HIGH-GAIN MONITOR TO DETERMINE ELECTRO-CEREBRAL SILENCE

• US 3,721,230 A
• Filed: 11/23/1970
• Issued: 03/20/1973
• Est. Priority Date: 11/23/1970
• Status: Expired due to Term

• Current Assignee: Robert S. Ziernicki
• Original Assignee: Robert S. Ziernicki
• Inventors: Ziernicki, Robert S.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/091,629
• Time in Patent Office: 848 Days
• Field of Search: 128/2.6B,2.6E,2.6G,2.6R,2.1B,2.1E,2.1R 330/14,69
• US Class Current: 600/544
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: Y10S 128/902 Biological signal amplifier

Abstract

An apparatus for measuring physiological conditions of human and animal bodies characterized by; in addition to a preamplifier, filter, amplifier, recorder, and power supply; a common mode noise rejection circuit and a shield for the noise-sensitive components; whereby the apparatus may be employed at a patient'"'"''"'"'s location, even in the presence of electrical noise. The apparatus is characterized by other improved concepts that are also disclosed; such as, front end loading of paper for the recorder; a channel selector for selecting the electrodes to be monitored; a small portable unit that includes a self-contained calibrate and test circuit to ensure correct operation regardless of the electrical noise in a given area or location; and a specific electrical schematic diagram.

Claims

1. Apparatus for determining physiological conditions in human and animal bodies, said apparatus having a sensitivity 1,000 times greater than that normally necessary for electrocardiographs and sufficient to provide the criteria of death through indication of electro-cerebral silence, comprising:

a. a plurality of electrode means for detecting bioelectric outputs from spaced locations carried by said bodies and including leads for connecting with a plurality of input terminals of a preamplifier section;

b. a portable unit employing miniaturized, solid state circuit elements, and including;

i. power conductor means for supplying power when connected with a source of power;

ii. a preamplifier secton connected with said power conductor means and having a common mode noise rejection circuit means that has a plurality of input terminals that are connected with a plurality of said electrode means;

said common mode noise rejection circuit means comprising a pair of operational amplifiers that are connected in a differential amplifier configuration with a noninverting input terminal of each operational amplifier being connected with a respective one of said input terminals of said preamplifier section and having a respective output conductor;

a feedback network for each operational amplifier;

each operational amplifier in the differential amplifier configuration having its output conductor serially connected with its inverting input terminal via said feedback network for feedback; and

a cross-coupling resistor that is serially connected with respective inverting input terminals of said operational amplifiers;

all such that necessary high amplification of legitimate body signals is effected while maintaining low noise amplification and high input impedance sufficient to squelch gross noise signals, such as, a patient sweating or an electrode means slipping;

iii. filter means connected with said preamplifier section for removing predictable noise within a predetermined frequency range; and

iv. power amplifier section connected with said filter means;

c. shield means carried by said portable unit and encompassing said preamplifier section, said filter means, and said power amplifier section;

d. recorder means connected with said power amplifier section for recording with respect to time, an output therefrom;

e. a test switch connected with said input terminals; and

f. calibrate and test means carried by said portable unit and having test output terminals that are connected with said test switch for elEctrical connection with said input terminals of said preamplifier section for testing and calibrating said apparatus.

2. The apparatus of claim 1 wherein said filter means comprises a twin tee notch filter.

3. The apparatus of claim 1 wherein a power supply is connected to said power conductor means;

said power supply providing the requisite voltage when plugged into a conventional electrical outlet and having discrete voltage taps with decoupling means to minimize noise signals thereon.

4. The apparatus of claim 1 wherein said feedback network comprises a parallel connected resistor-capacitor network for feedback.

5. The apparatus of claim 4 wherein said preamplifier section includes a conversion means that is connected with said output conductors from said operational amplifiers and has a single second output conductor for converting said differential output of said common mode noise rejection circuit means to a single output;

said single second output conductor being connected with said filter means;

said conversion means comprising an additional operational amplifier having a plurality of input terminals that are connected with said output conductors from said operational amplifiers;

a parallel connected resistor-capacitor network;

said additional operational amplifier having its single second output terminal serially connected with one of its input terminals via said parallel connected resistor-capacitor network for feedback.

