Evaluation Of Peripheral Arterial Disease In A Patient Using An Oscillometric Pressure Signal Obtained At A Lower Extremity Of The Patient

• US 20120078125A1
• Filed: 09/22/2011
• Published: 03/29/2012
• Est. Priority Date: 09/23/2010
• Status: Active Grant

• Current Assignee: Cleveland Clinic Foundation, Summit Doppler Systems Incorporated
• Original Assignee: Summit Doppler Systems Incorporated
• Inventors: Jarrell, Kenneth E., Jones, David C., Gornik, Heather L., Wang, Xiaofeng
• Granted Patent: US 9,211,070 B2
• Time in Patent Office: Days
• US Class Current: 600/490
• 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 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• 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
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

Systems, methods, and products for determining indicated blood pressure values and/or characterizing a condition of a patient. The systems, methods, and products are capable of determining indicated blood pressure values in a lower extremity of a patient using an oscillometric technique. An oscillometric signal obtained from the lower extremity of the patient is analyzed, and the patient may be classified into one of a plurality of diagnostic classes. Each diagnostic class may have an associated ratio value. Based on the diagnostic class into which the patient is classified, a selected lower extremity characteristic ratio may be selected. A lower extremity indicated blood pressure value may be obtained by oscillometric processing using the selected ratio. This lower extremity indicated blood pressure value may be used with an upper extremity indicated blood pressure value to perform an extremity blood pressure ratio (EBPR) examination.

Claims

1. A method for determining an indicated blood pressure in a lower extremity of a patient, said method comprising:

obtaining an oscillometric pressure signal at a location on the lower extremity;

determining a maximum amplitude of the oscillometric pressure signal;

multiplying the maximum amplitude by a selected lower extremity characteristic ratio to obtain an adjusted amplitude within the oscillometric pressure signal corresponding with an indicated blood pressure in the lower extremity, wherein the selected lower extremity characteristic ratio is selected from a plurality of ratio values such that a first ratio value is selected from the plurality of ratio values if the patient is in a first diagnostic class, and a second ratio value is selected from the plurality of ratio values if the patient is in a second diagnostic class; and

determining the indicated blood pressure in the lower extremity from the adjusted amplitude.

2. The method of claim 1, further comprising:

performing a mathematical transform on the oscillometric pressure signal to produce a frequency domain representation of the oscillometric pressure signal; and

wherein said step of determining a maximum amplitude comprises using the frequency domain representation of the oscillometric pressure signal in determining the maximum amplitude of the oscillometric pressure signal at a fundamental frequency of the oscillometric pressure signal.

4. The method of claim 1, further comprising:

classifying the patient into one of the first diagnostic class and the second diagnostic class at least partially based on the maximum amplitude of the oscillometric pressure signal.

5. The method of claim 4, wherein the classifying includes comparing the maximum amplitude of the oscillometric pressure signal to a lower extremity threshold value.

6. The method of claim 1, further comprising:

determining an indicated blood pressure value in an upper extremity of the patient using an oscillometric technique, wherein an upper extremity characteristic ratio is used in determining the indicated blood pressure value in the upper extremity from an oscillometric pressure signal obtained at a location on the upper extremity.

7. The method of claim 6, further comprising:

characterizing the patient into one of the first diagnostic class and the second diagnostic class at least partially based on a comparison of the oscillometric pressure signal obtained at the location on the upper extremity and the oscillometric pressure signal obtained at the location on the lower extremity.

8. The method of claim 6, wherein the upper extremity characteristic ratio differs from the selected lower extremity characteristic ratio.

9. The method of claim 1, wherein the first diagnostic class comprises patients having a first severity of peripheral artery disease (PAD).

