US20080125700A1 - Methods and apparatuses for detecting medical device acceleration, temperature, and humidity conditions - Google Patents

Abstract

An ambulatory medical device for detecting acceleration, temperature, and/or humidity conditions in or around the medical device is provided. The medical device includes one or more acceleration, thermal, and/or humidity sensors which detect acceleration, temperature, and/or humidity conditions in or around the medical device. In response to detected conditions, the medical device may, among other things, alter the operation of the device, provide an alarm or warning to the user, or transmit data about the detected conditions to another device.

Description

FIELD OF THE INVENTION
• This invention relates generally to improvements in ambulatory medical devices, such as drug delivery systems or patient monitoring systems, and more specifically, to improved methods and apparatuses for detecting acceleration, temperature and humidity conditions in or around these ambulatory medical devices.
BACKGROUND OF THE INVENTION
• Ambulatory medical devices, such as drug delivery systems and patient monitoring systems, are used in the therapy of various diseases or medical disorders, such as diabetes mellitus, pulmonary hypertension, thalassemia, and chronic pain. Many such devices are adapted to be carried by the user, for example, by means of a belt clip or harness, in the user's clothing pocket, or attached to the user's body or clothing.
• A common drug delivery system includes a tubing arrangement to deliver medication to a user cutaneously or subcutaneously. For example, ambulatory infusion pumps are used in delivering a prescribed medication, such as insulin, to a user. In one form, these devices comprise a relatively compact pump housing adapted to receive a syringe or reservoir carrying a prescribed medication for administration to the user through infusion tubing and an associated catheter or infusion set.
• The external infusion pump may include a small drive motor connected via a suitable transmission assembly for motor-driven advancement of a reservoir piston to administer the medication to the user. Programmable controls can operate the drive motor continuously or at periodic intervals to obtain a closely controlled and accurate delivery of the medication over an extended period of time. Such infusion pumps are used to administer insulin and other medications, with exemplary pump constructions and systems being shown and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653; 5,097,122; 6,248,093; 6,362,591; 6,554,798; and 6,555,986, which are incorporated by reference herein.
• External infusion pumps of the general type described above have provided significant advantages and benefits with respect to accurate delivery of medication or other fluids over an extended period of time. The infusion pump can be designed to be extremely compact as well as water resistant, and may be carried by the user, for example, by means of a belt clip or harness, in the user's clothing pocket, or attached to the user's body or clothing. As a result, important medication can be delivered to the user with precision and in an automated manner, without significant restriction on the user's mobility or lifestyle, including in some cases the ability to participate in water sports.
• Due to their small size and portability, ambulatory medical devices can be subjected to a number of external conditions that may adversely affect their performance. For example, external infusion pumps can sustain an occlusion in the delivery tubing. Some pumps have alarm systems designed to detect and indicate pump malfunction or nondelivery of the medication as a result of occlusions. There exists, nevertheless, a need for further improvements in these ambulatory medical devices, particularly with respect to providing warnings or system operational changes in response to external conditions that may affect medical device performance.
BRIEF SUMMARY OF THE INVENTION
• Disclosed are ambulatory medical devices that are adapted for carrying by a person on an exterior of the person's body, and include acceleration, thermal, and/or humidity sensors for detecting conditions in or around the devices. In response to the detected conditions, the medical devices may, among other things, alter the operation of the devices, provide alarms or warnings to the user, or transmit data to another device.
• In one embodiment of the present invention, an ambulatory medical device such as an external infusion device for infusing fluid into a person from a reservoir comprises a housing adapted to be carried on an exterior of the person's body. The infusion device also includes a drive mechanism contained in the housing and operatively coupled to the reservoir to deliver the fluid from the reservoir into the person's body. The infusion device further includes a processor contained in the housing, and an indicator operatively coupled to the processor and adapted to indicate information about the infusion device to the person. An acceleration sensor also is coupled to the processor and is adapted to provide an acceleration output signal as a function of acceleration forces acting on the housing. The processor is adapted to control the infusion device in accordance with the acceleration output signal.
• In particular embodiments, the infusion device further includes a memory contained in the housing and coupled to the processor. The memory is adapted to store a predetermined acceleration threshold corresponding to an impact on the housing. If the acceleration output signal exceeds the predetermined acceleration threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the impact. Alternatively, the processor is adapted to control the infusion device by causing the drive mechanism to alter delivery of the fluid into the person's body. In further alternative embodiments, the infusion device also includes a transmitter/receiver coupled to the processor and adapted to communicate with a remote device, and the processor is adapted to control the infusion device by causing the transmitter/receiver to send information about the impact to the remote device.
• In some embodiments, the acceleration sensor is an accelerometer. In other embodiments, the acceleration sensor is an impact switch disposed within the housing.
• In additional embodiments, the infusion device also includes a memory contained in the housing and coupled to the processor. The memory is adapted to store a predetermined acceleration force corresponding to a physical activity of the person. If the acceleration output signal exceeds the predetermined acceleration force, the processor is adapted to control the infusion device by causing the indicator to notify the person about the physical activity. Alternatively, the processor is adapted to control the infusion device by causing the drive mechanism to alter delivery of the fluid into the person's body from a current delivery rate to a modified delivery rate. In further alternative embodiments, the infusion device also includes a transmitter/receiver coupled to the processor and adapted to communicate with a remote device, and the processor is adapted to control the infusion device by causing the transmitter/receiver to send information about the physical activity to the remote device. In other embodiments, the memory is further adapted to store data about at least one of frequency, duration, and intensity of the physical activity of the person.
• In another embodiment of the present invention, an ambulatory medical device such as an external infusion device for infusing fluid into a person from a reservoir comprises a housing adapted to be carried on an exterior of the person's body. The infusion device also includes a drive mechanism contained in the housing and operatively coupled to the reservoir to deliver the fluid from the reservoir into the person's body. The infusion device further includes a processor contained in the housing, and a memory coupled to the processor and adapted to store a predetermined temperature threshold. A thermal sensor is also coupled to the processor and adapted to provide a temperature output signal as a function of temperature in the housing. The processor is adapted to compare the temperature output signal with the predetermined temperature threshold, and to control the infusion device based on the temperature comparison.
• In particular embodiments, the infusion device further includes an indicator operatively coupled to the processor and adapted to indicate information to the person about the temperature output signal. In some embodiments, if the temperature output signal exceeds the predetermined temperature threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the temperature output signal. For example, the fluid infused into the person's body may be medication, and the predetermined temperature threshold may correspond to a temperature that causes the medication to degrade, so that the alarm or warning may indicate degradation of the medication to the person. In other embodiments, if the temperature output signal is less than the predetermined temperature threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the temperature output signal. For example, the infusion device may further include a battery that is adapted to provide power for the infusion device and has a discharge resistance that varies with temperature. The predetermined temperature threshold may correspond to a temperature that causes the discharge resistance of the battery to increase by at least 10 percent, so that the alarm or warning may indicate reduced life of the battery to the person.
• In additional embodiments, the infusion device includes a battery adapted to provide power for the infusion device. The processor is adapted to sample the battery at a first sampling frequency to determine remaining power of the battery. If the temperature output signal is less than the predetermined temperature threshold, the processor is further adapted to control the infusion device by altering sampling of the battery from the first sampling frequency to a second sampling frequency.
• In further embodiments, the memory is also adapted to store a predetermined force threshold corresponding to a fluid occlusion in the infusion device. If the temperature output signal is less than the predetermined temperature threshold, the processor is adapted to control the infusion device by modifying the predetermined force threshold to provide a modified force threshold.
• In yet another embodiment of the present invention, an ambulatory medical device such as an external infusion device comprises a housing adapted to be carried by a person and a processor contained in the housing. The infusion device also includes an indicator operatively coupled to the processor and adapted to indicate information about the infusion device to the person. A memory is coupled to the processor and adapted to store a predetermined humidity threshold. The infusion device further includes a humidity sensor coupled to the processor and adapted to provide a humidity output signal as a function of humidity in or around the housing. The processor is adapted to compare the humidity output signal with the predetermined humidity threshold, and to control the infusion device based on the humidity comparison.