6. The apparatus of claim 5 wherein said operational amplifiers and said additional operational amplifier are formed by at least medium scale integrated circuit techniques such that at least each operational amplifier is contained on a single monolithic semiconductor chip, whereby size is reduced sufficiently that said shield means can be employed and said unit still be practical and hand portable.

7. The apparatus of claim 6 wherein said operational amplifiers and said additional operational amplifier have an input off-set voltage less than about 5 millivolt, input off-set current less than about 200 nanoampere, an input resistance greater than about 150,000 ohms, open loop gain greater than about 25,000, and a common mode noise rejection ratio greater than about 70 decibels.

8. Apparatus for determining physiological conditions in human and animal bodies, said apparatus having a sensitivity 1,000 times greater than that normally necessary for electrocardiographs and sufficient to provide the criteria of death through indication of electro-cerebral silence, comprising:

a. a plurality of electrode means for detecting bioelectric outputs from spaced locations carried by said body and including leads for connecting with a plurality of input terminals of a preamplifier section;

b. a unit including a shield means encompassing;

i. a preamplifier section having a common mode noise rejection circuit means that has a plurality of input terminals that are connected with a plurality of said electrode means;

said common mode noise rejection circuit means comprising a pair of operational amplifiers that are connected in a differential amplifier configuration with a non-inverting input terminal of each operational amplifier being connected with a respective one of said input terminals of said preamplifier section and having a respective output conductor;

a feedback network for each operational amplifier;

each operational amplifier in the differential amplifier configuration having its output conductor serially connected with its inverting input terminal via said feedback network for feedback; and

a cross-coupling resistor that is serially connected with respective inverting input terminals of said operational amplifiers;

all such that necessary high amplification of legitimate body signals is effected while maintaining low noise amplification and high input impedance sufficient to squelch gross noise signals, such as a patient sweating or an electrode means slipping;

ii. filter means connected with said preamplifier section for removing predictable noise within a predetermined frequency range; and

iii. power amplifier section connected with said filter means;

c. a power conductor means connected with said preamplifier section for supplying power when connected with a source of power; and

d. recorder means connected with said power amplifier section for recording with respect to time, an output therefrom.

9. The apparatus of claim 8 wherein a parallel connected resistor-capacitor network is provided for each said operational amplifier;

and each operational amplifier in said differential amplifier configuration has its output conductor serially connected with its inverting input terminal via said parallel connected resistor-capacitor network for feedback.

10. The apparatus of claim 8 wherein said preamplifier section includes a conversion means that is connected with said output conductors from said operational amplifiers and has a single second output conductor for converting said differential output of said common mode noise rejection circuit means to a single output;

said single second output conductor being connected with said filter means.

11. The apparatus of claim 10 wherein said conversion means comprise an additional operational amplifier having a plurality of input terminals that are connected with said output terminals from said operational amplifiers;

a third parallel connected resistor-capacitor network is provided; and

said additional operational amplifier having its single second output conductor serially connected with one of its input terminals via said parallel connected resistor-capacitor network for feedback.

12. The apparatus of claim 11 wherein said operational amplifiers, including said additional operational amplifier, are formed by at least medium scale integrated circuit techniques such that at least each operational amplifier is contained on a single monolithic semiconductor chip, whereby size is reduced sufficiently that said shield means can be employed and said unit be practical and hand portable.

13. The apparatus of claim 12 wherein said operational amplifiers have an input off-set voltage less than about 5 millivolt, input off-set current less than about 200 nanoampere, an input resistance greater than about 150,000 ohms, open loop gain greater than about 25,000, and a common mode noise rejection ratio greater than about 70 decibels.

