Fluid volume determination for medical treatment system
First Claim
1. A method for determining a volume of fluid moved by a pump, the method including:
- measuring a first pressure for a pump control chamber when the pump control chamber is isolated from a reference chamber, the pump control chamber having a volume that varies at least in part based on movement of a portion of the pump;
measuring a second pressure for the reference chamber when the reference chamber is isolated from the pump control chamber, the reference chamber having a known volume;
measuring a third pressure associated with the pump control chamber after fluidly connecting the reference chamber and the pump control chamber, but before substantial equalization of pressures between the pump control and reference chambers has occurred;
measuring a fourth pressure associated with the reference chamber after fluidly connecting the reference chamber and the pump control chamber, but before substantial equalization of pressures between the pump control and reference chambers has occurred;
determining a volume for the pump control chamber based on the first, second, third and fourth measured pressures.
2 Assignments
0 Petitions
Accused Products
Abstract
A volume of fluid moved by a pump, such as a pump in an APD system, may be determined without direct measurement of the fluid, such as by flow meter, weight, etc. For example, a volume of a pump chamber (181) (having a movable element that varies the volume of the pump chamber) may be determined by measuring pressure in the pump chamber and a reference chamber, both while the two chambers are isolated from each other, and after the two chambers are fluidly connected so that pressures in the chambers may equalize. Equalization of the pressures may be assumed to occur in an adiabatic way, e.g., a mathematical model of the system that is based on an adiabatic pressure equalization process may be used to determine the pump chamber volume. In one embodiment, pressures measured after the chambers are fluidly connected may be measured at a time before complete pressure equalization has occurred, and thus the pressures for the pump and reference chambers measured after the chambers are fluidly connected may be unequal, yet still be used to determine the pump chamber volume.
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Citations
22 Claims
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1. A method for determining a volume of fluid moved by a pump, the method including:
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measuring a first pressure for a pump control chamber when the pump control chamber is isolated from a reference chamber, the pump control chamber having a volume that varies at least in part based on movement of a portion of the pump; measuring a second pressure for the reference chamber when the reference chamber is isolated from the pump control chamber, the reference chamber having a known volume; measuring a third pressure associated with the pump control chamber after fluidly connecting the reference chamber and the pump control chamber, but before substantial equalization of pressures between the pump control and reference chambers has occurred; measuring a fourth pressure associated with the reference chamber after fluidly connecting the reference chamber and the pump control chamber, but before substantial equalization of pressures between the pump control and reference chambers has occurred; determining a volume for the pump control chamber based on the first, second, third and fourth measured pressures. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 21, 22)
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12. A method for determining a volume of fluid moved by a pump, the method including:
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providing a fluid pump apparatus having a pump chamber separated from a pump control chamber by a movable membrane, and a reference chamber that is fluidly connectable to the pump control chamber; adjusting a first pressure in the pump control chamber to cause the membrane to move and thereby move fluid in the pump chamber; isolating the reference chamber from the pump control chamber and establishing a second pressure in the reference chamber that is different from a first pressure in the pump control chamber; fluidly connecting the reference chamber and the pump control chamber to initiate equalization of pressures in the pump control chamber and the reference chamber; and determining a volume for the pump control chamber based on the first and second pressures, at least one pressure for the reference and pump control chamber after the reference and pump control chambers are fluidly connected, and a model of adiabatic equalization of the pressures in the pump control and reference chambers. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification