RESPIRATION MONITOR

• US 3,802,419 A
• Filed: 04/11/1972
• Issued: 04/09/1974
• Est. Priority Date: 04/11/1972
• Status: Expired due to Term

• Current Assignee: John W. Yates
• Original Assignee: John W. Yates
• Inventors: Yates, John W.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/242,998
• Time in Patent Office: 728 Days
• Field of Search: 128/2.1R,2.1Z,2.5V
• US Class Current: 600/536
• CPC Class Codes: A61B 5/0809 by impedance pneumography

Abstract

Respiration is monitored by measuring a subject'"'"''"'"'s impedance by impressing an oscillator-controlled constant current source upon the subject. The output is fed to a differential amplifier, bandpass filtered, and full wave rectified. The differential amplifier can be switched to be fed by separate electrodes on the subject and not connected to the constant current source.

Claims

1. A system for monitoring the respiration of a subject having a basic body impedance and a changing thoracic impedance comprising:

a. an internal oscillator circuit;

b. a constant current source controlled by the oscillator;

c. a first pair of electrodes fed by the constant current source and adapted to be placed in contact with the subject;

d. a differential amplifier connected to the electrodes for measuring the potential difference therebetween;

e. a band-pass filter fed by the differential amplifier;

f. a full wave rectifier fed by the band-pass filter, the rectified output being a signal proportional to the basic body impedance and a signal proportional to the thoracic impedance change, the rectifier including;

1. first amplifier fed by the band-pass filter, 2. first and second resistors connected to the input terminal of the first amplifier, 3. a first diode having an anode connected to the first resistor and the cathode connected to the output of the first amplifier, 4. a second diode having an anode connected to the output of the first amplifier and the cathode connected to the second resistor, 5. a second amplifier having first and second inputs, the first input being connected to the cathode of the second diode, and 6. a third resistor interposed between the anode of the first diode and the second input of the second amplifier;

g. means for measuring the signal proporTional to the basic body impedance level fed by the rectifier; and

h. means for measuring the signal proportional to the thoracic impedance change fed by the rectifier.

2. A respiration monitoring system according to claim 1 which further comprises:

a. a second pair of electrodes connected to the subject; and

b. means for switching the input to the differential amplifier from the first pair of electrodes to the second pair of electrodes.

3. a first diode having an anode connected to the first resistor and the cathode connected to the output of the first amplifier,

4. A respiration monitoring system according to claim 2 which further comprises:

a. a high gain amplifier interposed between the rectifier and the basic body impedance measuring means; and

b. a low gain amplifier interposed between the rectifier and the thoracic impedance measuring means.

5. A respiration monitoring system according to claim 3 which further comprises:

a. a terminal for external oscillator connection; and

b. means for switching the input of the constant current source from the internal oscillator to the terminal for external oscillator connection.

6. a third resistor interposed between the anode of the first diode and the second input of the second amplifier;

g. means for measuring the signal proporTional to the basic body impedance level fed by the rectifier; and

h. means for measuring the signal proportional to the thoracic impedance change fed by the rectifier.