Continuous, non-invasive technique for measuring blood pressure using impedance plethysmography

摘要

Blood pressure is measured using the pulse transit time required for the blood volume pulsc to propagate between two locations in an animal (14). Impedance cardiography or plethysmography is employed to detect when the blood volume pulse occurs at one location. The cardiograph (12) or plethysmograph may detect thoracic impedance to determine when the aortic heart valve opens or it may detect impedance at one location on a limb of the animal (14). Occurrence of the blood volume pulse at another location can be determined by impedance plethysmography or another technique, such as pulse oximetry. The calculation of cardiac stroke volume can be employed to compensate the derivation of the blood pressure for effects due to blood vessel compliance. A non-continuous blood pressure monitor (32) may periodically provide a reference blood pressure measurement that is used to calibrate derivation (30) of the blood pressure based on the pulse transit time.