC signal of 32 kHz can be applied to the human body.
  • the sampling rate is 256 ksa/s.
  • the accuracy of the impedance measurement is not high, and generally 12bit to 13bit is sufficient.
  • the sampling accuracy is required to reach 5uV/lsb, so the accuracy should reach 20bit or more. Since the AED treatment system mainly focuses on the components of the ECG signal in the range of 0.5 to 40 hz, the sampling rate is set to 10 times, that is, 500 sa/s is sufficient.
  • the pace detection channel For the pace detection channel, consider the width of the pace pulse to be identified: 0.1ms ⁇ 2ms, and the amplitude is 2mv ⁇ 700mV. To ensure that at least one point can be sampled within a 0.1ms pulse, the sample rate is set to at least 10ksa/s. The sampling accuracy of the pace detection channel requires recognition of 2mv signals, so the sampling accuracy must be at least 200uV/lsb, that is, the accuracy is 16bit.
  • the patient impedance measurement has the highest sampling rate requirement, but the accuracy requirement is the lowest, while the ECG signal measurement has the highest sampling rate requirement, but the highest accuracy requirement, pace pulse The measurement requires the lowest sampling rate and the accuracy requirement is centered.
  • two or three of the three measurement channels of patient impedance, ECG signal, and Pace signal share a channel. Since the most important device in the channel is the analog-to-digital converter (ADC), sharing the channel means that the analog-to-digital converter must be shared, but for the analog-to-digital converter, only one sample can be used at the same time. Rate and accuracy sample the analog signal, and for the same analog-to-digital converter, the sampling rate and accuracy are a pair of contradictory parameters, so the shared analog-to-digital converter is difficult to satisfy more than two samples at the same time. And precision requirements.
  • ADC analog-to-digital converter
  • the analog-to-digital converter is first satisfied to meet the highest requirement of the sampling rate among the plurality of tested quantities, that is, oversampling is used, and then the oversampled signals are respectively sampled according to the set ratio in subsequent processing. The value is extracted, and the sampling rate is selected to meet the sampling rate requirement of each tested quantity. At the same time, the sampling accuracy of the oversampled signal is adjusted during the processing to meet the sampling accuracy requirements of each tested quantity.
  • the patient impedance measurement and the Pace pulse measurement can share one sampling channel, while the ECG waveform measurement uses one sampling channel alone.
  • patient impedance measurements and ECG waveform measurements can share a single sampling channel, while Pace pulse measurements use a single sampling channel.
  • Either ECG waveform measurement and Pace pulse measurement share one sampling channel, while patient impedance measurement uses one sampling channel alone.
  • the sampling rate of the analog-to-digital converter in the sampling channel is the same as the larger one of the sampling rates required for the two detected quantities, the extraction processing of the larger sampling rate may be omitted in the processor.
  • the patient impedance, the ECG waveform data, and the Pace pulse share the same sampling channel.
  • the AED front end measurement system includes two electrode sheets 21, a carrier drive circuit 22, a sampling circuit 23, and a processor 24.
  • the AC signal output of processor 24 is coupled to the input of carrier drive circuit 22.
  • the carrier driving circuit 22 divides the alternating current signal into two paths having different phases, and is coupled to the two electrode sheets 21 through the two output ends, respectively.
  • the sampling circuit 23 includes a sampling channel shared by the patient impedance measurement, the ECG waveform measurement, and the Pace pulse measurement, and the two input ends are respectively connected to the two electrode sheets 21.
  • the output of sampling circuit 23 is coupled to processor 24 via data interface 25 for the acquisition of patient impedance, ECG waveform data, and Pace pulse initial data.
  • the electrode sheet 21 may be various cylindrical conductors or sheet conductors.
  • carrier drive circuit 22 includes a bandpass filter 222, an amplifier 223, and a delay amplifier 224.
  • the input of bandpass filter 222 is coupled to the carrier signal output of processor 24.
  • the outputs of bandpass filters 222 are coupled to the inputs of amplifier 223 and delay amplifier 224, respectively.
  • the outputs of the amplifier 223 and the delay amplifier 224 are respectively coupled to the two electrode sheets 21.
  • the phase of the AC signal output by the delay amplifier 224 is delayed by a set phase from the AC signal output by the amplifier.
  • the delay amplifier 224 can be an inverting amplifier.
  • the AC signal output by the inverting amplifier is opposite to the phase of the AC signal output by the amplifier, and the signals opposite to each other are applied to the human body 20 to cancel each other.
  • the sampling circuit 23 includes a differential amplifier 232 and an analog to digital converter 233.
  • the two inputs of differential amplifier 232 are coupled to two electrode pads 21, respectively, and the output is coupled to analog to digital converter 233.
  • the differential amplifier 232 converts the human body's differential analog signal into a single-ended analog signal output, which is beneficial for suppressing the human body common mode signal.
  • the amplification factor of the differential amplifier 232 is controlled between 2 and 4, a polarization voltage range of +/- 1 V can be provided.
  • the supply voltage of the differential amplifier 232 can be further increased.
  • the analog-to-digital converter 233 samples the input analog signal at a set sampling rate, converts it into a digital signal, and outputs it to the processor 24.
  • the analog-to-digital converter of the sampling circuit can adopt successive approximation modulus (Successive approximation register, SAR) converter implementation, ie SAR ADC.
  • SAR successive approximation modulus
  • the analog to digital converter 233 is set to oversample at the time of sampling, and the set sampling rate is greater than or equal to the maximum sampling rate required for patient impedance measurement, ECG waveform data measurement, and Pace pulse measurement.
  • the patient impedance measurement requires the highest sampling rate, so the sampling rate of the analog-to-digital converter 233 is greater than or equal to the sampling rate required by the patient impedance measurement.
  • the sampling rate of analog to digital converter 233 is set to the sampling rate required for patient impedance measurements, such as 256 kSa/s.
  • the processor 24 controls the sampling timing of the analog to digital converter 233 through the data interface 25, for example, providing a clock signal to control the sampling rate of the analog to digital converter 233, and the like.
  • the sampling circuit 23 further includes two input protection circuits 231, which are respectively connected between the two input ends of the sampling channel differential amplifier 232 and the corresponding electrode pads for absorbing defibrillation.
  • the high voltage energy prevents the low voltage device in the sampling circuit from being damaged during defibrillation.
