Diastolic clamp for bioimpedance measuring device

摘要

An electrical bioimpedance measuring device is used to measure changes in the electrical resistance of a segment of the thorax of a human body caused by changes in the blood perfusion in that segment resulting from the pumping action of the heart. The electrical resistance of also changes as a result of respiration, and the respiratory-induced changes are typically much larger than the cardiac-induced changes and cause large changes in the voltages in the measuring equipment. In order to suppress the large voltage changes, a clamping circuit is included that is synchronized with the electrical activity of the heart. The clamping circuit is timed to clamp the voltages in the measuring equipment to a baseline reference voltage in the time preceding the beginning of mechanical systole. The voltage clamping is released during the mechanical systole of the heart so that the changes in the voltages (i.e., the bioimpedance changes) caused by the pumping action of the heart during mechanical systole can be measured.