Importance

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Abstract

First and second means respectively provide for a passage of first and second particular volumes of fluid from first and second sources at first and second controlled rates to a patient. Each of the first and second means is constructed to provide on a positive basis for the flow of fluid at the particular one of the first and second controlled rates. Third means are operatively coupled to the first and second means for providing for an initial operation of the first means in producing a passage of fluid from the first source to the patient. Fourth means are responsive to the passage of the first particular volume of fluid to the patient for interrupting the operation of the first means and instituting the operation of the second means in providing for the passage of fluid from the second source to the patient. The passage of fluid from the first means to the patient is also interrupted when all of the fluid has passed from the source. At such a time, an air sensor associated with microbore tubing indicates that fluid is no longer passing through the tubing. At such a time, however, a drip chamber receiving the fluid from the microbore tubing still has fluid because the volume of the drip chamber is greater than the volume of the microbore tubing. Since the fluid from the drip chamber is introduced to the first means for passage on a controlled basis to the patient, the air sensor becomes operative to interrupt the flow of fluid to the patient at a time when air bubbles cannot flow to the patient. The drip chamber is made from a resilient material so that it can be initially operated to squeeze into the source any air bubbles existing in the drip chamber before fluid starts to pass from the first source to the patient.

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First Claim