  • the specific implementation of the input protection circuit can be conducted by grounding the gas discharge tube to conduct the defibrillation AC high voltage to the earth.
  • the specific implementation of the input protection circuit can also use the high-energy pulse resistor and the diode clamp to limit the input voltage to the set potential.
  • the processor 24 generates an AC signal of a certain characteristic through a built-in or external digital-to-analog converter.
  • the AC signal can be a sine wave or a square wave.
  • the sine wave can avoid aliasing interference of the carrier signal on the ECG signal path, so it is preferably a sine wave signal.
  • the AC signal is filtered by the band pass filter 222 and amplified by the amplification circuit to be driven to the human body.
  • the human body itself is equivalent to an impedance, and there is a contact impedance between the electrode sheet 21 and the human body, and the equivalent circuit thereof is as shown in FIG.
  • Z1 and Z2 are the equivalent output impedance of the carrier drive circuit, that is, the contact impedance between the electrode piece and the human body.
  • Z3 is the impedance to be measured, that is, the impedance of the human body itself.
  • the alternating signal generates a voltage division signal at both terminals of the electrode sheet 21 by applying the electrode sheet to the human body.
  • the sampling circuit 23 is used for conditioning and collecting the partial pressure signal generated after the AC signal passes through the human body. Specifically, the original signal on the electrode sheet is detected by direct current coupling. In order to obtain higher resolution and sampling accuracy, the ADC with higher sampling speed is used to oversample the front-end data, and then the signal extraction processing is performed.
  • the sampling rate of the ADC is generally 12bit ⁇ 13bit, and the sampling rate is above 500kSa/s. Since the carrier frequency of the AC signal is generally 20 kHz to 30 kHz, the bandwidth of the sampling circuit 23 is set to about 40 kHz to ensure that the impedance signal can be sampled.
  • the ADC sample rate is set to 500kHz, which allows the carrier signal to be fully digitized.
  • the processor 24 After receiving the digital sampling signal output by the sampling circuit 23, the processor 24 performs signal extraction processing on the digital sampling signal in three ways according to the requirements of the sampling rate and the accuracy of the patient impedance measurement, the ECG waveform data measurement, and the Pace pulse measurement.
  • the processor 24 includes a patient impedance calculation processing module, an ECG waveform data extraction processing module, and a Pace pulse processing module. After the processing, the impedance measurement value, the ECG detection raw data, and the Pace detection raw data are respectively obtained.
  • the patient impedance calculation processing module includes a band pass filtering unit 241 for band-pass filtering the digital sampled signal output from the shared sampling channel, and a calculating unit 242 for calculating the patient impedance based on the filtered digital sampled signal.
  • the calculation unit 242 outputs the patient impedance value to the external lead state determination unit 243, and performs an analysis judgment as to whether the electrode piece and the patient connection are good.
  • the patient impedance calculation processing module first performs band pass filtering on the digital sampled signal to filter out noise interference.
  • the center frequency of the filtering bandwidth can be 30KHz.
  • the patient impedance is then calculated based on the filtered digital sampled signal.
  • the patient impedance is obtained, for example, by calculating the peak-to-peak value of the waveform.
  • the calculated patient impedance is then analyzed, for example, by comparing the calculated patient impedance to a given range to determine if the electrode sheet is in good contact with the human body.
  • the method for determining whether the electrode sheet is in good contact with the patient is that the processor 24 outputs two AC signals of different frequencies, and determines whether the electrode sheet is in good contact with the patient according to the signal collected by the sampling circuit.
  • the equivalent circuit of the electrode sheet 21 in contact with the patient is shown in FIG. 3, and the specific equivalent circuit thereof is shown in FIG. 5.
  • Z1 (Z2) consists of a series of R1 (R3), C1 (C3), and R2//C2 (R4//C4).
  • R1 (R3) is the defibrillation pulse energy absorption resistor.
  • C1 (C3) is an AC coupling capacitor that prevents DC coupling to the human body and causes damage to the human body.
  • R2//C2 (R4//C4) is the contact impedance of the electrode sheet and the human body, and R5 is the patient's chest impedance. In the actual clinical environment, the R2//C2 (R4//C4) part is often affected by poor contact between the electrode and the human body (skin dryness, bumpy road surface, etc.), which may result in a large impedance measurement or direct reporting loss.
  • R2//C2, R4//C4 will change accordingly.
  • the carrier frequency of the AC signal exceeds a certain value, the influence of the RC network composed of R2//C2 and R4//C4 on the impedance measurement of the human body is basically negligible.
  • the electrode sheet 21 electrode plate
  • the values of the R2//C2 (R4//C4) network are small and substantially fixed. At this time, the high-pass cutoff frequency is high, and two different frequency carrier drives are measured.
  • the impedance values will be basically the same.
  • the value of the R2//C2 (R4//C4) network is large or fluctuating, and the corresponding high-pass cutoff frequency is small, and different carrier frequencies are used at this time.
  • the measured impedance values will vary greatly. It can be seen from the above analysis that by comparing the two measured impedance values by the AC signal driving at different frequencies, the contact state of the external lead can be obtained in more detail, and the alarm information is provided.
  • the Pace pulse processing specifically includes: performing second low-pass filtering on the digital sampled signal to limit the bandwidth to within 2 kHz, and extracting the sampled value according to the Pace sampling rate based on the filtered digital sampled signal, and reducing the sampling rate to 10 Ksa by extraction. A value above s. Thereby Pace detects the raw data.
  • the Pace pulse processing module includes a second low pass filtering unit 244 for low pass filtering the digital sampled signal output from the shared sampling channel, and a Pace pulse based on the filtered digital sampled signal.
  • a second decimation unit 245 that measures the required sampling rate for sampling value extraction, and a second decimation unit outputs Pace detection raw data to the Pace detection raw data analysis unit 246.
  • the ECG waveform data extraction process specifically includes: performing first low-pass filtering on the digital sampled signal to limit the bandwidth to within 30 Hz to ensure the system signal-to-noise ratio, based on the filtered digital sampling.
  • the signal is sampled according to the ECG sampling rate, and the sampling rate is reduced to 500 sa/s. Thereby the ECG detection raw data is obtained.
  • the ECG waveform data extraction processing module includes a first low pass filtering unit 247 for low pass filtering the digital sampled signal output by the shared sampling channel, and a filtered digital sampled signal according to the ECG waveform measurement
  • the first sampling unit 248 that performs sampling value extraction at the required sampling rate, the first extraction unit outputs ECG detection raw data to the ECG detection original data analyzing unit 249.