• In particular embodiments, if the humidity output signal exceeds the predetermined humidity threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the humidity output signal. For example, the predetermined humidity threshold may correspond to entry of water into the housing, and the indicator is adapted to provide the alarm or warning to the person about the entry of water into the housing. In other embodiments, if the humidity output signal is less than the predetermined humidity threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the humidity output signal. For example, the predetermined humidity threshold may correspond to a humidity level that causes the infusion device to be susceptible to damage due to static electricity, and the indicator is adapted to provide the alarm or warning to the person about the static electricity.
• There are additional aspects to the present invention. It should therefore be understood that the preceding is merely a brief summary of some embodiments and aspects of the present inventions. Additional embodiments and aspects of the present inventions are referenced below. It should further be understood that numerous changes to the disclosed embodiments can be made without departing from the spirit or scope of the invention. The preceding summary therefore is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by appended claims and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is aperspective view of an infusion pump according to an embodiment of the present invention.
• FIG. 2 is a side plan, cut-away view of an infusion pump drive system in accordance with an embodiment of the present invention.
• FIG. 3 is a simplified block diagram of an infusion pump and system in accordance with an embodiment of the present invention.
• FIG. 4 is a simplified schematic diagram of an impact switch in accordance with one embodiment of the invention.
• FIG. 5 is a simplified schematic diagram of an impact switch in accordance with an alternative embodiment of the invention.
• FIG. 6 is a simplified schematic diagram of an impact switch in accordance with an alternative embodiment of the invention.
• FIG. 7 is a simplified schematic diagram of an impact switch in accordance with an alternative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
• In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several embodiments of the present invention. It is understood that other embodiments may be used, and structural and operational changes may be made without departing from the scope of the present invention.
• As shown in the drawings for purposes of illustration, the invention is embodied in an ambulatory medical device that includes acceleration, thermal, and/or humidity sensors for detecting acceleration, temperature, and/or humidity conditions in or around the medical device. In response to detected conditions, the medical device may alter operation of the medical device, provide alarm or text messages to the user, and/or transmit data about the detected conditions to another device or system. In one embodiment, the medical device is a drug delivery system, such as an external infusion pump for delivering insulin into the body of a user. However, in alternative embodiments, the medical device may be other drug delivery systems for delivering other fluids into the body of the user, such as medication other than insulin (e.g., HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, and anti-cancer treatments), chemicals, enzymes, antigens, hormones, vitamins, or the like. In other alternative embodiments, the medical device may be a patient monitoring system, such as a continuous glucose monitoring system for determining glucose levels in the blood or other bodily fluids of the user. In further alternative embodiments, the medical device may be other patient monitoring systems (e.g., pulse rate monitors, electrocardiogram monitors, and the like, such as the Holter monitor) for determining the concentrations, levels, or quantities of other characteristics, analytes, or agents in the user, such as hormones, cholesterol, oxygen, pH, lactate, heart rate, respiratory rate, medication concentrations, viral loads (e.g., HIV), or the like.
• One example of an ambulatory medical device is theexternal infusion pump100 shown inFIG. 1. Thepump100 includes ahousing101 that contains an electronics compartment (not shown), including a processor (not shown) for running programs and controlling thepump100. Thepump100 may be programmed by a care provider, such as a physician or trained medical personnel, or by the user. To program thepump100, an individual utilizes adisplay102 and a keypad ofbuttons104,106,108,110, and112 located on thehousing101 to access and/or modify control parameters and data for thepump100. Thedisplay102 provides information regarding program parameters, delivery profiles, pump operation, alarms, warnings, statuses, or the like. In the embodiment shown inFIG. 1, thepump100 has five buttons or keys including an Up-Arrow key104, an ACT (activate)key106, a Down-Arrow key108, an ESC (escape)Key110, and anExpress Bolus key112. In alternative embodiments, thepump100 may utilize more or less keys or have different key arrangements than those illustrated in the figure. Thepump100 uses the control parameters to calculate and issue commands that affect the rate and/or frequency that thepump100 delivers fluid, preferably medication such as insulin, through a fitting202 andflexible tubing204, and into an infusion set206 that is adhered to the body of the user.
• FIG. 2 illustrates a drive system for aninfusion pump301 according to an embodiment of the present invention. Thepump301 includes ahousing318 that contains anelectronics compartment310. Theelectronics compartment310 houses a power supply (not shown) for providing power to operate thepump301, and system electronics for thepump301, including a processor (not shown) for running programs and controlling thepump301. Thehousing318 of thepump301 also contains a drive mechanism including amotor302,gear box306,drive screw303,slide304,stopper307, andreservoir305, which are generally concentrically aligned. Themotor302 rotates thedrive screw303 via thegear box306. Thedrive screw303 has external threads, which engageinternal threads322 on acylindrical bore320 running most of the length of theslide304. Thus, the rotational torque of thedrive screw303 is translated into axial force on theslide304. Theslide304 further includes one ormore tabs314 that fit within one ormore slots316 in thehousing318 to prevent theslide304 from rotating with respect to thehousing318. As thedrive screw303 rotates, theslide304 is forced to travel along its axis. Theslide304 is in removable contact with thestopper307 within thereservoir305. As theslide304 advances into thereservoir305, thestopper307 is displaced forcing fluid out of thereservoir305, through a fitting308 andtubing309, and into an infusion set (not shown) attached to the body of the user.
• Asensor311 is positioned between themotor302 and thehousing318 to detect forces translated from fluid pressure within thereservoir305 through thestopper307,slide304,drive screw303, and thegear box306 to themotor302. Thesensor311 provides a range of measurements based on the detected forces. However, because theinfusion pump301 can be carried by users who engage in a variety of physical activities and travel, thepump301 can be subjected to various environmental changes that do not always result in occlusions, but nevertheless can either adversely affect performance of thepump301 or indicate a need to vary operation of thepump301 due to changing medication needs of the user. Therefore, thepump301 also includes acceleration, thermal, and/or humidity sensors (not shown) which, as explained in greater detail below, can detect acceleration, temperature, and/or humidity conditions in or around thepump301, and in response to the detected conditions, thepump301 may alter its operation, provide an alarm or text message to the user, or transmit data to another device.
• FIG. 3 illustrates one hardware and software environment in which certain embodiments of the present invention may be implemented. In one embodiment, an ambulatory medical device is a drug delivery system, such as an external infusion pump, for regulating the delivery of medication such as insulin into the body of a user. Examples of the infusion pump may be of the type shown and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653; 5,097,122; 5,505,709; 6,248,093; 6,362,591; 6,554,798; 6,555,986; and 6,752,787, which are herein incorporated by reference.
• As shown inFIG. 3, theinfusion pump410 includes ahousing420 that contains aprocessor418 adapted to control thepump410. Theprocessor418 is coupled to adrive mechanism432, which is connected to areservoir434 containing fluid. Thedrive mechanism432 causes the fluid to be delivered from thereservoir434, and then into a body of a user through tubing and aninfusion set438. Theprocessor418 is also coupled to aninternal memory device422 that stores programs, historical data, user-defined information, and parameters. In one embodiment, thememory422 is a flash memory and SRAM; however, in alternative embodiments, thememory422 may comprise other devices, such as ROM, DRAM, RAM, EPROM, dynamic storage such as other flash memory, or an energy efficient hard-drive.
• Theinfusion pump410 is programmed by a user input device, such as akeypad424 mounted on the exterior of thehousing420 and coupled to theprocessor418. An individual, such as a care provider or a user, presses keys on thekeypad424 to display and scroll through information, call up menus, select menu items, select control parameters, change control parameters (change values or settings), enter information, turn on a backlight, and the like. Feedback from theinfusion pump410 on status or programming changes is provided to the individual on an indication device, such as visually on adisplay428, audibly through an audible alarm430 (e.g., piezo buzzer, annuciator, speaker, or the like), and/or tactilely through avibration alarm416. The individual may activate or deactivate theaudible alarm430 and/or thevibration alarm416 by accessing control parameters on thepump410. Feedback from theinfusion pump410 may include signals that notify the individual of modifications to the control parameters, announce that theinfusion pump410 is about to initiate a particular operation, indicate a mode of operation, provide a warning (for instance to indicate a low fluid level in the reservoir or low battery power), present an alarm (such as from a timer or a clock), present an error message to indicate a malfunction of the system (such as an occlusion that restricts the delivery of the fluid, a software error, or the like), request input, confirm that communication has been established, and the like. Alarms and warnings may start out at a low level and escalate until acknowledged by the user. In particular embodiments, the alarm intensity changes over time. If the individual does not respond to the alarm, the alarm may change tone, change volume, increase the vibration amplitude or frequency, project a brighter light or a different color light, flash, flash at a different frequency, and the like. In alternative embodiments, the intensity may vary up or down, or alternatively, the intensity may be constant. In other alternative embodiments, the intensity may change by activating different alarm types over time.
