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Automatic control method for supplying anaesthetic to a low flow-type closed circuit

  • US 6,523,537 B1
  • Filed: 12/04/2000
  • Issued: 02/25/2003
  • Est. Priority Date: 04/14/1998
  • Status: Expired due to Fees
First Claim
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1. A method of automatic control for the supply of a volatile anaesthetic to a closed anaesthetic circuit of low flow, which comprises the stage of mixing fresh gas and volatile anaesthetic before introducing the mixture into the patient, the method comprising the steps of:

  • a) setting a ventilatory rate (VR) of the patient;

    b) automatically setting a flow of fresh gas (FFG) to 10% of the VR;

    c) determining a fraction inhaled (% IF) and exhaled (% EF) by the patient of volatile anaesthetic;

    d) setting a dial of an anaesthetic vaporiser to a value resulting from multiplying by 10 a differential of the inhaled fraction (% IF) and exhaled fraction (% EF) of volatile anaesthetic by the patient, wherein a concentration of anaesthetic at an output of the anaesthetic vaporizer (% dial) is equal to (% IF−

    % EF)×

    10, and changing, in a same proportion, the opening of said dial every time that said differential of inhaled fraction (% IF) and exhaled fraction (% EF) of volatile anaesthetic by the patient varies;

    e) supplying a quantity of anaesthetic to a circuit (QASC) that covers at least a total quantity of anaesthetic consumed by the patient (TQAC) by means of opening of the dial of the anaesthetic vaporizer; and

    f) mixing the quantity of anaesthetic with the FFG before introducing said mixture into the patient.

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