  • the impedance calculation processing module, the ECG waveform data extraction processing module, and the Pace pulse processing module may be implemented by separate hardware or by software.
  • the processor determines if it is appropriate to use the shock therapy and, if appropriate, controls subsequent charging and discharging.
  • the driving voltage amplitude of the AC signal is increased as much as possible, and the amplification factor and the supply voltage of the amplifier and the delay amplifier are configured to satisfy the following conditions: 1.
  • the current flowing through the patient's body is less than the safety current. ; 2, the input sampling channel signal will not cause the sampling channel to saturate.
  • Superimposing the signal of a certain characteristic on the sampling signal can eliminate the influence of the ADC's own conversion error (INL, DNL, etc.) during oversampling, and further improve the effect of oversampling.
  • the front-end measurement system by oversampling the original data, and then filtering and extracting the over-sampled data in subsequent processing, the over-sampled data becomes conformed to each tested quantity.
  • the sampling rate and accuracy required data so that a variety of tested quantities can share a single sampling channel.
  • the above defibrillator front-end measurement system reduces hardware, further reducing hardware-to-hardware connection nodes, thereby reducing interference introduced by the nodes.
  • the instrument can be reduced by the dispersion of hardware, and the experiment proves that the accuracy of the measurement results of the instrument is improved.
  • the volume of the instrument is correspondingly reduced, and the cost is correspondingly reduced.
  • a front end measurement method of an automatic external defibrillator includes the following steps:
  • S20 Detecting signals on two electrode sheets and performing data sampling.
  • the tested quantity is any one of patient impedance, ECG waveform data, and Pace pulse.
  • the sampling rate of the shared sampling channel is greater than or equal to the largest of the sampling rates required by the at least two tested quantities corresponding to the shared sampling channel.
  • the digital sampling signal outputted by the shared sampling channel is received by the processor, and the digital sampling signal is divided into at least two paths, and the signal extraction processing is performed according to the required sampling rate and accuracy requirements.
  • the defibrillator when the defibrillator is self-tested, if the test load is not removed, the defibrillator will enter the AED mode after being turned on, and the front end data will be automatically collected. Since the front end of the electrode sheet 21 is connected to the test load, the defibrillator recognizes that the outside is connected to the human body, resulting in an erroneous analysis result that may result in delayed treatment.
  • the power-on self-test is used to identify whether the defibrillator is connected to the test load. When the external test load is used, it is driven by two different frequency AC carrier signals, and the measured impedance values are basically the same.
  • the external test load identification includes the following steps:
  • Step S101 after detecting the power-up signal of the defibrillator or the instruction for identifying the external test load, the processor outputs an AC signal of the first frequency;
  • Step S102 sampling waveform data based on the first frequency from the electrode sheet
  • Step S103 calculating a first impedance value based on the sampled data
  • Step S104 outputting an alternating current signal of a second frequency, the second frequency being different from the first frequency
  • Step S105 sampling waveform data based on the second frequency from the electrode sheet
  • Step S106 calculating a second impedance value based on the sampled data
  • Step S107 calculating an absolute value of the difference between the first impedance value and the second impedance value, and determining whether the absolute value is less than the set threshold. If yes, the defibrillator is considered to be externally connected to the test load.
  • the set threshold is a relatively small value, such as 10 ⁇ . If the absolute value of the difference between the two measurements is less than the set threshold, then the defibrillator is considered to be externally connected to the test load, and step 108 is performed. Otherwise, if the absolute value of the difference between the two measurements is greater than or equal to the set threshold, then the defibrillator is considered to have no external test load and normal testing can be performed.
  • step 108 the instrument is externally connected to the test load.
  • the operator can use the defibrillator normally after the test load is removed.
  • the external test load identification and the patient impedance test can be judged together, and the flowchart thereof is as shown in FIG.
  • the processor After detecting the power-on signal of the defibrillator or identifying the external test load, the processor outputs an AC signal of the first frequency.
  • step S105 determining the magnitude of the first impedance value, when the first impedance value is greater than 3k ohms, the end of the detection, reporting the lead-off; when the first impedance value is less than 3k ohms, proceeds to step S106;
  • the impedance value is usually found based on the sampling voltage value and the corresponding curve of the sampled voltage value and the impedance, but due to the drift of the parameters of the various devices of the system, the actual impedance will be based on the sampled voltage value at the sampling voltage.
  • the impedance values found on the corresponding curves of the values and impedances are different. Therefore, in the present embodiment, a calibration circuit 26 is further included. As shown in FIG. 9, the calibration circuit 26 includes a switch 261, a first calibration resistor 262, and a second calibration resistor 263.
  • the two inputs of switch 261 are coupled to the outputs of two input protection circuits 231, which are coupled to both ends of first calibration resistor 262 or to both ends of second calibration resistor 263 according to control. Specifically, the first calibration resistor 262 and the second calibration resistor 263 have different resistance values.
  • the switch 261 can be a double pole switch or a processor controlled multiplexer.
  • switch 261 When calibration is required, switch 261 is coupled to first calibration resistor 262, which produces an alternating current signal applied to first calibration resistor 262 while sampling the original signal to obtain a first sampled voltage value. Switch 261 is then coupled to second calibration resistor 263, which produces an alternating current signal applied to second calibration resistor 263 while sampling the original signal to obtain a second sampled voltage value. A corresponding curve of the original sample value and the impedance stored by the defibrillator is updated by using the obtained first sampled voltage value and the second sampled voltage value.
  • the measured sample voltage value and the impedance are approximately linear.
  • the relationship between the sampled voltage value and the impedance exhibits a certain curve, and two curves are obtained by respectively connecting the first calibration resistor and the second calibration resistor. Click to establish a relationship between the measured impedance value and the sampled voltage value.

