Computer assisted admittance plethysmograph
First Claim
1. A method of measuring the conductance and conductance changes in a body segment, comprising the steps of:
- applying an alternating current signal to said body segment;
measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal;
producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; and
dividing said second signal by said first signal thereby producing a divided voltage signal,whereby the divided voltage signal is proportional to the conductance of said body segment.
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Abstract
An improved method and apparatus for measuring the pulsatile volume and net inflow in a body segment (e.g. a limb) is disclosed. An amplitude stabilized oscillator of high quality is utilized, together with normalization of the output signal measured at the body segment relative to the input signal delivered to the body segment such that an improved signal-to-noise ratio is achieved. In addition, utilizing a digital computer and an EKG signal as a time reference, the individual plethysmograph volume pulse and its first derivative are selectively averaged over many beats, thus further improving the signal-to-noise ratio and allowing a more critical examination of the wave profile. The outputs from the computer include the plethysmogram, the first and second derivatives thereof, the averaged EKG waveform, and the absolute physiologic values of peak-to-peak pulsatile volume, and peak net inflow.
61 Citations
28 Claims
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1. A method of measuring the conductance and conductance changes in a body segment, comprising the steps of:
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applying an alternating current signal to said body segment; measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal; producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; and dividing said second signal by said first signal thereby producing a divided voltage signal, whereby the divided voltage signal is proportional to the conductance of said body segment. - View Dependent Claims (28)
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2. A method of measuring the volume and volume changes in a body segment, comprising the steps of:
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applying an alternating current signal to on body segment; measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal; producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; and dividing said second signal by said first signal thereby producing a divided voltage signal, whereby the divided voltage signal is proportional to the volume of said body segment.
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3. A method of measuring pulsatile volume of a fluid in a body segment, comprising the steps of:
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applying an alternating current signal to said body segment; measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal; producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; dividing said second signal by said first signal thereby producing a divided voltage signal; and filtering said divided voltage signal, whereby said filtered signal is proportional to the pulsatile volume of said fluid. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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11. A method of measuring at least one of the pulsatile volume and net inflow of a body segment using an electrical plethysmograph having a pulsatile volume signal and a net inflow signal as outputs, comprising:
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converting said pulsatile volume signal to a digitized volume signal; generating a synchronous signal having an identifiable characteristic which occurs in a fixed time arrangement with the generator of the pulsatile fluid flow; converting said synchronous signal to a digitized synchronous signal; locating in time an identifiable characteristic of said digitized synchronous signal; and sampling said digitized volume signal over a predetermined period of time beginning with said identifiable characteristic of said digitized synchronous signal. - View Dependent Claims (12, 13, 14, 15, 16)
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17. Apparatus for measuring the conductance and conductance change in a body segment, comprising:
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means for applying an alternating current signal to said body segment; means for measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal; means for producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; and means for dividing said second signal by said first signal thereby producing a divided voltage signal.
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18. Apparatus for measuring the volume and volume changes in a body segment, comprising:
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means for applying an alternating current signal to said body segment; means for measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal; means for producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; and means for dividing said second signal by said first signal thereby producing a divided voltage signal.
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19. Apparatus for measuring pulsatile volume of a fluid in a body segment, comprising:
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means for applying an alternating current signal to said body segment; means for measuring the resulting voltage signal across said body segment caused by the application of said alternating current signal; means for producing a first signal corresponding to the magnitude of the alternating current signal and a second signal corresponding to the magnitude of the resulting voltage signal; means for dividing said second signal by said first signal thereby producing a divided voltage signal; and means for filtering said divided voltage signal, whereby said filtered signal is proportional to the pulsatile volume of said fluid. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. Apparatus for measuring at least one of the pulsatile volume and net inflow of a body segment using an electrical plethysmograph having a pulsatile volume signal and a net inflow signal as outputs, comprising:
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means for converting said pulsatile volume signal to a digitized volume signal; means for generating a synchronous signal having an identifiable characteristic which occurs in a fixed time arrangement with the generator of the pulsatile fluid flow; means for converting said synchronous signal to a digitized synchronous signal; means for locating in time an identifiable characteristic of said digitized synchronous signal; and means for sampling said digitized volume signal over a predetermined period of time beginning with said identifiable characteristic of said digitized sychronous signal.
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Specification