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Air bubble detecting and discriminating circuit arrangement and method

  • US 4,565,500 A
  • Filed: 02/24/1983
  • Issued: 01/21/1986
  • Est. Priority Date: 02/24/1983
  • Status: Expired due to Fees
First Claim
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1. A peristaltic infusion pump, assembly, comprising:

  • (a) means including a continuous length of tubing adapted for connection at one end to a supply of fluid and at its opposite end to a patient;

    (b) means including a variable speed motor acting on said tubing for peristaltically pumping said fluid therethrough at a flow rate proportionate to the speed of said motor, whereby any air bubbles in said fluid will move with the latter at the same flow rate;

    (c) means for detecting the presence of said air bubbles, if any, as they pass through a fixed point along the path of movement through said tubing, said detecting means being capable of producing a first signal in response to the presence of an air bubble at said fixed point and for the duration that the detected bubble passes through said point, the length of said first signal corresponding to the length of the detected bubble; and

    (d) means including said motor responsive to said detecting means for distinguishing between detected bubbles of at least a predetermined size which can cause problems from smaller nuisance bubbles which do not, regradless of the flow rate of the fluid, said distinguishing means including means for producing an alarm signal only if problem bubbles are detected, said distinguishing means being capable of producing a second signal for a predetermined period of time after initiation of said first signal, said second period of time being inversely proportionate to the speed of said motor, and said distinguishing means being capable of producing said alarm signal only during the presence of both said first and second signals, said time delay distinguishing between the larger problem bubbles and the smaller nuisance bubbles regardless of the flow rate of the fluid and bubbles.

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