Electrocardiogram (ECG): It is a graph that records the changes of electrical activity of the heart in each cardiac cycle from the body surface with an electrocardiograph. Second, teach the use of electrocardiograph, explain the precautions and operation steps, and then under the guidance of the teacher, divide the students into groups and practice drawing with each other. Operational considerations: 1. Check whether the power supply voltage is consistent with the specified voltage of the machine. 2. Check whether the brush of the electrocardiograph is in zero position or fixed position, if not, turn it back to the designated position. 3. Check whether the machines, wires and accessories are complete. Operating steps: 1. Explain the significance of ECG examination to the examinee, tell him that the examination is painless and harmless, dispel worries, relieve tension, relax muscles and guide him to lie on his back on the examination bed. 2. Connect the grounding wire and check whether the grounding is reliable again. 3. Connect the power cord, turn on the power switch and preheat the machine. 4. Connect wires according to regulations. Firstly, the bilateral wrists and the upper part of the medial malleolus on both sides of the subject were exposed, and the skin was scrubbed and degreased with alcohol gauze to make the skin red. Then apply conductive liquid to keep the skin in good contact with the electrode, and fix the electrode plate according to the requirements of right upper limb → red line, left upper limb → yellow line, left lower limb → green line, right lower limb → black line (connected with ground wire) and chest → white line. The connection mode and electrode position of ECG leads are uniformly stipulated in the world, forming a universal and standardized lead system-conventional lead. Comprises limb leads (6), standard limb leads (3 bipolar leads), unipolar pressurized limb leads (3) and chest leads (6 unipolar leads). The monitoring electrode position of chest lead: V 1, the fourth intercostal space on the right edge of sternum. V2, the fourth intercostal space on the left side of sternum. The midpoint of the connecting line between V3, V2 and V4. V4, intersection of left clavicle midline and fifth intercostal. V5, V4 level of left axillary front line. V6, left axillary midline V4 level. V7, the left posterior axillary line V4 is horizontal. V8, the left scapula line V4 is horizontal. V9, the left paravertebral line V4 is horizontal. V3R~V6R, where the right chest is symmetrical with V3~V6. 5. Correct the paper feed speed, brush position and temperature of the electrocardiograph, apply standard voltage, and make it 10mm= 1mV after correction. 6. Toggle the switches one by one according to the lead knob switch sequence, and record the electrocardiogram of twelve leads I, II, III, aVR, aVL, aVF, V 1, V2, V3, V4, V5 and V6 in turn. 7. After the inspection, check again for omissions, false errors, etc. , and mark the lead name, the name of the patient and the examination time on the ECG paper. 8. Turn the lead switch back to the "0" position, turn off the power switch, and then remove the wire. Three, the measurement chart of various bands, waveforms, ECG axis, heart rate, familiar with its name and writing. (1) ECG waveform and significance of each part: 1. P wave: It represents the potential change during atrial excitation. In normal electrocardiogram, P wave in lead I and II is upward, and P wave in lead aVR is inverted. The P wave of aVL, III, V 1, V2 and other leads can be upward, inverted or bidirectional. The top of normal upward P wave is smooth, and the time limit is
Voltage: < < 0.25mV, time limit: < < 0. 12s.
PR interval
0. 12s-0.2s
Qrs complex
Time limit: < < 0. 10s, Q wave: < < 0.04s, voltage: aVF.