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Measurement of gas concentration in exhaled breath

  • US 5,069,220 A
  • Filed: 05/26/1989
  • Issued: 12/03/1991
  • Est. Priority Date: 05/26/1989
  • Status: Expired due to Fees
First Claim
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1. A method of measuring the concentration of a selected constituent gas in the exhaled breath of a patient, comprising the steps of:

  • (a) receiving an expiratory gas stream from the patient;

    (b) measuring the flow rate of the expiratory gas stream and generating a flow rate signal;

    (c) generating a tidal volume signal in response to the flow rate signal;

    (d) generating a sample control signal in response to the tidal volume signal and the flow rate signal to mark an interval within the end tidal periods of several successive expiratory gas streams from the patient;

    (e) extracting a sample of each of the several expiratory gas streams during the marked interval in response to the sample control signal;

    (f) accumulating each extracted sample of the expiratory gas streams in a variable volume reservoir;

    (g) transferring the accumulated gas samples within the variable volume reservoir into a sample cell in response to the variable volume reaching a predetermined limit; and

    (h) measuring the concentration of the selected constituent gas in the volume of gas contained in the sample cell.

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