Devices for measuring cardiovascular properties suffer from the problem that the measurement itself interferes with the state of the subject, thereby leading to erroneous results. In addition, current cuff-based methods may impart a significant physiological impact. In current cuff-based methods, the systolic blood pressure is obtained by completely or at least substantially constricting an artery, which in most cases is the brachial artery in the upper arm. Such constriction of the artery affects pulse pressure propagation and pulse pressure shapes, which may only be tolerated in the peripheral system. Further, the diastolic pressure is derived from measurements obtained when the transmural pressure (pressure difference between the outside and the inside of an artery) is close to zero, which implies those measurements are made under conditions that are far from normal.
In addition, traditional methods based on inflatable cuffs and measurements performed in a clinical environment may have psychological effects causing changes in a patient's blood pressure. For example, the psychological effects of being in clinical environment may cause an elevation in the patient's blood pressure. The phenomenon is commonly called “white coat syndrome” or “white coat hypertension.” In an additional example, a patient's blood pressure may be elevated during normal daily activities but not in a clinical setting. This phenomenon is commonly called “masked hypertension.”
USPTO Backgrounds
USPTO Backgrounds