14. Apparatus for determining physiological conditions in human and animal bodies, said apparatus having a sensitivity 1,000 times greater than that normally necessary for electrocardiographs and sufficient to provide the criteria of death through indication of electro-cerebral silence, comprising:

a. a plurality of electrode means for detecting bioelectric outputs from spaced locations carried by said bodies and including leads for connecting with a plurality of input terminals of a preamplifier section;

b. a portable unit employing miniaturized, solid state circuit elements and including;

i. power conductor means for supplying power to said portable unit when connected with a source of power;

ii. a preamplifier section having a common mode noise rejection circuit means that has input terminals that are connected with a plurality of said electrode means;

said common mode noise rejection circuit means comprising a pair of operational amplifiers that are connected in a differential amplifier configuration with a noninverting input terminal of each operational amplifier being connected with a respective one of said input terminals of said preamplifier section and having a respective output conductor;

a feedback network for each operational amplifier;

each operational amplifier in the differential amplifier configuration having its output conductor serially connected with its inverting input terminal via said feedback network for feedback; and

a cross-coupling resistor that is seriAlly connected with respective inverting input terminals of said operational amplifiers;

all such that necessary high amplification of legitimate body signals is effected while maintaining low noise amplification and high input impedance sufficient to squelch gross noise signals, such as a patient sweating or an electrode means slipping;

iii. filter means connected with said preamplifier section for removing predictable noise within a predetermined frequency range; and

iv. power amplifier section connected with said filter means;

c. shield means carried by said portable unit and encompassing said preamplifier section, said filter means, and said power amplifier section;

d. recorder means for recording comprising a pen means for marking, pen drive means for driving said pen means, said pen drive means being drivingly connected with said pen means and responsively connected with the output of said power amplifier section; and

a chart drive means for advancing said chart at a predetermined rate with respect to time;

said recorder means having a front end panel means that opens outwardly from the front end of said unit and that has a mounting means for loading and unloading a roll of paper and said chart comprises a roll of paper that is readily loaded into said mounting means;

said chart and said pen means being compatible so that said pen means is able to make a record on said chart.

15. The apparatus of claim 14 wherein said pen is a thermal stylus and said chart is a heat sensitive paper.

16. Apparatus for determining physiological conditions in human and animal bodies, said apparatus having a sensitivity 1,000 times greater than that normally necessary for electrocardiographs and sufficient to provide the criteria of death through indication of electro-cerebral silence, comprising:

a. a plurality of electrode means for detecting bioelectric outputs from spaced locations carried by said bodies and including leads for connecting with a plurality of input terminals of a preamplifier section;

b. channel selector means connected with said plurality of electrode means and having a selector switch means that has a pair of output terminals and that is operable to select and connect a predetermined pair of said electrode means with said output terminals;

c. a portable unit employing miniaturized, solid state circuit elements, and including;

i. power conductor means for supplying power when connected with a source of power;

ii. a preamplifier section connected with said power conductor means and having a common mode noise rejection circuit means that has input terminals that are connected with said pair of output terminals;

said common mode noise rejection circuit means comprising a pair of operational amplifiers that are connected in a differential amplifier configuration with a non-inverting input terminal of each operational amplifier being connected with a respective one of said input terminals of said preamplifier section and having a respective output conductor;

a feedback network for each operational amplifier;

each operational amplifier in the differential amplifier configuration having its output conductor serially connected with its inverting input terminal via said feedback network for feedback; and

a cross-coupling resistor that is serially connected with respective inverting input terminals of said operational amplifiers;

all such that necessary high amplification of legitimate body signals is effected while maintaining low noise amplification and high input impedance sufficient to squelch gross noise signals, such as a patient sweating or an electrode means slipping;

iii. filter means connected with said preamplifier section for removing predictable noise within a predetermined frequency range; and

iv. power amplifier section connected with said filter means;

d. shield means carried by said portable unit and encompassing said preamplifier section, said filter means, and said power amplifier sEction; and

e. recorder means connected with said power amplifier section for recording with respect to time, an output therefrom.

17. The apparatus of claim 16 wherein a pair of short conductor means are provided with said portable unit and said channel selector means is carried by said portable unit and has its output terminals connected therewith by said pair of short conductor means.

18. The apparatus of claim 16 wherein a test switch means is connected with said input terminals of said common mode noise rejection circuit means for testing and calibrating said apparatus;

and said portable unit has a self-contained calibrate and test means that has test output terminals that are connected with said test switch means.

19. The apparatus of claim 18 wherein said test switch means is also connected with said output terminals of said channel selector means for connecting said input terminals of said common mode noise rejection circuit means with either said test output terminals or said output terminals of said channel selector means.