Apparatus and method for measuring blood pressure with motion artifacts elimination

• US 8,647,282 B2
• Filed: 07/07/2010
• Issued: 02/11/2014
• Est. Priority Date: 09/03/2009
• Status: Active Grant

• Current Assignee: Quanta Computer
• Original Assignee: Quanta Computer
• Inventors: Shih, Yi-Cheng, Yen, Shih-Chieh
• Primary Examiner(s): Mallari, Patricia
• Assistant Examiner(s): CATINA, MICHAEL ANTHONY
• Application Number:
  US12/831,406
• Publication Number:
  US 20110054331A1
• Time in Patent Office: 1,315 Days
• Field of Search: 600/481, 600/485, 600490-496, 600/500
• US Class Current: 600/494
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00

Abstract

The invention discloses an apparatus and method for measuring a blood pressure. In particular, the method and apparatus according to the invention are capable of eliminating motion artifacts induced by, for example, talking, irregular breathing, frequent swallowing, coughing, shaking, and so on motions of a subject. The method and apparatus according to the invention utilizes a set of fuzzy logic rules and a curve-fitting way to eliminate the motion artifacts.

Claims

1. An apparatus for measuring a blood pressure of a subject susceptible to noise during measurement, comprising:

a cuff configured to be placed around the subject'"'"'s arm containing an artery;

an inflating unit, coupled to the cuff, for inflating the cuff;

a pressure transducer coupled to the cuff; and

a controlling/processing unit, coupled to the cuff, the inflating unit and the pressure transducer, respectively, for controlling the inflating unit to inflate the cuff to an initial inflation pressure, controlling the cuff to be deflated from the initial inflation pressure, obtaining a cuff pressure signal and a sequence of raw oscillometric pulse amplitudes (raw OA) relating to counter-pressure of the artery from the pressure transducer as the cuff is deflated from the initial inflation pressure, calculating a respective weight ω

for each of the raw oscillometric pulse amplitudes, the respective weight ω

being indicative of level of noise corresponding to the raw oscillometric pulse amplitude and being obtained based on variation rate of oscillometric pulse amplitudes neighboring to each raw oscillometric pulse amplitude, modifying each of the raw oscillometric pulse amplitudes based on the respective weight ω

to obtain a sequence of current oscillometric pulse amplitudes (current OA) replacing the raw oscillometric pulse amplitudes, defining a maximum oscillometric pulse amplitude among the current oscillometric pulse amplitudes, determining a systolic pressure relating to the blood pressure of the subject based on the maximum oscillometric pulse amplitude, the cuff pressure signal and a first ratio, and determining a diastolic pressure relating to the blood pressure of the subject based on the maximum oscillometric pulse amplitude, the cuff pressure signal and a second ratio, wherein the controlling/processing unit modifies each of the raw oscillometric pulse amplitudes (raw OA) by the steps of;

utilizing the raw oscillometric pulse amplitudes neighboring said one raw oscillometric pulse amplitude (OA) having respective weights higher than a threshold value to calculate a respective target oscillometric pulse amplitude (target OA) in a curve-fitting way; and

calculating the current oscillometric pulse amplitude (current OA) by the following formula;

current OA=ω

×

raw OA+(1−

ω

)×

target OA.

2. The apparatus of claim 1, further comprising a measuring device, coupled to the controlling/processing unit and disposed in the cuff, for measuring a circumference value relating to the subject'"'"'s arm wherein the controlling/processing unit comprises a lookup table, obtains the circumference value from the measuring device, and determines the first ratio and the second ratio in accordance with the circumference value and the lookup table.

3. The apparatus of claim 1, wherein the controlling/processing unit applies a set of fuzzy logic rules to the raw oscillometric pulse amplitudes to calculate the respective weight ω

for each of the raw oscillometric pulse amplitudes.

4. A method for measuring a blood pressure of a subject susceptible to noise during measurement by use of a cuff configured to be placed around the subject'"'"'s arm containing an artery, said method comprising the steps of:

inflating the cuff to an initial inflation pressure by an inflating unit;

obtaining a cuff pressure signal and a sequence of raw oscillometric pulse amplitudes relating to counter-pressure of the artery from a pressure transducer coupled to the cuff as the cuff is deflated from the initial inflation pressure;

calculating a respective weight ω

for each of the raw oscillometric pulse amplitudes by a processor unit, the respective weight ω

being indicative of level of noise corresponding to the raw oscillometric pulse amplitude and being obtained based on variation rate of oscillometric pulse amplitudes neighboring to each raw oscillometric pulse amplitude;

based on the respective weight ω

, modifying each of the raw oscillometric pulse amplitudes to obtain a sequence of current oscillometric pulse amplitudes replacing the raw oscillometric pulse amplitudes by the processor unit, wherein the processing unit modifies each of the raw oscillometric pulse amplitudes (raw OA) by the steps of;

utilizing the raw oscillometric pulse amplitudes neighboring said one raw oscillometric pulse amplitude (OA) having respective weights higher than a threshold value to calculate a respective target oscillometric pulse amplitude (target OA) in a curve-fitting way; and

calculating the current oscillometric pulse amplitude (current OA) by the following formula;

current OA=ω

×

raw OA+(1−

ω

)×

target OA;

defining a maximum oscillometric pulse amplitude among the current oscillometric pulse amplitudes by the processor unit; and

based on the maximum oscillometric pulse amplitude, the cuff pressure signal, a first ratio and a second ratio, determining a systolic pressure and a diastolic pressure relating to the blood pressure of the subject by the processor unit.

5. The method of claim 4, further comprising the steps of:

obtaining a circumference value relating to the subject'"'"'s arm the cuff pressure signal from a measuring device in the cuff; and

determining the first ratio and the second ratio in accordance with the circumference value and a lookup table by the processor unit.

6. The method of claim 4, wherein the step of calculating the respective weight ω

for each of the raw oscillometric pulse amplitudes is performed by applying a set of fuzzy logic rules to the raw oscillometric pulse amplitudes.