• In further alternative embodiments, thekeypad424 may be omitted, and thedisplay428 may be used as a touch screen input device. In yet other alternative embodiments, theinfusion pump410 may be programmed by commands received from a remote programmer415 (e.g., PDA, programmer dedicated to communication with theinfusion pump410, or the like) through a transmitter/receiver417 that is coupled to theprocessor418. Theremote programmer415 may be used to program theinfusion pump410 in addition to thekeypad424,display428,audible alarm430, and/orvibration alarm416. Alternatively, thekeypad424,display428,audible alarm430, and/orvibration alarm416 may be omitted, and all programming may be handled by theremote programmer415. In other alternative embodiments, theinfusion pump410 may be programmed through an interface, such as a cable or communication station, using a computer or the like.
• In the illustrated embodiment, apower supply440, such as a battery, provides the power to operate theinfusion pump410. In particular embodiments, the power supply is one or more replaceable AAA batteries. Energy storage devices such as capacitors, backup batteries, or the like provide temporary power to maintain the memory during power supply replacement. In alternative embodiments, the power supply is one or more button batteries, zinc air batteries, alkaline batteries, lithium batteries, lithium silver oxide batteries, AA batteries, or the like. In still further alternative embodiments, the power supply is rechargeable.
• Theinfusion pump410 may also allow the user to transfer or download information (e.g., infusion pump history data, sensor data, data from other medical devices, updates to programs, or the like) between thememory422 of theinfusion pump410 and an external device, such as theremote programmer415, a computer, another medical device (e.g., blood glucose meter, glucose monitor), or the like. For example, information may be transferred to and/or from theinfusion pump410 through an interface, such as a cable or communication station, to a computer, or alternatively, over the Internet to a remote server, for storage. Alternatively, information may be transferred to and/or from the transmitter/receiver417 of theinfusion pump410 via a wireless or wired connection to a transmitter/receiver in an external device, such as an external communication link, computer, theremote programmer415, or the like. The transmitter/receiver417 of theinfusion pump410 may communicate with external devices using radio frequencies; however, alternative embodiments may use optical, infrared (IR), ultrasonic frequencies, magnetic effects, electrical cables, or the like.
• In other alternative embodiments, the infusion pump may include separate durable and disposable housing portions that selectively engage and disengage from each other. The durable housing portion may include the electronics (e.g., processor, memory, and the like) and drive mechanism, and the disposable housing portion may include the reservoir and/or other components that may be disposed of after a prescribed period. Such an infusion pump may be of the type shown and described in U.S. Provisional Application Ser. No. 60/678,290 filed May 6, 2005 and entitled “Infusion Device and Method with Disposable Portion,” U.S. application Ser. No. 11/211,095 filed Aug. 23, 2005 and entitled “Infusion Device and Method with Disposable Portion,” and U.S. application Ser. No. 11/210,467 filed Aug. 23, 2005 and entitled “Infusion Device and Method with Drive Device in Infusion Device and Method with Drive Device in Separable Durable Housing,” all of which are herein incorporated by reference. Such an infusion pump may also be of the type shown and described in U.S. Provisional Application Ser. No. 60/839,821 filed Aug. 23, 2006 and entitled “Systems and Methods Allowing for Reservoir Filling and Infusion Medium Delivery,” U.S. Provisional Application Ser. No. 60/839,822 filed Aug. 23, 2006 and entitled “Infusion Medium Delivery Device and Method with Drive Device for Driving Plunger in Reservoir,” U.S. Provisional Application Ser. No. 60/839,832 filed Aug. 23, 2006 and entitled “Infusion Medium Delivery Device and Method with Compressible or Curved Reservoir or Conduit,” U.S. Provisional Application Ser. No. 60/839,840 filed Aug. 23, 2006 and entitled “Infusion Medium Delivery System, Device and Method with Needle Inserter and Needle Inserter Device and Method,” and U.S. Provisional Application Ser. No. 60/839,741 filed Aug. 23, 2006 and entitled “Infusion Pumps and Methods and Delivery Devices and Methods with Same,” all of which are herein incorporated by reference.
• As previously discussed, ambulatory medical devices, including drug delivery systems such as an external infusion pump, may encounter various environmental changes that could adversely affect performance. For example, a pump can be damaged if dropped or bumped onto a hard object or surface such as a floor, doorway, counter or desk. If the pump is dropped or bumped with sufficient force, it may become damaged to an extent that it cannot adequately perform its intended functions. The tubing, infusion set, or reservoir may become damaged such that medication leaks out and is not delivered to the user. Also, the pump housing may become cracked, or the electronics or power supply or drive mechanism contained within the pump may become damaged by the impact. If the pump lacks the ability to detect and alarm for this condition, the user may not receive the expected medication and may experience adverse effects such as hyperglycemia. Additionally, if the pump becomes damaged due to an impact, it would be useful to indicate this condition to the user, such as by an alarm (display, audio or vibratory), thus notifying him or her of the need to check the pump for damage. Furthermore, if the pump is dropped or bumped with sufficient force along the axis of the reservoir, unintended medication delivery may occur. The user may unexpectedly receive medication, and as a result, experience hypoglycemia. It would be useful to notify the user of the impact so that the user could take preventative measures to avoid hypoglycemia.
• Ambulatory medical devices may also come into contact with external fluids such as water or cleaning agents. For example, some external infusion pumps are labeled for use in water. If the pump housing becomes cracked due to an impact, fluid may be able to enter the pump, and as a result, the pump may no longer function properly. Again, it would be useful to notify the user of this potential condition, thus permitting a self-check of the pump or notification of the manufacturer or a repair facility for assistance.
• Therefore, theinfusion pump410 further includes anacceleration sensor414, athermal sensor426, and ahumidity sensor412. The acceleration, thermal, andhumidity sensors414,426, and412 are coupled to and communicate with theprocessor418. For example, based on data from the acceleration, thermal, and/orhumidity sensors414,426, and412, theprocessor418 may: (1) cause thedrive mechanism432 to alter the fluid delivery rate, (2) activate thedisplay428,audible alarm430, and/orvibration alarm416 to provide alarms or warnings to the user, and/or (3) utilize the transmitter/receiver417 to send data to another device, such as theremote programmer415 or other remote devices or systems via remote data communication network(s). Examples of communication between the pump410 (or other medical device) and a remote device or system via a remote data communication network may be of the type shown and described in U.S. application Ser. No. 11/414,160 filed Apr. 28, 2006 and entitled “Remote Monitoring for Networked Fluid Infusion Systems,” which is herein incorporated by reference. For example, thepump410 may transmit information (e.g., warnings, alarms, notifications) based on data from the acceleration, thermal, and/orhumidity sensors414,426, and412 to a remote device carried by the user's caregiver or physician via a computer network, pager network, cellular telecommunication network, satellite communication network, or the like. Additionally, thememory422 is adapted to store values associated with the outputs of theacceleration sensor414, thethermal sensor426, and thehumidity sensor412, as well as values associated with predetermined acceleration forces, temperatures, and humidity levels.
• In alternative embodiments of the present invention, the ambulatory medical device may be other drug delivery systems for delivering other fluids into the body of the user, such as medication other than insulin (e.g., HIV drugs, drugs to treat pulmonary hypertension, iron chelation drugs, pain medications, and anti-cancer treatments), chemicals, enzymes, antigens, hormones, vitamins, or the like. In other alternative embodiments, the medical device may be a patient monitoring system, such as a continuous glucose monitoring system, for obtaining an indication of glucose levels in the blood or other fluids in the body of a user. Examples of the continuous glucose monitoring system may be of the type shown and described in U.S. Pat. Nos. 6,248,067; 6,418,332; 6,424,847; 6,809,653; and 6,895,263, which are herein incorporated by reference. In further alternative embodiments, the medical device may be other patient monitoring systems (e.g., pulse rate monitors, electrocardiogram monitors, and the like, such as the Holter monitor) for determining the concentrations, levels, or quantities of other characteristics, analytes, or agents in the user, such as hormones, cholesterol, oxygen, pH, lactate, heart rate, respiratory rate, medication concentrations, viral loads (e.g., HIV), or the like. Such medical devices may include acceleration, thermal, and/or humidity sensors similar to thesensors414,426, and412.
• In particular embodiments, anacceleration sensor414 is included within an ambulatory medical device such as theinfusion pump410 and is used as an indicator of potential damage to thepump410 due to an impact. In one embodiment, theacceleration sensor414 is an accelerometer which provides a signal that is proportional to the acceleration (or deceleration) forces (i.e., the rate of change of velocity with respect to time) to which thepump410 is subjected. Theprocessor418 within thepump410 monitors the signal from the accelerometer for a value larger than a predetermined or programmed threshold stored inmemory422, and if the accelerometer signal reaches that threshold, theprocessor418 causes an alarm or warning to be provided to the user visually on thedisplay428, audibly by theaudible alarm430, and/or tactilely with thevibration alarm416. The acceleration threshold may be determined by testing or other methods to be the acceleration which may potentially cause damage to any part of thepump410.
• Accelerometers typically have one or more axes of sensitivity. In the simplest form, the accelerometer can have a single axis of sensitivity. Therefore, the signal generated from the accelerometer will be the vector sum of accelerations along that axis. This property can be beneficial since the accelerometer can be mounted such that its axis of sensitivity is aligned with the direction of most concern within the ambulatory medical device.
