Noncontactive arterial blood pressure monitor and measuring method

• US 4,846,189 A
• Filed: 06/29/1987
• Issued: 07/11/1989
• Est. Priority Date: 06/29/1987
• Status: Expired due to Fees

• Current Assignee: Physical Optics Corporation
• Original Assignee: Physical Optics Corporation
• Inventors: Sun, Shuxing
• Primary Examiner(s): Jaworski, Francis
• Application Number:
  US07/068,107
• Time in Patent Office: 743 Days
• Field of Search: 128/679-683, 128/666-667, 128/687-690
• US Class Current: 600/492
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/02241 of small dimensions, e.g. adapted to fingers
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors

Abstract

An automatic, continuous, non-occlusive blood pressure monitor includes a pressure applying cuff for temporarily applying pressure to a person'"'"'s finger, a light source for illuminating the finger and an artery in the finger, a photosensor for detecting light transmitted through or reflected from the finger and for producing a signal representing relative volume of a unit length of the artery, a pressure sensor for producing a pressure signal representing the pressure applied by the cuff to the finger, and a microprocessor for developing from the relative volume signal and the pressure signal a formulation of arterial pressure P(t) as a function of relative arterial volume, and for calculating the arterial pressure P(t) from the relative volume signals.

Claims

1. An apparatus for automatically measuring a person'"'"'s blood pressure comprising:

means for applying pressure to a body part of the person in response to a pressure supply signal, and for temporarily occluding the flow of blood on said body part by application of said pressure;

means for directing light toward the body part and an artery in the body part;

means for directing the intensity of light passing through or reflected by the body part and artery and for producing therefrom a signal V(t) representing the relative volume of a unit length of the artery, and having an AC component and DC component;

means for detecting the pressure applied to the body part and producing a signal P_c (t) representing said detected pressure; and

processor means for

(a) calculating means pressure P_m and systolic pressure P_s from said signal P_c (t) and said AC component of said signal V(t)

(b) thereafter controlling said means for applying pressure so as to remove the pressure from the body part,

(c) calculating a formulation of arterial pressure P(t) as a function of relative arterial volume V(t) using said means pressure P_m and systolic pressure P_s, and

(d) for continuously using said signal V(t) for calculating the arterial pressure P(t) of the person from said signal V(t).

2. Apparatus as in claim 1 further comprising display means coupled to the processor means for displaying the calculated arterial pressure P(t).

3. Apparatus as in claim 1 wherein said processor means comprises a microprocessor.

4. A process for automatically measuring the blood pressure of a person comprising the steps of

(a) temporarily occluding the flow of blood on a body part of the person by application of a pressure,

(b) directing light toward the body part and an artery in the body part,

(c) detecting the intensity of light passed through or reflected by the body part and artery and producing therefrom a signal P_c (t) representing the relative volume of a unit length of the artery, and having an AC component and DC component,

(d) detecting the pressure applied to the body part and producing a signal P_c (t) representing that pressure,

(e) calculating mean pressure P_m and systolic pressure P_s from the signal P_c (t) and AC component of the signal V(t),

(f) removing the pressure from the body part,

(g) calculating a formulation of arterial pressure P(t) as a function of a relative arterial volume V(t) using the mean pressure P_m and systolic P_s,

(h) continuously produce the signal V(t) as in step (c) but without application of pressure to said part, and

(i) calculating the arterial pressure P(t) of the person from the signal V(t). person from signal V(t).

5. A process as in claim 4 wherein steps (a) and (f) comprise automatically applying pressure to and removing pressure from the body part under control of a microprocessor.

6. A process as in claim 4 wherein step (g) comprises the steps of

(j) calculating parameters for the Hardy model compliance curve for the person, represented by

7. A process as in claim 4 wherein step (g) comprises

(l) selecting a value for diastolic pressure P_d to be