Method and apparatus for monitoring and diagnosing hypertension and congestive heart failure

• US 4,899,758 A
• Filed: 08/02/1988
• Issued: 02/13/1990
• Est. Priority Date: 01/31/1986
• Status: Expired due to Term

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Cohn, Jay N., Finkelstein, Stanley M.
• Primary Examiner(s): JAWORSKI, FRANCIS J
• Application Number:
  US07/228,820
• Time in Patent Office: 560 Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence

Abstract

Apparatus and method for monitoring and diagnosing CHF and hypertension includes digitizing brachial artery pulses and determining C₂ from modified Windkessel model. CHF and hypertension are monitored and diagnosed by tracking C₂ values and testing values against a disease discriminating threshold of 0.08 ml/mm Hg.

Claims

1. A congestive heart failure monitor comprising:

RAM means for storing data;

input means for receiving and storing a cardiac output

transducer means for converting an arterial pressure to a corresponding electrical analog signal;

analog to digital converter means for receiving said analog signal and digitizing it at a predetermined sampling rate;

means for storing digitized samples produced by said converter means in said RAM means, said samples being stored over a time interval so that one or more pressure waves, each corresponding to a beat of the human heart, are digitized and stored in said RAM means as a series data bytes, each byte representing the instantaneous pressure of the arterial pressure;

means for determining a mean arterial pressure value from said stored data bytes and storing said value;

means for determining the value of the parameter C₂ of the modified Windkessel model from the pulse contour of the diastolic portion of said waves and from said stored mean arterial pressure value and said stored cardiac output value;

means for testing said C₂ value against a predetermined threshold value of approximately 0.07 ml/mm Hg indicative of a congestive heart failure condition and identifying a congestive heart failure condition for C₂ values below said threshold; and

means for indicating said identified condition to a user of said vascular compliance monitor.

3. A monitor according to claim 1 or 2 wherein said transducer means is connected for converting a brachial artery pressure.

2. A congestive heart failure monitor comprising:

RAM means for storing data;

input means for receiving and storing a cardiac output value;

transducer means for converting an arterial pressure to a corresponding electrical analog signal;

analog to digital converter means for receiving said analog signal and digitizing it at a predetermined sampling rate;

means for storing digitized samples produced by said converter means in said RAM means, said samples being stored over a time interval so that one or more pressure waves, each corresponding to a beat of the human heart, are digitized and stored in said RAM means as a series of data bytes, each byte representing the instantaneous pressure of the arterial pressure;

means for determining a mean arterial pressure value from said stored data bytes and storing said value;

means for determining the value of the parameter C₂ of the modified Windkessel model from the pulse contour of the diastolic portion of said waves and from said stored mean arterial pressure value and cardiac output value;

means for storing a plurality of C₂ values from a plurality of individual determinations done at successive times by said means for determining whereby a plurality of C₂ values may be accumulated over a period of time;

means for determining the slope of said stored accumulated C₂ values over time;

means for inspecting said slope and determining if said accumulated C₂ values are trending upward or downward and identifying a deteriorating CHF condition if said slope is negative and identifying an improving CHF condition if said slope is positive; and

means for indicating the identified improving or deteriorating condition to the user of said monitor whereby congestive heart failure may be monitored.

4. A method of diagnosing congestive heart failure, comprising the steps of:

(a) obtaining a cardiac output value;

(b) measuring arterial pressure using a transducer, said transducer producing an electrical analog signal corresponding to said arterial pressure;

(c) sampling said analog signal over time at a predetermined sampling rate to provide a series of values representing one or more pressure waves each corresponding to a beat of the human heart;

(d) determining the mean arterial pressure from said series of values;

(e) determining the value of the parameter C₂ of the modified Windkessel model from the pulse contour of the diastolic portion of said one or more waves as represented by said series of values and from said mean arterial pressure and cardiac output value; and

(f) testing said C₂ value against a predetermined threshold value below which C₂ values are associated with a congestive heart failure condition whereby a CHF condition may be identified.

5. The method of claim 4 wherein the predetermined threshold value is approximately 0.07 ml/mm Hg.

6. The method of claim 4 wherein the predetermined threshold value is greater than 0.07 ml/mm Hg to allow for a margin of error in identifying congestive heart failure.

