There are many applications in academic, industrial, and medical fields, as well as others, that can benefit from devices and methods capable of accurately and controllably delivering fluids, including liquids and gases, and that benefit from administering fluids in known and controlled quantities. Such devices and methods may be particularly useful in the medical field where many treatments include the administration of a known amount of a substance at predetermined intervals.
Insulin-injecting pumps have been developed for the administration of insulin for those suffering from both Type I and Type II diabetes. Recently, continuous subcutaneous insulin injection and/or infusion therapy with portable infusion devices has been adapted for the treatment of diabetes. Such therapy may include the regular and/or continuous injection or infusion of insulin into the skin of a person suffering from diabetes, and offers an alternative to multiple daily injections of insulin by an insulin syringe or an insulin pen. Such pumps can be ambulatory/portable infusion pumps that are worn by the user and that may use replaceable cartridges. Examples of such pumps and various features that can be associated with such pumps include those disclosed in U.S. patent application Ser. Nos. 13/557,163, 12/714,299, 12/538,018, U.S. Provisional Patent Application No. 61/655,883, U.S. Provisional Patent Application No. 61/656,967 and U.S. Pat. No. 8,287,495, each of which is incorporated herein by reference.
There are, however, some drawbacks associated with the use of subcutaneous injection syringes and/or some currently available infusion pumps for the delivery of insulin and other fluids. Infusion pumps generally deliver fluids to patients through a flexible line having a lumen through which the fluid is pumped from the device to the patient. These fluid lines can become occluded such that fluid cannot be pumped through the line to the patient. Early detection of an occlusion condition is important because the patient may not be receiving the prescribed amount of fluid, which can be harmful and in some instances even fatal. Although there are a number of systems that address the occlusion issue by incorporating sensors to sense whether pressure has increased in the fluid line, such systems can suffer from drawbacks related to accuracy, and from the cost associated with the use of sensors in disposable cartridges. For example, when measuring small signals over long periods of time, sensor drift or other long term systematic effects, such as temperature or ambient pressure changes, can affect the accuracy of the readings taken with such sensors.
There is an ongoing need for improvement in systems and methods for detecting occlusions in ambulatory infusion pumps.