Rechargeable battery backup apparatus and method for insulin pump

An apparatus and method for allowing an operator of a portable infusion device continue to operate the device after the primary battery source becomes depleted. The invention contemplates providing a secondary, rechargeable battery in addition to the primary battery, to allow the infusion device to operate even in the instance of a sudden drop in primary battery voltage. The apparatus includes a housing accommodating a syringe, where the syringe contains a liquid to be infused. Also included is a motor, a drive system operatively connected to the motor, where the drive system advances a piston of the syringe in order to expel the liquid from a barrel of the syringe. A power source is in electrical contact with and supplies power to the motor. The power source includes a primary battery module, and a rechargeable battery module, wherein the primary battery source supplies power to the rechargeable battery module. The result is a fail-safe system of alerting the user of low or critical battery conditions.

CROSS-REFERENCE TO RELATED APPLICATION

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for detecting a low or critical battery condition in an infusion pump by providing a backup, rechargeable battery and for allowing the user to continue use of the infusion pump even after the depletion of the primary battery.

BACKGROUND OF THE INVENTION

Insulin pump systems allow patients to administer safe doses of an intravenous or subcutaneous medication at will, without the need for constant supervision by medical staff. These devices often include a housing that houses a cartridge, a motor, a drive system, and a power supply, such as a battery, which supplies power to the motor. The outside of the housing provides key pad entry for allowing the patient to program the rate of insulin delivery and to modify the delivery rate according to the patient's expected or actual carbohydrate intake.

Recent changes in disposable battery design have resulted in battery voltage curves that remain substantially constant throughout the life of the battery. While the voltage of older types of disposable battery chemistry enables voltages to decrease gradually with use, new disposable batteries remain consistent throughout the battery's life until a short drop-off in voltage occurs. While this may prove to be harmless for certain products, it can be devastating to a portable insulin pump user. Portable insulin pump users rely on the infusion of insulin at preprogrammed times. A low battery condition may lead to an incorrect dosage or even lead to a missed dosage, resulting in an insulin pump that stops operating without warning. The results can obviously be devastating to the user.

International Standards IEC 60601-2-24 and 60601-1-8 govern the general requirements, tests and guidance for alarm system in medical electrical equipment, including infusion pumps and controllers. These standards require that infusion pumps include adequate alarm systems to notify the user when a low or critical battery condition is about to occur. However, it has recently become increasingly difficult to detect critical battery conditions with new disposable batteries in a timely matter due to the severe and sudden decline in voltage at the end of battery life. Because of the rapid decrease in voltage of disposable batteries onboard the insulin pump, there is currently no adequate means to detect a low or critical battery voltage condition.

Therefore, what is needed is an apparatus and method that can detect a low or critical battery condition in an infusion pump in a timely manner and can allow the user to continue to operate for a period of time after the primary disposable battery becomes depleted.

SUMMARY OF THE INVENTION

The present invention advantageously provides an apparatus and method for allowing an operator of a portable infusion device continue to operate the device after the primary battery source becomes depleted. The invention contemplates providing a secondary, rechargeable battery in addition to the primary battery, to allow the infusion device to operate even in the instance of a sudden drop in primary battery voltage. The result is a fail-safe system of alerting the user of low or critical battery conditions.

In one embodiment, an infusion pump is provided where the infusion pump includes a housing accommodating a syringe, where the syringe contains a liquid to be infused, a motor within the housing, a drive system operatively connected to the motor, where the drive system advances a piston of the syringe to expel the liquid from a barrel of the syringe, and a power source, in electrical contact with and supplying power to the motor. The power source includes a primary battery module, and a rechargeable battery module, wherein the primary battery source supplies power to the rechargeable battery module.

In another embodiment, a power source module for use in an infusion pump is provided. The power source includes a primary battery, a rechargeable battery, a recharging circuit for recharging the rechargeable battery, a power source selector module for selecting one of the primary battery or the rechargeable battery, and one or more voltage converters.

In yet another embodiment, a method of detecting a critical primary battery condition in an infusion pump is provided. The method includes providing a rechargeable battery, providing a primary battery, wherein the infusion pump is initially powered via the primary battery, detecting when the primary battery reaches a critical battery condition, upon the primary battery reaching the critical battery condition, powering the infusion pump via the rechargeable battery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIG. 1, a portable pump apparatus for use in an ambulatory injection system, such as an insulin injection system, is shown. The apparatus includes a housing10, which is designed to fit conveniently in the pocket of a user or to be attached to a belt clip. A cassette14, such as a disposable or reusable syringe, is selectively received within the housing10. The syringe14holds a supply of a medicament, such as insulin, for injection into a diabetic person, or other user in need of the medicament. The syringe14includes a barrel16, which defines an internal chamber18for holding the medicament, a dispensing outlet20connected with one end of the barrel16, and an opening22at an opposite end of the barrel16. A plunger or piston24is received within the barrel16via the opening22for reciprocal motion within the barrel16for ejecting the medicament from the barrel. The piston24includes a head portion or cap26, which seals the opening22, and a longitudinally extending cylindrical or frustoconical portion28, extending from the head portion, which defines an internal piston chamber30with an open end32furthest from the barrel16.