• If there is concern for damage to the medical device along multiple directions (axes), then multiple, single-axis accelerometers can be used. Alternatively, a single acceleration sensor may have multiple axes of sensitivity and detect acceleration in a plurality of directions. One example of such an acceleration sensor is described in U.S. Pat. No. 5,833,713. Again, this sensor can be mounted in the medical device in an orientation that monitors acceleration signals in the desired directions.
• If there is concern for damage to the medical device due to impact in any direction, then a 3-axis accelerometer can be used, such as one manufactured by Entran Devices, Inc., Fairfield, N.J. A 3-axis orthogonal accelerometer can be mounted as a discrete component within the medical device, such as within the housing, attached to a mechanical component, or directly on a printed circuit board. For example, such an accelerometer could be mounted within thehousing420 of thepump410, attached to a component of thedrive mechanism432, or directly on the circuit board that includes theprocessor418 or other electronic components.
• Furthermore, if it is desirable to have different levels of sensitivity along multiple axes, then an accelerometer with discrete axes of sensitivity can be mounted along each of those axes (i.e. orthogonal or not orthogonal) and monitored and processed independently. For example, theacceleration sensor414 within thepump410 can be an orthogonal 3-axis accelerometer and monitor the signals from each axis independently. If, in this example, it is desired to have different levels of sensitivity along the axis of thereservoir434, the axis perpendicular to thedisplay428, and the corresponding orthogonal axis, then the accelerometer can be mounted so that each of the three orthogonal sensor axes is aligned with one of those directions. Thus, each of these axes can be monitored independently and produce acceleration signals corresponding to impacts in those directions.
• Varying acceleration threshold levels can be programmed into thepump410 for each of these axes or combination of axes to produce the appropriate alarm or warning messages. For example, a light impact generating a relatively low acceleration level can result in a warning to the user to look for potential damage to his/herpump410, whereas a hard impact generating a relatively high acceleration level can result in an alarm and instructions for the user to call the manufacturer and return thepump410 for analysis. Theprocessor418 may activate thedisplay428,audible alarm430, and/orvibration alarm416 to provide alarms or warnings to the user. For example, thepump410 can alarm and instruct the user to investigate damage, such as a leaking infusion set438 orbroken reservoir434, a crackedpump housing420 or damage to thepower supply440 or other electronic components. Thepump410 can also instruct the user to perform a self-check, or it can automatically run a self-check to identify damage that may not be visible to the user. Further, theprocessor418 may cause thedrive mechanism432 to alter the delivery of fluid to the user or activate the transmitter/receiver417 to cause data, such as alarms, to be sent to another device, such as theremote programmer415.
• Accelerometers are based on several different technologies, such as piezoelectric, thermal, servo, strain gauge, capacitance, micro-electro-mechanical systems (“MEMS”), and resonance shift. Each of these technologies has different advantages. Piezoelectric (“PE”) sensors generate a charge when strained. Since PE sensors generate their own signal, they are referred to as active sensors. However, PE sensors provide only an AC response, and thus, can only detect impacts or shock to the medical device. Such PE sensors are available from several companies including Measurement Specialties, Inc., Fairfield, N.J.
• Another class of sensors is referred to as passive sensors, which change some measurable property when strained. For example, a piezoresistive sensor changes its resistance when strained. Piezoresistive sensors provide both an AC and DC response, and thus, can detect both impacts or shock to, as well as slight tilt or movement of, the medical device. However, in order to measure the change in resistance, piezoresistive sensors require a constant power supply. Other examples of passive sensors include capacitive based sensors which measure a change in capacitance when strained, and resonance shift sensors which measure a shift in frequency when loaded or strained.
• The choice of sensor technology depends on the available power supply, the need to measure a steady-state (DC) input, and the desired frequency of measurement. In the case of many ambulatory medical devices such as external infusion pumps, the power supply is limited to a battery. In one embodiment of such a medical device, continuous non-DC measurement may be desired. Therefore, a sensor technology that requires very low power to operate is often desirable for such medical devices. Since piezoresistive sensors require a constant power supply to operate, this sensor technology may not be appropriate. However, since piezoelectric sensors are active devices that can generate a signal, less power may be required to operate them, and thus, they may be a more desirable sensor technology for battery-powered, ambulatory medical devices such as external infusion pumps.
• In alternative embodiments, theacceleration sensor414 incorporated into an ambulatory medical device such as theinfusion pump410 may be an impact or acceleration switch, which provides an “on” or “off” output signal when its seismic mass is subjected to a predetermined level of acceleration.FIG. 4 shows a simplistic representation of animpact switch601 with an “on” or “off” state. Theswitch601 includes aseismic mass618 comprised of an electricallyconductive arm602 and an electricallyconductive plug606. Thearm602 is pivotably coupled to ahousing604 of the medical device, and theplug606 is mounted on the free end of thearm602. Theplug606 is electrically coupled to thearm602, and thearm602 is electrically coupled to anelectrical output614. In yet another embodiment, theplug606 may be omitted, and theseismic mass618 may simply include thearm602 having a free end and adapted to be held by a latch mechanism.
• Theswitch601 also includes a first electricallyconductive latch608 and a second electricallyconductive latch616, which are adapted to releasably secure theplug606 and are electrically coupled to anelectrical input612. In the illustrated embodiment, the first andsecond latches608 and616 are latch springs having a concave-shaped cross section. Theplug606 has a complementary concave-shaped cross-section that allows theplug606 to mate with either of the latch springs608 or616. However, in other embodiments, thelatches608 and616 and theplug606 may have alternative geometries or latching mechanisms.
• In the illustrated embodiment, theswitch601 further includes twoopposed springs610 that bias thearm602 such that theplug606 is in a spaced-apart relationship between thefirst latch608 and thesecond latch616. In one embodiment, thesprings610 may be coil springs; however, in alternative embodiments, thesprings610 may be other biasing elements, such as leaf springs or the like.
• Referring back toFIG. 4, when the medical device is subjected to an acceleration force of a predetermined magnitude and direction along an axis of sensitivity of theswitch601, thearm602 will pivot toward one of thelatches608 or616, and theplug606 will be releasably secured by thatlatch608 or616. As a result, a circuit between theelectrical input612 and theelectrical output614 will be closed, thereby providing an output signal that indicates the medical device has been subjected to an acceleration force of the predetermined magnitude and direction along the axis of sensitivity of the medical device.
• One advantage of an impact switch that can maintain its “on/off” state relates to the operation of the electronics within a battery-operated, ambulatory medical device such as an external infusion pump. It is common for certain sub-systems requiring higher power (e.g., microprocessor, power supply, motor, or measurement system) to shut down when not in use, and then “wake-up” only during scheduled times to perform their operation or function, in order to extend battery life. Because the switch can maintain its change of state (i.e., the electrical connection between the electrical input and electrical output) due to an impact, the medical device does not have to continuously monitor for a signal from the impact switch. Thus, the medical device can shut down certain system electronics when not in use, and wait until the next time the system electronics “wake-up” to check for a signal from the switch. As described above, the appropriate alarms or warnings can be provided to the user upon detecting a signal from the impact switch. Alternatively, the switch can cause the drive system to be shut down so that the drive system cannot be inadvertently activated due to the impact.
• FIG. 5 shows an alternative embodiment of animpact switch701 that can maintain its “on/off” state. Theswitch701 includes aseismic mass718 comprised of an electricallyconductive arm702 and an electricallyconductive contact member706. Thearm702 is pivotably coupled to ahousing704 of the medical device, and thecontact member706 is mounted on the free end of thearm702. Thearm702 and thecontact member706 are electrically coupled to one another and to a switchelectrical output714. In another embodiment, thecontact member706 may be omitted, and theseismic mass718 may simply include thearm702 having a free end and adapted to abut and be held in position by an electromagnet.
• Theswitch701 also includes first andsecond electromagnets708 and720, which are adapted to generate magnetic fields that individually have sufficient strength to releasably hold thecontact member706, at least a portion of which is constructed of a ferromagnetic material. The first andsecond electromagnets708 and720 are also electrically coupled to a switchelectrical input712. Power to theelectromagnets708 and720 for generating the magnetic fields is provided via a magnetelectrical input722 and a magnetelectrical output724. Areset switch716 electrically connects the magnetelectrical input722 to the magnetelectrical output724 when theswitch716 is closed, thus shunting the electricity flow from theelectromagnets708 and720 and causing the magnetic field to collapse.
• In the illustrated embodiment, theswitch701 further includes twoopposed springs710 that bias thearm702 such that thecontact member706 is in a spaced-apart relationship between the first andsecond electromagnets708,720. In one embodiment, thesprings710 may be coil springs; however, in alternative embodiments, thesprings710 may be other biasing elements, such as leaf springs or the like.
• Referring back toFIG. 5, when theswitch701 is subjected to an acceleration force of a predetermined magnitude and direction along an axis of sensitivity of theswitch701, thearm702 will pivot toward one of theelectromagnets708 or720, and thecontact member706 will abut theelectromagnet708 or720 and be releasably held in position by its magnetic field. As a result, a circuit between the switchelectrical input712 and the switchelectrical output714 is closed, thereby providing an output signal that indicates the medical device has been subjected to an acceleration force of the predetermined magnitude and direction along the axis of sensitivity of the medical device. When it is desired to reset theimpact switch701, thereset switch716 is closed, thus collapsing the magnetic fields and releasing thecontact member706 to return to its initial position between theelectromagnets708 and720.
