Apparatus and method for sensing cardiac performance

• US 5,086,776 A
• Filed: 03/06/1990
• Issued: 02/11/1992
• Est. Priority Date: 03/06/1990
• Status: Expired due to Fees

• Current Assignee: Precision Diagnostics Incorporated (Bruker Corporation)
• Original Assignee: Precision Diagnostics Incorporated (Bruker Corporation)
• Inventors: Jurgensen, Russell P., Fowler, Franklin S. Jr.
• Primary Examiner(s): Jaworski, Francis
• Assistant Examiner(s): Manuel, George
• Application Number:
  US07/490,044
• Time in Patent Office: 707 Days
• Field of Search: 128/661.07, 128/661.08, 128/661.09, 128/661.10, 128/715
• US Class Current: 600/455
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 7/045 Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021
• CPC Class Codes: A61B 8/04 Measuring blood pressure

Abstract

An apparatus and method for sensing cardiac performance by providing real time values of left ventricular performance of ambulatory or inactive subjects. Noninvasive sensors such as noise reducing phonocardiographic sensors, multi-crystal piezoelectric doppler pulse wave sensors, volume oscillometric pulse wave sensors, and electrocardiographic sensors develop a plurality of electrical signals representing certain key physiological functions. These electrical signals are uniquely conditioned and combined by a central processing unit and associated programs to yield real time outputs of Left Ventricular Ejection Time, Systolic Time Interval and Ejection Fraction for either ambulatory or inactive patients. These values are displayed, along with analog patient cardiac-based waveforms, on a recording device and may be used for future play-back.

Claims

1. An apparatus for sensing cardiac performance comprising:

a plurality of noninvasive sensors adapted to be attached to a patient for producing electrical analog sensor signals representing cardiac wave initiation points, high-frequency components of second heart sounds, arterial pulse wave initiation points, and arterial pulse wave dicrotic notches;

means for processing said electrical analog signals to produce a signal representing systolic time intervals as a responsive function of said electrical analog sensor signals; and

means for producing an electrical signal representing ejection fractions as a responsive function of said signal representing systolic time intervals.

2. The apparatus of claim 1, wherein said means for processing said electrical analog sensor signals comprises means for producing an electrical signal representing ejection fractions as a responsive function of said signal representing systolic time intervals.

3. The apparatus of claim 1, further comprising a signal display means for displaying graphic representations of at least certain of said electrical analog sensor signals from said noninvasive sensors and for displaying the level of said signal representing said ejection fractions.

4. The apparatus of claim 1, wherein said noninvasive sensors include a sensor for measuring arterial pulse wave doppler shifts comprising:

sound wave generating means;

sound wave receiving means;

a sensor body for holding said sound wave generating means and sound wave receiving means in proximity to an artery of a patient; and

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by said sound wave generating means and received by said sound wave receiving means, the frequency shift being based on the velocity of blood cells within the artery.

5. The apparatus of claim 4, wherein said sound wave generating means comprises a plurality of electrical to sound transducers arranged on said sensor body in proximity to said sound wave receiving means.

6. The apparatus of claim 4, wherein said sound wave receiving means comprises a plurality of sound to electrical signal transducers arranged on said sensor body in proximity to said sound wave generating means.

7. The apparatus of claim 4, wherein said sound wave generating means comprises a plurality of transmit transducers arrayed along a transmit axis on said sensor body, and said sound wave receiving means comprises a plurality of sound to electrical signal transducers arrayed along a receive axis on said sensor body, said transmit axis and said receive axis being substantially parallel and separated so that at least certain transmit transducers and certain receive transducers are positioned relative to the patient'"'"'s artery for deriving said frequency shift as a result of velocity of blood cells within the artery.

8. The apparatus of claim 4, wherein said signal conditioning and processing means comprises oscillator means and demodulator means, said oscillator means being coupled to said sound generating means and to said demodulator means for causing sound waves to be generated by said sound wave generating means, and to provide a transmit carrier signal to said demodulator means, said demodulator means also being coupled to said sound wave receiving means so that sound wave receiving signals are demodulated by said demodulator means relative to said transmit carrier signal to produce an output signal representing the frequency shift based on the velocity of blood cells within the artery.

9. The apparatus of claim 8, further comprising band pass filter means interposed between said sound wave receiving means and said demodulator means.

