Method and apparatus for producing a central pressure waveform in an oscillometric blood pressure system
First Claim
1. A method for estimating forward and reflected components of the aortic blood pressure waveform from an aortic pressure waveform obtained from a blood pressure cuff, said method comprising the steps of:
- a. inflating a blood pressure cuff on a brachial artery of an arm to a pressure at least as great as the diastolic pressure;
b. holding the molar amount of fluid in the blood pressure cuff constant;
c. sensing a sequence of cuff pressure waveforms associated with the brachial artery that result from at least one cardiac ejection cycle;
d. determining the portion of the aortic pressure waveform, P, that occurs during diastole;
e. finding two parameters, γ and
PRes fitting an exponential decay to the diastolic portion of the waveform P, to determine an exponentially decaying pressure, PDecay;
f. assuming a form of the incident waveform emanating from the heart, PIncident;
g. calculating a reflected wave, PIliac, from PIncident and a predetermined model of reflection from the distal aorta;
h. calculating a pressure wave PValve representing a further reflection of the reflected wave PIliac from the aortic valve, wherein the further reflection substantially only occurs during diastole;
i. calculating the parameters, α and
β
, that best fit an equation of the form PEst=PRes+α
PIncident+β
(PIliac+PValve)+PDecay to the measured aortic pressure waveform P; and
j. calculating the incident wave according to α
×
PIncident and the reflected wave according to β
×
PIliac.
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Abstract
A central arterial blood pressure waveform is developed from pressure waveforms obtained from proximal and distal blood pressure cuffs on the brachial artery of an arm that are inflated to a supra-systolic pressure. The proximal and distal cuff pressure waveforms associated with at least one cardiac ejection cycle are sensed. The propagation times of a blood pressure pulse from the entry of the artery to the proximal cuff and from the proximal cuff to the distal cuff are calculated, permitting calculation of a reflection coefficient of the pressure pulse at one of the proximal and distal cuffs. Assuming a physical model of wave propagation along the artery between the aorta and the proximal and distal cuffs, an estimated pressure waveform at the opening of the artery can be determined.
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Citations
5 Claims
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1. A method for estimating forward and reflected components of the aortic blood pressure waveform from an aortic pressure waveform obtained from a blood pressure cuff, said method comprising the steps of:
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a. inflating a blood pressure cuff on a brachial artery of an arm to a pressure at least as great as the diastolic pressure; b. holding the molar amount of fluid in the blood pressure cuff constant; c. sensing a sequence of cuff pressure waveforms associated with the brachial artery that result from at least one cardiac ejection cycle; d. determining the portion of the aortic pressure waveform, P, that occurs during diastole; e. finding two parameters, γ and
PRes fitting an exponential decay to the diastolic portion of the waveform P, to determine an exponentially decaying pressure, PDecay;f. assuming a form of the incident waveform emanating from the heart, PIncident; g. calculating a reflected wave, PIliac, from PIncident and a predetermined model of reflection from the distal aorta; h. calculating a pressure wave PValve representing a further reflection of the reflected wave PIliac from the aortic valve, wherein the further reflection substantially only occurs during diastole; i. calculating the parameters, α and
β
, that best fit an equation of the form PEst=PRes+α
PIncident+β
(PIliac+PValve)+PDecay to the measured aortic pressure waveform P; andj. calculating the incident wave according to α
×
PIncident and the reflected wave according to β
×
PIliac. - View Dependent Claims (2, 3, 4, 5)
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Specification