• As with theswitch601 ofFIG. 4, thisswitch701 ofFIG. 5 also will latch its condition upon experiencing a predetermined acceleration force. However, this type ofswitch701 may be better suited for reset following acknowledgement of an alarm sinceelectromagnets708 and720 are used to hold thecontact member706. The use of a switch, such as thereset switch716 ofFIG. 5, to reset theimpact switch701 after an alarm may be more convenient in some applications than the use of a mechanical release mechanism to release the latch plug606 from one of thelatches608 or616 in the embodiment ofFIG. 4.
• FIG. 7 illustrates another embodiment of animpact switch901 that can be incorporated as anacceleration sensor414 into an ambulatory medical device such as anexternal infusion pump410. Theimpact switch901 includes aseismic mass904 comprised of an electricallyconductive arm member902 and an electricallyconductive impact head906. Thearm902 has one end rigidly coupled to ahousing916 of the medical device. Alternatively, thearm902 may be coupled to electronics (not shown) contained within the housing of the medical device. In the illustrated embodiment, theimpact head906 is mounted on the free end of thearm902 and is electrically coupled to thearm902. Thearm902 is constructed of a material that permits resilient deflection and is electrically coupled to anelectrical output914. For example, thearm902 can be constructed of stainless steel or beryllium copper, or other materials having the desired resiliency and electrical conductivity.
• Theswitch901 also includes two electricallyconductive contacts908 and910, which are fixedly mounted adjacent to theimpact head906 and are electrically coupled to anelectrical input912. Thus, theimpact head906 is in a spaced-apart relationship between thecontacts908 and910 when no acceleration force acts on the medical device.
• When the medical device is subjected to an acceleration force of a predetermined magnitude and direction along an axis of sensitivity of theswitch901, thearm902 will deflect toward one of thecontacts908 or910, and thehead906 will briefly touch thatcontact908 or910 before returning to its equilibrium position. When this occurs, the electrical circuit between theelectrical input912 and theelectrical output914 is momentarily closed, thus producing a voltage spike or pulse at theelectrical output914. System electronics monitor theoutput914 for such a voltage pulse, and provide an appropriate alarm or other indication as described above when such a pulse is detected.
• FIG. 6 shows yet another embodiment of animpact switch801, which employs a principle similar to that of theswitch901 ofFIG. 7. However, theswitch801 ofFIG. 6 can provide an output signal as a function of predetermined acceleration forces along two, three or more axes of sensitivity of theswitch801. Additionally, theswitch801 can have the same or different levels of sensitivity (i.e., respond to different acceleration forces) along each axis of sensitivity of theswitch801. Theswitch801 includes a seismic mass comprised of a hook-shapedarm member804 rigidly coupled to ahousing802 of the medical device and an electricallyconductive impact head808 secured to the free end of thearm804. Thearm804 is electrically conductive and is electrically coupled to anelectrical output812.
• Thearm804 is constructed of a material that allows for resilient deflection, and due to its hook shape, is adapted for deflection along a plurality of imaginary lines of motion in three dimensions. For example, thearm804 can be constructed of stainless steel, beryllium copper, or other materials having the desired resiliency and electrical conductivity. Alternatively, the arm can be made of nonconductive material having the desired resiliency, such as plastic, and a flexible wire having the desired electrical conductivity can be integrated with the arm. Each of the imaginary lines of motion defines an imaginary plane. Thus, a plurality of imaginary planes are defined, some of which have a relationship other than being parallel to one another, including planes that are generally orthogonal to one another in three dimensions. In the illustrated embodiment, thearm804 has a hook or bend with a curvature of approximately 90 degrees. In other embodiments, the curvature may be less or more than 90 degrees, such as, for example, a curvature of between 45 degrees and 135 degrees.
• Five electricallyconductive contact surfaces806a-806eare fixedly mounted to form a conductive, generally box-shapedenclosure806 having an open end. Theenclosure806 generally surrounds both theimpact head808 as well as a portion of the free end of thearm804. All of thecontact surfaces806a-806eare electrically coupled to anelectrical input810. Theimpact head808 is in a spaced apart relationship with each of thesurfaces806a-806ewhen no acceleration force acts on the medical device.
• When an acceleration force of a predetermined magnitude and direction acts on the medical device, thearm804 deflects and theimpact head808 briefly touches one of thecontact surfaces806a-806ebefore returning to the equilibrium position. When this occurs, the electrical circuit between theelectrical input810 and theelectrical output812 is momentarily completed, thus producing a voltage spike or pulse at theelectrical output812. System electronics monitor theoutput812 for such a voltage pulse, and provide an appropriate alarm or other indication as described above when such a pulse is detected.
• Although the embodiment ofFIG. 6 involves five generally planar-shaped contact surfaces that form a generally box-shaped enclosure, other embodiments may include a greater or lesser number of contact surfaces having different shapes that may or may not form an enclosure. For example, one embodiment may include only two planar-shaped contact surfaces that are oriented generally orthogonal to one another. On the other hand, other embodiments may include a plurality of contact surfaces that form any polyhedron-shaped enclosure having geometries other than the box-shaped enclosure ofFIG. 6 or that form a spherical or cylindrical-shaped enclosure.
• With respect to the embodiments of bothFIGS. 6 and 7, various impact acceleration set points can be established by varying the length of thearm804 or902, the curvature of the bend in thearm804 inFIG. 6, the cross-sectional shape of thearm804 or902, the material from which thearm804 or902 is constructed, the density of the material from which theimpact head808 or906 is constructed, and the distance between theimpact head808 or906 and thecontact surface806a-eor908 and910 at equilibrium (i.e. when no acceleration force is being applied to theswitch801 or901). In other alternative embodiments, theimpact head808 or906 may be omitted, and thearm804 or902 may come into contact with thecontact surfaces806a-eor908 and910 to close the electrical circuit and produce an output signal at theelectrical output812 or912.
• As described above, an acceleration sensor such as an accelerometer or impact switch may be used to detect and report potential damage to an ambulatory medical device due to shock or impact. Additionally, an accelerometer can be used to detect physical activities of the user, and then the user's therapy can be adjusted or operation of the medical device can otherwise be altered in response to the detected activity of the user, as will be described below.
• The accelerometers described above can be carried or worn by individuals to monitor their physical activities, including exercise. Such physical activity generally results in an accelerometer frequency output in the range of 10-60 Hz, up to 100 Hz. Typically, each type of physical activity in which the user engages (e.g., running, walking, sitting, etc.) generates a different frequency that can be detected and identified. Thus, in other embodiments of the present invention, an ambulatory medical device such as theexternal infusion pump410 may include anacceleration sensor414 such as one or more accelerometers that provide signals as a function of a plurality of acceleration forces acting on thepump410 and corresponding to physical activity of the user. In one embodiment, thepump410 may determine that the user is engaging in physical activity if the output signal of theacceleration sensor414 exceeds a predetermined acceleration force that is known to correspond to such physical activity. In other embodiments, thepump410 may determine that the user is engaging in physical activity based on a trace or pattern of output signals from theacceleration sensor414. For example, running may result in one trace or pattern of varying magnitudes of output signals from theacceleration sensor414, while walking may result in another trace or pattern of varying magnitudes of output signals from theacceleration sensor414. The pump monitors the physical activity of the user and responds accordingly by providing messages or alarms to the user (i.e., visually on thedisplay428, audibly by thespeaker430, and/or tactilely via the vibration alarm416), adjusting the delivery of medication to the user, or otherwise altering the operation of thepump410.
• For example, some users require less medication, such as insulin, during periods of intense exercise and/or for certain periods of time after such exercise. Theacceleration sensor414 incorporated into thepump410 may be used to detect such exercise or other physical activity by the user. In response to the detected exercise or physical activity, thepump410 can notify the user to decrease the medication delivery rate. In alternative embodiments, thepump410 can automatically decrease the medication delivery rate. Moreover, thepump410 can apply a time delay between detecting the commencement of exercise and decreasing the medication delivery rate. The time delay may be a predetermined period of time for the pump410 (e.g., 5 minutes), or alternatively, the user may program the length of the delay. Furthermore, thepump410 may vary the length of the delay based on the duration and/or intensity of the exercise. In still other embodiments, thepump410 may change the nocturnal delivery rate (i.e., the delivery rate when the user is sleeping) in response to detected exercise earlier in the day.
• In particular embodiments, thepump410 allows the user to program the amount of decrease in the medication delivery rate during and/or after the period of exercise. For example, the user can enter a percentage decrease of the current delivery rate to be used when exercise is detected. Alternatively, the user can set a specified delivery rate to be used when exercise is detected. The delivery rate during and/or after exercise may be any rate that is lower than the delivery rate used when not exercising, including no medication delivery during exercise.
