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.
46 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:
-
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