Blood pressure monitoring system

• US 4,617,937 A
• Filed: 09/20/1985
• Issued: 10/21/1986
• Est. Priority Date: 02/21/1985
• Status: Expired due to Term

• Current Assignee: Colin Electronics Co., Ltd.
• Original Assignee: Nippon Colin
• Inventors: Peel, Harry H., Brisco, John S., Moczygemba, Mark E., Neatherlin, Robert L., Sargent, Brenda A.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Jaworski, Francis J.
• Application Number:
  US06/778,290
• Time in Patent Office: 396 Days
• Field of Search: 128/680-683, 128/709, 128/696, 128/691
• US Class Current: 600/493
• CPC Class Codes: A61B 5/02208 using the Korotkoff method
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/222 combined with detection or measurement of physiological parameters, e.g. heart rate
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/329 Load diagnosis, e.g. cardiac stress tests
• CPC Class Codes: A61B 5/4884 inducing physiological or psychological stress, e.g. applications for stress testing
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence

Abstract

A blood pressure monitoring system is disclosed for monitoring blood pressure during stress testing or other physical activity as well as when quiescent. The blood pressure monitoring system of the present invention includes an inflatable cuff utilized in conjunction with a controllable electric air pump and deflation valve. Audio transducers are utilized to detect pulse sound at the proximal and distal edges of the inflatable cuff and pulse sound amplitudes as well as the time delay between pulse sounds proximal to the cuff and distal to the cuff are determined. Pulse sound amplitudes are then multiplied by time delay values for selected cuff pressures to generate a greatly enhanced blood pressure evaluation curve. In a preferred mode of the present invention digital filters and statistical analysis are then employed to determine systolic and diastolic blood pressure from the evaluation curve. Further novel features of the blood pressure monitoring system of the present invention include the ability of the system to select a trigger signal from multiple electrocardiographic leads by selecting the particular electrocardiographic lead with the least amount of noise present and the capability of modifying the inflation pressure and deflation rate of the cuff to permit either maximum accuracy or minimum measurement time during operation.

Claims

1. A blood pressure monitoring system for measuring blood pressure during stress testing or other physical activity, said blood pressure monitoring system comprising:

an inflatable cuff adapted to encircle a patient'"'"'s arm;

means for inflating and deflating said inflatable cuff within a selected range of pressures;

pressure transducer means responsive to cuff pressure and having an output signal indicative thereof;

audio transducer means for detecting pulse sounds at said inflatable cuff;

a plurality of electrocardiographic leads, each coupling an electrocardiographic signal from said patient; and

controller means comprising;

trigger signal generation means coupled to said plurality of electrocardiographic leads for periodically measuring the amount of noise present on each of said plurality of electrocardiographic leads and for selecting a particular lead having the least amount of noise to be utilized as a trigger signal; and

measurement means for obtaining a measure of systolic and diastolic blood pressure from said pulse sounds at selected cuff pressures in response to said trigger signal.

2. The blood pressure monitoring system according to claim 1 wherein said means for inflating and deflating said inflatable cuff comprises at least one electric air pump and a controllable deflation valve.

3. The blood pressure monitoring system according to claim 1 wherein said controllable deflation valve deflates and inflatable cuff at a rate of between 3 mmHg and 5 mmHg per heartbeat.

4. The blood pressure monitoring system according to claim 1 wherein said plurality of electrocardiographic Leads comprises three electrocardiographic Leads.

5. The blood pressure monitoring system according to claim 1 wherein said controller means comprises an appropriately programmed microprocessor.

6. The blood pressure monitoring system according to claim 1 wherein said trigger signal generation means further includes means for detecting the presence or absence of an electrocardiographic signal and wherein loss of said signal from said particular Lead will cause a second Lead to be utilized for trigger signal generation.

7. The blood pressure monitoring system according to claim 1 wherein said trigger signal generation means periodically measures the amount of 60 Hertz noise on each of said plurality of electrocardiographic Leads.