• In other embodiments, thepump410 may correlate the detected duration and intensity of physical activity to caloric burn. This correlation may be performed utilizing known algorithms and data correlating exercise to caloric burn that are preprogrammed into thepump410 and/or input into thepump410 by the user or caregiver. Based on the estimated caloric burn, thepump410 may notify the user of possible hypoglycemia if the caloric burn is high, or alternatively, suggest more exercise for the user if the caloric burn is low. Thepump410 may also modify the medication delivery rate based on the estimated caloric burn. For example, thepump410 may decrease the medication delivery rate if the caloric burn is high.
• In alternative embodiments, thepump410 may deliver medications or fluids other than insulin. As a result, in some embodiments, the user may desire more medication or other fluids during exercise. Thus, in response to the detected exercise or physical activity by the user, the delivery rate may be increased in a manner similar to that described above for decreasing the delivery rate. For example, the pump may deliver medications or other fluids such as nutrients, vitamins, minerals, steroids, anabolic drugs, glucose, salts, sources of energy, painkillers, drugs to enhance oxygen uptake, fluids for hydration, or the like.
• In particular embodiments, theacceleration sensor414 incorporated into thepump410 may also be used to detect the cessation of exercise or physical activity by the user. In response to the detected cessation of exercise or physical activity, thepump410 can remind the user to return to the normal, programmed delivery rate. In alternative embodiments, thepump410 can automatically return to the normal, programmed delivery rate. Additionally, the pump may apply a time delay between detecting the cessation of exercise and returning to the normal, programmed delivery rate.
• For some users, the length of the delay between ending exercise and returning to the normal, programmed delivery rate may be dependent on the duration of the exercise. For example, if the user has exercised for 30 minutes or less, thepump410 may delay for a period of 5 minutes after the user has stopped exercising, and then return to the normal, programmed delivery rate. In another example, if the user has exercised for more than 30 minutes, thepump410 may delay for a period of 10 minutes after the user has stopped exercising, and then return to the normal, programmed delivery rate. Other time periods of delay or exercise may be used. In alternative embodiments, the user may program the length of the delay between detecting the cessation of exercise and returning to the normal, programmed delivery rate.
• In further alternative embodiments, thepump410 may change the delivery rate gradually from the normal programmed delivery rate to the exercise delivery rate, and from the exercise delivery rate to the normal programmed delivery rate. These gradual changes in rates or dosages can occur over a period of time in a generally linear manner, a generally quadratic manner, a generally exponential manner, or a generally logarithmic manner.
• In other embodiments, exercise characteristics, such as frequency, duration, and/or intensity, may be detected by theacceleration sensor414 incorporated into the ambulatory medical device such as theinfusion pump410, and then stored in a history file or database. In one embodiment, the exercise characteristics may be downloaded from the transmitter/receiver417 via a wired or wireless connection to a computer, PDA, the Internet, or the like, where an exercise history file or database is maintained. Alternatively, the exercise history file may be stored and maintained in thememory422 of thepump410. The history file is analyzed to determine if the user's exercise routine has changed, and if so, the user is notified to re-evaluate his or her medication delivery rate.
• For example, some users may require more or less medication, such as insulin, depending on their exercise routine. For users who have significantly increased their exercise routine and improved their physical conditioning, the amount of insulin required per gram of carbohydrate ingested (i.e., carbohydrate ratio) and/or the amount of insulin required to lower their blood glucose level a certain number of units (i.e., insulin sensitivity) may decrease. On the other hand, for users who have significantly decreased their exercise routine and lost some physical conditioning, the amount of insulin required per gram of carbohydrate ingested (i.e., carbohydrate ratio) and/or the amount of insulin required to lower their blood glucose level a certain number of units (i.e., insulin sensitivity) may increase.
• In some embodiments, the user may be notified when his or her exercise routine has changed throughout a period of three months. Alternatively, users can be notified when their exercise routine has changed for longer or shorter periods of time. For example, some users with diabetes may require a different amount of insulin when they are ill compared to when they are healthy. Thus, if such a user is ill and cannot exercise, then after just 2 or 3 days, the pump can notify the user to re-evaluate his/her carbohydrate ratio and/or insulin sensitivity.
• In particular embodiments, the exercise history file may be maintained and analyzed on a device other than thepump410, such as a computer, PDA, the Internet, or the like. The user may then be notified that his/her exercise routine has changed and/or to re-evaluate his/her medication delivery rate by email, while operating a computer program, while communicating with a web site, or the like. Alternatively, the user can receive this notification from the user's glucose meter or monitoring system, PDA, cell phone, or the like. In further alternative embodiments, this notification can be transmitted to the transmitter/receiver417, and then provided to the user by thepump410 visually on thedisplay428, audibly by theaudible alarm430, and/or tactilely via thevibration alarm416. In other embodiments, the exercise history file may be maintained and analyzed on thepump410. Thepump410 then notifies the user that the user's exercise routine has changed and/or to re-evaluate the user's medication delivery rate visually on thedisplay428, audibly by theaudible alarm430, and/or tactilely via thevibration alarm416. In alternative embodiments, the transmitter/receiver417 may be utilized to communicate this notification to a device other than theinfusion pump410 so that the user can receive this notification as described above, such as by email, while operating a computer program, while communicating with a web site, or the like. Alternatively, the user can receive this notification from the user's glucose meter or monitoring system, PDA, cell phone, or the like.
• In further alternative embodiments, sensing devices other than anacceleration sensor414 incorporated into theinfusion pump410 may be used to detect exercise, such as for example, a respiratory rate measuring device, a blood glucose monitor, a heart rate measurement device, a blood oxygen sensor, a body temperature sensor, or the like. These sensing devices can communicate with thepump410 via the transmitter/receiver417, and thepump410 can maintain and analyze the exercise history file and/or modify the medication delivery rate. In other alternative embodiments, these sensing devices can communicate with a device external to the pump410 (e.g., computer, PDA, the Internet), which stores and analyzes the exercise history file. If thepump410 or device external to the pump410 (e.g., computer, PDA, the Internet) determines that the user's exercise routine has changed, the user can be notified of such change and/or to re-evaluate his/her medication delivery rate by thepump410 or other external device as described above.
• In addition to acceleration, other environmental conditions can adversely affect the performance of ambulatory medical devices such as theinfusion pump410. For example, temperature extremes can affect both performance of theinfusion pump410 as well as certain medications, such as insulin. Thus, an ambulatory medical device such as theinfusion pump410 may also include a temperature orthermal sensor426, which allows thepump410 to notify the user when thepump410 is exposed to varying or extreme temperatures (hot or cold). Temperature sensing can be used, for example, to estimate the effect of temperature on the performance of thepump410 itself, the pump'spower supply440 such as a battery, and/or degradation of insulin or other medication. Thethermal sensor426 may be any of the known thermal sensors, including, for example, thermoresistors (thermistors), thermocouples, thermal flow rate sensors, resistance temperature detectors (“RTDs”), platinum resistors, diode temperature sensors, silicon transistor thermometers, integrated temperature transducers, PTAT circuits, thermopiles, pyroelectric thermometers, quartz thermometers, and the like.
• RTD's operate on the principle that the electrical resistance of many metals, such as platinum, aluminum and copper, or the like will increase over a certain range of temperatures. A fine wire of metal is wound on a core to obtain a high level of resistance or is patterned as a thin film on a substrate. The varying resistance is then measured as a function of temperature.
• A thermistor sensor also operates on the principle of varying electrical resistances as a function of temperature. However, these devices are made from various nonmetallic conductors (e.g., metal oxides and silicon) and can offer the advantage of higher thermal coefficients of resistance and greater sensitivities (ΔR/ΔT). Moreover, some types of thermistors provide increasing electrical resistance as temperature increases, whereas other types provide decreasing resistance.
• A thermocouple sensor consists of two dissimilar metals that are bonded together by welding or other means. The bimetallic junction develops a small voltage that varies with temperature. Thermocouples are relatively inexpensive and provide moderately accurate and consistent measurements. However, one disadvantage is that they produce very small output voltages which are comparable to the voltages developed at the junctions formed where the thermocouple wire is connected to other components. This must be compensated for in the associated circuitry.
• Many temperature sensor integrated circuit devices operate on the principle that at a constant current bias, the voltage drop across a silicon P-N diode junction can vary with temperature. Because the P-N junction is the basic building block of diodes, transistors, and ICs, temperature sensing can be incorporated at a relatively low cost.
• There are various uses for a temperature orthermal sensor426 in an ambulatory medical device such as theinfusion pump410. In one embodiment, theinfusion pump410 uses thetemperature sensor426 for warning purposes. In extreme environments, medication such as insulin can degrade and become less effective. Also, electronic components of thepump410 may malfunction (e.g., thedisplay428 may go blank). Thethermal sensor426 is used to measure or detect temperature conditions to which thepump410 is subjected, and in response to the detected temperature, thepump410 can notify the user of potential problems due to the temperature before they occur (e.g., insulin degradation, electronics malfunction). Additionally, if thethermal sensor426 detects a sufficiently high or low temperature, problems such as insulin degradation may have already occurred. Thus, thepump410 can provide the user with an alarm to notify the user of the insulin degradation.
