Patent Application
20160317739
This invention relates to portable external infusion systems.
Diabetes is a disease in which the body does not produce or properly use insulin. Approximately 13 million people in the United States have been diagnosed with some form of diabetes. Type 1 diabetes results from the body's failure to produce insulin. Type 2 diabetes results from insulin resistance in which the body fails to properly use insulin. To effectively manage the disease, diabetics must closely monitor and manage their blood glucose levels through exercise, diet and medication. In particular, both Type 1 and Type 2 diabetics rely on insulin delivery to control their diabetes. Traditionally, insulin has been injected with a syringe multiple times during the day, usually self-administered by the diabetic. In recent years, external infusion pump therapy has been increasing, especially for delivering insulin to diabetics using devices worn on a belt, in a pocket, or the like, with the insulin delivered from a reservoir via a catheter with a percutaneous needle or cannula placed in the subcutaneous tissue.
External infusion devices allow Type 1 and Type 2 diabetics to better manage and control their diabetes. The external infusion device is intended to be used continuously and delivers insulin twenty-four hours a day according to a programmed plan unique to each pump wearer. A small amount of insulin, or a basal rate, is given continually. This insulin keeps the user's blood glucose levels in the desired range between meals and overnight. When food is eaten, the user programs the external infusion device to deliver a bolus of insulin matched to the amount of food that will be consumed. The user determines how much insulin will be given based on factors including insulin sensitivity, insulin duration, insulin-on-board, and the like. In many instances, external infusion devices include a processor that assists the user in making therapy decisions based on information provided by the user including blood glucose levels, carbohydrate intake, and/or information from the external infusion device. Exemplary devices are described in U.S. Pat. No. 6,554,798 issued on Apr. 29, 2003 to Mann et al., and entitled “External Infusion Device with Remote Programming, Bolus Estimator and/or Vibration Alarm Capabilities,” which is specifically incorporated by reference herein.
Users of external infusion device therapy rely on the precision and control of the therapy. It is important to minimize unexpected compromises of the infusion device, such as unnoticed cracks that allow liquids to leak into the device. Such leaks could lead to unpredictable device behavior or even failure of the device. Thus, having reliable and robust leak detection is highly desirable so users can engage in activities such as bathing, showering or even walking in the rain without compromising their confidence in the reliability of their external infusion device.
In one embodiment a medical therapy system including liquid detection is disclosed. A medical therapy includes a case with an interior and an exterior. Within the interior of the case is the liquid detection system that includes a first electrode set with a first positive electrode and a first negative electrode. The liquid detection system further includes an impedance measurement circuit coupled to the first electrode set to determine impedance values between the first positive electrode and the first negative electrode. A threshold detector compares impedance values between the first electrode set to a first threshold impedance. A microprocessor is programmed to initiate an alarm when measured impedance from the first electrode set is below the first threshold impedance.
In another embodiment a method of detecting fluid is disclosed. The method includes an operation that sets a first threshold impedance. In another operation impedance between a first set of electrodes is measured. Another operation stores the measured impedance to a memory while still another operation compares the measured impedance to the first threshold impedance. The method activates an alarm if the measured impedance is below the threshold impedance.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention.
A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures.
As shown in the drawings for purposes of illustration, the invention is embodied as an element or component within a portable infusion system. While many embodiments describe measuring impedance between electrodes to determine the presence of liquid, the extent of the disclosure should not be construed to exclude measuring capacitance, inductance or resistance to accomplish the same objective. Rather, impedance along with capacitance, inductance, and resistance should all be considered interchangeable to those skilled in the art as being able to determine whether liquid is present on electrodes.
In some embodiments the case 102 is made from polycarbonate, acrylonitrile butadiene styrene (ABS), or copolyester materials such as Eastman TRITAN to increase durability and to minimize the likelihood of liquid ingress such as water. In one embodiment, during the manufacturing process the case 102 is ultrasonically welded to completely seal major openings in the case. However, the case 102 does include other openings such as those for the reservoir 104 and battery, which are protected against liquid ingress by flexible o-rings with interference fits to their mating components. Furthermore, the reservoir 104 is designed to minimize the likelihood of fluid from the reservoir 104 leaking into the case 102. However, regardless of how robust and durable the case 102 and reservoir 104 are designed, real world usage can include repeated drops, crushes and pressure fluctuations that can eventually compromise the integrity of the case 102.
