Apparatus and methods for the noninvasive measurement of cardiovascular system parameters
First Claim
1. An apparatus for measuring cardiovascular system parameters of a living subject, comprising:
- means for modelling the parameters of the living subject with 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;
first transducer means for sensing a time varying arterial pressure pulse waveform from the living subject and converting said pressure pulse waveform to an electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject;
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 the cardiovascular system parameters from said capacitor value.
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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.
130 Citations
15 Claims
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1. An apparatus for measuring cardiovascular system parameters of a living subject, comprising:
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means for modelling the parameters of the living subject with 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; first transducer means for sensing a time varying arterial pressure pulse waveform from the living subject and converting said pressure pulse waveform to an electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject; 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 the cardiovascular system parameters from said capacitor value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for noninvasively measuring cardiovascular system parameters of a living subject, comprising the steps of:
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providing a lumped element electric circuit model analogous to the living subject'"'"'s cardiovascular system for modelling the parameters of the living subject, said circuit model including a systolic capacitor analogous to arterial compliance during systole; sensing a time varying arterial pressure pulse waveform from the living subject; converting said pressure pulse waveform to an electrical voltage waveform having voltages corresponding to systolic and diastolic arterial pressures of the subject; 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 computing the cardiovascular system parameters from said capacitor value. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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Specification