หน่วยความดันโลหิต

The unit dates to the mercury manometers used in early sphygmomanometers, where pressure literally raised a column of liquid mercury. Normal adult blood pressure is below 120/80 mmHg; hypertension stage 1 begins at 130/80 mmHg. Although mercury instruments are now largely replaced by electronic sensors for safety reasons, mmHg remains the universal clinical standard because of its century-long reference base.