Oscillometric non-invasive method for measuring blood pressure and apparatus for automated oscillometric blood pressure measuring

• US 4,984,577 A
• Filed: 03/20/1989
• Issued: 01/15/1991
• Est. Priority Date: 03/20/1989
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Frankenreiter, Michael
• Primary Examiner(s): Hindenburg, Max
• Assistant Examiner(s): LACYK, JOHN P
• Application Number:
  US07/326,147
• Time in Patent Office: 666 Days
• Field of Search: 128/672, 128/677-686
• US Class Current: 600/494
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02225 using the oscillometric method

Abstract

A method and an apparatus for automatic oscillometric blood pressure measuring determines a sequence of peak amplitudes. Two points p_e1, p_e2 are evaluated on an envelope (10) of said peak sequence, said points p_e1, p_e2 are the base for determining blood pressure values such as mean, diastolic and systolic pressures.

Claims

1. An oscillometric non-invasive method for measuring blood pressure, comprising the steps of:

(a) applying a blood pressure cuff about a subject'"'"'s limb containing an artery;

(b) inflating said cuff to a cuff pressure above the systolic blood pressure of said artery, therby occluding said artery;

(c) reducing said cuff pressure step by step, thereby permitting an increasing flow through the progressively less occluded artery;

(d) monitoring arterial counterpressure oscillations at each cuff pressure reducing step;

(e) converting said counterpressure oscillations to voltage signals;

(f) processing said voltage signals into a sequence of peak amplitudes enveloped by an envelope;

(g) evaluating at least two points p_e1 and p_e2 on said envelope, the first point p_e1 disposed within an area of a decreasing branch of said envelope, said area corresponding to situations wherein the contact between said cuff and said limb is sufficiently strong for obtaining correct peak amplitudes, the second point p_e2 disposed on an increasing branch of said envelope;

(h) determining at least two cuff pressure values, said pressure values including values p₁ and p₂ corresponding respectively to said points p_e1 and p_e2 ; and

(i) determining mean, systolic, and diastolic pressures using said at least cuff pressure values p₁ and p₂.

2. A method as recited in claim 1 wherein step (g) further comprises evaluating said two points p_e1 and p_e2 at the same level of said envelope.

3. A method as recited in claim 2 wherein step (g) further comprises evaluating said two points p_e1 and p_e2 on said envelope (10) within the range of 0.65 to 0.85 of the maximum of said sequence of peak amplitudes.

4. A method as recited in claim 2 wherein step (g) further comprises evaluating said two points p_e1 and p_e2 on said envelope at 3/4 of the maximum of said sequence of peak amplitudes.

5. A method as recited in claim 2 wherein step (i) further comprises determining said mean pressure by approximating said envelope between p_e1 and p_e2 to a triangle according to equation 1,

6. A method as recited in claim 1 wherein step (i) further comprises determining said diastolic and systolic pressures according to equations 2 and 3,

7. An apparatus for automatic oscillometric blood pressure measuring, comprising:

an inflatable and deflatable cuff;

controlling means for controlling cuff pressures, so as to inflate said cuff to a maximum cuff pressure and deflate said cuff in predetermined cuff pressure reducing steps;

monitoring means for monitoring arterial counterpressure oscillations at each of said cuff pressure reducing steps;

pressure transducer means coupled to said cuff for converting said counterpressure oscillations to voltage signals;

processing means for processing said voltage signals into a sequence of peak amplitudes, said sequence being enveloped by an envelope;

evaluating means for evaluating at least two points p_e1 and p_e2 on said envelope, the first point p_e1 disposed within an area of a decreasing branch of said envelope, said area corresponding to situations wherein the contact between said cuff and a limb of said subject is sufficiently strong for obtaining correct peak amplitudes, the second point p_e2 disposed on an increasing branch of said envelope; and

determining means for determining cuff pressure values p₁ and p₂ corresponding to said points p_e1 and p_e2, said determining means further determining mean, systolic, and diastolic pressures using said cuff pressure values p₁ and p₂.

8. An apparatus as recited in claim 7 wherein said evaluating means evaluate said first and second points p_e1 and p_e2 at the same level of said envelope.

9. An apparatus as recited in claim 8 wherein said evaluating means evaluate said two points p_e1 and p_e2 on said envelope (10) within the range of 0.65 to 0.85 of the maximum of said sequence of peak amplitudes.

10. An apparatus as recited in claim 8 wherein said evaluating means evaluate said two points p_e1 and p_e2 on said envelope (10) at 3/4 of the maximum of said sequence of peak amplitudes.

11. An apparatus as recited in claim 8 wherein said determining means determine mean pressure value according to equation 1:

space="preserve" listing-type="equation">mean pressure=p.sub.1 +1/3(p.sub.2 -p.sub.1) Eq. 1

12. An apparatus as recited in claim 8 wherein said determining means determine systolic and diastolic pressures according to equations 2 and 3:

space="preserve" listing-type="equation">systolic pressure=p.sub.2 +1/3(p.sub.2 -p.sub.1) Eq. 2

space="preserve" listing-type="equation">diastolic pressure=p.sub.1 -1/6(p.sub.2 -p.sub.1) Eq. 3