• In operation, thethermal sensor426 provides an output signal as a function of the temperature in thehousing420. Theprocessor418 converts the output signal to a value, and compares that value with a predetermined temperature value stored in thememory422 that is associated with a predetermined temperature. If the temperature measured by thethermal sensor426 exceeds the predetermined temperature, theprocessor418 may provide an alarm to the user (i.e., tactilely via thevibration alarm416, audibly by theaudible alarm430, and/or visually on the display428) to indicate that thepump410 has been subjected to extremely high temperatures, and as a result, to check the pump (e.g., whether insulin degradation has occurred, the display has malfunctioned).
• Additionally, in cold environments, there may be a higher occurrence of medication flow stoppage due to the reduced viscosity of some medications such as insulin. The lower viscosity fluid requires a higher force to deliver the fluid from the reservoir, through the tubing, and into the infusion set adhered to the patient. However, this higher delivery force can be more likely to trigger a false occlusion alarm as compared with pump operations at warmer temperatures. Accordingly, in another embodiment of the present invention, for an ambulatory medical device such as theinfusion pump301 which utilizes aforce sensor311 to detect occlusions, the programmed occlusion alarm limits are made dependent on the measured temperatures to which thepump301 is subjected. When the temperature decreases, the pump occlusion alarm limit is increased accordingly.
• In operation, thememory422 stores a predetermined temperature value associated with a predetermined temperature and a predetermined force threshold value associated with a predetermined force threshold corresponding to a fluid occlusion. Thethermal sensor426 provides an output signal as a function of the temperature in thehousing420. Theprocessor418 converts the output signal to a value, and compares that value with the predetermined temperature value. If the temperature measured by thethermal sensor426 is less than the predetermined temperature, theprocessor418 alters the predetermined force threshold value to provide a modified force threshold value. In other words, the force threshold corresponding to an occlusion is changed. Subsequently, if a measured force (as measured, for example, by the force sensor311) exceeds the modified force threshold value, theprocessor418 provides an alarm to the user (i.e., visually on thedisplay428, audibly by theaudible alarm430, and/or tactilely via the vibration alarm416) to indicate the occlusion.
• In other embodiments, temperature data is used to modify a delivery pulse of the pump. For example, in some ambulatory medical devices such as theinfusion pump410, friction within thedrive mechanism432 and/orreservoir434 is often dependent on the temperature at which thepump410 is operating. As temperature decreases, friction increases, and as a result, more energy is required by thedrive mechanism432 to deliver fluid out of thereservoir434. Therefore, thethermal sensor426 can measure the temperature within thepump housing420. Theprocessor418 compares the measured temperature with a predetermined temperature stored in thememory422. If the measured temperature is below the predetermined temperature, theprocessor418 increases the delivery pulse, for example, by increasing the duration or the amount of energy in the delivery pulse.
• In yet another embodiment, temperature data is used as an indicator of reduced battery life. For example, in some ambulatory medical devices such as theinfusion pump410, alkaline-manganese dioxide batteries can be used as thepower supply440. Battery performance is often dependent on the temperature at which the battery is operating. As temperature decreases, the discharge resistance of the battery increases, thereby reducing the battery's life. Therefore, thethermal sensor426 can measure the temperature within thepump housing420. Theprocessor418 compares the measured temperature with a predetermined temperature stored in thememory422. For example, the predetermined temperature may be a temperature that causes a battery discharge resistance increase of 10, 15, 25, 50 percent or some other percentage. If the measured temperature is below the predetermined temperature, thepump410 provides an alarm to the user, indicating that battery life may be reduced due to the temperature to which thepump410 is subjected.
• Additionally, in other embodiments, an ambulatory medical device such as theinfusion pump410 uses temperature data to modify battery measurement algorithms. In one embodiment, when the temperature decreases, the measurement frequency of thepower supply440 such as the battery may be increased to ensure that there is adequate power for effective operation of thepump410. For example, in theinfusion pump410, a battery measurement may be taken every hour. Since the act of taking this measurement requires power, it can be important to minimize the frequency of battery measurements. On the other hand, if there are external conditions that effectively reduce the battery performance, such as lower temperatures, it may be desirable to modify thepump410 to take battery measurements differently, possibly more frequently, so that appropriate low battery and dead battery conditions can be detected earlier than otherwise.
• Thus, theprocessor418 samples the output voltage of thebattery440 at a first sampling frequency. Thethermal sensor426 provides an output signal as a function of the temperature in thehousing420. Theprocessor418 converts the output signal to a value and compares that value with a predetermined temperature value stored in thememory422 corresponding to a predetermined temperature. If the temperature measured by thethermal sensor426 is less than the predetermined temperature, theprocessor418 alters the battery voltage sampling from the first sampling frequency to a second sampling frequency in accordance with this comparison.
• Humidity is yet another environmental variable that can affect performance of an ambulatory medical device such as theinfusion pump410. In one embodiment, thehumidity sensor412 is incorporated within theinfusion pump410, and provides an output signal as a function of humidity levels in thehousing420. Alternatively, thehumidity sensor412 can be disposed to provide an output signal as a function of humidity levels external to thehousing420.
• Theprocessor418 converts the output signal from the humidity sensor to a value, and compares that value with a predetermined value stored in thememory422 that is associated with a predetermined humidity level. Based on the comparison, theprocessor418 then provides a warning or alarm to the user (i.e., visually on thedisplay428, audibly by theaudible alarm430, and/or tactilely via the vibration alarm416). Thehumidity sensor412 may be any of the known humidity sensors, including capacitive humidity sensors, resistive humidity sensors, and thermal conductivity humidity sensors.
• Capacitive humidity sensors consist of a substrate on which a thin film of polymer or metal oxide is deposited between two conductive electrodes. The sensing surface is coated with a porous metal electrode to protect it from contamination and exposure to condensation. The change in the dielectric constant of a capacitive humidity sensor is proportional to the relative humidity of the surrounding environment.
• Resistive humidity sensors measure the change in electrical impedance of a hygroscopic medium such as a conductive polymer, salt, or treated substrate. The impedance change is typically inversely proportional to the humidity level. Resistive sensors frequently consist of noble metal electrodes deposited on a substrate. The substrate can be coated with a salt or conductive polymer. When it is dissolved or suspended in a liquid binder, it functions as a vehicle to evenly coat the sensor.
• Thermal conductivity humidity sensors measure the absolute humidity by quantifying the difference in the thermal conductivity between dry air and air containing water vapor. They usually consist of two thermistor elements in a bridge circuit—one is encapsulated in a gas, such as dry nitrogen, and the other is exposed to the environment. When current is passed through the thermistors, resistive heating increases their temperature. The heat dissipated from the encapsulated thermistor is greater than the exposed thermistor due to the difference in the thermal conductivity of the water vapor as compared to dry nitrogen. Since the heat dissipated yields different operating temperatures, the difference in resistance of the thermistors is proportional to the humidity.
• In particular embodiments, humidity measurements from within an ambulatory medical device such as theinfusion pump410 are used to detect a breach in the pump's watertight integrity. Thehumidity sensor412 may measure the humidity level within thehousing420 of thepump410, and theprocessor418 may compare the measured humidity with a predetermined humidity level stored in thememory422. For example, the predetermined humidity level may be a very high humidity level (e.g., greater than 90%, 80%, or some other percentage) within thehousing420 of thepump410 that may indicate possible water intrusion into thepump410 due to a damagedhousing420. If the measured humidity exceeds the predetermined humidity level, thepump410 notifies the user and indicates the necessity to perform some self-test or investigation, or to contact the manufacturer for service. This notification can be provided tactilely via thevibration alarm416, audibly by theaudible alarm430, and/or visually on thedisplay428. Alternatively, theprocessor418 can activate the transmitter/receiver417, which can send the humidity level information to an external device for analysis or notification to the user.
• Although some ambulatory medical devices are designed to be resistant to the effects of static electricity, it nevertheless is possible that high levels of static discharge can cause such a device to alarm. A significant environmental parameter affecting the generation of static electricity is humidity. The effects of static electricity increase with a decrease in humidity. Therefore, in another embodiment, thehumidity sensor412 in an ambulatory medical device such as theinfusion pump410 can measure humidity external to thepump410, and the user can then be notified of high humidity conditions. Alternatively, humidity measured by thehumidity sensor412 from within thepump410 can also be used.
• However, there likely will be a time lag between a change in external humidity and the detection of such a change by thehumidity sensor412 that measures internal humidity.
• Thus, there is disclosed an ambulatory medical device that is adapted for carrying by a person, preferably by external attachment to the person's body. The ambulatory medical device has acceleration, thermal and/or humidity sensors which, along with system electronics, control the device by, among other things, altering the operation of the device, providing an alarm or text message to the user, and/or transmitting data to another device.
• 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 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 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.

