BLOOD PRESSURE INDICATOR AND NOISE

• US 3,651,798 A
• Filed: 05/15/1970
• Issued: 03/28/1972
• Est. Priority Date: 05/15/1970
• Status: Expired due to Term

• Current Assignee: Warner-Lambert Company (Pfizer Inc.)
• Original Assignee: Martin H. Wilcox, Paul H. Egli, Warren W. Brenner
• Inventors: Egli, Paul H., Brenner, Warren W., Wilcox, Martin H.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/037,543
• Time in Patent Office: 683 Days
• Field of Search: 128/2.5A,2.5M,2.5P,2.5Q,2.5R,2.5S,2.5T,2.6A,2.6F,2.6R 179/1ST 307/227,273,274,275
• 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 7/045 Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

An electronic blood pressure indicator for use with conventional inflatable arm cuff apparatus and a mercury or aneroid manometer, comprising a microphone for translation of arterial blood flow sounds into electrical signals, a narrow bandpass amplifier circuit which filters extraneous frequencies and amplifies a narrow band of low frequencies containing essential arterial blood flow information, a discriminator which senses signal strength and passes only signals exceeding a predetermined value, a pulse generator which provides a pulse output corresponding to blood flow pulses passed by the discriminator, the pulse generator cooperating with switch means to drive an indicator to provide a visual indication of the arterial blood flow sounds, and a dual lockout circuit which blocks incoming signals and spurious pulses from the pulse generator.

Claims

1. Blood pressure indicator apparatus for indicating the blood pressure of an individual by detecting auscultatory signals originating in the individual, said blood pressure indicator apparatus comprising:

a. microphone transducer means, adapted to be placed against an arm of said individual, for generating electrical signals representative of blood flow sounds within said arm of said individual;

b. narrow bandpass amplifier means having input terminals connected to the output terminals of said microphone transducer means for amplifying said representative signals, having filter sections providing for the amplification only of a narrow bandwidth of low frequency signals corresponding to the appreciable bandwidth of said blood flow signals;

c. discriminator means connected to and driven by said amplifier means for providing output responsive only to signal amplitudes greater than a predetermined amplitude;

d. pulse generator means connected to and driven by said discriminator means for providing output pulses of fixed amplitude and time duration responsive to the output signals of said discriminator means;

e. indicator means for providing a visual output corresponding to the output pulses of said pulse generator means;

f. switch means connected to and driven by the output of said pulse generator means and connected to and driving said indicator means for driving said indicator means in response to the output of said pulse generator means;

g. lockout means connected to said indicator means and to the input of said pulse generator means, for locking out the operation of said pulse generator means for a fixed predetermined time period subsequent to each pulse operation of said indicator means; and

, h. power supply means connected to said indicator means, said switch means, said pulse generator means, said discriminator means, and said narrow bandpass amplifier means for energizing same.

2. The apparatus as described in claim 1 wherein said lockout means comprises a capacitor, a low time constant path through which said capacitor discharges when said switch means switches on said indicator means, a second and higher time constant path through which said capacitor charges when said switch means switches said indicator means off, and a normally open transistor switch connected in shunting relationship to the input of said pulse generator means and connected to said second path such that said pulse generator means is held inactive for appreciably the time constant of said second path.

3. The apparatus as described in claim 1 wherein said pulse generator means comprises two transistors of opposite polarity, each having an output terminal, an input terminal, and a common terminal, a direct coupling resistance network connecting the output terminal of the first of said transistors to the input terminal of said second transistor, a second normally non-signal coupling network connecting the output terminal of said second transistor to the input terminal of said first transistor, said second network containing a capacitor in series with a second resistance network to provide a fixed time period of signal coupling from the output terminal of said second transistor to the input terminal of said first transistor.

4. The apparatus as described in claim 3 wherein each of said common terminals is connected to a respective voltage reference, and each of said input terminals is resistively connected to its respective common terminal, thereby maintaining each of said transistors non-conducting except when generating a pulse in response to a signal from said discriminator means.

5. The apparatus as described in claim 4 wherein a diode is in series with the base-to-emitter junction of said first transistor, said series combination constituting said discriminator means.

6. The apparatus as described in claim 1 wherein said microphone transducer means has a circular front housing and a rectangular back housing, and has a trimming resistor in parallel with its output terminals for standardizing the microphone output voltage.

7. The apparatus as described in claim 1 wherein an unregulated power supply is connected to said indicator means, and a regulated power supply is connected to said switch means, said pulse generator means, said discriminator means, and said narrow bandpass amplifier means.

8. In an electronic instrument for amplifying a pulse train and for providing an indication of such pulses which exceed a predetermined lower limit in amplitude, a combined discriminator and pulse generator circuit comprising:

a. a first diode, a first transistor with its base-to-emitter junction in series with said first diode, both said diode and said junction having forward bias voltages cooperating to provide a discriminator turn-on voltage level;

b. a second transistor having an opposite polarity, and a resistive network for connecting the collector of said first transistor to the base of said second transistor;

c. a second diode, and a capacitor and first resistor in series connected between the collector of said second transistor and the base of said first transistor through said second diode, thereby providing a feedback path from the output of said second transistor to the input of said first transistor;

d. a third diode and a second resistor in series, connected to and providing a discharge path for said capacitor;

e. said capacitor having a charging path through said second diode and said first resistor, said charging path cooperating with said first and second transistors to turn on both said transistors when an input voltage in excess of said turn-on voltage is applied to the input of said first diode and to turN off said first and second transistors after a predetermined time period, thereby providing a pulse output;

f. said discharge path resetting said combined circuit to a condition to provide a next pulse output;

g. switch means connected to and driven by the output of said second transistor for providing a switchable output; and

h. lockout means connected to the output of said switch means and to the input of said first transistor, for locking out the operation of said combined discriminator and pulse generator circuit for a fixed pre-determined time period subsequent to each of said pulse outputs.

9. The apparatus as described in claim 8 wherein said lockout means comprises a capacitor, a low time constant path through which said capacitor discharges when said switch means switches on, a second and higher time constant path through which said capacitor charges when said switch means switches off, and a normally open transistor switch connected in shunting relationship to the input of said first transistor and connected to said second path such that said first transistor is held inactive for a second predetermined time period of about the time constant of said second path.