Medicine delivery device having detachable pressure sensing unit

A fluid medicament delivery device includes a patient attachment unit and a separate indicator unit. The patient attachment unit includes a housing and a fluid channel located therein, wherein at least a portion of the fluid channel includes a flexible member substantially coterminous with the housing. The separate indicator unit is adapted to be detachably coupled to the housing of the patient attachment unit and includes a first sensing element for contacting the flexible member when the indicator unit is coupled to the housing to sense a flexure of the flexible member.

FIELD OF THE INVENTION

This invention relates generally to medicament delivery devices and, more specifically, to medicament infusion devices that utilize a reusable indicator unit and a disposable medicament-delivery unit.

BACKGROUND

Medicament infusion devices are utilized to deliver liquid fluid medicine to patients. For example, insulin infusion devices are often used by persons with diabetes to maintain adequate insulin levels throughout the day or to increase insulin levels during mealtime. These insulin infusion devices can replace the syringe-based injections common among those with diabetes.

Insulin infusion devices are available in several forms, and include several common components. Generally, an infusion device includes a housing that may be worn on a patient's clothing (a belt, for example) or on the patient himself, and that contains a number of mechanical and electrical components. A reservoir holds the insulin and an electro-mechanical pump mechanism (various types are used) delivers the insulin as needed to the patient. Battery-powered electronics control the pump and ensure that the device is operating properly. Various sensors communicate with the electronics and other components to detect occlusions, sound alarms, measure remaining insulin capacity, etc.

While these devices are useful, they do suffer from several shortcomings. First, the high expense of the devices makes them accessible to fewer people than the diabetic population members who may benefit from their use. Second, failure or malfunction of one component requires repair or replacement of the entire device, a costly scenario. For example, if the pump fails, often the entire unit (including the properly functioning—and expensive—electronics) must be replaced. Third, over time the device gets dirty due to repeated uses, which requires periodic cleaning and may cause a failure condition at a later date.

SUMMARY OF THE INVENTION

What is needed, then, is a medicament infusion device that utilizes low-cost components, some of which may be replaced periodically after use, without having to dispose of other expensive, but operational, components in the device.

In one aspect, the invention relates to a fluid medicament delivery device having a patient attachment unit that includes a housing and a fluid channel located therein, such that at least a portion of the fluid channel has a flexible member substantially coterminous with the housing. The fluid medicament delivery device includes a separate indicator unit adapted to be detachably coupled to the housing of the patient attachment unit. The indicator unit includes a first sensing element for contacting the flexible member when the indicator unit is coupled to the housing, such that the first sensing element senses a flexure of the flexible member. In an embodiment of the foregoing aspect, the indicator unit also includes a second sensing element for sensing a pressure external to the housing. In another embodiment, the pressure external to the housing includes an ambient pressure.

In an embodiment of the above aspect, the first sensing element includes a pressure sensor. In another embodiment, the first sensing element also includes at least one of a fluid and a gel adapted to contact the flexible member, such that the flexure of the flexible member is transmitted by the at least one of the fluid and the gel to the pressure sensor. In yet another embodiment, the separate indicator unit defines a well for containing at least one of the liquid and the gel. In still another embodiment, the separate indicator unit includes a raised lip surrounding the well, such that the raised lip is disposed above a proximate portion of the separate indicator unit. In another embodiment, the raised lip is adapted to contact the housing of the patient attachment unit.

In another embodiment of the above aspect, the second sensing element includes a pressure sensor adapted to sense the pressure external to the housing, and at least one of a fluid and a gel adapted to transmit the pressure external to the housing to the pressure sensor. In an embodiment, the housing has a hermetically-sealed housing defining an interior space and including at least one substantially flexible housing portion. The substantially flexible housing portion is adapted for transmitting the pressure external to the housing to the interior space. In still another embodiment, the substantially flexible housing portion is located on a portion of the patient attachment unit facing the separate indicator unit and the second sensing element is located on a portion of the separate indicator unit facing the patient attachment unit, when the patient attachment unit is coupled to the separate indicator unit.

In yet another embodiment of the foregoing aspect, the patient attachment unit is adapted for adhesion to a skin surface of a patient. In an embodiment, the fluid medicament delivery device also includes a processor adapted for interpreting a signal from a pressure sensor, such that the signal is sent to the processor based at least in part on the flexure of the flexible member.

