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System and method for flow triggering of pressure supported ventilation by comparison of inhalation and exhalation flow rates

  • US 5,660,171 A
  • Filed: 08/21/1996
  • Issued: 08/26/1997
  • Est. Priority Date: 05/11/1990
  • Status: Expired due to Term
First Claim
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1. A method of controlling flow of ventilation to a patient supplied with a preinspiratory, continuous flow of breathing gas from a ventilation system having a source of breathing gas, a patient breathing attachment, an exhalation valve, and a functionally open breathing gas flow path in fluid communication with said source of breathing gas, said ventilation flow path including at least one flow sensor located between said patient breathing attachment and said exhalation valve for measuring a flow rate of said breathing gas from said patient breathing attachment through said exhalation valve, the steps of the method comprising:

  • delivering a predetermined rate of flow of said breathing gas from said source to said patient breathing attachment;

    measuring said flow rate of breathing gas from said source of breathing gas to said patient breathing attachment to determine a gas supply flow rate;

    measuring said flow rate of breathing gas from said patient breathing attachment through said exhalation valve at a location in said ventilation flow path between said breathing attachment and said exhalation valve to determine an exiting gas flow rate;

    determining patient inspiratory effort in said flow path by comparing said gas supply flow rate with said exiting gas flow rate;

    generating pressure support in said delivered flow of gas when said inspiratory effort exceeds a predetermined threshold value; and

    restoring delivery of said breathing gas from said source to said patient breathing attachment at a preinspiratory, continuous rate of flow before a patient'"'"'s next inspiratory effort.

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