(i) ECG machine: the device that takes the weak current (mv level) generated by the heart, amplifies it and records an ECG is called a cardiograph.
(II) Basic structure and function of ECG machine
(III) Classification of ECG machine
ECG machine is classified according to the main original device; electron tube, transistor, small scale integrated circuit, large scale integrated circuit.
Categorized by channel: single-channel, multi-channel (the national standard for classification of medical instruments and equipment for more than three channels for multi-channel including three-channel), commonly used three-channel, four-channel, six-channel, eight-channel, twelve-channel. At present, the domestic application of single-channel and three-channel. Internationally, we advocate the application of 12-channel synchronized electrocardiographs to improve the diagnostic level of electrocardiograms, which is the development trend in the future. We advocate the application of twelve-channel synchronized electrocardiograph.
Categorized by power supply: AC, AC/DC, DC.
Categorized by recording method: currently used hot pen type, thermal vibration type, computer needle printing, inkjet, laser printing.
Categorized by model: portable, handheld, desktop.
Categorized by function: ordinary single-function electrocardiograph, computerized automatic test analysis report storage and other multi-function.
(D) the main performance of the electrocardiogram machine technical indicators electrocardiogram machine performance is good or bad, often expressed in its technical indicators:
1, sensitivity (gain): electrocardiogram machine sensitivity (gain) refers to the input of 1mv voltage, tracer bias amplitude. Expressed in mm/mv. EKG sensitivity is 1cm/mv. Maximum sensitivity is generally required to reach 20mm?mv. EKG sensitivity is generally divided into three grades, 5/mm/mv, 10/mm/mv, 20mm/mv. The sensitivity threshold is not greater than 20 μvp-p.
2. Noise: Due to the irregularity of the electronic movement within the components in the amplifier, the EKG can still output irregular signals when no signal is added. The noise voltage folded into the input is not greater than 15μvp-p.
3. Damping: The oscillating force that counteracts the oscillation that occurs in the recorder is called damping. In electrocardiography, the recorder can not be allowed to move at Ning's own oscillation frequency, because it will cause waveform distortion.
4, frequency response: sensitivity with the frequency of the input signal and the relationship is called frequency response. ECG machine regulations 1-75HZ.
5, time constant: is the step waveform from the final value down to its 37% of the time experienced. Time constant ≥ 3.2 seconds.
6, linear: the output response of the ECG machine when the waveform is the same as the input signal and the amplitude varies with the same multiple of the input, the system is called a linear system.
In the operating frequency range of the output signal peak value between 5-50mm, the linear deviation should be less than 5% of the output peak value, the output signal amplitude <5mm, the non-linear deviation should not be greater than 0.25mm.
EKG machine in a variety of positions of the stylus in the tracer, if the same signal is input, the magnitude of the stylus deflection is the same. Then it is called a good linearity of the ECG machine, if the linearity is not good, it will make the ECG waveform distortion. This is the shift linearity. Electrocardiogram is specified in the range of ± 20mm, shift nonlinearity is not greater than ± 10%.
7, *** mode rejection ratio: differential mode input sensitivity and *** mode input sensitivity ratio is *** mode rejection ratio. He reacts to the anti-interference ability of ECG.
The *** mode rejection ratio of each lead of the ECG should be greater than 1000:1. The current ECG machine is generally 89dB.
8, input impedance: not less than 2.5MΩ
9, baseline stability: when the power supply voltage is stable, the baseline drift of not more than 1mm. baseline stability is an important indicator of the stability of the ECG machine itself and the ability to adapt to the fluctuation of the power grid voltage. The baseline stability is an important indicator of the stability of the ECG itself and its ability to adapt to voltage fluctuations in the power grid.
10, paper speed: at least 25mm / s; 50mm / s two error is not greater than ± 5%.
11, hysteresis: recording system hysteresis is not greater than 0.5mm.
12, calibration voltage: DC 1mV error is not greater than ± 5%.
13, withstand polarization voltage: ± 300mv polarization voltage, sensitivity change is not greater than ± 5%.
14, inter-channel interference: multi-channel electrocardiographic provocation machine due to inter-channel interference generated by the stroke recording degree is not greater than 0.5mm.