In embodiments where the infusion system 100, 100′, or infusion pump 101′ is used for diabetes therapy the user relies on precision control provided by the electronics within the infusion pump 101. Accordingly, integrity of the respective cases is important to protect sensitive electronics within the case from exposure to liquid. Liquid within the case can compromise the entire infusion system leading to malfunctions, unpredictable behavior or even complete failure of the infusion pump. As users rely on the infusion system to regulate blood sugar, detection and notification of the user regarding liquid in the pump case results in users having an opportunity to contact customer service to troubleshoot potential issues with the infusion system before catastrophic failure occurs.
In one embodiment electrodes 200a and 200b are comb shaped electrodes that include teeth that are offset as shown in
In some embodiments the threshold detector 204 is set low enough that impedance values caused by a worst case humidity condition does not trigger the wakeup to the microprocessor 206. For example, based on the operating parameters of the infusion system, the infusion pump can be placed in a maximum humidity environment with liquid detection circuits throughout the interior of the case. The minimum impedance values for the liquid detection circuits can be measured when the pump is operated within the maximum humidity environment thereby establishing a threshold value.
In other embodiments, the threshold detector 204 is set so a relatively high impedance value triggers the wakeup function of the microprocessor 206. In these embodiments, the wakeup function additionally activates the optional logging and analysis of impedance values to determine if fluctuations in ambient humidity caused the initial threshold detection. This embodiment can be beneficial for portable electronic systems because it can reduce power draw from the liquid detection circuit. Thus, when a relatively high threshold impedance value is registered, the liquid detection circuit begins recording impedance values in order to create an impedance history that can be analyzed for patterns caused by fluctuations in ambient humidity.
In still further embodiments, impedance values can be correlated to time using a clock 212 in order to create a dynamic threshold based on previous temporal impedance measurements. For example, the liquid detection circuit measures and records impedance values that decrease between 8 AM and 2 PM corresponding to increasing ambient humidity. Accordingly, the following day, the threshold values can be dynamically changed to reflect the ambient humidity of the previous day. Thus, as the humidity increases and decreases throughout the day, the threshold impedance value can dynamically change based on previously recorded data to avoid false alarms. Another technique that can be used to compensate for humidity and avoid false alarms of liquid on the electrodes is to monitor the rate of change of impedance.
Other embodiments include optional communication module 214 coupled with the microprocessor 206. The communication module 214 can include, but is not limited to wireless communication protocols such as Wi-Fi, BLUETOOH, BLUETOOTH LOW ENERGY, ZIGBEE, Z-WAVE, LTE and NFC. The communication module 214 enables access to location information along with corresponding weather data and weather forecasts that can be utilized to dynamically change the threshold impedance value of the liquid detection system.
In some embodiments, when the liquid detection system shown in
In some embodiments if operation 302 is initiated via software, operation 308 records the measured impedance to memory. In embodiments where operation 302 is initiated by hardware, the measured impedance is passed to a threshold detector circuit 318 that executes operation 320 to determine if the rate of change of impedance is indicative of liquid in the case. If operation 320 indicates liquid is in the case operation 310 wakes up the processor and operation 306 records the measured impedance to memory. In many embodiments regardless of whether the trigger of operation 302 is hardware, software or combinations of both, a time associated with the impedance measurement is also recorded into memory.
Operation 312 applies a fluid detection algorithm to the impedance values stored in memory resulting in operation 314 that determines if liquid is detected. If operation 314 detects liquid operation 316 activates an alarm. The alarm that is activated can be audible, tactile (vibration), visual or a combination thereof. If operation 314 does not detect liquid, operation 308 waits until the next impedance measurement is taken via operation 302.
In many embodiments a power supply within the transmitter 402 allows the transmitter to be reused with multiple sensors before being disposed of or alternatively being recharged. However, when the sensor is inserted into the user it is possible, however unlikely, for bodily fluid such as blood to be released from the insertion site. Thus, due to the possible introduction of fluid near the port 406 it would be beneficial to include a fluid detection system within the transmitter 402. Accordingly, the fluid detection system described above should not be construed to be used exclusively with infusion systems, subcutaneous sensors, or even electronic devices having cases. Instead, the fluid detection system described above could be used in any application requiring the detection of liquid. Examples include, but are not limited to detection of undesirable liquid leakage proximate to intravenous injection sites or catheter sites. In still other embodiments, the liquid detection system could be adapted to measure humidity based on impedance between the electrodes.
While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive. The scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