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Abstract

一种自动体外除颤仪的前端测量系统、自动体外除颤仪和测量方法，通过对原始数据进行采样时，先使模数转换器进行过采样，然后在后续处理时对过采样的信号分别按照设定的比率进行采样值提取，从而可实现将患者阻抗、ECG信号和Pace信号三个测量通道中的两个或三个共用一个采用通道，因此上述自动体外除颤仪的前端测量系统可减少测量系统中的硬件，并进而减少了因硬件多而带来的器件分散性问题和节点干扰问题，提高了仪器测量结果的准确性。

Description

自动体外除颤仪及其前端测量系统和测量方法
【技术领域】
本申请涉及医疗上应用的除颤仪，尤其涉及一种自动体外除颤仪及其前端测量系统和测量方法。
【背景技术】
自动体外除颤仪（Automatic External Defibrillator, AED）是一种广泛使用的除颤设备，它因为操作简单、体积小等优点被越来越多的人所接受。在欧美发达国家，AED广泛应用于车站、机场、学校等公共场所。
目前较为常用的除颤方法是双相波除颤。在除颤治疗之前，首先将电极片与患者身体（例如人体）的合适部位接触，AED治疗系统需对治疗相关的信息进行采集并分析，得出是否需要电击治疗。具体包括：1、测量电极片和人体接触回路的阻抗信息，通过检测人体阻抗判断电极片和人体是否接触良好、病人是否有运动等，同时作为后续双相波电击除颤调整参数的参考。2、检测患者是否存在有内置起搏器，当检测到患者有内置起搏器时，将起搏器的Pace标记同步传送给分析算法。3、通过治疗电极片（ 2-lead II ） 采集人体的心电图（Electrocardiograph, ECG）波形数据，综合上述对接触阻抗、起搏（Pace）信号和ECG波形数据的分析结果，可确定患者是否准备好，是否为可除颤节律。若检测到除颤节律，则启动充放电装置对患者进行治疗。在启动充放电装置对患者进行电击治疗之前进行的检测通常称为除颤仪前端测量，可以看出，精确测量人体阻抗、pace标记、ECG波形数据等信号并进行分析是除颤治疗是否成功的关键。
由于在检测和分析过程中，人体阻抗、Pace信号和ECG波形数据对信号的采样率和精度的要求各不相同。不同的采样率和精度，要求使用具有不同采样率和采样精度的AD转换器。而对于AD转换器而言，采样率和精度是一对相互矛盾的参数，即采样率高的AD转换器，其精度不高；精度高的AD转换器，其采样率不高。这使得检测人体阻抗、Pace信号和ECG波形数据必须分成三个独立的通道进行测量，以符合各自要求的采样率和精度。如图1所示，AED前端测量系统包括三个测量通道，分别为ECG测量通道13、人体阻抗测量通道14和Pace脉冲检测通道15，然后三路采样数据分别送入处理器MCU 16中进行计算和分析，当检测到可除颤节律并且人体阻抗测量值在可除颤范围（电极片已可靠连接到人体）时，处理器MCU 6控制启动充电电路18给储能装置17充电，充电完成之后，提示操作者进行放电，然后通过放电电路12和电极片11对人体10进行放电，完成治疗。
目前，接触阻抗、Pace信号和ECG波形数据的检测方案如下：
人体阻抗测量采用载波驱动法，即对人体施加交流小信号，通过对人体上分压得到的载波分量并进行调理、A/D转换可得到人体的阻抗。
Pace检测采用硬件比较器实现，通常包括前级放大、滤波（高通、低通、带通）、后级放大、双限比较等部分。
ECG采样电路采用交流耦合，两级放大的结构实现。常包括输入级除颤保护及滤波、前级放大、高通滤波及后级放大等部分组成。
但这种三个测量通道独立使用的方案得出的结果准确性还有待提高。
【发明内容】
基于此，有必要提供一种能够提高仪器测量结果的准确性的自动体外除颤仪、自动体外除颤仪的前端测量系统和测量方法。
一种自动体外除颤仪的前端测量系统，包括：
两个电极片；
载波驱动电路，用于对产生的交流信号进行放大，并输出处理后的两路交流信号至所述两个电极片；
采样电路，至少包括一个采样通道，其中至少一个采样通道为共用采样通道，所述共用采样通道为对应的至少两种不同的被测试量共用的测量通道，所述被测试量为患者阻抗、ECG波形数据和Pace脉冲中的任一种，所述共用采样通道包括差分放大器和模数转换器，所述差分放大器的两个输入端分别耦合到所述两个电极片，所述差分放大器的输出端耦合到所述模数转换器，所述模数转换器对输入的模拟信号经设定采样率采样后转换为数字信号并输出，所述模数转换器的采样率大于或等于所述共用采样通道对应的至少两种被测试量所要求的采样率中的最大者；及
处理器，用于产生交流信号并输出到载波驱动电路，所述处理器耦合到所述采样电路，以控制所述采样电路并接收所述采样电路输出的数字采样信号，针对所述共用采样通道输出的所述数字采样信号分成至少两路，并按照所述被测试量对采样率和精度的要求进行信号提取处理。
一种包括如上所述的前端测量系统的自动体外除颤仪。
一种自动体外除颤仪的前端测量方法，包括：
通过与患者身体合适部位接触的两个电极片向患者施加载波信号；
检测所述两个电极片上的信号并进行数据采样，在数据采样过程中，至少两种不同的被测试量共用一个采样通道，所述被测试量为患者阻抗、ECG波形数据和Pace脉冲中的任一种，所述共用采样通道的采样率大于或等于所述共用采样通道对应的至少两种被测试量所要求的采样率中的最大者；及
通过处理器接收所述共用采样通道输出的数字采样信号，将所述数字采样信号分成至少两路，并按照被测试量对采样率和精度的要求进行信号提取处理。
在上述自动体外除颤仪、其前端测量系统和测量方法中，对原始数据进行采样时，先使模数转换器进行过采样，然后在后续处理时对过采样的信号分别按照设定的比率进行采样值提取，从而可实现将患者阻抗、ECG信号和Pace信号三个测量通道中的两个或三个共用一个采用通道，因此可减少采样电路中的硬件，并进而减少了因硬件多而带来的器件分散性问题和节点干扰问题，提高了仪器测量结果的准确性。
【附图说明】
在附图中，类似的附图标记表示相同的、功能上类似的和/或结构上类似的元件。应该理解，这些附图仅用于描绘各具体实施例，而不应被认为是对范围的限制。
