METHOD AND SYSTEM FOR ESTIMATION OF ARTERIAL PRESSURE

• US 3,552,383 A
• Filed: 01/08/1969
• Issued: 01/05/1971
• Est. Priority Date: 01/08/1969
• Status: Expired due to Term

• Current Assignee: Krueger Dean T E, Louis C. Sheppard
• Original Assignee: Krueger Dean T E, Louis C. Sheppard
• Inventors: KRUEGER DEAN T E, Sheppard, Louis C.
• Application Number:
  US04/789,778
• Time in Patent Office: 727 Days
• US Class Current: 600/495
• CPC Class Codes: A61B 5/02208 using the Korotkoff method
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A method and apparatus for automatically following and monitoring systolic and diastolic blood pressure in an animal organism is disclosed. The pressure of an occluding cuff on the organism is controlled by decisional logic to increase or decrease in fixed increments the pressure in the cuff. The decision to increase or decrease depends upon the existence and amplitude of the Korotkoff sounds detected during a sample period which may comprise a preset number of heartbeats. The Korotkoff signals are analyzed for the purpose of indicating whether the cuff pressure is just above or just below the systolic (or diastolic) blood pressure and the actual cuff pressure is changed accordingly. Multiple samples are made for systolic blood pressure and those samples for which an acceptable Korotkoff pulse is detected are averaged. Then multiple samples are made for diastolic blood pressure. The method and apparatus is based on the typical Korotkoff sound envelope seen when going from above systolic pressure to below diastolic pressure.

Claims

1. A method for tracking a blood pressure of an animal organism, comprising the steps of:

a. applying a first pressure to a member of said organism;

b. sensing a selected parameter of Korotkoff sounds resulting from said first pressure;

c. placing each of said sounds into at least one of a plurality of groups based upon specified ranges of said parameter;

d. generating, for a determinate time interval, a characteristic measure for each of a plurality of said groups;

e. combining said plurality of measures with each other to form a pressure-correction representation; and

f. applying a second pressure to said member in response to said representation.

2. The method of claim 1 wherein said parameter is the intensity of each of said sounds.

3. The method of claim 2 wherein each of said measures indicates the number of said sounds placed within its associated group during said interval.

4. The method of claim 3 wherein said pressure-correction representation is further formed in response to the selection of one of a plurality of blood pressure types to be tracked.

5. The method of claim 3 wherein said pressure-correction representation is further formed in response to a pressure-correction representation formed for a preceding time interval.

6. The method of claim 3 wherein a first of said groups has an intensity range extending from a first threshold to a second threshold, and wherein a second of said groups has an intensity range exceeding said second threshold.

7. The method of claim 6 wherein each of said measures assumes a first value when said number is less than unity, a second value when said number is unity, and a third value when said number is greater than unity.

8. The method of claim 7 wherein said pressure-correction representation has a first magnitude when the measure of said second group assumes said first value, and when the measure of said second group assumes said second value unless the measure of said first group also assumes said second value.

9. The method of claim 7 wherein said representation has a second magnitude when the measure of said second group assumes said third value unless the measure of said first group also assumes said third value.

10. The method of claim 7 wherein said representation has the same magnitude as that of a pressure-correction representation formed for a preceding interval when said first and second measures both assume said second value, and when said first and second measures both assume said third value.

11. The method of claim 8 wherein said first magnitude is positive and said second magnitude is negative for a first blood pressure type, and wherein said first magnitude is negative and said second magnitude is positive for a second blood pressure type.

12. The method of claim 2 wherein the duration of said time interval is established by counting a predetermined number of heartbeats of said organism.

13. The method of claim 2 wherein said interval is delayed with respect to the time of occuRrence of said heartbeats.

14. The method of claim 2 wherein said pressure-correction representation has a substantially constant absolute magnitude and a variable sign.

15. The method of claim 2 wherein said second pressure is applied after a predetermined time lag from the time at which said representation is formed.

