FETAL HEART RATE AND INTRA-UTERINE PRESSURE MONITOR SYSTEM

• US 3,599,628 A
• Filed: 05/03/1968
• Issued: 08/17/1971
• Est. Priority Date: 05/03/1968
• Status: Expired due to Term

• Current Assignee: Thomas J. Abbenante, Victor H. Gieler, Weiss Robert E Montgomery Gerh
• Original Assignee: Thomas J. Abbenante, Victor H. Gieler, Weiss Robert E Montgomery Gerh
• Inventors: Abbenante, Thomas J., Gieler, Victor H., WEISS ROBERT E MONTGOMERY GERH
• Application Number:
  US04/726,428
• Time in Patent Office: 1,201 Days
• US Class Current: 600/511
• CPC Class Codes: A61B 5/02411 of foetuses
• CPC Class Codes: A61B 5/033 Uterine pressure
• CPC Class Codes: A61B 5/4362 Assessing foetal parameters

Abstract

This disclosure relates to a device for monitoring fetal heart beat and intrauterine pressure and correlating the same to determine fetal distress. The fetal heart rate monitor employs a photoelectric AGC circuit, a frequency selector producing a ringing output at the dominant frequency of the fetal EKG complex, digital counters to measure the interval between successive heart beats, a digitalto-analog converter and a two-channel recorder. The intrauterine pressure monitor features a liquid-filled tube connected to a bridge-type pressure transducer, an oscillator for supplying power to the bridge, a differential amplifier for sensing bridge unbalance and a rectifier connected to the amplifier, gated by a pulse from the oscillator and producing a voltage to be recorded on the second channel of the recorder.

Claims

1. A system for monitoring heart rate comprising means for detecting the electrocardiograph complex of a subject, amplifying means for controlling the amplitude of the detected complex to an essentially constant value, means responsive to said amplifying means for detecting a predetermined amplitude of each complex, means for measuring the time interval between each detected predetermined complex amplitude, means responsive to said time interval measuring means for indicating the rate of successive heart beats and further means responsive to said time interval measuring means for indicating differentials in the intervals between successive heart beats.

2. A system for monitoring the condition of a fetus in the uterus comprising means for detecting the electrocardiograph complex of a fetus, means for controlling the amplitude of the detected complex to an essentially constant value means for detecting the peak of each complex, means for measuring the time interval between each complex peak, means responsive to said measuring means for indicating the rate of successive heart beats, means for monitoring intrauterine pressure, and means for recording the fetal heart rate and intrauterine pressure simultaneously with respect to a common time base.

3. The system of claim 2 wherein said means for recording comprises a strip recorder having a stylus for recording each of the heart rate and compression, and means for calibrating the heart rate stylus at a plurality of rates.

4. A system for monitoring heart rate comprising means derived signals inductive of the heartbeat of a subject, means for amplifying the detected complexes to an essentially constant value, means responsive to said amplifying means for detecting a predetermined amplitude of each derived signal, a counting device for counting a plurality of pulses, a pulse generator, means for applying the pulses of said pulse generator to said counting device between the detected predetermined amplitudes the derived signals to derive a numerical count proportional to the time between successive derived signal and means for deriving a signal proportional to the number of pulses counted by said counting means between successive derived signals.

5. The system of claim 4 further including numerical storage means, means responsive to receipt of a signal indicator of a derived signal for storing the numerical content of said counter in said storage means and resetting said counting device for another count, said means for deriving a signal proportional to the number of pulses being responsive to the count in said storage means to provide a signal inversely proportional in magnitude to the stored numerical count.

6. The system of claim 5 further including means responsive to the resetting of said counting device for indicating the difference in time between derived signals.

7. The system of claim 4 wherein said amplifying means includes automatic gain control means for amplifying the derived signals to an essentially constant value, and means for detecting a predetermined amplitude of each amplified complex, the pulses of said pulse generator being applied to said counting device between detections of said predetermined amplitude of successive derived signals.

8. A system for detecting the difference in time interval between successive heart beats of a subject comprising means for detecting the eleCtrocardiograph complex of the subject, means responsive to detection of the complex for establishing a numerical representation of the time between detection of a first and a second complex, means for storing said representation and subtracting therefrom a numerical representation of the time between said second and a third complex to derive a numerical representation of the time difference in the interval between said first and second signals and said second and third signals, and means for indicating said time difference between successive signals.

9. An instrument for monitoring the condition of a fetus in the uterus, comprising means for detecting the heart beat of the fetus, counting means for measuring the time interval between successive heart beats and establishing a numerical representation of the time interval between successive heart beats, means for measuring the intrauterine pressure, means responsive to said numerical representation for providing a signal indicative of fetal heart rate, means responsive to said measuring means for deriving a signal indicative of intrauterine pressure, and means for simultaneously displaying a representation of the derived signals in timed relation.

10. The system of claim 9 wherein said means for displaying is a strip recorder.

11. The system of claim 9 wherein said detecting means includes an electrode connectable to the fetus and said means for measuring comprises a pressure-sensitive transducer and a catheter for liquid-coupling said transducer to the uterus.

12. The system of claim 9 further including means for displaying EKG. complex of the detected heart beat.

13. The system of claim 9 further including means for providing a heart rate calibration frequency, and means for causing said display means to indicate the calibration frequency.

