Method and apparatus for ultrasonic detection of air bubbles
First Claim
1. An inclusion detector for detecting the presence of inclusions in a flow of a liquid while compensating for changes in the detection environment comprising:
- a conduit;
transmitting means for transmitting a signal through a liquid flowing in the conduit at a transmitted signal level;
receiving means for receiving and interpreting the signal transmitted by the transmitting means, a change in a received signal level being indicative of the presence of an inclusion in the liquid flow; and
signal adjusting means for adjusting the transmitted signal level to maintain an average value of the received signal level at a relatively constant value.
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Accused Products
Abstract
Inclusions in a liquid flow, such as air bubbles in a blood flow, are detected by transmitting a signal through the fluid and receiving and interpreting the received signal based on the expected degree of attenuation for the liquid and the inclusions. The amplitude of the transmitted signal is automatically adjusted to maintain a constant average amplitude of the detected signal, thus compensating for changes in the detection environment. The average amplitude of the transmitted signal is controlled by integrating the received signal using an integrator with a time constant longer than the time constant of the expected inclusion signals, and comparing the integrated signal to a constant reference level.
The presence of microbubbles is detected and a signal comprising a string of high frequency pulses is generated while the microbubbles are present. By counting the pulses, in conjunction with knowledge about the flow of liquid and the anticipated size of the microbubbles, an estimate of the total amount of air infused into the patient within a given time period is calculated.
A tubing holder for retaining a flexible tube in an inclusion detector has tubing retention grooves formed into tubing engagement faces, the tubing engagement faces being spaced closer together than the tube diameter. The tube is inserted into the tubing holder by compressing and deforming it against the tubing engagement faces, until it reaches the tubing retaining grooves.
256 Citations
45 Claims
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1. An inclusion detector for detecting the presence of inclusions in a flow of a liquid while compensating for changes in the detection environment comprising:
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a conduit; transmitting means for transmitting a signal through a liquid flowing in the conduit at a transmitted signal level; receiving means for receiving and interpreting the signal transmitted by the transmitting means, a change in a received signal level being indicative of the presence of an inclusion in the liquid flow; and signal adjusting means for adjusting the transmitted signal level to maintain an average value of the received signal level at a relatively constant value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for detecting the presence of inclusions in a liquid flowing in a conduit while compensating for changes in the detection environment comprising:
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transmitting a signal through the liquid at a transmitted signal level; receiving the signal at a received signal level; interpreting the signal to detect the presence or absence of an inclusion, a sudden change in the received signal level being indicative of the presence of an inclusion; and adjusting the transmitted signal level to maintain the received signal level at a relatively constant level. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. An extracorporeal blood processing apparatus comprising:
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a conduit for conveying blood; transmitting means for transmitting an ultrasonic signal through the blood conveyed in the conduit at a transmitted signal level; receiving means for receiving and interpreting the ultrasonic signal transmitted by the transmitting means, a relatively sudden change in a received signal level being indicative of the presence of at least one bubble of at least one of air or gas in the blood; and signal adjusting means for adjusting the transmitted signal level to maintain an average value of the received signal level at a relatively constant value. - View Dependent Claims (37)
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38. A tubing holder for retaining flexible tubing in contact with at least one ultrasonic transducer comprising:
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a first mounting block; a first generally planar tubing engagement face having an axis and a first leading edge generally parallel to the axis; a first tubing retaining groove recessed into the first tubing engagement face, the first tubing engagement groove being generally parallel to the axis and spaced a predetermined distance from the leading edge and having a generally arcuate cross sectional configuration; a first ultrasonic transducer mounted in the first mounting block below and in proximity with the first tubing retaining groove; a second mounting block; a second generally planar tubing engagement face having an axis and a second leading edge generally parallel to the axis; a second tubing retaining groove recessed into the second tubing engagement face, the second tubing engagement groove being generally parallel to the axis and spaced a predetermined distance from the leading edge and having a generally arcuate cross sectional configuration; and a housing securing and supporting the first and second mounting blocks in a relationship wherein; the first tubing engagement face faces the second tubing engagement face, is generally parallel to the second tubing engagement face and is spaced a predetermined distance from the second tubing engagement face; the first leading edge is generally parallel to and opposite the second leading edge; the first tubing retaining groove is generally parallel to and opposite the second tubing retaining groove; and the predetermined distance is selected to permit the tubing to be inserted between the first tubing engagement face and the second tubing engagement face at the location of the first and second leading edges when the tubing is relatively greatly compressed, and retained in the first and second tubing retaining grooves when the tubing is relatively less compressed. - View Dependent Claims (39, 40)
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41. A method for measuring the amount of air in the form of microbubbles in a liquid flowing in a tube comprising:
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transmitting a signal through the liquid at a transmitted signal level; receiving the signal at a received signal level; interpreting the signal to detect the presence or absence of a microbubble, a change in the received signal level being indicative of the presence of a microbubble; generating at least one logic signal pulse for each microbubble detected; counting the number of logic pulses generated over a predetermined time period; establishing the number of logic signal pulses that represent one microbubble and ascertaining the number of microbubbles in the tube during the predetermined time period;
wherein;the logic pulses are generated at a predetermined frequency during a detection time period when a microbubble is detected; and the establishing step comprises; determining a value of a constant that is directly proportional to the frequency at which the logic pulses are generated and directly proportional to an expected microbubble size; and dividing the constant by a flow rate of the liquid in the tube. - View Dependent Claims (43, 44, 45)
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42. The method defined in claim 42 wherein the ascertaining step further comprises:
dividing the number of logic pulses counted over the predetermined time period by the number of logic pulses that represent one microbubble.
Specification