Why Does Blood Pressure Tend to Drop With Repeated Measurements?

The reason why blood pressure readings decrease with each measurement is that applying pressure to the cuff is necessary during blood pressure measurement. Multiple measurements can stimulate the blood vessels, causing them to contract, which results in a decrease in blood pressure. Therefore, there are regulations on the number of blood pressure measurements in clinical practice, and it is not the case that the more measurements, the better.

When measuring blood pressure, the cuff should be tied with a gap of one finger width. If the cuff is tied too tightly, it will put pressure on the brachial artery. With only a small amount of additional air injected, the blood flow in the brachial artery can be blocked, resulting in a lower blood pressure reading. When measuring blood pressure consecutively, there is residual air in the cuff, which, like a tightly tied cuff, puts pressure on the brachial artery itself, leading to lower blood pressure readings. Therefore, there should be at least a one-minute interval between two measurements, and the air in the cuff should be squeezed out, and the average of the measurements should be recorded.

Currently, based on clinical guidelines, it is recommended to use an electronic blood pressure monitor for self-measurement of blood pressure, both in the clinic and at home. There are also requirements for the number of measurements using an electronic blood pressure monitor. Typically, two consecutive measurements are recommended, with an interval of 1-2 minutes between them. If the blood pressure readings from the two measurements differ significantly, such as exceeding 5mmHg, a third measurement should be taken. The first reading is discarded, and the average of the second and third readings is considered as the blood pressure value for this measurement. In clinical practice, it is often observed that the first and second readings may differ significantly, but the difference between the second and third readings is usually small and rarely exceeds 5mmHg. In this case, there is no need for a fourth measurement.