10. The method of claim 9, wherein the first severity of PAD corresponds to patients having moderate to severe PAD.

11. The method of claim 9, wherein the first ratio value is not less than about 0.67 and not greater than about 0.73.

13. The method of claim 9, wherein the second diagnostic class comprises patients having a second severity of PAD.

14. The method of claim 13, wherein the second severity of PAD corresponds to patients having mild to no PAD.

15. The method of claim 13, wherein the second ratio value is not less than about 0.56 and not greater than about 0.63

17. The method of claim 6, wherein the indicated blood pressure values in the upper and lower extremities comprise systolic pressure values.

18. The method of claim 17, further comprising:

calculating a ratio of the indicated blood pressure values in the lower extremity and the upper extremity to produce a blood pressure ratio.

19. The method of claim 18, further comprising:

reporting the blood pressure ratio to a user.

20. The method of claim 18, wherein the location on the lower extremity comprises the ankle and the location on the upper extremity comprises the upper arm.

21. The method of claim 20, wherein the blood pressure ratio comprises an ankle-brachial pressure index (ABI).

22. The method of claim 1, wherein said maximum amplitude is determined by analyzing a window of interest of the oscillometric pressure signal.

23. The method of claim 1, wherein said obtaining comprises:

occluding blood flow within a portion of the lower extremity with a pressure applicator;

controllably releasing pressure of the pressure applicator over a period of time;

generating a pressure signal as pressure of the pressure applicator is released; and

removing a portion of the pressure signal to obtain the oscillometric pressure signal therefrom.

3. (canceled)

12. (canceled)

16. (canceled)

24. A system operable to determine an indicated blood pressure value at a lower extremity of a patient, said system comprising:

a first pressure applicator positionable at a location on the lower extremity of a patient, said first pressure applicator being controllable to apply a pressure to occlude blood flow in a portion of the lower extremity and to reduce the pressure applied thereby to permit blood flow to return in the portion of the lower extremity;

a processor in operative communication with said first pressure applicator;

a first pressure transducer in operative communication with said first pressure applicator to obtain a first oscillometric pressure signal from the lower extremity as pressure applied by the first pressure applicator to the lower extremity is reduced, wherein said first pressure transducer is in operative communication with said processor;

a blood pressure determination module executable by said processor, the blood pressure determination module being operable to detect a maximum amplitude of the first oscillometric pressure signal, multiply the maximum amplitude of the first oscillometric pressure signal by a selected lower extremity characteristic ratio to provide an adjusted amplitude associated with the first oscillometric pressure signal to obtain an indicated blood pressure value in the lower extremity; and

a selection module executable by said processor, said selection module being operable to select the selected lower extremity characteristic ratio from a plurality of ratio values such that a first ratio value is selected from the plurality of ratio values if the patient is in a first diagnostic class and a second ratio value is selected from the plurality of ratio values if the patient is in a second diagnostic class.

25. The system of claim 24, wherein at least one of the blood pressure determination module and the selection module comprise machine readable code stored on a memory in operative communication with said processor, and wherein said processor is operable to execute said machine readable code to execute said at least one of the blood pressure determination module and the selection module.

26. The system of claim 24, further comprising:

a transform module executable by said processor to transform the first oscillometric pressure signal into a frequency domain representation of the first oscillometric pressure signal, and wherein the blood pressure determination module is operable to utilize the frequency domain representation of the first oscillometric pressure signal in determining the maximum amplitude at the fundamental frequency of the first oscillometric pressure signal.

28. The system of claim 24, wherein said selection module is operable to select said selected lower extremity characterization ratio at least partially based on a comparison of the maximum amplitude of the first oscillometric pressure signal to a threshold value.

29. The system of claim 24, further comprising:

a second pressure applicator positionable at a location on an upper extremity of a patient, said second pressure applicator being controllable to apply a pressure to occlude blood flow in a portion of the upper extremity and to reduce the pressure applied thereby to permit blood flow to return in the portion of the upper extremity; and

a second pressure transducer in operative communication with said second pressure applicator to obtain a second oscillometric pressure signal from the upper extremity as pressure applied by the second pressure applicator to the upper extremity is reduced;

wherein the selection module is further operable to compare the first oscillometric pressure signal to the second oscillometric pressure signal to characterize the patient into one of the first diagnostic class and the second diagnostic class.