图1为除颤仪的结构示意图；
图2为一实施方式的除颤仪前端测量系统的结构示意图；
图3为一实施方式的电极片和人体接触的等效电路图；
图4为一实施方式的处理器对采样数据进行的信号提取处理示意图；
图5为一实施方式的电极片和人体接触的具体的等效电路图；
图6为一实施方式的自动体外除颤仪的前端测量方法的流程图；
图7为一实施方式的外接测试负载识别步骤的流程图；
图8为另一实施方式的外接测试负载识别步骤的流程图；及
图9为一实施方式的带有校准电路的前端测量系统结构示意图。
【具体实施方式】
下面通过具体实施方式结合附图对本发明作进一步详细说明。以下说明时以除颤仪应用于人体（即患者为人）为例进行说明，本领域技术人员应当理解，除颤仪还可以应用于其他动物患者。
在除颤仪前端系统对患者阻抗、ECG波形数据和Pace脉冲进行检测和分析时，虽然数据来源可以都从电极片获得，但三者对于采样数据的采样率和精度有不同的要求。人体阻抗测量一般采用交流小信号施加到人体的测量方法。由于是交流信号对信号的频率有一定要求，不能太小。临床证明，频率大的话对人体的伤害会小一些。考虑到实际系统实现及数据处理，可选用32kHz的交流信号施加到人体。为了保证32kHz的信号能够基本不失真的采样下来，一般需要至少8倍的采样率，即采样率为256ksa/s。但阻抗测量部分对精度要求不高，一般12bit到13bit就足够。对于ECG测量通道，根据ECG算法分析的要求，采样精度要求达到5uV/lsb，所以精度要达到20bit以上。由于AED治疗系统主要关注ECG信号在0.5~40hz范围内的成分，所以采样率定为10倍，即500sa/s即已足够。对于pace检测通道，考虑到要识别的pace脉冲的宽度为：0.1ms~2ms，幅度为：2mv~700mV。为保证在0.1ms的脉冲内至少能采样一个点，采样率至少设定为10ksa/s。pace检测通道的采样精度要求能识别2mv的信号，所以采样精度至少要能达到200uV/lsb，即精度就要达到16bit。可见，在患者阻抗、ECG信号和Pace信号三个测量通道中，患者阻抗测量对采样率要求最高，但对精度要求最低，而ECG信号测量对采样率要求居中，但对精度要求最高，pace脉冲测量对采样率要求最低，对精度要求居中。
在一实施方式中，将患者阻抗、ECG信号和Pace信号三个测量通道中的两个或三个共用一个采用通道。由于在采用通道中，最重要的器件就是模数转换器（ADC），共用采用通道即意味着必然共用模数转换器，但对于模数转换器而言，其同一时间只能以一种采样率和精度对模拟信号进行采样，并且对于同一个模数转换器，其采样率和精度是一对相互矛盾的参数，因此共用的模数转换器难以同时满足两个以上的被测试量采样率和精度的要求。在本实施例中，先使模数转换器满足共用的多个被测试量中采样率的最高要求，即采用过采样，然后在后续处理时对过采样的信号分别按照设定的比率进行采样值抽取，抽取后使采样率符合每个被测试量的采样率要求。同时在处理过程中对过采样信号的采样精度进行调整，使其符合每个被测试量的采样精度的要求。在其他实施例中，患者阻抗测量和Pace脉冲测量可以共用一个采样通道，而ECG波形测量单独使用一个采样通道。或者患者阻抗测量和ECG波形测量可以共用一个采样通道，而Pace脉冲测量单独使用一个采样通道。或者ECG波形测量和Pace脉冲测量共用一个采样通道，而患者阻抗测量单独使用一个采样通道。当采样通道中模数转换器的采样率与两个被检测量要求的采样率中较大者相同时，在处理器中可省略对该采样率较大者的抽取处理。
请参考图2，在一实施方式中，在除颤仪前端测量系统包括该前端测量系统中，患者阻抗、ECG波形数据和Pace脉冲共用同一个采样通道。AED前端测量系统包括两个电极片21、载波驱动电路22、采样电路23和处理器24。处理器24的交流信号输出端与载波驱动电路22的输入端连接。载波驱动电路22将交流信号分为相位不同的两路，通过两个输出端分别对应耦合到两个电极片21。采样电路23包括患者阻抗测量、ECG波形测量和Pace脉冲测量共用的一个采样通道，其两个输入端分别对应连接到两个电极片21。采样电路23的输出端通过数据接口25连接到处理器24，用于完成患者阻抗、ECG波形数据和Pace脉冲最初数据的采集。
电极片21可以为各种圆柱形导体或片状导体。
在一实施例中，载波驱动电路22包括带通滤波器222、放大器223和延迟放大器224。带通滤波器222的输入端耦合到处理器24的载波信号输出端。带通滤波器222的输出端分别耦合到放大器223和延迟放大器224的输入端。放大器223和延迟放大器224的输出端分别对应耦合到两个电极片21。延迟放大器224输出的交流信号的相位相比放大器输出的交流信号延迟一设定相位。具体地，延迟放大器224可以为反相放大器。反相放大器输出的交流信号与放大器输出的交流信号相位相反，相位相反的信号施加在人体20上后其对人体的作用可相互抵消。
在一实施例中，采样电路23包括差分放大器232和模数转换器233。差分放大器232的两个输入端分别耦合到两个电极片21，输出端耦合到模数转换器233。差分放大器232将人体差分的模拟信号转换为单端的模拟信号输出，有利于抑制人体共模信号。当差分放大器232的放大倍数控制在2~4之间时，可以提供+/-1V的极化电压范围。为了提高差分放大器232的共模抑制比和极化电压范围，可以进一步提高差分放大器232的供电电压。模数转换器233对输入的模拟信号经设定采样率采样后转换为数字信号并输出至处理器24。采样电路的模数转换器可采用逐次逼近型模数 （Successive approximation register，SAR）转换器实现，即SAR ADC。模数转换器233在采样时设定为过采样，其设定的采样率大于或等于患者阻抗测量、ECG波形数据测量和Pace脉冲测量所要求的最大采样率。其中，患者阻抗测量要求的采样率最大，因此模数转换器233的采样率大于或等于患者阻抗测量要求的采样率。为简化处理器24的后续处理，模数转换器233的采样率设定为患者阻抗测量要求的采样率，例如256ksa/s。处理器24通过数据接口25控制模数转换器233的采样时序，例如提供时钟信号控制模数转换器233的采样率等。
