Wrist worn ECG monitor

• US 5,351,695 A
• Filed: 01/07/1993
• Issued: 10/04/1994
• Est. Priority Date: 12/26/1991
• Status: Expired due to Fees

• Current Assignee: Card Guard Technologies Inc. (Koninklijke Philips N.V.)
• Original Assignee: Instromedix, Inc. (Koninklijke Philips N.V.)
• Inventors: Homayoun, Habib, Mills, Gary N.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/001,748
• Time in Patent Office: 635 Days
• Field of Search: 128/696, 128/901, 128/702, 128/710
• US Class Current: 600/508
• CPC Class Codes: A61B 5/332 Portable devices specially adapted therefor
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal
• CPC Class Codes: Y10S 128/904 Telephone telemetry

Abstract

A compact, lightweight wrist-worn cardiac data and event monitor having dry skin electrodes integral with the monitor'"'"'s housing is disclosed. Preferably, the skin electrodes are made of titanium nitride-plated stainless steel and form inner, wrist-contacting, and outer, other hand'"'"'s palm-contactable regions of the housing. Chronometric and other multiple functions are provided to increase the functional density of the monitor by partitioning and very-large-scale-integrating the circuitry, which includes signal detection; data conversion, storage, display and telecommunication; and external pushbutton controls operable by the patient'"'"'s other hand. In accordance with the preferred embodiment, a telephonic transmitter is integrally included within the housing for remote diagnostic purposes without the need for external connections. By a preferred method of the invention, a simplified digital filter implemented in firmware ensures that only ECG and event data are recorded at the exclusion of noise and motion artifacts. By another preferred method of the invention, a battery life prediction method is used to extend the useful life of the battery and to indicate to the patient when the battery should be replaced. Event data that may be recorded and tele-transmitted along with the ECG data include time-of-day or elapsed time markers, as well as markers or indications of the detection of any pulses produced, for example, by an implanted pacemaker or an implanted cardio-verter/defibrillator monitor (ICDM).

Claims

1. For use with a wrist-worn ECG data monitor, a method for digitally filtering successive ECG data samples comprising:

providing successive ECG data samples;

initializing a first and second filter output value;

first calculating a first filter output value equal to a first weighted average of plural ones of such successive ECG data samples, wherein the contributions of said ones to said weighted average are related to one another by powers of two;

second calculating a second filter output value equal to a second weighted average of at least one said first filter output value and at least one said second filter output value, wherein the contributions of said output values to said second weighted average are related to one another by powers of two;

repeating said first and second calculating steps to produce a succession of digitally filtered output values; and

processing said succession of digitally filtered output values into a record of filtered ECG data.

2. The method of claim 1, wherein said first and second calculating steps are performed by bit shifting.

3. For use with an ECG data monitor, a method for digitally filtering an ECG signal comprising:

sampling an analog ECG signal at a predetermined frequency to produce a succession of plural signal-representative ECG data of a predetermined number p;

digitally filtering said produced ECG data by evaluating an expression of the form

space="preserve" listing-type="equation">A(0)=m.sup.±

1 Σ

nX(p),

where X(p) is one of the succession of ECG data produced by said sampling and where A(0) is the output value produced by said evaluating,

wherein m is an integer power of two, wherein n is zero or an integer power of two and where p is an integer including zero;

repeating said sampling and filtering to produce a succession of filtered output values produced by said evaluating; and

processing said succession of filtered output values into a record of filtered ECG data.

4. For use with an ECG data monitor, a method for digitally filtering an ECG signal comprising:

providing an analog ECG signal;

digitizing the analog ECG signal to produce a plurality of signal-representative ECG data bit strings with each data bit string including a plurality of bits;

first shifting selected ones of said ECG data bit strings an integer number of bits in either direction in accordance with a first predetermined algorithm to produce a plurality of modified ECG data bit strings;

summing selected ones of said modified ECG data bit strings to produce a weighted average of said ECG data bit string plurality;

second shifting said weighted average an integer number of bits in either direction in accordance with a second predetermined algorithm to produce a filtered ECG output data bit string; and

processing said ECG output data bit string into a record of filtered ECG data.

5. A method for filtering an ECG signal comprising:

providing an ECG data monitor;

monitoring a patient with the ECG data monitor to produce a plurality of signal-representative ECG data bit strings with each data bit string including a plurality of bits;

first shifting selected ones of said ECG data bit strings an integer number of bits in either direction in accordance with a first predetermined algorithm to produce a plurality of modified ECG data bit strings;

summing selected ones of said modified ECG data bit strings to produce a weighted average of said ECG data bit string plurality;

second shifting said weighted average an integer number of bits in either direction in accordance with a second predetermined algorithm to produce a filtered ECG output data bit string; and

processing said ECG output data bit string into a record of filtered ECG data.

6. A method for digitally filtering an ECG signal comprising:

providing an ECG data monitor;

monitoring a patient with the ECG data monitor to produce an analog ECG signal;

converting the analog ECG signal into a plurality of signal-representative ECG data bit strings with each data bit string including a plurality of bits;

first shifting selected ones of said ECG data bit strings an integer number of bits in either direction in accordance with a first predetermined algorithm to produce a plurality of modified ECG data bit strings;

summing selected ones of said modified ECG data bit strings to produce a weighted average of said ECG data bit string plurality;

second shifting said weighted average an integer number of bits in either direction in accordance with a second predetermined algorithm to produce a filtered ECG output data bit string; and

processing said ECG output data bit string into a record of filtered ECG data.

