Method of measuring blood pressure with a photoplethysmograph

Details

Inventors: Jones, Paul H.; Wang, Wei-Min;
Assignee: SpaceLabs, Inc. (Redmond, WA)
Primary Examiner: Smith; Ruth S.
Assistant Examiner: Nasser; Robert L.
Attorney, Agent or Firm: Seed and Berry

A method and apparatus for determining arterial blood pressures using a photoplethysmograph is provided. In the inventive method the photoplethysmograph output is calibrated to the patient using an auxiliary blood pressure determining instrument, a constant k particular to the patient's arterial blood pressure-volume relationship is determined and is stored for later use; at the time of measurement information is obtained from the photoplethysmograph output; and a computer determines the patient's systolic and diastolic blood pressure.

DETAILED DESCRIPTION It is an object of this invention to provide an improved method for continuously and non-invasively measuring arterial blood pressure.
It is another object of the present invention to provide an improved method and system for non-invasively determining arterial systolic and diastolic blood pressures with a photoplethysmograph.
These and other objects, which will become apparent as the invention is more fully described below, are obtained by providing a method and apparatus for determining arterial blood pressures using a photoplethysmograph.
The inventive method comprises the steps of calibrating the photoplethysmograph output with a patient's arterial blood pressure to determine an arterial constant k in the formula, .
psi.
=.
psi.
.
sub.
inf (1-Kexp(-kP)) where .
psi.
is the arterial blood volume, .
psi.
.
sub.
inf is a conversion constant corresponding to arterial blood volume at infinite pressure, K and k are arterial constants for the patient, and P is the instantaneous arterial blood pressure; gathering data from the photoplethysmograph output during a measurement period; and computing the arterial systolic and diastolic pressures at the measurement period using the evaluated arterial constant k and the data gathered during the measurement period.

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