Methods and apparatus for nonivasive monitoring of dynamic cardiac performance
First Claim
1. Apparatus for noninvasively monitoring cardiovascular system parameters of a living subject comprising:
- means for sensing a first time varying pulse waveform in the vicinity of the carotid artery externally of the body of the subject and for converting the first pulse waveform to a first time varying electrical representation;
means for sensing a second time varying pulse waveform in the vicinity of the femoral artery externally of the body of the subject and for converting the second pulse waveform to a second time varying electrical representation;
means for digitizing said first and second time varying representations;
means for providing diastolic and systolic blood pressure measurements sensed externally of the body of the subject;
a digital signal processor having means for receiving said digitized first and second time varying representations and said measured blood pressure parameters and for calibrating said first and second digitized representations to provide first and second sets of time varying blood pressure representations, said processor further comprising means for converting said first and second sets of time varying blood pressure representations by Fast Fourier Transform to first and second sets of harmonically related blood pressure components in the frequency domain, means for comparing corresponding ones of said components in said first and second harmonically related sets to determine amplitude and phase transfer function components of the portion of the cardiovascular system between said carotid and femoral arteries, means for simulating said portion of said cardiovascular system by a hybrid electrical circuit model having at least three variable parameters, means for determining corresponding amplitude and phase transfer function components of said hybrid model of said portion of said system and for adjusting said parameters of said hybrid model so as to substantially match said transfer functions of said model and said portion of said cardiovascular system, and means for determining cardiac output utilizing said adjusted parameters of said hybrid model and said first set of time varying blood pressure representations.
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Abstract
Apparatus for noninvasively monitoring cardiovascular system parameters of a living subject comprises means for sensing waveforms externally of the body of the subject above the carotid and femoral arteries, means for non-invasively calibrating and digitizing the pulse waveforms, and a digital signal processor having means for converting the digitized, calibrated pulse information by Fast Fourier Transform to first and second sets of harmonically related blood pressure components in the frequency domain, means for comparing corresponding ones of the components in the first and second harmonically related sets to determine amplitude and phase transfer function components of the portion of the cardiovascular system between the carotid and femoral arteries, means for simulating the portion of the system by a hybrid electrical circuit model having at least three variable parameters, means for determining corresponding amplitude and phase transfer function components of the hybrid model and for adjusting the variable parameters so as to substantially match the transfer functions of the model and the portion of the cardiovascular system, and means for determining cardiac output utilizing the adjusted parameters of the hybrid model and the calibrated pulse information.
156 Citations
16 Claims
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1. Apparatus for noninvasively monitoring cardiovascular system parameters of a living subject comprising:
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means for sensing a first time varying pulse waveform in the vicinity of the carotid artery externally of the body of the subject and for converting the first pulse waveform to a first time varying electrical representation; means for sensing a second time varying pulse waveform in the vicinity of the femoral artery externally of the body of the subject and for converting the second pulse waveform to a second time varying electrical representation; means for digitizing said first and second time varying representations; means for providing diastolic and systolic blood pressure measurements sensed externally of the body of the subject; a digital signal processor having means for receiving said digitized first and second time varying representations and said measured blood pressure parameters and for calibrating said first and second digitized representations to provide first and second sets of time varying blood pressure representations, said processor further comprising means for converting said first and second sets of time varying blood pressure representations by Fast Fourier Transform to first and second sets of harmonically related blood pressure components in the frequency domain, means for comparing corresponding ones of said components in said first and second harmonically related sets to determine amplitude and phase transfer function components of the portion of the cardiovascular system between said carotid and femoral arteries, means for simulating said portion of said cardiovascular system by a hybrid electrical circuit model having at least three variable parameters, means for determining corresponding amplitude and phase transfer function components of said hybrid model of said portion of said system and for adjusting said parameters of said hybrid model so as to substantially match said transfer functions of said model and said portion of said cardiovascular system, and means for determining cardiac output utilizing said adjusted parameters of said hybrid model and said first set of time varying blood pressure representations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for noninvasively monitoring cardiovascular system parameters of a living subject comprising the steps of:
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externally sensing a carotid pulse and a femoral pulse of said subject; converting said carotid and femoral pulses to respective carotid and femoral pulse electrical voltage waveforms; digitizing both electrical voltage waveforms; calibrating said digitized pulse waveforms with respect to amplitude; subjecting said digitized waveforms to a Fast Fourier Transform by converting to harmonically related frequency components; comparing amplitude and phase for each pair of carotid and femoral frequency components to derive measured phase and amplitude transfer functions for the subject; storing in a computer a hybrid mathematical model of a human aorta; automatically varying, by means of a matching optimization program stored in said computer, at least three predetermined parameters of the model; deriving corresponding transfer function components of the model and comparing such components to the measured transfer function of the subject after each adjustment until a substantial match of the measured and calculated transfer functions is obtained; determining the input impedance of the optimized model utilizing the adjusted, matched parameters; determining aortic flow components from the impedance parameter of the model and the calibrated, measured carotid pressure information of the subject; converting the aortic flow components to the time domain by Inverse Fast Fourier Transform; and determining the time integral of the transformed flow information to provide stroke volume. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification