The maximum range measured by a mercury column sphygmomanometer is 240 mmHg and does not normally exceed 200 mmHg. Hypertension is a clinical syndrome mainly characterized by elevated arterial pressure in the body circulation or accompanied by functional or organic damage to the heart, brain, kidney and other organs. Mild hypertension has a systolic blood pressure of 140-159 mmHg and a diastolic blood pressure of 90-99 mmHg; moderate hypertension has a systolic blood pressure of 160-179 mmHg and a diastolic blood pressure of 100-109 mmHg; and severe hypertension has a systolic blood pressure of ≥180 mmHg and a diastolic blood pressure of ≥110 mmHg. If the systolic blood pressure reaches 200 mmHg, it may lead to heart failure , blood supply disorders in the brain and other symptoms. Hypertension is one of the most common chronic diseases and a risk factor for cardiovascular and cerebrovascular diseases, and patients with hypertension are advised to measure their blood pressure regularly.