Claims (28)

1. An external infusion device for infusing fluid into a person from a reservoir, comprising:

a housing adapted to be carried by on an exterior of the person;

a drive mechanism contained in the housing and operatively coupled to the reservoir to deliver fluid from the reservoir into the person's body;

a processor contained in the housing;

a memory coupled to the processor and adapted to store a predetermined temperature threshold; and

a thermal sensor coupled to the processor and adapted to provide a temperature output signal as a function of temperature in the housing;

wherein the processor is adapted to compare the temperature output signal with the predetermined temperature threshold, and to control the infusion device based on the temperature comparison.

2. The external infusion device ofclaim 1, wherein the thermal sensor is one of a thermoresistor, a thermocouple, a thermal flow rate sensor, a resistance temperature detector, a platinum resistor, a diode temperature sensor, a silicon transistor thermometer, an integrated temperature transducer, a PTAT circuit, a thermopile, a pyroelectric thermometer, and a quartz thermometer.

3. The external infusion device ofclaim 1, further comprising an indicator operatively coupled to the processor and adapted to provide at least one of a visual indication, an audible indication, or a tactile indication to indicate information to the person about the infusion device.

4. The external infusion device ofclaim 3, wherein if the temperature output signal exceeds the predetermined temperature threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the temperature output signal.

5. The external infusion device ofclaim 4, wherein the fluid infused into the person is medication, and the predetermined temperature threshold corresponds to a temperature that causes the medication to degrade, and further wherein the alarm or warning indicates degradation of the medication to the person.

6. The external infusion device ofclaim 4, wherein the predetermined temperature threshold corresponds to a temperature that causes the indicator to malfunction, and further wherein the alarm or warning indicates malfunction of the indicator to the person.

7. The external infusion device ofclaim 3, wherein if the temperature output signal is less than the predetermined temperature threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the temperature output signal.

8. The external infusion device ofclaim 7, further comprising a battery contained in the housing and adapted to provide power for the infusion device, wherein the battery has a discharge resistance, and wherein the predetermined temperature threshold corresponds to a temperature that causes the discharge resistance of the battery to increase by at least 10 percent, and further wherein the alarm or warning indicates reduced life of the battery to the person.

9. The external infusion device ofclaim 7, further comprising a battery contained in the housing and adapted to provide power for the infusion device, wherein the processor is adapted to sample the battery at a first sampling frequency to determine remaining power of the battery, and further wherein if the temperature output signal is less than the predetermined temperature threshold, the processor is further adapted to control the infusion device by altering sampling of the battery from the first sampling frequency to a second sampling frequency.

10. The external infusion device ofclaim 7, wherein the memory is further adapted to store a predetermined force threshold corresponding to a fluid occlusion in the infusion device, and further wherein if the temperature output signal is less than the predetermined temperature threshold, the processor is further adapted to control the infusion device by modifying the predetermined force threshold to provide a modified force threshold.

11. The external infusion device ofclaim 1, further comprising a transmitter/receiver contained in the housing and coupled to the processor, wherein the transmitter/receiver is adapted to communicate with a remote device, and further wherein the processor is adapted to control the infusion device by causing the transmitter/receiver to send information about the infusion device to the remote device based on the temperature comparison.

12. An external infusion device for infusing fluid into a person, comprising:

a housing adapted to be carried by on an exterior of the person's body;

a processor contained in the housing;

an indicator operatively coupled to the processor and adapted to provide at least one of a visual indication, an audible indication, or a tactile indication to indicate information about the infusion device to the person;

a memory coupled to the processor and adapted to store a predetermined humidity threshold; and

a humidity sensor coupled to the processor and adapted to provide a humidity output signal as a function of humidity in or around the housing;

wherein the processor is adapted to compare the humidity output signal with the predetermined humidity threshold, and to control the infusion device based on the humidity comparison.

13. The external infusion device ofclaim 12, wherein the humidity sensor is one of a capacitive humidity sensor, a resistive humidity sensor, and a thermal conductivity humidity sensor.

14. The external infusion device ofclaim 12, wherein if the humidity output signal exceeds the predetermined humidity threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the humidity output signal.

15. The external infusion device ofclaim 14, wherein the predetermined humidity threshold corresponds to entry of water into the housing, and the indicator is adapted to provide the alarm or warning to the person about the entry of water into the housing.

16. The external infusion device ofclaim 12, wherein if the humidity output signal is less than the predetermined humidity threshold, the processor is adapted to control the infusion device by causing the indicator to provide an alarm or a warning to the person about the humidity output signal.

17. The external infusion device ofclaim 16, wherein the predetermined humidity threshold corresponds to a humidity level that causes the infusion device to be susceptible to damage due to static electricity, and the indicator is adapted to provide the alarm or warning to the person about the static electricity.

18. The external infusion device ofclaim 12, further comprising a transmitter/receiver contained in the housing and coupled to the processor, wherein the transmitter/receiver is adapted to communicate with a remote device, and further wherein the processor is adapted to control the infusion device by causing the transmitter/receiver to send information about the infusion device to the remote device based on the humidity comparison.

19. An external ambulatory medical device for use on a person's body, comprising:

a housing adapted to be carried by on an exterior of the person's body;

a processor contained in the housing;

an indicator operatively coupled to the processor and adapted to provide at least one of a visual indication, an audible indication, or a tactile indication to indicate information about the ambulatory medical device to the person;

a memory coupled to the processor and adapted to store a predetermined temperature threshold; and

a thermal sensor coupled to the processor and adapted to provide a temperature output signal as a function of temperature in the housing;

wherein the processor is adapted to compare the temperature output signal with the predetermined temperature threshold, and further wherein the processor is adapted to control the ambulatory medical device and the indicator is adapted to indicate information about the ambulatory medical device based on the temperature comparison.

20. The ambulatory medical device ofclaim 19, wherein the ambulatory medical device is an external infusion pump.

21. The ambulatory medical device ofclaim 19, wherein the ambulatory medical device is a glucose monitoring device.

22. The ambulatory medical device ofclaim 19, further comprising a transmitter/receiver contained in the housing and coupled to the processor, wherein the transmitter/receiver is adapted to communicate with a remote device, and further wherein the processor is adapted to control the ambulatory medical device by causing the transmitter/receiver to send information about the ambulatory medical device to the remote device based on the temperature comparison.

23. The ambulatory medical device ofclaim 19, wherein the thermal sensor is one of a thermoresistor, a thermocouple, a thermal flow rate sensor, a resistance temperature detector, a platinum resistor, a diode temperature sensor, a silicon transistor thermometer, an integrated temperature transducer, a PTAT circuit, a thermopile, a pyroelectric thermometer, and a quartz thermometer.

24. An external ambulatory medical device for use on a person's body, comprising:

a housing adapted to be carried by on an exterior of the person's body;

a processor contained in the housing;

an indicator operatively coupled to the processor and adapted to provide at least one of a visual indication, an audible indication, or a tactile indication to indicate information about the ambulatory medical device to the person;

a memory coupled to the processor and adapted to store a predetermined humidity threshold; and

a humidity sensor coupled to the processor and adapted to provide a humidity output signal as a function of humidity in or around the housing;

wherein the processor is adapted to compare the humidity output signal with the predetermined humidity threshold, and further wherein the processor is adapted to control the ambulatory medical device and the indicator is adapted to indicate information about the ambulatory medical device based on the humidity comparison.

25. The ambulatory medical device ofclaim 24, wherein the ambulatory medical device is an external infusion pump.

26. The ambulatory medical device ofclaim 24, wherein the ambulatory medical device is a glucose monitoring device.

27. The ambulatory medical device ofclaim 24, further comprising a transmitter/receiver contained in the housing and coupled to the processor, wherein the transmitter/receiver is adapted to communicate with a remote device, and further wherein the processor is adapted to control the ambulatory medical device by causing the transmitter/receiver to send information about the ambulatory medical device to the remote device based on the humidity comparison.

28. The ambulatory medical device ofclaim 24, wherein the humidity sensor is one of a capacitive humidity sensor, a resistive humidity sensor, and a thermal conductivity humidity sensor.

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