15, power supply leakage current: less than 100μA.
(D) the safety of the ECG machine: electrocardiographic machine is a direct connection with the human body of the electronic equipment, it must be very careful to pay attention to the safety of the human body. From the safety aspect of the ECG machine can be divided into three types: B type, BF type and CF type. (See the Chinese people's **** and national standards GB10793-89 electrocardiograph with safety requirements) according to the International Electrotechnical Commission (I, E, C) general provisions; medical electrical equipment and patients directly connected to the energy part is called the "application of the part". In order to further ensure patient safety, the application of medical electrical equipment is often added to the part of the isolation measures, photoelectric coupling, electromagnetic wave coupling, electromagnetic wave coupling, etc., according to the application of the part of the degree of isolation, medical electrical equipment is divided into B, BF and CF type.
Type B: there is no isolation in the application part.
Type BF: the application part of the floating ground isolation, can be used in vitro and in vivo, but can not be used directly in the heart.
Type CF: application of partial floating ground isolation, high protection of the electrodes, can be used directly in the heart. We recommend that all ECGs be of the CF type.
Single-channel and multi-channel electrocardiograph
Basic Parameters
1.1Environmental conditions for normal operation of the electrocardiograph:
Ambient temperature:+5--+40℃;
Relative temperature:≤80%;
Atmospheric pressure:750±30mmHg.
1.2Using power supply:
AC 220V.
AC 220V tolerance ±10%, 50Hz tolerance ±2%.
DC: DC voltage, battery specifications and hours of normal operation should be indicated.
1.3 Warm-up time:
Transistor: 2 minutes;
Electronic tube: 10 minutes.
1.4 Continuous working time:
AC: ≥4 hours
DC: ≥0.5 hours
1.5 Lead wire electrodes:
1.5.1 The position, marking and color coding of the electrodes must be in accordance with the requirements of Table 1.
Table 1
Lead wire electrode position Electrode sign symbol Color code Position on the surface of the follower body
Limb R
L
F Red
Yellow
Green Right arm
Left arm
Left leg
Thorax
(according to the Wilson method)
C
CA
CB
CC
C1
C2
C3
C4
C5
C6 White
White
White
White
White
White/Red
White/Yellow
White/green
White/brown
White/black
White/purple Single removable thoracic electrode
Three removable thoracic electrodes
Fourth intercostal space in the right end of the sternum
Fourth intercostal space in the left end of the sternum
Midway between C1 and C4, on the fifth rib
Left mid-clavicular line, fifth intercostal space
On the left anterior axillary line at the same level as C4
On the left mid-axillary line at the same level as C4
1.6 Minimum Configuration Requirements for the Lead Selector:
In single-channel electrocardiographs the lead selector must be capable of selecting the test standard voltages and have the ability to select at least the sequential selection of leads I, II, III, avR, avL, avF, and V.
In multichannel ECG, the lead selector must be able to select the test standard voltage and have at least sequential selection of leads I, II, III, avR, avL, avF, V1, V2, V3, V4, V5, and V6.
1.7 Recording pen deflection amplitude: ≥±20 mm.
1.8 External output;
1.8.1 Sensitivity: 1V/ mV±5%.
1.8.2 Output impedance: ≤100Ω
1.8.3 Output short circuit must not damage the machine.
1.9 External DC signal input
1.9.1 Sensitivity: 100mm/V±5%.
1.9.2 Input impedance: not less than 100kΩ to ground.
2, technical requirements
2.1 ECG machine shall comply with the requirements of this standard and be manufactured in accordance with the drawings and documents approved by the prescribed procedures.
2.2 All control devices of the instrument shall be installed correctly, firmly and reliably, and their roles shall be in accordance with the panel description.
2.3 Input Circuit
2.3.1 In the frequency range specified in paragraph 2.9.1, according to the test circuit in Figure 1 to measure the resistor and 4700pF capacitor in parallel with the impedance, the attenuation of the signal must be no greater than the value specified in Table 3.
