Method and apparatus for determining blood pressure and cardiovascular condition

• US 4,880,013 A
• Filed: 03/24/1988
• Issued: 11/14/1989
• Est. Priority Date: 03/24/1988
• Status: Expired due to Term

• Current Assignee: Pulse Metric Incorporated
• Original Assignee: Shiu-Shin Chio
• Inventors: Chio, Shiu-Shin
• Primary Examiner(s): Jaworski, Francis
• Application Number:
  US07/172,660
• Time in Patent Office: 600 Days
• Field of Search: 128/680-683, 364/413.03
• US Class Current: 600/494
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7242 using integration

Abstract

A method is disclosed for determining the blood pressure of a patient. The method includes the steps of affixing a non-invasive pressure inducing device and transducer to the patient. A data stream is obtained from the transducer. The data stream includes pressure data and pulsation signal data. The data stream is processed to create an information stream which correlates the pressure data and the pulsation signal data. The information stream includes at least two pulse maximum points and at least one pulse minimum point. At least one of the systolic, diastolic and mean arterial pressures of the patient are determined by choosing a pressure determination point in the information stream between the two pulse maximum points. Additionally, an apparatus for determining blood pressure is disclosed.

Claims

1. A method of determining blood pressure of a patient comprising the steps of:

a. affixing a non-invasive pressure inducing means and transducer means to the patient,

b. elevating the pressure induced by the pressure inducing means to a suprasystolic pressure,

c. decreasing the pressure induced by the pressure inducing means over time to a pressure below diastolic pressure,

d. obtaining a data stream from the transducer means, the data stream including pressure data and pulsation signal data,

e. processing said data stream to create an information stream which correlates the pressure data and the pulsation signal data, the information stream including at least two pulse maximum points and at least two pulse minimum points, and

f. examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures of the patient by selecting at least one of the at least two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressure of the patient.

2. The method of claim 1 wherein said at least two pulse maximum points comprise at least two consecutive pulse maximum points and the step of selecting at least one of the at least two pulse minimum points comprises the step of selecting a pulse minimum point between the at least two pulse maximum points which meets at least one of the following criteria:

(a) the pulse minimum point occurs between a pair of consecutive pulse maximum points wherein the first pulse maximum point is substantially less than the second pulse maximum point, and

(b) the pulse minimum point occurs between a pair of consecutive pulse maximum points wherein the first pulse maximum point is substantially greater than the second pulse maximum point.

3. The method of claim 1 further comprising the steps of providing a graphic display means and graphically displaying the information stream.

4. The method of claim 3 wherein the step of graphically displaying the information stream comprises the step of graphically displaying the pulsation signal data as a function of cuff pressure.

5. The method of claim 3 wherein the step of graphically displaying the information stream comprises the step of graphically displaying the pulsation signal data as a function of time.

6. The method of claim 3 wherein the step of providing a graphic display means comprises the step of providing a video display means.

7. The method of claim 3 wherein the step of providing a graphic display means comprises the step of providing a printer means.

8. The method of claim 1 wherein the step of creating an information stream comprises the step of creating a generally sinusoidal information stream curve, the at least two pulse maximum points comprising apex points of the generally sinusoidal information stream curve, and the at least two pulse minimum points comprise nadir points of the generally sinusoidal information stream curve, the generally sinusoidal information stream curve including at least one pulse cycle defined as an interval of the curve between a pair of consecutive pulse maximum points.

9. The method of claim 8 wherein the at least one pulse cycle includes a pulsation signal rapidly descending portion, a pulse signal trough portion and a pulse signal rapidly ascending portion.

10. The method of claim 9 wherein the step of examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures by selecting at least one of the at least two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressures of the patient comprises the step of selecting said at least one pulse minimum point as a point for determing the systolic pressure of the patient.

11. The method of claim 10 wherein the step of selecting the at least one pulse minimum point comprises the step of selecting the pulse minimum point of the pulse cycle wherein the pulse minimum point occurs at the beginning of the pulse signal trough portion of the pulse cycle.

12. The method of claim 10 wherein the step of selecting the at least one pulse minimum point comprises the step of selecting the pulse minimum point of the pulse cycle wherein the pulse minimum point occurs at the first data point of the pulse signal trough portion.

13. The method of claim 9 wherein the step of examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures by selecting at least one of the at least two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressure of the patient comprises the step of selecting said at least one pulse minimum point as a point for determining the diastolic pressure of the patient.

14. The method of claim 13 wherein the step of selecting the at least one pulse minimum point comprises the step of selecting the pulse minimum point of the pulse cycle wherein the pulse minimum point occurs at the end of the pulse signal trough portion adjacent to the pulse signal rapidly ascending portion.