In another aspect, the invention relates to a method of monitoring pressure within a fluid channel of a fluid medicament delivery device, the method including measuring an actual pressure of a fluid within the fluid channel, comparing the actual pressure to a pressure range including a maximum pressure and a minimum pressure, and sending a notification when the actual pressure is outside of the pressure range. In an embodiment, the method also includes measuring a pressure external to the fluid medicament delivery device.

In an embodiment of the above aspect, the method of monitoring pressure within a fluid channel of a fluid medicament delivery device also includes modifying the actual pressure based on the external pressure to obtain a corrected pressure, and comparing the corrected pressure to the pressure range. In another embodiment, the method also includes modifying the maximum pressure and a minimum pressure of the pressure range based on the external pressure to obtain a corrected pressure range, and comparing the corrected pressure range to the actual pressure. In still another embodiment, when the actual pressure exceeds the maximum pressure, the notification includes at least one of a downstream occlusion notification and a near-empty reservoir notification. In yet another embodiment, when the actual pressure is less than the minimum pressure, the notification includes at least one of an upstream occlusion notification and an empty reservoir notification.

In another aspect, the invention relates to a method of manufacturing a pressure sensing element, the method including securing a pressure sensor to a base, securing a template defining a well therein to the base, such that the pressure sensor is located in a bottom portion of the well. The method includes filling at least partially the well with a gel having a substantially liquid state, so that the well includes a filled portion and an unfilled portion, and the filled portion and the unfilled portion are characterized by a presence or an absence of gel. The method includes solidifying the gel in the filled portion to a substantially gelled state, and filling the unfilled portion with a gel having a substantially liquid state.

DETAILED DESCRIPTION

FIGS. 1 and 2depict an embodiment of an assembled fluid medicament delivery device100having at least two modules, a patient attachment unit110and a separate indicator unit120, each having a housing110a,120a, respectively. The depicted fluid medicament delivery device100, when assembled, defines a substantially oval shape, although other shapes (circular, oblong, elliptical, etc.) are also contemplated. In general, an assembled device having round corners, smooth edges, etc., may be desirable, since the device is designed to be worn on the skin of a patient, underneath clothing. Other aspects of the device that make it generally unobtrusive during wear include a small size (only about several inches across) and a low profile. Other device shapes and sizes are also contemplated.

The patient attachment unit110includes a bolus button268for delivering a dose of fluid medicament, as described below. A cannula insertion device (SeeFIG. 13A) inserts a cannula through the device110, subcutaneously through the skin S of a patient. Cannula insertion devices are described in U.S. patent application Ser. No. 12/250,760, filed Oct. 14, 2008, the disclosure of which is hereby incorporated by reference herein in its entirety. After insertion, the cannula insertion device is disconnected from the patient attachment unit110, and a cap112is used to seal the opening to prevent ingress of contaminants, moisture, etc. The separate indicator unit120includes an indicator button122. A textured edge124, may be present on all or part of the edge of the housing120ato provide a gripping surface during attachment and/or disconnection of the indicator unit120and the patient attachment unit110, as described in more detail below. Alternatively or additionally, the edge of patient attachment unit housing110amay also be textured.

The patient attachment unit110is connected to and in communication with the separate indicator unit120, as described in more detail below. The housings110a,120bof the patient attachment unit110and the indicator unit120meet at a curved interface114. Interfaces having other mating shapes are also contemplated. The bottom surface of the patient attachment unit110includes a patient attachment interface116. The patient attachment interface116may include one or more adhesive pads secured to the bottom surface of the patient attachment unit110for adhering the fluid medicament delivery device100to the skin S of a patient during use. The interface116may comprise any suitable configuration to adhere the patient attachment unit110to the skin S. In one embodiment, the interface116includes a plurality of discrete points of attachment. Other embodiments utilize concentric adhesive circles or ovals.

