Method and apparatus for measuring blood pressure and pulse rate

• US 4,245,648 A
• Filed: 09/20/1978
• Issued: 01/20/1981
• Est. Priority Date: 09/20/1978
• Status: Expired due to Term

• Current Assignee: Edward W. Slechta, Gordon A. Trimmer
• Original Assignee: Edward W. Slechta, Gordon A. Trimmer
• Inventors: Trimmer, Gordon A., Slechta, Edward W.
• Primary Examiner(s): Little, Willis
• Application Number:
  US05/943,915
• Time in Patent Office: 853 Days
• Field of Search: 128/687, 128/672, 128/700, 128/900, 128/677, 128/680, 128/681, 128/689, 73/141 A
• US Class Current: 600/493
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves

Abstract

The system of the present invention includes a sensor head which is coupled to an exteriorized artery. The sensor head includes electromechanical transducers at first and second locations which convert each periodic arterial pulse pressure wave passing the first and second locations into first and second periodic electrical waveforms. Electronic circuitry analyzes the first and second periodic electrical waveforms to determine the rise time of each periodic waveform produced by the first and second transducers. This electronic circuitry also analyzes the first and second periodic waveforms to determine the transit time of each pulse pressure wave between the first and second locations. An electronic computer utilizes the rise time and transit time data and certain calibration data to determine and display systolic pressure, diastolic pressure, and pulse rate immediately following each pulse pressure wave. The system of the present invention also computes and displays fifteen beat moving average values of the systolic pressure and diastolic pressure.

Claims

1. A method for measuring blood pressure and pulse rate comprising the steps of:

a. obtaining flow and no flow calibration data;

b. passively measuring the rise times of each naturally occurring arterial pulse pressure wave at first and second locations separated by a predetermined distance;

c. passively measuring the time required for each naturally occurring pulse pressure wave to travel between the first and second locations;

d. determining the root mean square value of the pulse pressure waveform; and

e. computing the systolic pressure, diastolic pressure and pulse rate for each naturally occurring pulse pressure wave.

2. The method of claim 1 further including the step of computing a multiple beat moving average value of systolic pressure and diastolic pressure.

3. The method of claim 1 further including the step of displaying the values of systolic pressure, diastolic pressure and pulse rate.

4. The method of claim 1 wherein the step of obtaining flow and no flow calibration data includes the step of measuring the systolic and diastolic blood pressures.

5. The method of claim 4 wherein the step of obtaining flow and no flow calibration data includes:

a. terminating the flow of blood through the artery; and

b. measuring the rise time of the arterial pulse pressure wave during the no flow condition.

6. The method of claim 1 including the further step of measuring the rise times of each arterial pulse pressure wave at repeatable points on the pulse pressure waveform produced by each sequential pulse pressure wave.

7. The method of claim 6 wherein the repeatable points occur between the minimum and maximum values of each pulse pressure waveform.

8. A blood pressure and pulse rate measurement system comprising:

a. means coupled to an exteriorized artery at first and second locations for passively converting each naturally occurring periodic arterial pulse pressure wave passing the first and second locations into first and second periodic electrical waveforms;

b. means coupled to said converting means for measuring the rise time of each of the first and second periodic waveforms;

c. means coupled to said converting means for measuring the transit time of each pulse pressure wave between the first and second locations; and

d. means coupled to said rise time measuring means and to said transit time measuring means for computing the systolic pressure, diastolic pressure and pulse rate for each pulse pressure wave.

9. The system of claim 8 wherein said converting means includes:

a. a first electromechanical transducer at the first location for generating the first periodic electrical waveform; and

b. a second electromechanical transducer positioned at the second location for generating the second periodic electrical waveform.

10. The system of claim 9 including:

a. first low pass filter means coupled to the output of said first transducer for passing only the low frequency component of the first periodic electrical waveform; and

b. second low pass filter means coupled to the output of said second transducer for passing only the low frequency component of the second periodic electrical waveform.

11. The system of claim 10 wherein said converting means includes analog to digital converter means coupled to the output of said first and second low pass filter means for converting the first and second periodic electrical waveforms into first and second digital signals.

12. The system of claim 8 further including means coupled to said computing means for visually displaying systolic pressure, diastolic pressure and pulse rate.

13. The system of claim 12 wherein said display means further includes:

a. digital indicator means for displaying systolic pressure, diastolic pressure and pulse rate; and

b. display controller means for receiving input data from said computing means and for controlling the operation of said digital indicator means.

14. The system of claim 8 wherein said computing means includes means for computing a multiple beat moving average value of the systolic pressure and diastolic pressure.

15. The system of claim 8 further including means coupled to said computing means for providing calibration data to said computing means and for designating limit inputs to said computing means.

16. The system of claim 15 further including alarm means coupled to said computing means for sounding an alarm when the systolic pressure, diastolic pressure or pulse rate deviate from predetermined limits.

17. The system of claim 8 wherein said computing means further includes a data recorder output.

18. The system of claim 9 wherein said first and second transducers are positioned in a sensor head.

19. The system of claim 18 wherein said first and second transducers within said sensor head are maintained at a predetermined fixed spacing.

20. The system of claim 19 wherein the predetermined fixed spacing between said first and second transducers is between two and ten centimeters.

21. The system of claim 19 wherein said first and said second transducers include piezoelectric crystals.

22. The system of claim 18 wherein said sensor head is maintained in position adjacent the exteriorized artery by attachment means.

23. The system of claim 22 wherein said attachment means includes a strap.

24. The system of claim 22 wherein the first and second transducers of said sensor head are adhesively secured to the exteriorized artery.

25. The system of claim 8 wherein said computing means includes a microprocessor.

26. The system of claim 9 wherein said first and second transducers are separately coupled to a single exteriorized artery.

27. The system of claim 26 wherein said first and second transducers are separated by a spacing in excess of ten centimeters.

28. The system of claim 24 wherein said first and second transducers are coupled to said exteriorized artery by a thin sheet of material having an adhesive layer on the upper and lower surfaces thereof.