在一实施例中，采样电路23还包括两个输入保护电路231，两个输入保护电路231分别连接在采样通道差分放大器232的两个输入端和对应的电极片之间，用于吸收除颤高压的能量，防止采样电路中的低压器件在除颤时损坏。输入保护电路的具体实现方式可以采用气体放电管接地的方式，将除颤的交流高压传导到大地。输入保护电路的具体实现方式也可以采用高能脉冲电阻和二极管嵌位的方式，将输入电压限定在设定的电位。
上述除颤仪前端测量系统的工作流程如下：
处理器24通过内置的或者外接的数模转换器产生一定特征的交流信号。交流信号可以采用正弦波或者方波，采用正弦波可避免载波信号对ECG信号通路造成混叠干扰，因此优选为正弦波信号。
交流信号经带通滤波器222滤波后经过放大电路放大后驱动到人体。当电极片21和人体接触后，人体自身相当于一个阻抗，电极片21和人体之间存在接触阻抗，其等效电路如图3所示。其中Z1和Z2为载波驱动电路的等效输出阻抗，即电极片和人体之间的接触阻抗。Z3为被测量阻抗，即人体自身的阻抗。交流信号通过施加电极片到人体后，在电极片21的两个端子产生分压信号。
采样电路23用于进行交流信号通过人体后产生的分压信号的调理和采集。具体地，采用直流耦合的方式检测电极片上的原始信号。为了得到更高的分辨率和采样精度，选用具有较高采样速度的ADC对前端数据进行过采样，后续进行信号提取处理。ADC采样率一般为12bit~13bit，采样率在500kSa/s以上。由于交流信号的载波频率一般为20kHz~30kHz，因此采样电路23的带宽设置为40kHz左右，以保证能对阻抗信号采样。ADC采样率设置为500kHz，这样可以完整的将载波信号进行数字化。
处理器24接收到采样电路23输出的数字采样信号后，按照患者阻抗测量、ECG波形数据测量和Pace脉冲测量对采样率和精度的要求对数字采样信号分三路进行信号提取处理。处理器24包括患者阻抗计算处理模块、ECG波形数据提取处理模块和Pace脉冲处理模块。处理后分别得到阻抗测量值、ECG检测原始数据和Pace检测原始数据。
如图4所示，对于患者阻抗的计算处理模块，由于前端的采样率符合患者阻抗测量要求的采样率，因此不需要对数字采样信号进行采样值抽取处理。患者阻抗计算处理模块包括用于对共用采样通道输出的数字采样信号进行带通滤波的带通滤波单元241，和基于滤波后的数字采样信号计算患者阻抗的计算单元242。计算单元242输出患者阻抗值至外部导联状况判断单元243，进行电极片和患者连接是否良好的分析判断。患者阻抗计算处理模块首先对数字采样信号进行带通滤波，滤除噪声干扰。滤波带宽的中心频率可以为30KHz。然后基于滤波后的数字采样信号计算患者阻抗。例如通过计算波形的峰峰值得到患者阻抗。然后对计算所得的患者阻抗进行分析，例如将计算所得的患者阻抗和给定范围进行比较，从而确定电极片和人体是否接触良好。在一实施例中，判断电极片与患者是否接触良好的方法为：处理器24输出两种不同频率的交流信号，并根据采样电路采集的信号判断电极片与患者是否接触良好。电极片21与患者接触的等效电路如图3所示，其具体等效电路如图5所示。其中Z1(Z2)由R1(R3)、C1(C3)、R2//C2(R4//C4)的串联组成。R1(R3)为除颤脉冲能量吸收电阻。C1(C3)为交流耦合电容，用于防止直流耦合到人体，对人体构成伤害。R2//C2(R4//C4)为电极片和人体的接触阻抗，R5为患者胸阻抗。在实际临床环境中，R2//C2(R4//C4)部分经常会受到电极片和人体接触不良（皮肤干燥、路面颠簸等）的影响，这样会导致阻抗测量值偏大或者直接报导联脱落而导致除颤治疗的延误，并最终导致急救失败。对于不同的接触程度（接触良好、接触不良等），R2//C2，R4//C4会随之变化。当交流信号的载波频率超过一定值后，由R2//C2以及R4//C4组成的RC网络对人体阻抗测量的影响基本可忽略。当电极片21（电极板）和人体接触良好时，R2//C2（R4//C4）网络的值均很小且基本固定，此时高通截止频率较高，两种不同频率载波驱动测得的阻抗值会基本一致。当电极片21（电极板）和人体接触不良或人体运动时，R2//C2（R4//C4）网络的值很大或有波动，对应的高通截止频率很小，此时采用不同载波频率测得的阻抗值会相差很大。由以上分析可知，通过不同频率的交流信号驱动，将两次测量阻抗值进行比较可以更加详细的得到外接导联的接触状况，提供报警信息。
Pace脉冲处理具体包括：对数字采样信号进行第二低通滤波，将带宽限制在2KHz以内，基于滤波后的数字采样信号按照Pace采样率进行采样值抽取，通过抽取，将采样率降低为10Ksa/s以上的一个值。从而得到Pace检测原始数据。请参阅图4，在一实施例中，Pace脉冲处理模块包括用于对共用采样通道输出的数字采样信号进行低通滤波第二低通滤波单元244，和基于滤波后的数字采样信号按照Pace脉冲测量所要求的采样率进行采样值抽取的第二抽取单元245，第二抽取单元输出Pace检测原始数据至Pace检测原始数据分析单元246。
请参阅图4，在一实施例中，ECG波形数据提取处理具体包括：对数字采样信号进行第一低通滤波，将带宽限制在30Hz以内，以保证系统信噪比，基于滤波后的数字采样信号按照ECG采样率进行采样值抽取，将采样率降低为500sa/s。从而得到ECG检测原始数据。在一实施例中，ECG波形数据提取处理模块包括用于对共用采样通道输出的数字采样信号进行低通滤波的第一低通滤波单元247，和基于滤波后的数字采样信号按照ECG波形测量所要求的采样率进行采样值抽取的第一抽取单元248，第一抽取单元输出ECG检测原始数据至ECG检测原始数据分析单元249。
在本实施例中，阻抗计算处理模块、ECG波形数据提取处理模块和Pace脉冲处理模块可通过分立的硬件实现，也可以通过软件实现。