10. The apparatus of claim 8, further comprising a gain stage means coupled to an output of said demodulator means for producing an audio output signal representing the frequency shift based on the velocity of blood cells within the patient'"'"'s artery.

11. The apparatus of claim 1, wherein said noninvasive sensors include a sensor for measuring cardiac sound waves comprising:

a body having a first chamber and a second chamber, said first chamber and said second chamber being substantially sound isolated with respect to each other;

a first sound sensor means in said first chamber for receiving patient cardiac sound waves and noise sound waves and for developing electrical signals based on the cardiac sound waves and noise sound waves;

a second sound sensor means in said second chamber for receiving only noise sound waves and for developing electrical signals based on the noise sound waves; and

signal conditioning and processing means for deriving a signal representing cardiac sound wave values based on the difference between said signals of said first sound sensor means and said signals of said second sound sensor means.

12. The apparatus of claim 11, wherein said cardiac sound wave sensor comprising:

signal differencing circuit means having a first input coupled to said first sound sensor means and a second input coupled to said second sound sensor means and having an output at which difference signal is produced;

adjustable gain means associated with said signal differencing circuit means for adjustably zeroing out a noise component in said difference signal;

switchable frequency window filter means coupled to said output of said signal differencing circuit means; and

variable output gain stage means coupled to said switchable frequency filter means, said variable output gain stage means having an output at which an audio signal is produced representing said cardiac sound waves.

13. The apparatus of claim 12, wherein said switchable frequency filter means comprises a binary switching means for controlling said filter means by a binary control signal.

14. The apparatus of claim 12 wherein said switchable frequency filter means comprises a switchable center frequency control means for selectively changing a center frequency of said filter means.

15. The apparatus of claim 12, further comprising a first input filter stage interposed between said first sound sensor means and said first input of said signal differencing circuit means, and a second input filter stage interposed between said second sound sensor means and second input of said signal differencing circuit means.

16. The apparatus of claim 1, wherein said noninvasive sensors include a sensor for measuring volume oscillometric pulse waves comprising:

an inflatable cuff means for converting a patient'"'"'s pulse waves into internal air pressure variations within said inflatable arm cuff means;

a pump means for inflating said inflatable arm cuff means;

an air line connecting said inflatable arm cuff means and said pump means;

a valve means for regulating air flow of said inflatable arm cuff means;

a pressure transducer means in said air line for converting said internal air pressure variations of said inflatable arm cuff means into electrical signals;

signal conditioning and processing means for deriving volume oscillometric pulse wave values based on said internal air pressure variations of said inflatable arm cuff means.

17. The apparatus of claim 16, wherein said signal conditioning and processing means for deriving volume oscillometric pulse wave values comprises a first signal path having a first filter means that filters out fluctuations in the output of said pressure transducer means so as to produce a signal representing patient blood pressure;

and

a second signal path means comprising filter means for extracting variations in the output of said pressure transducer means so as to produce a fluctuating signal representing the patient'"'"'s pulse wave, said second signal path comprising a differentiating means for differentiating a signal developed by said pressure transducer.

18. The apparatus of claim 17, wherein said second signal path comprises a low pass filter means coupled in said second signal path after said differentiating means.

19. An apparatus for sensing cardiac performance in substantially real time comprising:

a noninvasive electrocardiographic sensor means adapted to be attached to a patient for producing electrical analog signals representing cardiac wave initiation points;

a noninvasive phonocardiographic sensor means adapted to be attached to a patient for producing electrical analog signals representing high-frequency components of second heart sounds;

a noninvasive arterial volumetric pulse wave sensor means adapted to be attached to a patient for producing electrical analog signals representing arterial pulse wave initiation points and representing arterial pulse wave dicrotic notches;

a noninvasive arterial doppler pulse wave sensor means adapted to be attached to a patient for producing electrical analog signals representing arterial pulse wave initiation points and representing arterial pulse wave dicrotic notches;

an analog-digital converter for converting said analog electrical signals from said electrocardiographic sensor means, said phonocardiographic sensor means, said arterial volumetric pulse wave sensor means and said arterial doppler pulse wave sensor means into digital signals as a function of time; and