14. A system for monitoring the condition of a fetus in the uterus, comprising means for detecting from the fetus its electrocardiograph complex, means responsive to said detection means for measuring the time interval between each complex and deriving a signal indicating the fetal heart rate, means for monitoring the intrauterine pressure and deriving a signal indicative thereof, display means, and means for applying the rate signal and the pressure signal to said display means to simultaneously display indications of the heart rate and pressure with respect to a common time base.

15. The system of claim 14 wherein said detecting means includes electrode means directly connectable to the fetus.

16. The system of claim 14 wherein said means for monitoring comprises a pressure transducer adapted to yield an electrical signal responsive to fluid pressure applied thereto and catheter means for liquid coupling said transducer to the uterus.

17. The system of claim 14 wherein said means for deriving a rate signal comprises amplifying means for amplifying each detected electrocardiograph complex to an essentially constant amplitude, means for detecting a predetermined magnitude of each amplified complex, means for detecting the time interval between the detected predetermined magnitude of each complex, and means responsive to said time interval detecting means for providing a signal indicative of heart rate.

18. The system of claim 17 further comprising means for controlling the gain of said amplifying means as a function of said heart rate signal.

19. The system of claim 17 further including a frequency selector coupled to said amplifying means for selecting the predominant frequency wave of the complex, said predetermined amplitude detecting means being coupled to receive the output of said frequency selector.

20. The system of claim 20 further including a gain control circuit for said amplifying means comprising means for controlling the gain of said amplifying means in one direction as a function of the amplitude of the complex and in the opposite direction as a function of the rate indicative signal.

21. The system of claim 14 wherein said display mEans comprises a strip recorder having first and second stylii, and means for producing movement of said stylii in accordance with the amplitude of said rate and pressure signals.

22. The system of claim 20 wherein said peak detecting means comprise a tuned circuit ringing at the predominant frequency of the complex and providing a sinusoidal ringing signal in response to each complex, and means for detecting the change in direction of the waveform of the ringing signal to detect the peak thereof.

23. A system for monitoring the heart rate of a subject, comprising means for detecting the electrocardiograph complex of the subject, means for amplifying the detected complexes to an essentially constant amplitude, means for detecting a predetermined amplitude of each amplified complex, means for measuring the time interval between the detected predetermined amplitude of each complex, and means responsive to said means for measuring for providing a signal indicating the rate of occurrence of the complexes, said means for amplifying including gain control means operative as a function of amplitude of the detected signals and the rate signal to maintain the output signal at an essentially constant predetermined amplitude.

24. The system of claim 23 wherein said time interval measuring means comprises pulse counting means, a source of repetitively reoccurring pulses, means for applying the pulses from said source to said counting means to count the number of pulses occurring between detected predetermined amplitudes of successive complexes.

25. The system of claim 24 further including means for indicating the differential interval between successive complexes.

26. The system of claim 23 wherein said amplifying means includes a feedback circuit from the output thereof to the input thereof, a capacitor coupled to said feedback circuit and arranged to be charged by the output signal at said amplifier, means coupling an inversion of the rate signal to said capacitor, the charge on said capacitor controlling the gain of said amplifying means.

27. The system of claim 26 wherein said feedback circuit includes a photosensitive resistance, a lamp, a driver arranged to illuminate said lamp in response to the charge on said capacitor, the degree of illumination of said lamp controlling the effective resistance value of said photosensitive resistance and hence the magnitude of the feedback signal to the input of said amplifier.

28. An instrument for monitoring the condition of a fetus in the uterus, said instrument comprising means for detecting from the fetus its electrocardiograph complex, amplifying means for amplifying the detected complex to an essentially constant amplitude, means for detecting a predetermined level of each amplified complex, means for detecting the time interval between the detected predetermined levels of each complex, means responsive to said time interval detecting means for providing a signal indicative of heart rate, a pressure transducer adapted to yield an electrical signal responsive to fluid pressure applied thereto means for liquid coupling said transducer to the uterus, a strip recorder having first and second stylii, and means for producing movement of said first and second stylii responsive to the amplitudes of said rate and pressure signals to simultaneously display representations of the heart rate and uterine pressure with respect to a common time base.

29. A system for monitoring the condition of a fetus in the uterus comprising means for detecting the heart beat of the fetus, means for monitoring the intrauterine pressure, a pulse generator, pulse counting means, means for applying the pulses from said pulse generator to said counting means between successive heart beats, means responsive to the numerical count in said pulse counting means for providing a signal indicative of fetal heart rate, means responsive to said pressure monitoring means for providing a signal indicative of intrauterine pressure, signal responsive diSplay means, and means for applying the rate and pressure indicative signals to said display means to provide a display of indications of heart rate and intrauterine pressure in timed relation.

30. The system of claim 29 further including numerical storage means, means responsive to receipt of a signal indicative of a detected predetermined amplitude for storing the numerical content of said counter in said storage means and resetting said counting device for another count, said means for deriving a signal proportional to the number of pulses being responsive to the count in said storage means to provide a signal inversely proportional in magnitude to the stored numerical count.

31. The system of claim 29 wherein said detecting means includes an electrode connectable to the fetus and said means for monitoring comprises a pressure-sensitive transducer and a catheter for liquid coupling said transducer to the uterus.