实验证明，对前端原始数据进行过采样后，使噪声频谱分布在更宽的范围，在Pace脉冲处理和ECG波形数据提取处理过程中，通过低通滤波，可以滤除大部分噪声，从而减小了量化噪声的目的，相当于提高了采样精度。
根据分析模块240对患者阻抗、ECG波形数据和Pace脉冲的分析结果，处理器判断是否适合使用电击治疗，如果适合则控制进行后续的充电和放电。
在一实施例中，为了提高阻抗测量的精度，尽量提高交流信号的驱动电压幅度，放大器和延迟放大器的放大倍数和供电电压被配置为满足以下条件：1、流过患者身体的电流小于安全电流；2、输入采样通道的信号不会导致采样通道饱和。将一定特征的信号叠加在采样信号上，可消除在过采样过程中ADC本身转换误差（INL、DNL等）的影响，进一步提高过采样的效果。
可见，在上述除颤仪前端测量系统包括该前端测量系统中，通过对原始数据过采样，然后在后续处理中对过采样数据进行滤波和抽取，使得过采样的数据变为符合各被测试量采样率和精度要求的数据，从而使得多种被测试量可共用一个采样通道。上述除颤仪前端测量系统减少了硬件，进一步减少了硬件与硬件的连接节点，从而减少了由节点引入的干扰。更进一步地，由于减少了硬件，可以降低仪器受硬件的分散性影响，实验证明仪器测量结果的准确性得到提高。同时，因硬件的减少，也使仪器的体积相应减小，成本相应降低。
请参阅图6，一实施方式的自动体外除颤仪的前端测量方法，包括步骤：
S10、通过与患者身体合适部位接触的两个电极片向患者施加载波信号。
S20、检测两个电极片上的信号并进行数据采样，在数据采样过程中，至少两种不同的被测试量共用一个采样通道，被测试量为患者阻抗、ECG波形数据和Pace脉冲中的任一种，共用采样通道的采样率大于或等于共用采样通道对应的至少两种被测试量所要求的采样率中的最大者。
S30、通过处理器接收共用采样通道输出的数字采样信号，将数字采样信号分成至少两路，并按照被测试量对采样率和精度的要求进行信号提取处理。
在一实施例中，当除颤仪在自检后，如果测试负载没有取下，会导致除颤仪开机后即进入AED模式，会自动采集前端数据。由于电极片21的前端连接有测试负载，所以除颤仪识别外面连接到人体，导致可能得到错误的分析结果导致延迟治疗。通过上电自检来识别除颤仪是否外接测试负载。当外接测试负载时，采用两种不同频率的交流载波信号驱动，测得的阻抗值会基本一致。
请参考图7，外接测试负载识别包括以下步骤：
步骤S101，检测到除颤仪上电信号或识别外接测试负载的指令后，处理器输出第一频率的交流信号；
步骤S102，从电极片采样基于第一频率的波形数据；
步骤S103，基于采样数据计算第一阻抗值；
步骤S104，输出第二频率的交流信号，第二频率与第一频率不同；
步骤S105，从电极片采样基于第二频率的波形数据；
步骤S106，基于采样数据计算第二阻抗值；
步骤S107，计算第一阻抗值和第二阻抗值差值的绝对值，并判断绝对值是否小于设定的阈值，如果是，则认为除颤仪外接测试负载。
具体地，设定的阈值是一个比较小的值，例如10Ω。如果两次测量差值的绝对值小于设定的阈值，则认为除颤仪外接测试负载，执行步骤108。否则，如果两次测量差值的绝对值大于或等于设定的阈值，则认为除颤仪没有外接测试负载，可进行正常的测试。
步骤108，报仪器外接测试负载。操作人员将测试负载取下后即可正常使用除颤仪。
在另一实施例中，可将外接测试负载识别和患者阻抗测试一起判断，其流程图如图8所示。
S101、校准仪器；
S102、然后检测到除颤仪上电信号或识别外接测试负载的指令后，处理器输出第一频率的交流信号；
S103、从电极片采样基于第一频率的波形数据；
S104、基于采样数据计算第一阻抗值；
S105、判断第一阻抗值的大小，当第一阻抗值大于3k欧时，结束检测，报导联脱落；当第一阻抗值小于3k欧时，进入步骤S106;
S106、输出第二频率的交流信号，第二频率与第一频率不同；
S107、从电极片采样基于第二频率的波形数据；
S108、基于采样数据计算第二阻抗值；
S109、判断第二阻抗值的大小，当第二阻抗值是否大于10欧，若是，则结束检测，报外部短路；若否，则判断第一阻抗值和第二阻抗值差值的绝对值是否小于设定的阈值，如果是，则认为除颤仪外接测试负载。操作人员将测试负载取下后即可正常使用除颤仪；若否，则结束检测，取测得的第二抗阻值作为当前测量值。
在根据采样值进行阻抗计算时，通常是基于采样电压值在采样电压值和阻抗的对应曲线查到阻抗值，但由于系统各器件参数的漂移，实际的阻抗会和根据采样电压值在采样电压值和阻抗的对应曲线上查到的阻抗值有所不同。因此在本实施例中，还包括校准电路26，如图9所示，校准电路26包括开关261、第一校准电阻262和第二校准电阻263。开关261的两个输入端耦合到两个输入保护电路231的输出端，两个输出端根据控制耦合到第一校准电阻262的两端或耦合到第二校准电阻263的两端。具体地，第一校准电阻262和第二校准电阻263具有不同的阻值。开关261可以为双刀开关，也可以是处理器控制的多路开关。
当需要校准时，将开关261连接到第一校准电阻262，处理器产生交流信号施加到第一校准电阻262，同时采样原始信号，获得第一采样电压值。然后将开关261连接到第二校准电阻263，处理器产生交流信号施加到第二校准电阻263，同时采样原始信号，获得第二采样电压值。采用获得的第一采样电压值和第二采样电压值更新除颤仪存储的原采样值和阻抗的对应曲线。
在一定频率和幅度的载波驱动下，测得采样电压值和阻抗近似成线性关系。但由于系统的各种误差，例如电阻、电容以及各IC的分散性影响，采样电压值和阻抗的关系呈现一定的曲线，通过分别接入第一校准电阻和第二校准电阻测量得到曲线上两点，即可建立被测阻抗值和采样电压值的关系曲线。
以上所述实施例仅表达了本发明的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。

Claims (12)

  1. 一种自动体外除颤仪的前端测量系统，其特征在于，包括：
    两个电极片；
    载波驱动电路，用于对产生的交流信号进行放大，并输出处理后的两路交流信号至所述两个电极片；