8. A blood pressure monitoring system from measuring blood pressure during stress testing or other physical activity, said blood pressure monitoring system comprising:

an inflatable cuff adapted to encircle a patient'"'"'s arm;

means for inflating and inflatable cuff;

means for deflating said inflatable cuff at a selectable rate;

pressure transducer means responsive to cuff pressure and having an output signal indicative thereof;

audio transducer means for detecting pulse sounds at said inflatable cuff;

a plurality of electrocardiographic Leads, each coupling an electrocardiographic signal from said patient; and

controller means comprising;

trigger signal generation means coupled to said plurality of electrocardiographic Leads for periodically measuring the amount of noise present on each of said plurality of electrocardiographic Leads and for selecting a particular Lead having the least amount of noise to be utilized as a trigger signal;

deflation control means for selecting said selectable rate of deflation in response to said trigger signal wherein said deflation rate is controlled by said patient'"'"'s heart rate whereby maximum accuracy of blood measurement may be obtained; and

measurement means for obtaining a measure of systolic and diastolic blood pressure from said pulse sounds to selected cuff pressures in response to said trigger signal.

9. The blood pressure monitoring system according to claim 8 wherein said deflation control means also includes means for selecting a maximum permissible deflation rate whereby a minimum measurement times may be utilized.

10. The blood pressure monitoring system according to claim 8 wherein said means for inflating said inflatable cuff comprises at least one electric air pump.

11. The blood pressure monitoring system according to claim 8 wherein said means for deflating said inflatable cuff at a selectable rate comprises a controllable deflation valve.

12. The blood pressure monitoring system according to claim 8 wherein said plurality of electrocardiographic Leads comprises three electrocardiographic Leads.

13. The blood pressure monitoring system according to claim 8 wherein said controller means comprises an appropriately programmed microprocessor.

14. The blood pressure monitoring system according to claim 8 wherein said trigger signal generation means further includes means for detecting the presence or absence of an electrocardiographic signal and wherein said loss of said signal from said particular Lead will cause a second Lead to be utilized for trigger signal generation.

15. The blood pressure monitoring system according to claim 8 wherein said trigger signal generation means periodically measures the amount of 60 Hertz noise on each of said plurality of electrocardiographic Leads.

16. A blood pressure monitoring system for measuring blood pressure during stress testing or other physical activity, said blood pressure monitoring system comprising:

an inflatable cuff adapted to encircle a patient'"'"'s arm;

means for inflating said inflatable cuff to a selectable pressure;

means for deflating said inflatable cuff;

pressure transducer means responsive to cuff pressure and having an output signal indicative thereof;

audio transducer means for detecting pulse sounds at said inflatable cuff;

a plurality of electrocardiographic Leads, each coupling an electrocardiographic signal from said patient; and

controller means comprising;

trigger signal generation means coupled to said plurality of electrocardiographic Leads for periodically measuring the amount of noise present on each of said plurality of electrocardiographic Leads and for selecting a particular Lead having the least amount of noise to be utilized as a trigger signal;

measurement means for obtaining a measure of systolic and diastolic blood pressure from said pulse sounds at selected cuff pressures in response to said trigger signal; and

inflation control means for controlling inflation of said inflatable cuff to a selectable pressure which is based upon said measured systolic blood pressure.

17. The blood pressure monitoring system according to claim 16 wherein said means for inflating said inflatable cuff to a selectable pressure comprises at least one electric air pump.

18. The blood pressure monitoring system according to claim 16 wherein said means for deflating said deflatable cuff includes means for deflating said inflatable cuff at a selectable deflation rate.

19. The blood pressure monitoring system according to claim 18 further including deflation control means coupled to said trigger signal generation means for selecting said selectable deflation rate in response to said trigger signal wherein said deflation rate is controlled by said patient'"'"'s heart rate whereby maximum accuracy of blood pressure measurement may be obtained.

20. The blood pressure monitoring system according to claim 16 wherein said plurality of electrocardiographic Leads comprises three electrocardiographic Leads.

21. The blood pressure monitoring system according to claim 16 wherein said controller means comprises an appropriately programmed microprocessor.

22. The blood pressure monitoring system according to claim 16 wherein said trigger signal generation means further includes means for detecting the presence or absence of an electrocardiographic signal and wherein loss of said signal from said particular Lead will cause a second Lead to be utilized for trigger signal generation.

