End-tidal gas analysis apparatus for respirators

• US 3,910,261 A
• Filed: 06/11/1974
• Issued: 10/07/1975
• Est. Priority Date: 06/11/1974
• Status: Expired due to Term

• Current Assignee: Bear Medical Systems Inc.
• Original Assignee: Charles W. Ragsdale, James Weigl
• Inventors: Ragsdale, Charles W., Weigl, James
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Cohen, Lee S.
• Application Number:
  US05/478,429
• Time in Patent Office: 483 Days
• Field of Search: 128/2.07,2.08,2R,2C 73/421.5,23 23/254C,254R
• US Class Current: 600/532
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production

Abstract

Intermittently operated gas analysis apparatus and a method for monitoring the proportion of particular gases carried in the endtidal portion of breathing. An analysis sample is obtained, following a predetermined time delay, when a patient expires air into a respirator. The apparatus is rapidly deactuated at the beginning of inspiration, and remains off until the patient again expires breath. By an appropriate setting of the time delay, a gas sample that accurately represents the end-tidal condition may be obtained, making the analyzer particularly suitable for monitoring the CO2 content of expired breath.

Claims

1. End-tidal gas analysis apparatus suitable for use with a respirator of the type having an air source actuated in response to patient demand and a conduit system which includes inspiratory and expiratory conduits for respectively delivering air to and receiving air from a patient, said apparatus comprising:

means for analyzing gas contained in said conduit system, means for supplying gas from said conduit system to said analyzing means, actuator means adapted to sense the beginning of patient expiration and to initiate operation of said gas supplying means after a predetermined delay period following the beginning of said patient expiration, and deactuator means adapted to sense the beginning of patient inspiration and rapidly terminate operation of said gas supplying means in response thereto, said actuator means and deactuator means cooperating to operate said gas supplying means for substantially the full interval between the end of said delay period and the beginning of patient inspiration, and to inhibit operation of said gas supplying means during substantially the full remainder of the time the analysis apparatus is in use.

2. Apparatus according to claim 1, wherein said deactuator means includes a flow rate sensor adapted to sense gas flows associated with the beginning of inspiration.

3. Apparatus according to claim 1, wherein said gas supplying means includes means for extracting a gas sample from said respirator conduit system for delivery to said analyzing means, the operation of said extracting means being controlled by said actuator means and deactuator means.

4. Apparatus according to claim 1, wherein said deactuator means includes a gas flow rate sensor disposable in the inspiratory conduit, said sensor being adapted to produce a signal in response to a gas flow through said inspiratory conduit exceeding a predetermined threshold level, and a processing circuit means for a signal produced by said sensor.

5. End-tidal gas analysis apparatus suitable for use with a respirator of the type having an air source actuated in response to patient demand, a conduit system which includes inspiratory and expiratory conduits for respectively delivering air to and receiving air from a patient, and gas flow control valves disposed respectively in said inspiratory and expiratory conduits, said apparatus comprising:

means for analyzing gas contained in said conduit system, means for supplying gas from the portion of said conduit system between said flow control valves to said analyzing means, actuator means adapted to sense the beginning of patient expiration and to initiate operation of said gas suppling means after a predetermined period of time following the beginning of said patient expiration, and deactuator means adapted to sense the beginning of patient inspiration and rapidly terminate operation of said gas supplying means in response thereto, said actuator means and deactuator means cooperating to operate said gas supplying means for substantially the full interval between the end of said delay period and the beginning of patient inspiration, and to inhibit operation of said gas supplying means during substantially the full remainder of the time the analysis apparatus is in use.

6. End-tidal gas analysis apparatus suitable for use with a respirator of the type having an air source actuated in response to patient demand and a conduit system which includes inspiratory and expiratory conduits for respectively delivering air to and receiving air from a patient, said apparatus comprising:

a gas analysis device;

a pump means for pumping gas from said conduit system to said analysis device;

a signal processing circuit means controlling the operation of said pump means; and

first and second gas flow sensors disposable respectively in said expiratory and inspiratory conduits, said first and second sensors being respectively connected to said signal processing circuit means to provide input signals when the sensed gas flows exceed predetermined threshold rates;

said signal processing circuit means including means to actuate said pump means after a predetermined period of time following receipt of an input signal from said first sensor, and further including rapid response means to deactuate said pump means in response to an input signal from said second sensor.

7. End-tidal gas analysis apparatus suitable for use with the air supply of a respirator, comprising:

a conduit system including inspiratory and expiratory conduits for respectively delivering air from said air supply to and receiving air from a patient, gAs flow control valves disposed respectively in said inspiratory and expiratory conduits, means for analyzing gas contained in said conduit system, means for supplying gas from said conduit system to said analyzing means, including means for extracting a gas sample from the portion of said conduit system between said flow control valves, actuator means adapted to sense the beginning of patient expiration and to initiate operation of said extracting means after a predetermined delay period following the beginning of said patient expiration, and deactuator means adapted to sense the beginning of patient inspiration and rapidly terminate operation of said analyzing means in response thereto.

8. The method of analyzing end-tidal gas expired by a patient into a respirator conduit system, comprising the steps of:

providing a gas analysing means and a means for supplying gas thereto from said conduit system;

sensing an expiratory gas flow into the conduit system from the patient;

actuating the gas supplying means after a predetermined period of time following the beginning of expiration sensed in the conduit systems;

sensing an inspiratory gas flow from the conduit system to the patient; and

rapidly deactuating the gas supplying means in response to the beginning of inspiratory gas flow sensed in the conduit system

9. The method of claim 8, suitable for measuring the end-tidal CO2 content of an expiratory breath, wherein said predetermined time period is at least sufficient to reach the end tidal portion of expiration.