    采样电路，至少包括一个采样通道，其中至少一个采样通道为共用采样通道，所述共用采样通道为对应的至少两种不同的被测试量共用的测量通道，所述被测试量为患者阻抗、ECG波形数据和Pace脉冲中的任一种，所述共用采样通道包括差分放大器和模数转换器，所述差分放大器的两个输入端分别耦合到所述两个电极片，所述差分放大器的输出端耦合到所述模数转换器，所述模数转换器对输入的模拟信号经设定采样率采样后转换为数字信号并输出，所述模数转换器的采样率大于或等于所述共用采样通道对应的至少两种被测试量所要求的采样率中的最大者；及
    处理器，用于产生交流信号并输出到载波驱动电路，所述处理器耦合到所述采样电路，以控制所述采样电路并接收所述采样电路输出的数字采样信号，针对所述共用采样通道输出的所述数字采样信号分成至少两路，并按照所述被测试量对采样率和精度的要求进行信号提取处理。
  2. 根据权利要求1所述的系统，其特征在于，所述共用采样通道为患者阻抗、ECG波形数据和Pace脉冲共用的通道，所述共用采样通道的所述模数转换器的采样率等于患者阻抗测量所要求的采样率，所述处理器包括患者阻抗计算处理模块、ECG波形数据提取处理模块和Pace脉冲处理模块；
    所述患者阻抗计算处理模块包括用于对所述共用采样通道输出的数字采样信号进行带通滤波的带通滤波单元，和基于滤波后的数字采样信号计算患者阻抗的计算单元；
    所述ECG波形数据提取处理模块包括用于对所述共用采样通道输出的数字采样信号进行低通滤波的第一低通滤波单元，和基于滤波后的数字采样信号并按照ECG波形测量所要求的采样率进行采样值抽取的第一抽取单元，所述第一抽取单元输出ECG检测原始数据；
    所述Pace脉冲处理模块包括用于对所述共用采样通道输出的数字采样信号进行低通滤波第二低通滤波单元，和基于滤波后的数字采样信号并按照Pace脉冲测量所要求的采样率进行采样值抽取的第二抽取单元，所述第二抽取单元输出Pace检测原始数据。
  3. 根据权利要求1所述的系统，其特征在于，所述采样电路还包括两个输入保护电路，所述两个输入保护电路分别连接在采样通道的两个输入端和对应的电极片之间，用于吸收除颤高压的能量。
  4. 根据权利要求3所述的系统，其特征在于，还包括校准电路，所述校准电路包括开关、第一校准电阻和第二校准电阻，所述开关的两个输入端耦合到所述两个输入保护电路的输出端，两个输出端根据控制耦合到第一校准电阻两端或耦合到第二校准电阻两端，所述第一校准电阻和所述第二校准电阻具有不同的阻值。
  5. 根据权利要求1所述的系统，其特征在于，所述载波驱动电路包括带通滤波器、放大器和延迟放大器，所述带通滤波器的输入端耦合到所述处理器的载波信号输出端，所述带通滤波器的输出端分别耦合到所述放大器和所述延迟放大器的输入端，所述放大器和所述延迟放大器的输出端分别对应耦合到所述两个电极片，所述延迟放大器输出的交流信号的相位相比所述放大器输出的交流信号延迟一设定相位。
  6. 根据权利要求5所述的系统，其特征在于，所述延迟放大器为反相放大器，所述反相放大器输出的交流信号与所述放大器输出的交流信号相位相反。
  7. 根据权利要求5所述的系统，其特征在于，所述放大器和所述延迟放大器的放大倍数和供电电压被配置为在满足流过患者身体的电流小于安全电流且输入所述采样通道的信号不会导致所述采样通道饱和。
  8. 根据权利要求5所述的系统，其特征在于，所述处理器输出两种不同频率的交流信号，并根据所述采样电路采集的信号判断所述两个电极片与患者是否接触良好，或者所述处理器响应于上电信号输出两种不同频率的交流信号，并根据所述采样电路采集的信号判断所述两个电极片是否被外部导体短接。
  9. 一种包括如权利要求1所述的前端测量系统的自动体外除颤仪。
  10. 一种自动体外除颤仪的前端测量方法，其特征在于，包括：
    通过与患者身体合适部位接触的两个电极片向患者施加载波信号；
    检测所述两个电极片上的信号并进行数据采样，在数据采样过程中，至少两种不同的被测试量共用一个采样通道，所述被测试量为患者阻抗、ECG波形数据和Pace脉冲中的任一种，所述共用采样通道的采样率大于或等于所述共用采样通道对应的至少两种被测试量所要求的采样率中的最大者；及
    通过处理器接收所述共用采样通道输出的数字采样信号，将所述数字采样信号分成至少两路，并按照被测试量对采样率和精度的要求进行信号提取处理。
  11. 根据权利要求10所述的方法，其特征在于，所述患者阻抗、所述ECG波形数据和所述Pace脉冲共用一个采样通道，所述处理器将接收的所述共用采样通道输出的数字采样信号分别经患者阻抗计算处理、ECG波形数据提取处理和Pace脉冲处理；所述患者阻抗计算处理包括对所述数字采样信号进行带通滤波，基于滤波后的所述数字采样信号计算患者阻抗；所述ECG波形数据提取处理包括对所述数字采样信号进行第一低通滤波，基于滤波后的所述数字采样信号按照ECG采样率进行采样值抽取，从而得到ECG检测原始数据；Pace脉冲处理包括对所述数字采样信号进行第二低通滤波，基于滤波后的所述数字采样信号按照Pace采样率进行采样值抽取，从而得到Pace检测原始数据。
  12. 根据权利要求10所述的方法，其特征在于，还包括外接测试负载识别步骤，所述外接测试负载识别步骤包括：
    输出第一频率的交流信号；
    从电极片上采样基于第一频率的波形数据；
    基于采样数据计算第一阻抗值；
    输出第二频率的交流信号；
    从所述电极片上采样基于第二频率的波形数据；
    基于采样数据计算第二阻抗值；及
    计算第一阻抗值和第二阻抗值差值的绝对值，并判断所述绝对值是否小于设定的阈值，如果是，则认为除颤仪外接测试负载。
PCT/CN2014/074066 2013-07-05 2014-03-26 自动体外除颤仪及其前端测量系统和测量方法 Ceased WO2015000312A1 (zh)

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