Method and device for monitoring a flowing liquid for the presence of air
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Abstract
The present invention relates to a method and a device for monitoring a flowing medium, in particular the blood flowing in an extracorporeal blood circulation, for the presence of air, in particular micro-bubbles. A sequence of signal pulses or a continuous signal is injected into the flowing medium, and the signal pulses or continuous signal leaving the flowing medium are received. To detect micro-bubbles, a signal pattern that is characteristic of the variation over time of the received signal pulses or the continuous signal in a predetermined period of time is extracted from the signal received. The characteristic signal pattern is compared with one or more characteristic reference patterns, and the presence of air bubbles is determined if the characteristic signal pattern deviates from the characteristic reference pattern by a predetermined amount. Statistical characteristic variables, in particular the variance, are preferably determined from the signal patterns and compared with one another.
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Citations
32 Claims
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1-16. -16. (canceled)
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17. A method of monitoring a flowing medium for the presence of air comprising:
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coupling of a sequence of signal pulses or a continuous signal into the flowing medium; receiving the signal pulses or the continuous signal from the flowing liquid; extracting a signal pattern over a time interval that is characteristic of the variation over time of the signal pulses or the continuous signal received; comparing the signal pattern with one or more reference patterns; and determining that air is present in the flowing medium if the signal pattern differs from the one or more reference patterns by a preset amount. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A system for monitoring a flowing medium for the presence of air comprising:
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means for coupling a sequence of signal pulses or a continuous signal into the flowing medium; means for receiving the signal pulses or continuous signal emerging from the flowing liquid; and an analyzing unit comprising; means for extracting a signal pattern over a time interval that is characteristic of the variation over time of the signal pulses or the continuous signal received; and means for comparing the signal pattern with one or more reference patterns to determine that air is present if the signal pattern differs from the one or more reference pattern by a preset amount. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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32. A system for monitoring the presence of air in blood in an extra-corporeal blood circulatory system comprising:
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an ultrasonic emitter for coupling a sequence of signal pulses or a continuous signal into the flowing medium; an ultrasonic receiver for receiving the signal pulses or continuous signal emerging from the flowing liquid; and an analyzing unit comprising; a detector for extracting a signal pattern over a time interval that is characteristic of the variation over time of the signal pulses or the continuous signal received; and a microcontroller for comparing the signal pattern with one or more reference patterns to determine that air is present if the signal pattern differs from the one or more reference pattern by a preset amount.
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Specification