Pressure control system for continuous blood pressure monitor transducer

• US 4,836,213 A
• Filed: 02/25/1988
• Issued: 06/06/1989
• Est. Priority Date: 02/25/1988
• Status: Expired due to Term

• Current Assignee: Omron Healthcare Company Limited (Omron Corporation)
• Original Assignee: Nippon Colin Company Limited
• Inventors: Honeyager, Kevin S., Wenzel, Dennis J., Winter, Dean C.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Sykes, Angela D.
• Application Number:
  US07/160,134
• Time in Patent Office: 467 Days
• Field of Search: 128/672-690
• US Class Current: 600/485
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence

Abstract

A method for computing optimal hold down pressure for a transducer comprising an array of pressure sensing elements for generation of electrical waveforms indicative of blood pressure in an artery. Using the selected pressure sensing element that is determined to be positioned substantially over the center of the underlying artery, a set of data corresponding to the diastolic pressure and the pulse amplitude pressure is collected and stored. The diastolic pressures and pulse amplitude pressures are taken as a function of hold down pressure over a range of hold down pressures between the pressure at which the artery is unflattened and the pressure at which the artery is occluded. First and second polynomials are fitted to the diastolic pressure data set and the pulse amplitude data set, respectively. The hold-down pressure at the point of minimum slope of the first polynomial fitted to the diastolic versus hold-down pressures values provides one estimate of the correct hold-down pressure. Another estimate of the correct hold-down pressure using the pulse amplitude measurements is provided by locating the point where the slope of the second polynomial is zero. In another embodiment of the method of the present invention, the two above described estimates are combined into a single estimate.

Claims

1. A method for determining the optimum hold-down pressure for use in a blood pressure measuring system comprising steps of

applying a minimum hold-down pressure to an external pressure transducer that includes a pressure sensitive element and obtaining a continuous measurement of pulse pressure in an underlying artery,

obtaining a set of diastolic and systolic pressure measurements corresponding to a single hold-down pressure as the hold-down pressure is incremented;

computing a set of pulse amplitudes corresponding to each hold-down pressure by subtracting the corresponding diastolic from the corresponding systolic pressure;

fitting a first polynomial to the set of pulse amplitudes versus hold-down pressure, said polynomial describing the pulse amplitude as a function of the hold-down pressure designated herein as P(h);

fitting a second polynomial to the set of diastolic pressures versus hold-down pressures, said second polynomial describing the diastolic pressure as a function of the hold-down pressure and designated herein as D(h);

taking a first derivative with respect to the hold-down pressure of the polynomial D(h), designated herein as D'"'"'(h);

computing, for each discrete hold-down pressure, a function designated herein as G(h), wherein ##EQU4## selecting as the optimum hold-down pressure that pressure for which the computed G(h) is a maximum.

2. The method according to claim 1 wherein P(h) and D(h) are generated using a least squares calculation.

3. The method according to claim 2, wherein D(h) is a third order polynomial.

4. The method according to claim 3, wherein said P(h) is a third order polynomial.

5. The method according to claim 1, wherein a first derivative of G(h) is taken with respect to the hold-down pressure and the optimum hold-down pressure is selected as that for which said first derivative of G(h) is equal to zero.