Measure arterial blood pressure, commonly used is mercury sphygmomanometer or digital sphygmomanometer, the principle is through the cuff pumping pressure, blocking the brachial artery blood flow, and then slowly deflate, when the cuff pressure is less than the moment of systolic pressure, you can use the stethoscope to hear the blood flow to form the arterial pulsation sound, this is the systolic pressure is also called high pressure, is the maximum pressure generated by the contraction of the left ventricle. Continuing to deflate slowly, the arterial pulsation sound continues, and the moment the cuff pressure is greater than the diastolic pressure, the stethoscope hears the last arterial pulsation sound, which is the diastolic pressure, also called low pressure, and is the lowest pressure generated by the retraction of the large arteries. Indirect monitoring of arterial blood pressure through external pressure changes is a non-invasive way of measuring it. It is also possible to directly puncture the peripheral arterial vessels and connect the end of the indwelling sheath directly to a pressure-sensing device, which allows real-time detection of arterial blood pressure changes and is relatively accurate, as it is an invasive operation and is not recommended for routine use.