a means for processing said digital signals to derive average arterial pulse wave digital signals based on said digital signals representing said arterial pulse wave initiation points and said arterial pulse wave dicrotic notches received by said arterial volumetric pulse wave sensor means and by said arterial doppler pulse wave sensor means,

a heart rate value based on said digital signals representing said cardiac wave initiation points,

an electromechanical systole value based on said digital signals representing said cardiac wave initiation points and said high-frequency components of second heart sounds,

a left ventricular ejection time value based on said average arterial pulse wave digital signals representing said arterial pulse wave initiation points and said arterial pulse wave dicrotic notches,

a systolic time interval value based on said heart rate value, said electromechanical systole value and said left ventricular ejection time value, and

an ejection fraction value based on said systolic time interval value.

20. The apparatus of claim 19, further comprising a signal display means for displaying in real time graphic representations of said electrical analog signals from said noninvasive electrocardiographic sensor means, said noninvasive phonocardiographic sensor means, said noninvasive arterial volumetric pulse wave sensor means and said noninvasive arterial doppler sensor means, and for displaying in real time said heart rate value, said electromechanical systole value, said left ventricular ejection time value, said ejection fraction value, and average values based on a plurality of said ejection fraction values.

21. The apparatus of claim 19, wherein said means for processing said digital signals derives said systolic time interval value based on the following formula:

##EQU3## where EMS_corrected =EMS+2.0 HR where the patient is female;

EMS_corrected =EMS+2.1 HR where the patient is male;

LVET_corrected =LVET+1.6 HR where the patient is female;

LVET_corrected =LVET+1.7 HR where the patient is male;

HR=said heart rate value;

EMS=said electromechanical systole value;

LVET=said left ventricular ejection time value.

22. The apparatus of claim 19, wherein said means for processing said digital signals derives said ejection fraction value based on the following formula:

space="preserve" listing-type="equation">EF=1.125-STI 1.25

where STI=said systolic time interval value.

23. The apparatus of claim 19, further comprising a noninvasive thermister sensor means adapted to be attached to a patient for producing electrical analog signals representing skin temperature.

24. The apparatus of claim 19, further comprising a noninvasive oximeter sensor means adapted to be attached to a patient for producing electrical analog signals representing blood oxygenation level.

25. An apparatus for real time sensing of cardiac performance comprising:

a noninvasive electrocardiographic sensor means adapted to be attached to a patient for producing electrical analog signals representing cardiac wave initiation points;

a noninvasive phonocardiographic sensor means adapted to be attached to a patient for producing electrical analog signals representing high-frequency components of second heart sounds;

a noninvasive arterial volumetric pulse wave sensor means adapted to be attached to a patient for producing electrical analog signals representing arterial pulse wave initiation points and representing arterial pulse wave dicrotic notches;

a noninvasive arterial doppler pulse wave sensor means adapted to be attached to a patient for producing electrical analog signals representing arterial pulse wave initiation points and representing arterial pulse wave dicrotic notches;

an analog-digital converter for converting said analog electrical signals from said electrocardiographic sensor means, said phonocardiographic sensor means, said arterial volumetric pulse wave sensor means and said arterial doppler pulse wave sensor means into digital signals as a function of time;

a means for processing said digital signals to derive heart rate values based on said digital signals representing said cardiac wave initiation points,

a mean heart rate value based on a predetermined number of said heart rate values,

electromechanical systole values based on said digital signals representing said cardiac wave initiation points and said high frequency components of second heart sounds,

a mean electromechanical systole valve based on a predetermined number of electromechanical systole values,

a refined electromechanical systole value based on a number of said electromechanical systole values within a predetermined numerical range from said mean electromechanical systole value,

a corrected electromechanical systole value based on said refined electromechanical systole value and on patient sex,

a left ventricular ejection time value based on said digital signals representing said arterial pulse wave initiation points and said arterial pulse wave dicrotic notches converted from said analog signals, said digital signals received by at least one of said arterial volumetric pulse wave sensor means and said arterial doppler pulse wave sensor means,

a mean left ventricular ejection time valve based on a predetermined number of said left ventricular ejection time values,

a refined left ventricular ejection time value based on a number of said left ventricular ejection time values within a predetermined numerical range from said mean left ventricular ejection time value;

a corrected left ventricular ejection time value based on said refined left ventricular ejection time value and on patient sex,

a systolic time interval value based on said mean heart rate value, said corrected electromechanical systole value and said corrected left ventricular ejection time value, and

an ejection fraction value based on said systolic time interval value; and

a signal display means for displaying in real time graphic representations of said electrical analog signals from said noninvasive electrocardiographic sensor means, said noninvasive phonocardiographic sensor means, said noninvasive arterial volumetric pulse wave sensor means and said noninvasive arterial doppler sensor means and for displaying in real time said heart rate values, said corrected electromechanical systole value, said corrected left ventricular ejection time value, said ejection fraction value, and average ejection fraction values based on a plurality of said ejection fraction values.