16. The method of claim 2 further comprising the step of generating blood pressure indication from at least one of said applied pressures.

17. The method of claim 16 wherein said indication substantially equals said first applied pressure.

18. The method of claim 16 wherein said indication substantially equals said second applied pressure.

19. The method of claim 16 further comprising the step of detecting the existence of a preselected pattern of said measures, said blood pressure indication being made substantially equal to said second applied pressure when said pattern is detected during said interval.

20. The method of claim 19 wherein said indication is made substantially equal to said first applied pressure when said pattern is not detected during said interval.

21. The method of claim 19 wherein said pattern represents the presence of at least one of said sounds within at least one of said groups during said interval.

22. A method of tracking a blood pressure in an animal organism comprising the steps of:

a. applying constant pressure for a predetermined sample period to said organism;

b. detecting the Korotkoff sounds during said period resulting from said applied pressure;

c. analyzing said sounds on the basis of number and intensity to determine a probable direction of deviation between said constant pressure and the blood pressure being tracked; and

d. altering said applied pressure by a predetermined incremental amount in a direction opposite to said probable direction of deviation.

23. The method as claimed in claim 22 further comprising the steps of:

a. repeating (a) through (d) of claim 22 for a plurality of sample periods, said pressure being altered for each sample period; and

b. averaging all said constant pressures which cause at least one Korotkoff sound which meets a predetermined set of criteria.

24. The method as claimed in claim 23 wherein the step of analyzing comprises:

a. classifying said sounds into classes of acceptable and loud sounds according to their intensities relative to a predetermined set of criteria;

b. counting the loud and acceptable sounds occurring during a given sample period; and

c. generating an up or down pressure command signal dependent upon the number of loud and acceptable sounds occurring during said sample period and the particular blood pressure being tracked.

25. The method as claimed in claim 24 further comprising:

a. detecting the heartbeats of said organism; and

b. controlling the duration of said sample periods in accordance with a preset number of detected heartbeats.

26. The method as claimed in claim 25 wherein the blood pressure being tracked is the systolic blood pressure.

27. The method as claimed in claim 25 wherein the blood pressure being tracked is the diastolic blood pressure.

28. Apparatus for automatically tracking the blood pressure of a human organism comprising:

a. pressure applying means adapted to be connected to said organism for applying pressure thereto;

b. detecting means for detecting Korotkoff sounds resulting from certain pressure levels being applied to said organism; and

c. means for controlling incremental up and down variations in pressure applied by said pressure applying means in accordance with the number and a selected parameter of Korotkoff sounds detected over a predetermined sample period.

29. Apparatus as claimed in claim 28 wherein said means for controlling incremental up and down variation comprises:

a. voltage comparator means responsive to said detected Korotkoff sounds for generating two sets of signals corresponding to accEptable and loud sounds, respectively, whereby the classification of the sounds into acceptable and loud is a function of the sound intensity;

b. means for accumulating each of said two sets of signals for said predetermined sample period;

c. decisional logic means responsive to said accumulated two sets of signals for generating one of two pressure change command signals; and

d. means responsive to said generated command signal for changing by a predetermined incremental amount the pressure in said pressure applying means.

30. Apparatus as claimed in claim 29 wherein said two command signals are up and down command signals and said means for changing the pressure comprises;

a. a pressure servosystem connected to said pressure applying means for controlling the pressure in said pressure applying means in accordance with an analogue electrical quantity applied to a control input thereof;

b. a digital storage means for storing a digital quantity;

c. means responsive to said command up signal for increasing by an incremental amount the digital quantity stored in said digital storage means;

d. means responsive to said command down signal for decreasing by said incremental amount the digital quantity stored in said digital storage means; and

e. digital to analogue converter connected between said digital storage means and said pressure servo means for converting the digital quantity stored in said storage means into an analogue electrical quantity and applying said analogue electrical quantity to said control input.