Process for monitoring patients with chronic congestive heart failure

• US 5,788,643 A
• Filed: 04/22/1997
• Issued: 08/04/1998
• Est. Priority Date: 04/22/1997
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Zymed Medical Instrumentation Incorporated
• Inventors: Feldman, Charles L.
• Primary Examiner(s): Asher, Kimberly L.
• Application Number:
  US08/837,901
• Time in Patent Office: 469 Days
• Field of Search: 600/301, 600/305, 600/345, 600/382, 600/384, 600/547, 600/561, 600/481, 600/483, 600/506, 128/898
• US Class Current: 600/506
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/4869 Determining body composition

Abstract

In a process for monitoring patients with chronic congestive heart failure, a high frequency current is passed between electrodes applied to two limbs of a patient. The current, voltage and phase angle between the measured current and voltage are measured to enable the calculation of congestive heart failure (CHF) indicia values. The calculated CHF indicia values are then compared with baseline values established when the patient is in a known, stable condition. Intervention is initiated if the differences between the calculated CHF indicia values and the baseline values are outside of established tolerances. The CHF indicia values may include resistance, reactance, impedance, total body water and extracellular water. Moreover, the CHF indicia values may include a figure of merit indicative of the hydration status of the patient.

Claims

1. A process for monitoring patients with chronic congestive heart failure, comprising the steps of:

applying electrodes to two limbs of a patient;

passing a high frequency current between the electrodes;

measuring the current (I), voltage (V) and phase angle (φ

) between the voltage (V) and the measured current (I);

calculating congestive heart failure (CHF) indicia values based on the measured current (I), voltage (V) and phase angle (φ

); and

comparing the calculated CHF indicia values with baseline values to determine if differences therebetween are within established tolerances.

2. The process of claim 1, including the step of establishing the baseline values when the patient is in a known, stable condition.

3. The process of claim 2, including the step of initiating intervention when, during the comparing step, the differences between the calculated CHF indicia values and the baseline values are outside of established tolerances.

4. The process of claim 3, including the step of repeating the process for monitoring patients with chronic congestive heart failure at an interval determined by whether or not intervention was required.

5. The process of claim 3, wherein the calculated CHF indicia values include resistance (R) and reactance (Z_c).

6. The process of claim 5, wherein the calculated CHF indicia values include impedance (Z).

7. The process of claim 6, wherein a decrease in the phase angle (φ

) or any of the calculated CHF indicia values of resistance (R), reactance (Z_c) or impedance (Z), is an indicator of the need to initiate intervention.

8. The process of claim 7, wherein the tolerances from baseline values for the calculated CHF indicia values are on the order of five percent (5%) for resistance (R) and impedance (Z), ten percent (10%) for reactance (Z_c), and twenty percent (20%) for phase angle (φ

).

9. The process of claim 5, wherein the calculated CHF indicia values include total body water (TBW) and extracellular water (ECW).

10. The process of claim 9, wherein total body water (TBW) is calculated utilizing the formula:

space="preserve" listing-type="equation">TBW=0.377 Ht.sup.2 /R+0.14 Wt-0.08 Age+2.9 Gender+4.65 (Where Gender=1 for male and 0 for female), and

wherein extracellular water (ECW) is calculated utilizing the formula;

space="preserve" listing-type="equation">ECW=0.189 Ht.sup.2 /R+0.52 Wt-0.0002 Ht.sup.2 /Z.sub.c +1.03,

wherein Ht=the height of the patient and Wt=the weight of the patient.

11. The process of claim 9, wherein an increase in the calculated total body water (TBW) or extracellular water (ECW) is an indicator of the need to initiate intervention.

12. The process of claim 11, wherein the tolerances from baseline values for the calculated CHF indicia values are on the order of five percent (5%) for total body water (TBW) and extracellular water (ECW).

13. The process of claim 5, wherein the calculated CHF indicia values include a figure of merit indicative of the hydration status of the patient.

14. The process of claim 13, wherein the figure of merit is derived from the ratio of extracellular water (ECW) over fat-free mass (FFM).

15. The process of claim 14, wherein extracellular water (ECW) is calculated using the formula:

space="preserve" listing-type="equation">ECW=0.189 Ht.sup.2 /R+0.52 Wt-0.0002Ht.sup.2 /Z.sub.c +1.03, and

wherein fat-free mass (FFM) is calculated utilizing the formula;

space="preserve" listing-type="equation">FFM=-15.26-0.775(Ht.sup.2 /R)+0.146 Wt+0.185 Z.sub.c,

wherein Ht=the height of the patient and Wt=the weight of the patient.

16. The process of claim 14, wherein intervention is indicated when the ratio of extracellular water (ECW) to fat-free mass (FFM) is greater than approximately 0.30.

17. The process of claim 14, wherein an increase in the figure of merit on the order of one percent (1%) is an indicator of the need to initiate intervention.

18. A process for monitoring patients with chronic congestive heart failure, comprising the steps of:

applying electrodes to two points on the body of a patient;

passing a current at one or more high frequencies between the electrodes;

measuring the current (I) and voltage (V) at each frequency;

calculating congestive heart failure (CHF) indicia values based on the measured current(s) (I) and voltage(s) (V); and

comparing the calculated CHF indicia values with baseline values to determine if differences therebetween are within established tolerances.

