It is not usually necessary to hold one’s breath when performing an EKG; holding the breath reduces the oxygen supply to the heart muscle and increases the heart rate. However, if the ECG is measured, the doctor asks the tester to hold his breath, probably because the patient’s breathing affects the heart rhythm and heart rate. this situation is mostly found in patients with severe obesity, chronic lung disease or respiratory sinus arrhythmia, etc. 1, severe obesity: patients with severe obesity, due to the thicker fat layer, the patch is farther away from the heart, ECG monitoring may be more insensitive than usual. If you breathe at this time, with the undulation of the thorax, will lead to some deviations in the ECG indicators, affecting the diagnosis, so in such people do ECG monitoring, sometimes it is recommended to hold a breath; 2, chronic lung disease: for some patients with chronic lung disease, on the one hand, the thorax undulation during breathing is greater than normal people, easily affect the diagnosis of ECG. On the other hand, it may also be in testing whether the patient’s heart function can maintain the organism during respiratory distress; 3, respiratory sinus arrhythmia: thoracic undulation can have some effect on the ECG, so holding the breath for the ECG can observe whether the abnormality reappears. Especially when the patient has respiratory sinus arrhythmia, the ECG performance is directly related to breathing, and performing breath-holding can effectively determine the patient’s condition and understand the cause of the disease. In addition, when performing an ECG, patients should avoid other factors that may affect the results. It is necessary to rest for a period of time and test in a quiet state without excessive tension; also do not take foods and drugs that affect heart rhythm and heart rate, such as coffee, tea, etc. Wear loose clothing to facilitate full exposure of the examination site, and do not wear clothes that are prone to static electricity or with metal, which may affect the measurement results.