초록 ▼

Disclosed is a method and apparatus for detecting the presence of an embolism, such as air, during extracorporeal circulation in tubing carrying blood or other fluid such as would be present in the use of an artificial kidney machine. Electrodes are placed near the tubing to monitor the impedance th

Disclosed is a method and apparatus for detecting the presence of an embolism, such as air, during extracorporeal circulation in tubing carrying blood or other fluid such as would be present in the use of an artificial kidney machine. Electrodes are placed near the tubing to monitor the impedance thereof as well as the impedance of the fluid passing therethrough. An oscillator is attached to the electrodes and puts out a signal, the frequency of which is proportional to the basic impedance of the tubing and fluid. When an air bubble or the like passes the electrodes, the impedance will change causing a change in the frequency of the signal of the oscillator. The difference between the normal frequency and the changed frequency is indicative of the size of the embolism. Means are provided so that if a single embolism is large enough to cause damage to the patient or if a number of smaller emboli accumulate to the point of potentially causing damage to the patient, an alarm may be sounded or other remedial measures, such as system shutdown, could be taken. In addition, should the basic impedance of the fluid change, means are provided to prevent a false indication of an embolism.

대표청구항 ▼

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 elect

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, and control means receiving the output signal of said detector means and providing a plurality of output signals including an actuation signal indicative of the presence of at least one embolism, said control means including counter means and accumulation circuit means, said counter means receiving an output signal of said detector means and a frequency signal of said first oscillator means, said frequency signal incrementing said counter means only when said counter means receives a signal from said detector means, said 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 indicative of said predetermined accumulation, said counter means providing a second signal being indicative of the presence of a single embolism of predetermined size, and gate means receiving the output signal of said second counter means and said second signal from said counter means and selectively providing the actuation signal.