15. The method of claim 13 wherein the step of selecting the at least one pulse minimum point comprises the step of selecting the pulse minimum point of the pulse cycle wherein the pulse minimum point occurs in the pulse signal trough portion at the last data point of the pulse signal trough portion.

16. The method of claim 9 wherein the step of examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures by selecting at least one of the at least two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressures of the patient comprises the step of selecting said at least one pulse minimum point as a point for determining the mean arterial pressure of the patient.

17. The method of claim 16 wherein the step of selecting the at least one pulse minimum point comprises the step of selecting the pulse minimum point of the pulse cycle wherein the pulse minimum point occurs in the middle of the pulse signal trough portion of the pulse cycle.

18. The method of claim 16 wherein the step of selecting the at least one pulse minimum point comprises the step of selecting the pulse minimum point of the pulse cycle wherein the pulse minimum point occurs at a pressure data point generally equal to the average of the pressure data points of the two pulse maximum points which define the pulse cycle.

19. The method of claim 1 wherein the step of creating an information stream comprises the step of creating a generally sinusoidal information stream curve comprised of a series of pulse cycles, each pulse cycle being defined by an interval of the curve between adjacent pulse maximum points, and each cycle including a rapidly descending portion, a trough portion, a rapidly ascending portion, and the at least one of the at least two pulse minimum points comprises a point in the trough portion.

20. The method of claim 19 wherein the step of examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures by selecting at least one of the two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressures of the patient includes the step of selecting a pulse cycle in said series of pulse cycles wherein the pulse minimum point of the pulse cycle occurs adjacent to the beginning of the trough portion of the pulse cycle to determine the systolic pressure.

21. The method of claim 20 wherein said pulse cycle selected comprises the first pulse cycle of said series of pulse cycles wherein the pulse minimum point occurs adjacent to the beginning of the trough portion, and wherein the systolic pressure is determined by utilizing the pressure data at the pulse minimum point so chosen.

22. The method of claim 19 wherein the step of examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures by selecting at least one of the two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressures of the patient includes the step of selecting a pulse cycle in said series of pulse cycles wherein the pulse minimum point of the pulse cycle occurs adjacent to the end of the trough portion of the pulse cycle to determine the diastolic pressure.

23. The invention of claim 22 wherein the pulse cycle chosen comprises the first pulse cycle of said series of pulse cycles wherein the pulse minimum point occurs adjacent to the end of the trough portion, and wherein the diastolic pressure is determined by utilizing the pressure data at the pulse minimum point so chosen.

24. The method of claim 19 wherein the step of examining the information stream to determine at least one of the systolic, diastolic and mean arterial pressures by selecting at least one of the two pulse minimum points as a point for determining said at least one of the systolic, diastolic and mean arterial pressures of the patient includes the step of selecting a pulse cycle in said series of pulse cycles wherein the pulse minimum point of the pulse cycle occurs in the middle of the pulse cycle trough portion of the cycle to determine the mean arterial pressure.

25. The method of claim 1 further comprising the steps of providing a data storage means for storing the information of the data stream and storing the information of the data stream.

26. A method of determining mean arterial blood pressure of a patient comprising the steps of:

a. affixing a non-invasive pressure inducing means and transducer means to the patient;

b. obtaining a data stream from the transducer means, the data stream including pulsation signal data,

c. processing said data stream to create a generally sinusoidal information stream curve which includes pulsation signal data and time data, and has at least one apex point and at least one nadir point,

d. determining the patient'"'"'s systolic and diastolic pressure,

e. creating a scale of arterial pressures by setting the arterial pressure at the apex point to equal the determined systolic pressure, and setting the arterial pressure at the nadir point to equal the determined diastolic pressure,

f. selecting a pressure determination point in the information stream curve, and

g. utilizing the chosen pressure determination point, the scale of arterial pressures and the determined systolic and diastolic pressures to determine the patient'"'"'s mean arterial pressure.

27. The method of claim 26 wherein the step of creating a scale of arterial pressures comprises the step of creating the scale by linearly interpolating the arterial pressures.

28. The method of claim 26 wherein the step of selecting the pressure determination point comprises the step of selecting a data point in the information stream between the apex point and the nadir point, and utilizing arterial pulse pressure at the pressure determination point so selected to determine the mean arterial pressure.

29. The method of claim 26 wherein the step of selecting a data point in the information stream comprises the step of selecting a pressure determination point wherein the slope of said information stream curve changes significantly.

30. The method of claim 29 wherein the step of selecting a pressure determination point wherein the slope of the information stream curve changes significantly comprises the step of selecting a data point in the information stream curve wherein the slope increases significantly.

31. The method of claim 29 wherein the step of selecting a pressure determination point wherein the slope of the information stream curve changes significantly comprises the step of selecting a data point wherein the rate of change of the slope of the curve is maximized in the interval between said apex point and said nadir point.