10. A method according to claim 4 or 7 wherein said arterial pressure measured is a brachial artery pressure.

7. A method for monitoring congestive heart failure, comprising the steps of:

(a) obtaining a cardiac output value;

(b) measuring an arterial pressure using a transducer, said transducer producing an electrical analog signal corresponding to said arterial pressure;

(c) sampling said analog signal over time at a predetermined sampling rate to provide a series of values representing one or more pressure waves each corresponding to a beat of the human heart;

(d) determining the mean arterial pressure from said series of values;

(e) determining the value of the parameter C₂ of the modified Windkessel model from the pulse contour of the diastolic portion of said one or more waves as represented by said series of values and from said mean arterial pressure and cardiac output value;

(f) recording said determining C₂ value;

(g) repeating steps (a) through (f) at successive times to accumulate a plurality of recorded C₂ values over a period of time;

(h) comparing the first of said accumulated C₂ values against a predetermined diagnostic threshold value discriminating between C₂ values associated with a healthy condition;

(i) identifying an improving congestive heart failure condition when said first C₂ value is below said threshold value and the remaining C₂ values are trending toward said threshold value;

(j) identifying an improving healthy trend away from a congestive heart failure condition when said first C₂ value is above said threshold value and the remaining C₂ values are trending away from said threshold value;

(k) identifying a deteriorating congestive heart failure condition when said first C₂ value is below said threshold value and the remaining C₂ values are trending away from said threshold value; and

(1) identifying a trend toward a congestive heart failure condition when said first C₂ value is above said threshold value and the remaining C₂ values are trending toward said threshold value.

8. The method of claim 7 wherein the predetermined diagnostic threshold value is approximately 0.07 ml/mm Hg.

9. The method of claim 7 wherein the predetermined diagnostic threshold value is greater than 0.07 ml/mm Hg to allow for a margin of error in identifying a congestive heart failure condition.

11. A method of diagnosing congestive heart failure, comprising the steps of:

(a) obtaining a cardiac output value;

(b) measuring arterial pressure over time to obtain a representation of one or more pressure waves each corresponding to a beat of the human heart;

(c) determining the mean arterial pressure;

(d) determining the value of the parameter C₂ of the modified Windkessel model from the pulse contour of the diastolic portion of said one or more waves and from said mean arterial pressure and cardiac output value; and

(e) testing said C₂ value against a predetermined diagnostic threshold value below which C₂ values are associated with a congestive heart failure condition whereby a CHF condition may be identified.

13. A method according to claim 11 or 12 wherein said arterial pressure is measured from the brachial artery.

14. A method according to claim 11 or 12 wherein said predetermined diagnostic threshold value is approximately 0.07 ml/mm Hg.

15. A method according to claim 11 or 12 wherein predetermined diagnostic threshold value is greater than 0.07 ml/mm Hg to allow for a margin of error in identifying congestive heart failure.

12. A method for monitoring congestive heart failure, comprising the steps of:

(a) obtaining a cardiac output value;

(b) measuring arterial pressure over time to obtain a representation of one or more pressure waves each corresponding to a beat of the human heart;

(c) determining the mean arterial pressure;

(d) determining the value of the parameter C₂ of the modified Windkessel model from the pulse contour of the diastolic portion of said one or more waves and from said mean arterial pressure and cardiac output value;

(e) recording said determined C₂ value;

(f) repeating steps (a) through (e) at successive times to accumulate a plurality of recorded C₂ values over a period of time;

(g) comparing the first of said accumulated C₂ values against a predetermined diagnostic threshold value discriminating between C₂ values associated with a congestive heart failure condition and those C₂ values associated with a healthy condition;

(h) identifying an improving congestive heart failure condition when said first C₂ value is below said threshold value and the remaining C₂ values are trending toward said threshold value; and

(i) identifying an improving healthy trend away from a congestive heart failure condition when said first C₂ value is above said threshold value and the remaining C₂ values are trending away from said threshold value;

(j) identifying a deteriorating congestive heart failure condition when said first C₂ values is below said threshold value and the remaining C₂ values are trending away from said threshold value; and

(k) identifying a trend toward a congestive heart failure condition when said first C₂ value is above said threshold value and the remaining C₂ values are trending toward said threshold value.