Infusion pump and method for use
View Patent ↗A fluid dispensing system provides a non-contact method of monitoring the change in the fluid volume over time. This approach avoids the use of probes or sensors that come into direct contact with the fluid to be dispensed. The system comprises an apparatus comprising three chambers. The first chamber has a fixed volume and contains a pressurized gas. A solenoid valve is used to control the flow of gas from the first chamber into the second. The second chamber is sealed so that the combined mass of air in the first and second chambers remains fixed. The third chamber is adjacent to the second and contains medication in the form of incompressible fluid that is to be administered to a human or animal subject via a suitable delivery port. A piston is disposed between the second and third chambers and is movable responsive to the flow of gas into the second chamber to dispense fluid from the third chamber as desired. By sensing the pressure in the first and second chambers at any point in time, a processor is programmed to calculate the flow rate or dispensed volume of the fluid being delivered using principles derived from the Ideal Gas Law.
1. A method of measuring a fluid flow rate comprising:
(a) providing a first chamber containing a gas;
(b) providing a second chamber;
(c) transferring said gas from said first chamber to said second chamber;
(d) sensing the pressure in said first chamber;
(e) sensing the pressure in said second chamber;
(f) providing a third chamber containing a fluid and a port for delivery of said fluid;
(g) providing a boundary to separate said second chamber from said third chamber, said boundary moving as said gas is transferred from said first chamber into said second chamber, thus expelling said fluid through said port; and
(h) calculating the dispensed volume of fluid from said third chamber based upon the pressures sensed in said first chamber and said second chamber.
2. The method as recited in claim 1 , wherein said boundary comprises an interface between said gas and said fluid.
3. The method as recited in claim 1 , wherein said boundary comprises a membrane.
4. The method as recited in claim 1 , wherein said boundary comprises a piston.
5. A method for determining an unknown volume of compressible fluid in a chamber, comprising:
(a) providing a device having a first chamber and a second chamber, wherein said first chamber contains a gas and has a fixed volume;
(b) transferring said gas from said first chamber to said second chamber;
(c) sensing a pressure in said first chamber;
(d) simultaneously sensing a pressure in said second chamber; and
(e) calculating the volume of said second chamber using the pressure values sensed in steps (c) and (d) and the fixed volume of the first chamber.