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Apparatus and method for monitoring air emboli during extracorporeal circulation

  • US 4,014,206 A
  • Filed: 03/31/1975
  • Issued: 03/29/1977
  • Est. Priority Date: 03/31/1975
  • Status: Expired due to Term
First Claim
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1. Apparatus for detecting at least one embolism contained in a fluid during extracorporeal circulation of the fluid in a tubing comprising:

  • means to monitor the electrical impedance of the tubing, fluid and any emboli contained therein having an output signal whose voltage is proportional to the electrical impedance of the tubing, fluid and any emboli contained therein,first oscillator means receiving the output signal from said means to monitor and providing at least one output signal whose frequency is proportional to the electrical impedance of the tubing, fluid and any emboli contained therein,second oscillator means having an output signal whose frequency is proportional to the electrical impedance of the fluid and tubing,detector means receiving the output signals from said first and second oscillator means and providing an output signal the duration of which is indicative of the difference between the frequencies of the output signals of said first and second oscillator means,said detector means having an electrical feedback loop, said second oscillator means being in said feedback loop, integrator means in said feedback loop and proviging an output signal which is the time integral of the input thereto, said integrator means receiving the output signal of said detector means and providing said output signal to said second oscillator means, the output of said second oscillator means being fed back to said detector means to complete the feedback loop, andcontrol means for providing an actuation signal indicative of the presence of at least one embolism includingcounter means receiving the output signal of said detector means and a frequency signal of said first oscillator means and providing a plurality of output signals, said frequency signal incrementing said counter means only when said counter means receives a signal from said detector means,accumulation circuit means including multivibrator means receiving a first signal of said counter means and providing a periodic output signal as long as it is receiving the first output signal, and second counter means having a predetermined accumulation of emboli stored therein and counting each periodic signal from said multivibrator means to provide an output signal when said predetermined accumulation is reached, andgate means receiving the output signal of said second counter means and a second signal from said counter means being indicative of the presence of a single embolism of predetermined size, said gate means providing the actuation signal.

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