19. The process of claim 18, including the steps of establishing baseline values determined when the patient is in a known, stable condition, initiating intervention when, during the comparing step, the differences between the calculated CHF indicia values and the baseline values are outside of established tolerances, and repeating the process for monitoring patients with chronic congestive heart failure at an interval determined by whether or not intervention was required.

20. The process of claim 19, wherein the calculated CHF indicia values include total body water (TBW) and extracellular water (ECW), and wherein an increase in the calculated total body water (TBW) or extracellular water (ECW) is an indicator of the need to initiate intervention.

21. The process of claim 20, wherein the tolerances from baseline values for the calculated CHF indicia values are on the order of five percent (5%) for total body water (TBW) and extracellular water (ECW).

22. The process of claim 20, wherein the calculated CHF indicia values include a figure of merit, derived from the ratio of extracellular water (ECW) over fat-free mass (FFM), that is indicative of the hydration status of the patient.

23. The process of claim 22, wherein intervention is indicated when the ratio of extracellular water (ECW) to fat-free mass (FFM) is greater than approximately 0.30, or there is an increase in the figure of merit on the order of one percent (1%).

24. The process of claim 19, including the step of measuring the phase angle (φ

) between the measured current (I) and voltage (V) at each frequency, and wherein the calculated CHF indicia values include resistance (R), reactance (Z_c), and impedance (Z).

25. The process of claim 24, wherein a decrease in the phase angle (φ

) or any of the calculated CHF indicia values of resistance (R), reactance (Z_c) or impedance (Z), is an indicator of the need to initiate intervention.

26. The process of claim 24, wherein the tolerances from baseline values for the calculated CHF indicia values are on the order of five percent (5%) for resistance (R) and impedance (Z), ten percent (10%) for reactance (Z_c), and twenty percent (20%) for phase angle (φ

).

27. A process for monitoring patients with chronic congestive heart failure, comprising the steps of:

applying electrodes to two limbs of a patient;

passing a high frequency current between the electrodes;

measuring the current (I), voltage (V) and phase angle (φ

) between the voltage (V) and the measured current (I);

calculating congestive heart failure (CHF) indicia values, including resistance (R) and reactance (Z_c), based on the measured current (I), voltage (V) and phase angle (φ

);

comparing the calculated CHF indicia values with baseline values to determine if differences therebetween are within established tolerances;

initiating intervention when, during the comparing step, the differences between the calculated CHF indicia values and the baseline values are outside of established tolerances; and

repeating the process for monitoring patients with chronic congestive heart failure at an interval determined by whether or not intervention was required.

28. The process of claim 27, including the step of establishing the baseline values when the patient is in a known, stable condition.

29. The process of claim 28, wherein the calculated CHF indicia values include impedance (Z), and wherein a decrease in the phase angle (φ

) or any of the calculated CHF indicia values of resistance (R), reactance (Z_c) or impedance (Z), is an indicator of the need to initiate intervention.

30. The process of claim 29, wherein the tolerances from baseline values for the calculated CHF indicia values are on the order of five percent (5%) for resistance (R) and impedance (Z), ten percent (10%) for reactance (Z_c), and twenty percent (20%) for phase angle (φ

).

31. The process of claim 27, wherein the calculated CHF indicia values include total body water (TBW) and extracellular water (ECW), and wherein an increase in the calculated total body water (TBW) or extracellular water (ECW) is an indicator of the need to initiate intervention.

32. The process of claim 31, wherein total body water (TBW) is calculated utilizing the formula:

space="preserve" listing-type="equation">TBW=0.377 Ht.sup.2 /R+0.14 Wt-0.08 Age+2.9 Gender+4.65 (Where Gender=1 for male and 0 for female), and

wherein extracellular water (ECW) is calculated utilizing the formula;

space="preserve" listing-type="equation">ECW=0.189 Ht.sup.2 /R+0.52 Wt-0.0002 Ht.sup.2 /Z.sub.c +1.03,

wherein Ht=the height of the patient and Wt=the weight of the patient.

33. The process of claim 31, wherein the tolerances from baseline values for the calculated CHF indicia values are on the order of five percent (5%) for total body water (TBW) and extracellular water (ECW).

34. The process of claim 27, wherein the calculated CHF indicia values include a figure of merit indicative of the hydration status of the patient.

35. The process of claim 34, wherein the figure of merit is derived from the ratio of extracellular water (ECW) over fat-free mass (FFM), wherein intervention is indicated when the ratio of extracellular water (ECW) to fat-free mass (FFM) is greater than approximately 0.30, and wherein an increase in the figure of merit on the order of one percent (1%) is an indicator of the need to initiate intervention.

36. The process of claim 35, wherein extracellular water (ECW) is calculated using the formula:

space="preserve" listing-type="equation">ECW=0.189 Ht.sup.2 /R+0.52 Wt-0.0002 Ht.sup.2 /Z.sub.c +1.03, and

wherein fat-free mass (FFM) is calculated utilizing the formula;

space="preserve" listing-type="equation">FFM=-15.26-0.775 (Ht.sup.2 /R)+0.146 Wt+0.185 Z.sub.c,

wherein Ht=the height of the patient and Wt=the weight of the patient.