Mounted within the housing10, are a motor34and a drive system36for incrementally advancing the piston24to eject aliquots of the medicament according to a preprogrammed injection schedule. The motor34is under the control of a microprocessor-controller38, which is preferably housed within the housing10. Power for the motor and other operative components of the pump system is supplied by a battery40, or other source of power. The motor34is preferably a stepper motor, which rotates in finite, small increments or steps. The drive system36includes a drive shaft42, which is coupled to the motor so that it rotates a small portion of a revolution with each step of the motor. For example, the motor34may advance twenty steps to turn the drive shaft42one complete revolution. As shown inFIG. 1, the drive shaft42is aligned generally concentrically with the longitudinal axis x of the syringe barrel16and piston24and rotates generally about this axis.

An encoder50is attached to an armature of the motor34to detect when the steps (i.e., rotations) are occurring. For example, a two-phase encoder alternatively registers a “zero” or a “one” output with each successive step of the encoder. The microprocessor-controller38is equipped with processing software or hardware to detect the change in output of the encoder and thereby determine whether the motor34is advancing as instructed.

FIG. 2shows a top view of an insulin pump that incorporates the present invention. Housing10can be comprised of plastic or any other type of shatter-resistant material. Housing10may also be waterproof. Screen46allows the user to view such indicators such as the current basal rate, the amount and time of the previous bolus, the insulin volume and the current date and time settings. The up and down buttons64may be used in order illuminate the pump's screen46. This allows for easy viewing of the pump's menus and messages. Infusion set66connects to the syringe cap at an approximate 90 degree angle to protect the luer-lock connector and to protect the user against inadvertent injury.

FIG. 3is an electrical schematic illustrating the power source of the present invention. A primary power source50, such as a CR2 battery, supplies power to the infusion pump10. The primary battery powers a +5V boost converter52. The output of the boost converter52is regulated to +5 volts and supplies power to both a Li-Ion charge controller54and a DC-DC converter58, such as a +3.3 DC-DC buck-boost converter.

The Li-Ion charge controller54controls the charging of a rechargeable battery56. The rechargeable battery56could be, for example, a Lithium Ion (Li-Ion) rechargeable battery. The rechargeable battery56supplies power to the buck-boost converter58through one or more diodes64. This occurs at times when the CR2 battery50reaches a critical voltage level, is removed or is exhausted. A critical battery level can be any predefined voltage level. Rechargeable battery56may also supply backup power to a clock62, such as SH3000 Real Time Clock (RTC). A voltage monitor60turns off the buck-boost converter58in order to save the final energy remaining in the rechargeable battery56for use by the RTC62.

Charge controller54can also provide multiple switching to more than one input source of power for charging the Li-Ion rechargeable battery56. More specifically, such external charging power sources68,70can employ connection to external power conversion components that include, for example, photo-electric generation cells, photo-voltaics, fuel cells, peltier thermo-electric converters and the like. As such, external environmentally available energy sources can be used to maintain trickle charge to the Li-Ion battery56and maintain it's longevity of charge for greater periods of time. This functionality obviates the need for manual attendance to periodic replacement of the disposable batteries to maintain rechargeable Li-Ion battery charge above the minimum charge level (i.e., 0.8V) below which can lead to permanent battery curve degradation. Such functionality allows the user of the insulin infusion pump to subject the unit to extended periods of storage so long as the storage conditions provide the necessary environmental energy input (i.e. light, heat, etc.).

It should be noted that the schematic illustration ofFIG. 3is an exemplary embodiment of the power supply of the present invention. Variations of the schematic ofFIG. 3are within the scope of the invention. The system described herein provides a rechargeable battery56that serves as a backup energy source to primary battery50. Because of the rapid voltage decrease in modern disposable batteries, electrical medical devices such as infusion pumps cannot adequately warn the user of a low or critical battery level in enough time to allow the user to take corrective action, i.e., replace the primary battery. The use of a second, rechargeable battery56will allow the infusion pump to continue normal operation and enable the initiation of an alarm indicating when a low or critical battery level has been reached, thus giving the user enough time to take corrective action without the danger of the infusion pump completely shutting down.