SELF CALIBRATING TIDAL VOLUME IMPEDANCE PNEUMOGRAPH

• US 3,690,143 A
• Filed: 11/27/1970
• Issued: 09/12/1972
• Est. Priority Date: 11/27/1970
• Status: Expired due to Term

• Current Assignee: Warner-Lambert Company (Pfizer Inc.)
• Original Assignee: Christopher C. Day
• Inventors: Day, Christopher C.
• Primary Examiner(s): Prince, Louis R.
• Assistant Examiner(s): Henry, II, William A.
• Application Number:
  US05/093,068
• Time in Patent Office: 655 Days
• Field of Search: 73/1R 128/2.08
• US Class Current: 73/1.73
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity

Abstract

A method of automatically calibrating an electronic respiration monitoring system including a pneumograph responsive to changes in thoracic inpedance of a breathing patient for providing an analog signal proportional to breath volume and a volumecalibrated inflatable bag. The method comprises the steps of: (a) operatively associating the pneumograph with the thorax of the patient; (b) positioning said bag in association with the patient with the bag being arranged to capture gases exhaled by the patient; (c) determining maximum filling of said bag; and (d) automatically calibrating said system upon the filling of the bag.

Claims

1. A method of automatically calibrating an electronic respiration monitoring system including (1) impedance means responsive to changes in thoracic impedance of a breathing patient for providing an analog signal proportional to breath volume and (2) a volume-calibrated inflatable bag, said method comprising the steps of:

a. operatively associating said impedance means with the thorax of said patient;

b. positioning said bag in association with said patient, said bag arranged to capture gases exhaled by said patient;

c. determining maximum filling of said bag; and

, d. automatically calibrating said system upon the filling of said bag.

2. A method as recited in claim 1 and wherein said system is arranged to measure tidal volume of respiration, said method further comprising the steps of:

e. activating a calibration switch to concurrently obtain zero system gain, discharge residual voltage from a second capacitor, and enable two gates;

f. charging a first capacitor by said analog signal during exhalation into said bag;

g. obtaining a trigger signal upon inflation of said bag to its maximum volume;

h. passing said trigger signal through one of said gates;

i. stopping the charging of said first capacitor in response to said trigger signal;

j. holding steady the voltage of said charGed first capacitor as a calibration voltage;

k. transferring said calibration voltage from said first capacitor to said second capacitor during inhalation to obtain a transferred calibration voltage;

l. said transferred voltage activating a servo loop through the other of said gates to obtain calibrated gain; and

, m. disabling both of said gates to ready said system for tidal volume measurement.

3. A method as recited in claim 2 and wherein the step of activating said servo loop further comprises:

n. activating a motor in response to said transferred calibration voltage;

o. driving a potentiometer wiper by said motor to obtain a feedback voltage;

p. subtracting a reference voltage from said feedback voltage to obtain an error voltage; and

, q. applying said error voltage to said motor to position said potentiometer wiper.