Table 3
Lead Selector Position Lead Electrode K Open Stroke Deflection Peak to Peak (mm)
Connected to P1 Connected to P2 Single-channel electrocardiograph Multi-channel electrocardiograph
Ⅰ, Ⅱ, avR, avL, avF, V1 R
R
R All other lead electrodes
R All Other lead electrodes All other lead electrodes 8
3
2 8
Ⅰ, Ⅱ, avR, avL, avF, V2 L
L
L All other lead electrodes
All other lead electrodes
All other lead electrodes 8
3
2 <
I, II, avR, avL, avF, V3 F
F
F All other lead electrodes
All other lead electrodes
all other lead electrodes
All other lead electrodes 8
3
2
Vi (i is 1-6) Ci All other lead electrodes 8
Vx, Vy, Vz A, C, F, M I, E, H -
After reaching the values specified in Table 3, the single-ended input impedance in a single-channel cardioelectric power generator is approximated to be 2.5 MΩ at 10 Hz; and the impedance of a single equalization network is not less than 600 kΩ.
2.3.2 Input loop current: Each input loop current should be no greater than 0.1 μA.
2.4 Standard voltage: 1mV±5%.
2.5 Sensitivity:
2.5.1 Maximum sensitivity: ≥20mm/mV.
2.5.2 Standard sensitivity: 10±0.2 mm/mV.
2.5.3 Sensitivity control: Provide at least 5, 10 and 20mm/mV, and the turn indeed error is ±5%.
2.5.4 Polarization Voltage Resistance: Add ±300mV DC polarization voltage, the sensitivity change is not more than ±5%.
2.5.5 Minimum detection signal: to produce 0.2mm peak-to-peak deflection of the 10Hz sinusoidal signal can be detected.
2.6 Noise level:
Input and neutral electrode access between the 51 kΩ resistor and 0.047 μF capacitor in parallel impedance, in the frequency range specified in paragraph 2.9.1, folded to the input side of the noise level is not greater than 20 μvp-p.
2.7 Interference resistance
2.7.1 Electrocardiogram machine leads * * * ** mode suppression ratio should be greater than 1000:1.
2.7.2 ECG suppression of 10V*** mode signals presented to the patient, according to the test circuit simulation test in Figure 4, in the case of each lead respectively access to the simulation of the electrode-skin imbalance impedance (51 kΩ in parallel with a 0.047μF capacitor), the amplitude of the record must be no more than 10mm
2.850Hz interference suppression filter: ≥20dB.
2.9 Frequency characteristics
2.9.1 Amplitude frequency characteristics: based on 10Hz, 1-75Hz +0.4 dB, 3.0dB
2.9.3 Low-frequency characteristics: time constant ≥3.2 seconds.
2.10 Linearity: within the range of ± 20mm, shift non-linearity is not greater than ± 10%.
2.11 Baseline stability.
2.11.1 When the supply voltage is stable: the drift of the baseline is not more than 1mm
2.11.2 When the supply voltage fluctuates transiently: the drift of the baseline is not more than 1mm
2.11.3 When the operation switch is turned from "closed" to "observation", the drift of the baseline is not more than 1mm
2.11.3 The operation switch is turned from "closed" to "observation".
2.11.3 When the operation switch from "closed" to "observe", the baseline drift is not more than 1mm
2.11.4 The effect of sensitivity changes on the baseline: in the absence of a signal input, the baseline by the change in sensitivity of the displacement of not more than 2mm
2.11.5 Temperature drift: in the temperature range of +5-40 ℃, the baseline drift on average does not exceed 0.5mm / ℃
2.12 Walking about2.12 Walking about
2.12 Walking about
2.12 Approximate speed: at least two grades of 25mm/s and 50mm/s, with an error of not more than ±5.2.13 Hysteresis: the hysteresis of the recording system is not more than 0.5mm
2.14 Inter-channel influence of multichannel electrocardiography machine: in any channel of the multichannel electrocardiography machine, deflections due to the influence of the inter-channel is not more than 0.5mm.
p>2.15 Insulation performance
2.15.1 The insulation resistance between the input end of the power supply line and the chassis before shall be not less than 50 MΩ.
2.15.2 After the electrocardiographic provocation machine has been subjected to the humidity test under storage and transportation conditions and passed the specified recovery time, the insulation resistance between the input end of the power supply line and the chassis shall be not less than MΩ.
2.15.3 The insulation resistance between the input end of the power cord and the chassis shall be