30. The system of claim 29, wherein the blood pressure determination module is further operable to detect a maximum amplitude of the second oscillometric pressure signal, multiply the maximum amplitude of the second oscillometric pressure signal by an upper extremity characteristic ratio to provide an adjusted amplitude associated with the second oscillometric pressure signal to obtain an indicated blood pressure in the upper extremity.

31. The system of claim 30, wherein the upper extremity characteristic ratio is different than the selected lower extremity characteristic ratio.

32. The system of claim 30, wherein the indicated blood pressure values in the upper and lower extremities comprise systolic pressure values.

33. The system of claim 32, wherein the processor is operable to calculate a ratio of the indicated blood pressure values in the lower and the upper extremities to produce a blood pressure ratio.

34. The system of claim 33, wherein the location on the lower extremity comprises the ankle of the patient, and the location on the upper extremity comprises the arm of the patient.

35. The system of claim 34, wherein the blood pressure ratio comprises an ankle-brachial pressure index (ABI).

37. The system of claim 24, wherein said blood pressure determination module is operable to determine said maximum amplitude of the first oscillometric pressure signal within a window of interest of the first oscillometric pressure signal.

27. (canceled)

36. (canceled)

38. A method of determining corresponding indicated blood pressure values in an upper extremity and a lower extremity of a patient, said method comprising:

determining an indicated blood pressure value in the upper extremity of the patient using an oscillometric technique, wherein an upper extremity characteristic ratio is used in determining the indicated blood pressure value in the upper extremity from an oscillometric pressure signal obtained at a location on the upper extremity; and

determining an indicated blood pressure value in the lower extremity of the patient using an oscillometric technique, wherein a selected lower extremity characteristic ratio is used in determining the indicated blood pressure value in the lower extremity from an oscillometric pressure signal obtained at a location on the lower extremity, wherein said selected lower extremity characteristic ratio differs from the upper extremity characteristic ratio;

wherein said selected lower extremity characteristic ratio is selected from a plurality of ratio values such that a first ratio value is selected from the plurality of ratio values if the patient is in a first diagnostic class, and a second ratio value is selected from the plurality of ratio values if the patient is in a second diagnostic class.

39-45. -45. (canceled)

46. A system operable to detect one or more characteristics useful for characterizing a patient into one of a first diagnostic class characterized as having a first severity of peripheral arterial disease (PAD) and a second diagnostic class characterized as having a second severity of PAD, said system comprising:

a first pressure applicator positionable at a first location on the lower extremity of the patient to occlude blood flow in a portion of the lower extremity;

a processor in operative communication with said first pressure applicator;

a first pressure transducer in operative communication with said first pressure applicator to obtain a first oscillometric pressure signal from the lower extremity as pressure applied by the first pressure applicator to the lower extremity is reduced under control of the processor, wherein said first pressure transducer is in operative communication with said processor; and

a classification module executable by said processor, the classification module being operable to compare the first oscillometric pressure signal to a lower extremity threshold value to classify a patient into one of the first diagnostic class and the second diagnostic class.

47-52. -52. (canceled)

53. A method for detecting one or more characteristics useful for characterizing a patient into one of a first diagnostic class characterized as having a first severity of peripheral artery disease (PAD) and a second diagnostic class characterized as having a second severity of PAD, said method comprising:

obtaining an oscillometric pressure signal at a location on a lower extremity of the patient;

determining a maximum amplitude for the oscillometric pressure signal to provide a maximum amplitude value for the oscillometric pressure signal;

comparing the maximum amplitude value to a lower extremity threshold value; and

characterizing the patient as being in one of the first diagnostic class and the second diagnostic class at least partially based on the comparing step.

54-63. -63. (canceled)