Method for long-term measurement of blood pressure
The "Novel method for low stress, non-invasive long-term measurement of blood pressure" is one of the winners of the "Innovation Competition for the Promotion of Medical Technology 2008". It was awarded and funded by the Federal Ministry of Education and Research (BMBF).
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Blood pressure is the most important parameter in cardiovascular diseases. Forty million people in Germany suffer from high blood pressure, which can lead to coronary heart disease, stroke, heart failure or renal failure. Cardiovascular diseases are the main cause of death in Germany, with a high percentage of 43 %. Treatment and prevention require knowledge of the patient's blood pressure during a continuous period up to 24 hours. State-of-the-art are automatic devices, which measure blood pressure every 15/30 minutes for 24 hours. The conventional method is based on the Riva-Rocci principle with an arm cuff. This measurement demands interruption of all movement to avoid motion artifacts. Also, this technique is somewhat painful because of venous congestion. Thus the patient is alarmed at the beginning of each measurement and his blood pressure changes – artifacts are produced. For these reasons the long-term blood pressure measurement is not as frequently used as necessary.
The new method is also based on the Riva-Rocci principle. However, instead of occluding all vessels in the arm or hand, only one artery is occluded. This is a superficial artery such as the radial artery or temporal artery. The artery is occluded by a balloon which is fixed on the skin by an adhesive. This is a low-load measurement technique because only a small area of tissue is pressurized. Blood flow in the artery is measured using Doppler Ultrasound. The blood velocity curve is correlated with the externally applied pressure in the balloon. The balloon occludes the artery until blood flow stops. The balloon pressure is decreased until blood flows into the artery again for the first time. At this point the balloon pressure is equal to the systolic blood pressure. Between the systolic and diastolic values, the blood flows only through the artery when the pressure in the artery is higher than that in the balloon. The time in which no blood flow is detected decreases with decreasing balloon pressure. Diastolic blood pressure is reached if this time equals zero. The new method can be used to measure systolic and diastolic blood pressure.