7. A method for digitally filtering successive ECG data samples comprising:

providing an ECG data monitor;

initializing a first and second filter output value;

monitoring a patient with the ECG data monitor to produce an analog ECG signal;

sampling the analog ECG signal to produce successive ECG data samples;

first calculating a first filter output value equal to a first weighted average of plural ones of such successive ECG data samples, wherein the contributions of said ones to said weighted average are related to one another by powers of two;

second calculating a second filter output value equal to a second weighted average of at least one first filter output value and at least one output value of a previous one of said second calculating steps, wherein the contributions of said output values to said second weighted average are related to one another by powers of two;

repeating said first and second calculating steps to produce digitally filtered output data for further processing as a candidate QRS complex; and

processing said digitally filtered output data into a record of filtered ECG data.

8. The method of claim 7, wherein said first and second calculating steps are performed by bit shifting.

9. For use with an ECG data monitor, a method for digitally filtering an ECG signal comprising:

monitoring a patient with the ECG data monitor to produce an analog ECG signal;

sampling the analog ECG signal at a predetermined frequency to produce a succession of plural signal-representative ECG data of a predetermined number p;

converting said produced ECG data into filtered output values by evaluating an expression of the form

space="preserve" listing-type="equation">A(0)=m.sup.±

1 Σ

nX(p),

where X(p) is one of the succession of ECG data produced by said sampling and where A(0) is the output value produced by said evaluating,

wherein m is an integer power of two, wherein n is zero or an integer power of two and where p is an integer including zero;

repeating said sampling and converting to produce a succession of filtered output values produced by said evaluating; and

processing said succession of filtered output values into a record of filtered ECG data.

10. For use with a wrist-worn ECG data monitor, a method for digitally filtering successive ECG data samples comprising:

sampling ECG data at a predetermined rate;

calculating a filtered output value by evaluating an expression of the form

space="preserve" listing-type="equation">A(0)=1/m[X(0)+nX(-1)+X(-2)],

where X(0) is a current ECG data sample, X(-1) is an immediately preceding ECG data sample, X(-2) is an ECG data sample immediately preceding said X(-1) ECG data sample and A(0)is said output value resulting from said evaluating, and wherein m and n are integer powers of two;

repeating said sampling and calculating to produce a succession of filtered output values; and

processing said succession of filtered output values into a record of filtered ECG data.

11. For use with a wrist-worn ECG data monitor a method for digitally filtering successive ECG data samples comprising:

sampling ECG data;

calculating a filtered output value by evaluating an expression of the form

space="preserve" listing-type="equation">A(0)=1/m[X(0)+nX(-1)+X(-2)],

where X(0) is a current ECG data sample, X(-1) is an immediately preceding ECG data sample, X(-2) is an ECG data sample immediately preceding said X(-1) ECG data sample and A(0) is said output value resulting from said evaluating, and wherein m and n are integer powers of two;

repeating said sampling and said calculating, wherein said sampling of successive ECG data samples is performed at a rate calculated to provide a predetermined digital filter frequency response;

repeating said sampling and calculating to produce a succession of filtered output values; and

processing said succession of filtered output values into a record of filtered ECG data.

12. The method of claim 11 or 3, wherein said evaluating is performed by bit shifting.

13. A method for digitally filtering successive ECG data samples comprising:

providing an ECG data monitor;

monitoring a patient with the ECG data monitor to produce ECG data;

sampling said ECG data at a predetermined rate;

calculating a filtered output value by evaluating an expression of the form

space="preserve" listing-type="equation">A(0)=1/m[X(0)+nX(-1)+X(-2)],

where X(0) is a current ECG data sample, X(-1) is an immediately preceding ECG data sample, X(-2) is an ECG data sample immediately preceding said X(-1) ECG data sample and A(0) is said output value resulting from said evaluating, and wherein m and n are integer powers of two;

repeating said sampling and calculating to produce a succession of filtered output values; and

processing said succession of filtered output values into a record of filtered ECG data.

16. The method of claim 5,6,7,8,13,14 or 9, further comprising the step of attaching the ECG data monitor to the wrist of the patient being monitored.

14. A method for digitally filtering successive ECG data samples comprising:

providing an ECG data monitor;

monitoring a patient with the ECG data monitor to produce ECG data;

sampling said ECG data;

converting said sampled ECG data into a filtered output value by evaluating an expression of the form

space="preserve" listing-type="equation">A(0)=1/m[X(0)+nX(-1)+X(-2)],

where X(0) is a current ECG data sample, X(-1) is an immediately preceding ECG data sample, X(-2) is an ECG data sample immediately preceding said X(-1) ECG data sample and A(0) is said output value resulting from said evaluating, and wherein m and n are integer powers of two;

repeating said sampling and said converting, wherein said sampling of successive ECG data samples is performed at a rate calculated to provide a predetermined digital filter frequency response;

repeating said sampling and calculating to produce a succession of filtered output values; and

processing said succession of filtered output values into a record of filtered ECG data.

15. The method of claim 14 or 9, whereto said evaluating is performed by bit shifting.