23. A blood pressure monitoring system, comprising:

an inflatable cuff adapted to encircle a patient'"'"'s arm, said inflatable cuff having a proximal edge disposed toward said patient'"'"'shoulder and a distal edge disposed toward said patient'"'"'s elbow;

means for inflating and deflating said inflatable cuff within a selected range of pressures;

pressure transducer means responsive to cuff pressure and having an output signal indicative thereof;

proximal audio transducer means for detecting pulse sounds at said proximal edge of said inflatable cuff and for generating an output signal indicative thereof;

distal audio transducer means for detecting pulse sounds at said distal edge of said inflatable cuff and for generating an output signal indicative thereof; and

, controller means comprising;

amplitude measurement means coupled to said distal audio transducer means and said pressure transducer means for measuring the amplitude of pulse sound detected at said distal audio transducer means at selected cuff pressures;

time delay measurement means coupled to said distal audio transducer means, said proximal audio transducer means and said pressure transducer means for measuring the time delay between a pulse sound detected at said proximal audio transducer means and said pulse sound detected at said distal audio transducer means at selected cuff pressures; and

,

processing means for multiplying the amplitude of pulse sound detected at said distal audio transducer means by said time delay between said pulse sound detected at said proximal audio transducer means and said pulse sound detected at said distal audio transducer means at each of said selected cuff pressures to obtain a measurement of systolic and diastolic blood pressure therefrom.

24. The blood pressure monitoring system according to claim 23 wherein said means for inflating and deflating said inflatable cuff comprises at least one electric air pump and a controllable deflation valve.

25. The blood pressure monitoring system according to claim 23 wherein said controllable deflation valve deflates said inflatable cuff at a rate of between 3 mmHg and 5 mmHg per heartbeat.

26. The blood pressure monitoring system according to claim 23 wherein said proximal audio transducer and said distal audio transducer comprise microphones for converting audio inputs to an electrical output signal.

27. The blood pressure monitoring system as claimed in claim 23, including:

a plurality of electrocardiograph Leads, each coupling an electrocardiographic signal from said patient;

and said controller means includes trigger signal generation means coupled to said plurality of electrocardiographic Leads for periodically measuring the amount of noise present on each of said plurality of electrocardiograph Leads and for selecting a particular Lead having the least amount of noise to be utilized as a trigger signal, wherein said amplitude measurement means and said time delay measurement means operate in response to said trigger signal, and filter means coupled to said processing means for filtering the product resultant from multiplying the amplitude by the time delay.

28. The blood pressure monitoring system according to claim 27 wherein said plurality of electrocardiographic Leads comprise three electrocardiographic Leads.

29. The blood pressure monitoring system according to claim 27 wherein said controller means comprises an appropriately programmed microprocessor.

30. The blood pressure monitoring system according to claim 27 wherein said trigger signal generation means further includes means for detecting the presence or absence of an electrocardiographic signal and wherein the loss of said signal from said particular Lead will cause a second Lead to be utilized for trigger signal generation.

31. The blood pressure monitoring system according to claim 27 wherein said trigger signal generation means periodically measures the amount of 60 Hertz noise on each of said plurality of electrocardiographic Leads.

32. The blood pressure monitoring system according to claim 27 wherein said filter means includes means for performing statistical analysis of said resultant product to obtain a more accurate measure of systolic and diastolic blood pressure.

33. A method of obtaining accurate blood pressure measurement comprising the steps of:

placing an inflatable cuff around the arm of a patient;

inflating said inflatable cuff to a selected pressure;

slowing deflating said inflatable cuff;

measuring the amplitude of pulse sounds above and below said inflatable cuff at selected cuff pressures;

measuring the time delay between each pulse sound above said inflatable cuff and said pulse sound below said inflatable cuff at selected cuff pressures; and

multiplying said amplitude of said pulse sound below said inflatable cuff at selected cuff pressures by said time delay between said pulse sound above said inflatable cuff and said pulse sound below said inflatable cuff at said selected cuff pressures to obtain a measure of systolic and diastolic blood pressure.

34. The method as claimed in claim 33, including the step of filtering the product resultant from said multiplying step.