26. A noninvasive sensor for measuring arterial pulse wave doppler shifts comprising:

a plurality of sound wave generating means;

a plurality of sound wave receiving means;

a sensor body for holding said sound wave generating means in proximity to an artery of a patient; and

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by at least one of said sound wave generating means and received by at least one of said sound wave receiving means, the frequency shift based on the velocity of blood cells within the artery.

27. The apparatus of claim 26, wherein said plurality of sound wave generating means comprises a plurality of electrical to sound transducers arranged on said sensor body in proximity to said plurality of sound wave receiving means.

28. The apparatus of claim 26, wherein said plurality of sound wave receiving means comprises a plurality of sound to electrical signal transducers arranged on said sensor body in proximity to said plurality of sound wave generating means.

29. The apparatus of claim 26, wherein said plurality of sound wave generating means comprises a plurality of transmit transducers arrayed along a transmit axis on said sensor body, and said plurality of sound wave receiving means comprises a plurality of sound to electrical signal transducers arrayed along a receive axis on said sensor body, said transmit axis and said receive axis being substantially parallel and separated so that at least certain transmit transducers and certain receive transducers are positioned relative to the patient'"'"'s artery for deriving said frequency shift as a result of velocity of blood cells within the artery.

30. The apparatus of claim 26, wherein said signal conditioning and processing means comprises oscillator means and demodulator means, said oscillator means being coupled to said plurality of sound generating means and to said demodulator means for causing sound waves to be generated by said sound wave generating means, and to provide a transmit carrier signal to said demodulator means, said demodulator means also being coupled to said plurality of sound wave receiving means so that sound wave receiving signals are demodulated by said demodulator means relative to said transmit carrier signal to produce an output signal representing the frequency shift based on the velocity of blood cells within the artery.

31. The apparatus of claim 30, further comprising band pass filter means interposed between said plurality of sound wave receiving means and said demodulator means.

32. The apparatus of claim 31, further comprising a gain stage means coupled to an output of said demodulator means for producing an audio output signal representing the frequency shift based on the velocity of blood cells within the patient'"'"'s artery.

33. An apparatus for sensing cardiac performance comprising:

a plurality of non-invasive sensors adapted to be attached to a patient for producing electrical analog sensor signals representing cardiac wave initiation points, high-frequency components of second heart sounds, arterial pulse wave initiation points, and arterial pulse wave dicrotic notches;

means for processing said electrical analog signals to produce a signal representing systolic time intervals as a responsive function of said electrical analog sensor signals including means for producing an electrical signal representing ejection fractions as a responsive function of said systolic time intervals; and

signal display means for displaying graphic representations of at least certain of said electrical analog sensor signals from said non-invasive sensors and for displaying the level of said signal representing said ejection fractions.

34. An apparatus for sensing cardiac performance comprising:

a plurality of non-invasive sensor adapted to be attached to a patient for producing electrical analog sensor signals representing cardiac wave initiation points, high-frequency components of second heart sounds, arterial pulse wave initiation points, and arterial pulse wave dicrotic notches;

means for processing said electrical analog signals to produce a signal representing systolic time intervals as a responsive function of said electrical analog sensor signals;

wherein said non-invasive sensors include a sensor for measuring arterial pulse wave doppler shifts comprising;

sound wave generating means;

sound wave receiving means;

a sensor body for holding said sound wave generating means and sound wave receiving means is proximity to an artery of a patient; and

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by said sound wave generating means and received by said sound wave receiving means, the frequency shift being based on the velocity of blood cells within the artery;

said signal conditioning and processing means comprises oscillator means and demodulator means, said oscillator means being coupled to said sound generating means and to said demodulator means for causing sound waves to be generated by said sound wave generating means, and to provide a transmit carrier signal to said demodulator means, said demodulator means also being coupled to said sound wave receiving means so that sound wave receiving signals are demodulated by said demodulator means relative to said transmit carrier signals to produce an output signal representing the frequency shift based on the velocity of blood cells within the artery.

