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Cannula position detection

  • US 5,423,743 A
  • Filed: 09/17/1993
  • Issued: 06/13/1995
  • Est. Priority Date: 09/17/1993
  • Status: Expired due to Term
First Claim
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1. A method for determining the position of a cannula inserted into the vascular system of a patient, the cannula coupled to the downstream end of a conduit that is connected at its upstream end to a reservoir of fluid, the method comprising the steps of:

  • a. establishing a baseline pressure based on the pressure in the conduit when no flow of fluid is occurring;

    b. moving a first predetermined quantity of fluid towards the upstream end of the conduit;

    c. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the upstream end;

    d. moving a second predetermined quantity of fluid towards the downstream end of the conduit;

    e. measuring the pressure in the conduit during the step of moving the predetermined quantity of fluid towards the downstream end;

    f. summing the differences between the measured pressures and the baseline pressure;

    g. normalizing the pressure difference sum by the predetermined quantity of fluid;

    h. comparing the normalized sum to a predetermined range; and

    i. providing an alarm if the normalized sum is outside the predetermined rangej. wherein steps (a), (f), (g), (h), and (i) are performed by a processor.

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