32. The method of claim 26 wherein the step of selecting a pressure determination point in the information stream curve comprises the step of selecting a pressure determination point in the information stream curve wherein the rate of change of arterial pressure as a function of time decreases significantly.

33. The method of claim 26 wherein the step of selecting a pressure determination point comprises the step of selecting a pressure determination point in the information stream curve at a point wherein the pressure exerted on the patient by said pressure inducing means is less than the patient'"'"'s diastolic pressure.

34. An apparatus for determining blood pressure of a patient comprising:

a. a non-invasive pressure inducing means and transducer means attachable to the patient for providing a data stream including pressure data and pulsation signal data,

b. an analog to digital convertor means having a resolution of at least about twelve bits,

c. processing means cooperable with the analog to digital convertor means for processing the data to create a generally sinusoidal information stream curve of at least one pulse cycle of the patient which correlates the pressure data and the pulsation signal data, the information stream curve being comprised of at least about one hundred items of pressure data and pulsation signal data per second, and including a rapidly descending portion, a trough portion, and a rapidly ascending portion, and

d. means for analyzing the information stream curve trough portion to determine at least one of the systolic pressure, diastolic pressure, and mean arterial pressure of the patient.

35. The apparatus of claim 34 further comprising a graphic display means for graphically displaying the information stream so created.

36. The apparatus of claim 35 wherein the graphic display means comprises a printer means.

37. A method of determining the condition of the cardiovascular system of a patient comprising the steps of:

(a) affixing a non-invasive pressure inducing means and transducer means to the patient,

(b) obtaining a data stream from the transducer means during such time as the pressure induced by the pressure inducing means is at a suprasystolic pressure, the data stream including pulsation signal data,

(c) processing said data stream to create an information system which includes pulsation signal data and time data,

(d) processing the information stream to create a first derivative stream which includes information relating to the rate of change of the data of the information stream, and an integration stream, and

(e) examining at least one of the information stream, first derivative stream and integration stream at said suprasystolic pressure to determine the condition of the patient'"'"'s cardiovascular system.

38. The method of claim 37 further comprising the steps of providing a graphic display means and graphically displaying the information stream as an arterial pulse curve and the first derivative stream as a first derivative curve.

39. The method of claim 37 wherein the step of examining at least one of the information stream, first derivative stream and integration stream comprises the step of examining the integration stream to determine the strength of the heart contraction of the patient.

40. The method of claim 37 wherein the step of examining at least one of the information stream, first derivative stream and integration stream comprises the step of detecting the presence of cardiovascular noises by examining the first derivative stream.

41. A method of determining the condition of the cardiovascular system of a patient comprising the steps of:

(a) affixing a non-invasive pressure inducing means and transducer means to the patient,

(b) obtaining a data stream from the transducer means during such time as the pressure induced by the pressure inducing means is at a sub-diastolic pressure, the data stream including pulsation signal data,

(c) processing said data stream to create an information stream which includes pulsation signal data and time data,

(d) processing the information stream to create a first derivative stream which includes information relating to the rate of change of the data of the information stream and an integration stream, and

(e) examining at least one of the information stream, first derivative stream and integration stream at said sub-diastolic pressure to determine the condition of the patient'"'"'s cardiovascular system.

42. The method of claim 41 wherein the step of examining at least one of the information stream, first derivative stream and integration stream comprises the step of examining the integration stream to determine information about the flow of blood in the circulatory system of the patient.

43. A method for determining mean arterial blood pressure of a patient comprising the steps of:

(a) affixing a non-invasive pressure inducing means and transducer means to the patient,

(b) obtaining a data stream from the transducer means, the data stream including pulsation signal data,

(c) processing said data stream to create an information stream which includes pulsation signal data and time data,

(d) determining the patient'"'"'s systolic and diastolic pressure,

(e) selecting a pressure determination point in the information stream at a pressure less than the patient'"'"'s determined diastolic pressure, and

(f) utilizing the selected pressure determination point, and the determined sytolic and diastolic pressures to determine the patient'"'"'s mean arterial pressure.

44. A method for determining mean arterial blood pressure of a patient comprising the steps of:

(a) affixing a non-invasive pressure inducing means and transducer means to the patient,

(b) obtaining a data stream from the transducer means, the data stream including pulsation signal data,

(c) processing the data stream to create a generally sinusoidal information stream curve which includes pulsation signal data and time data, and has at least one apex point and at least one nadir point,

(d) determining the patient'"'"'s sytolic and diastolic pressure,

(e) selecting a pressure determination point in the information stream curve between the at least one apex point and the at least one nadir point wherein the slope of the information stream curve changes significantly.