35. An apparatus for sensing cardiac performance comprising:

a plurality of non-invasive sensors adapted to be attached to a patient for producing electrical analog sensor signals representing cardiac wave initiation points, high-frequency cardiac wave initiation points, high-frequency components of second heart sounds, arterial pulse wave initiation points, and arterial pulse wave dicrotic notches;

means for processing said electrical analog signals to produce a signal representing systolic time intervals as a responsive function of said electrical analog sensor signals;

wherein said non-invasive sensors include a sensor for measuring volume oscillometric pulse waves comprising;

p2 an inflatable cuff means for converting a patient'"'"'s pulse waves into internal air pressure variations within said inflatable arm cuff means;

a pump means for inflating said inflatable arm cuff means;

an air line connecting said inflatable arm cuff means and said pump means;

a valve means for regulating air flow of said inflatable arm cuff means;

a pressure transducer means in said air line for converting said internal air pressure variations of said inflatable arm cuff means into electrical signals;

signal conditioning and processing means for deriving volume oscillometric pulse wave values based on said internal air pressure variations of said inflatable arm cuff means.

36. A non-invasive sensor for measuring arterial pulse wave doppler shifts comprising:

a plurality of sound wave generating means;

a plurality of sound wave receiving means;

a sensor body for holding said sound wave generating means in proximity to an artery of a patient;

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by at least one of said sound wave generating means and received by at least one of said sound wave receiving means, the frequency shift based on the velocity of blood cells within the artery;

wherein said plurality of sound wave generating means comprises a plurality of electrical to sound transducers arranged on said sensor body in proximity to said plurality of sound wave receiving means.

37. A non-invasive sensor for measuring arterial pulse wave doppler shifts comprising:

a plurality of sound wave generating means;

a plurality of sound wave receiving means;

a sensor body for holding said sound wave generating means in proximity to an artery of a patient; and

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by at least one of said sound wave generating means and received by at least one of said sound wave receiving means, the frequency shift based on the velocity of blood cells within the artery;

wherein said plurality of sound wave receiving means comprise a plurality of sound to electrical signal transducers arranged on said sensor body in proximity to said plurality of sound wave generating means.

38. A non-invasive sensor for measuring arterial pulse wave doppler shifts comprising:

a plurality of sound wave generating means;

a plurality of sound wave receiving means;

a sensor body for holding said sound wave generating means in proximity to an artery of a patient; and

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by at least one of said sound wave generating means and received by at least one of said sound wave receiving means, the frequency shift based on the velocity of blood cells within the artery; and

wherein said plurality of sound wave generating means comprise a plurality of transmit transducers arrayed along a transmit axis on said sensor body, said plurality of sound wave receiving means comprise a plurality of sound to electrical signal transducers arrayed along a receive axis on said sensor body, said transmit axis and said receive axis being substantially parallel and separated so that at least certain transmit transducers and certain receive transducers are positioned relative to the patient'"'"'s artery for deriving said frequency shift as a result of velocity of blood cells within the artery.

39. A non-invasive sensor for measuring arterial pulse wave doppler shifts comprising:

a plurality of sound wave generating means;

a plurality of sound wave receiving means;

a sensor body for holding said sound wave generating means in proximity to an artery of a patient; and

signal conditioning and processing means for deriving a frequency shift in a sound wave transmitted by at least one of said sound wave generating means and received by at least one of said sound wave receiving means, the frequency shift based on the velocity of blood cells within the artery, wherein said signal conditioning and processing means comprises oscillator means and demodulator means, said oscillator means being coupled to said plurality of sound generating means and to said demodulator means for causing sound waves to be generated by said sound wave generating means, and to provide a transmit carrier signal to said demodulator means, said demodulator means also being coupled to said plurality of sound wave receiving means so that sound wave receiving signals are demodulated by said demodulator means relative to said transmit carrier signal to produce an output signal representing the frequency shift based on the velocity of blood cells within the artery.