Apparatus and methods for the noninvasive measurment of cardiovascular

Abstract

Apparatus and methods for noninvasively measuring cardiovascular system parameters. According to a first preferred embodiment, the apparatus generates a time varying electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject, the parameters being modelled by a lumped element electric circuit model analogous to the living subject's cardiovascular system, said circuit model including a systolic capacitor analogous to arterial compliance during systole, said apparatus comprising means for computing the value of said systolic capacitor from a measurement of an elapsed time between two voltage levels within a portion of said voltage waveform corresponding to systole, according to a predetermined criteria; and means for computing at least one said cardiovascular system parameter from said capacitor value. According to a second embodiment, a time-varying systolic arterial compliance is measured by measuring an arterial pulse pressure waveform. A third embodiment discloses a method of measuring cardiac output noninvasively from a cuff measurement of a patient's systolic minus diastolic blood pressure and a heart rate measurement. Cardiac output equations are derived from an unmodified Windkessel circuit model which models arterial compliance as a single lumped capacitance. General formulas for the value of the lumped capacitance are provided which are used to more accurately compute cardiac output from this circuit model.