Blood pressure lying amount is lower than sitting, similar to the upright tilt test. The basic principle is that when lying blood is evenly distributed throughout the body, once there is a change in position, from lying to sitting, blood is easy to pool to the lower parts of the body, most commonly the lower limbs, the amount of blood flowing back to the heart will be reduced, the heart will reduce the amount of blood discharge, causing blood pressure to fall. If a normal person will be regulated through a series of cardiovascular reflexes, it will eventually cause an increase in heart rate and peripheral vascular resistance to ensure that blood pressure does not fall excessively, and diastolic blood pressure will increase by 10 mmHg, while systolic blood pressure will remain basically unchanged. In patients with postural hypotension, the regulation ability is significantly weakened, which will cause a significant drop in blood pressure, such as a systolic drop of 20 mmHg or a diastolic drop of 10 mmHg or more, and attention should be paid to slow changes in body position to avoid causing a rapid drop in blood pressure.