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Method for measuring the anesthetic agent consumption in a ventilation system

  • US 9,770,569 B2
  • Filed: 05/31/2007
  • Issued: 09/26/2017
  • Est. Priority Date: 06/10/2006
  • Status: Active Grant
First Claim
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1. A method for measuring consumption of an anesthetic agent over a time interval, the method comprising the steps of:

  • providing a ventilation system comprising a breathing circuit, an inspiratory line, an expiratory line and a Y-piece connecting the inspiratory line and the expiratory line to a patient, a gas mixer providing fresh gas to the breathing circuit, a manually actuatable anesthetic agent metering device for metering anesthetic to the fresh gas that is added to the breathing circuit, a gas measuring unit measuring anesthetic gas concentration at the Y-piece, an inspiratory volume flow measuring unit, at least a further volume flow measuring unit and a ventilating drive connected to the breathing circuit;

    providing a control and computer unit operatively connected to each of the gas measuring unit, the inspiratory volume flow measuring unit, the further volume flow measuring unit and the ventilating drive and not electrically and not operatively connected to the manually actuatable anesthetic agent metering device;

    manually setting and manually adjusting the setting of the manually actuatable anesthetic agent metering device to set and manually adjust an anesthetic concentration of anesthetic metered to the fresh gas and feeding the fresh gas with the set and adjusted anesthetic concentration to the breathing circuit during the course of a ventilation system procedure, wherein the manually actuatable anesthetic agent metering device does not communicate electronically with the ventilation system during the course of the ventilation system procedure;

    determining an inspiratory anesthetic gas concentration of the anesthetic agent and an expiratory anesthetic gas concentration of the anesthetic agent with the gas measuring unit;

    calculating a patient uptake anesthetic gas volume flow by multiplying a difference of the inspiratory anesthetic gas concentration and the expiratory anesthetic gas concentration with a measured inspiratory breathing minute volume flow;

    determining an anesthetic gas removal volume flow via an anesthetic gas removal conducting line;

    determining at least one further anesthetic gas volume flow of the ventilation system, the determination comprising determining any combination of;

    an anesthetic gas leakage volume flow from a patient loop;

    an anesthetic gas quantity drawn off volume flow of the gas measuring unit that is not returned to the ventilation system; and

    an anesthetic gas concentration increase volume flow for an increase of anesthetic gas concentration in the ventilation system;

    integrating a patient uptake anesthetic gas volume flow and the at least one further anesthetic gas volume flow over the time interval corresponding to a duration of a ventilation system procedure to provide a value of a volume of anesthetic gas consumed by the ventilation system during the ventilation system procedure; and

    recording the value, wherein;

    the at least a further volume flow measuring unit comprises or is associated with the gas mixer;

    a CO2 absorber is connected to the breathing circuit;

    the anesthetic gas removal volume flow is a removal volume flow via an anesthetic gas removal conducting line multiplied by the expiratory anesthetic gas concentration wherein the removal volume flow is determined from a total fresh gas volume flow supplied as determined by the gas mixer to the ventilation system reduced by a total gas uptake of the patient, reduced by a gas quantity consumed by a leakage volume flow by the ventilation system and reduced by a CO2 volume absorbed in the CO2 absorber wherein the CO2 volume is an expiratory CO2 concentration multiplied by an expiratory exhaled volume flow of the patient.

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