The indicator button122may be used by the patient to test the functioning of the fluid medicament delivery device100or to cancel a notification presently being delivered or to prompt for a repetition of a previous message or other information stored by the indicator unit. Actuating the indicator button122may initiate one or more tests to indicate to the patient various operational or therapy states of the device100, such as whether the separate indicator unit120is properly mounted to the patient attachment unit110, whether an internal battery has sufficient power for continued use, and/or whether pressure sensing within the device110is operating properly. Other tests are also contemplated. A single indicator button, such as that depicted inFIG. 1, may be used to run one or more tests. The medicament delivery device100may be programmed to recognize patterns of actuations of the indicator button to initiate certain test routines. That is, two actuations in quick succession may initiate a “Battery Power Available” test routine, three actuations in quick succession may initiate a “Pressure Sensor Check” test routine, etc. Other combinations of short actuations and long actuations (e.g., Short, Long, Short; Long, Long, Short, etc.) are also contemplated to initiate any number of test routines. Alternatively or additionally, two or more buttons or other input features may be included on the device, for initiating one or more separate tests. Positive or negative feedback of the test results may be provided to the patient in the form of audible sounds of differing tones or durations, illumination/delumination of lights, vibrations, and combinations thereof. In certain embodiments, light emitting diodes (LEDs) may be used to illuminate the button itself or may illuminate portions of the indicator unit housing to provide feedback to the patient. Graphical indicia or alphanumeric information may be displayed on a suitable output device.

FIG. 3is a schematic diagram of an exemplary infusion device micro-fluidic circuit250that may be incorporated into the fluid medicament delivery device100described herein. Other infusion devices having micro-fluidic circuits are described in U.S. Patent Application Publication No. 2005/0165384, published Jul. 28, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety. The micro-fluidic circuit250includes a pressurized reservoir252that is, in this case, an elastomer bladder. Alternatively, a flexible vessel or bag compressed by a spring may be utilized. A fill port254is used to introduce fluid, such as insulin, to the micro-fluidic circuit250. In this micro-fluidic circuit250, introducing insulin via the fill port254fills both the reservoir252and a variable-volume bolus reservoir256. Check valves258prevent backflow of insulin in a number of locations.

During use, insulin is forced from the reservoir252by elastic contraction of the elastomer, through a filter260, and into two parallel flowpaths, a basal flowpath262and a bolus flowpath264. The basal flowpath262delivers a constant dose or steady-state level of insulin to a patient; the bolus flowpath264delivers a bolus dose of insulin to the patient as needed or desired by the patient, for example, in conjunction with a meal. The basal flowpath262includes a first pressure sensor266A or other pressure or flow sensors in communication with the flowpath262, for example, at a mid-point in the basal flowpath. In an alternative embodiment, the first pressure sensor266A or first sensing element262may be placed further upstream or downstream in the basal flowpath, as desired. In another alternative embodiment, a plurality of pressure sensors in communication with the basal flowpath262may be utilized. A second pressure sensor266B or second sensing element is exposed to ambient air pressure P. The function of and relationship between the pressure sensors266A,266B is described in more detail below. In one embodiment, the pressure sensors266A,266B consist of micro-electronic-mechanical system (MEMS) sensors. Each MEMS sensor is about 2 mm square but sensors having different dimensions may also be used. Both MEMS sensors are contained within the indicator unit120. InFIG. 3, the pressure sensor266A communicates with a portion of the basal circuit262between two flow restrictors274A,274B (e.g., microcapillaries). In one embodiment, this portion between the flow restrictors274A,274B may be a pressure sensor chamber, as described in more detail below. The pressure sensor266A senses pressure changes in the basal flowpath262, which may be indicative of occlusion conditions that increase pressure therein. The pressure sensor266B senses changes in ambient air pressure external to the fluid medicament delivery device100. The pressure sensors266A,266B are absolute pressure sensors, but a single relative pressure sensor may also be utilized. A relative pressure sensor, e.g., a gauge MEMS sensor, may be used to replace both absolute pressure sensors.

To deliver a bolus via the bolus flowpath264, the patient presses a button268that drives a single stroke (delivering a single dose) of a bolus displacement chamber270and opens two valves272. The valves272are in series for redundancy safety purposes. An optional flow restrictor274C regulates, in part, the fluid flow through the bolus flowpath264. The parallel flowpaths262,264join at a common channel276just before an internal chamber or a cannula void278. The cannula void278is formed in a cannula base280, which allows a point of connection to a cannula282. The cannula282extends below the skin S of a patient, thus delivering the insulin subcutaneously. In one embodiment, the actuation of the bolus button268may be sensed by the indicator unit120with, for example, a magnetic sensor, a Hall effect sensor, or a switch. In an alternative embodiment of the present invention, at least one pressure sensor may be placed in the bolus flowpath264, thereby allowing the indicator unit120to sense the actuation of the bolus button268. Conduits284having diameters larger than those of the flow restrictors274A,274B,274C connect the various components.

FIG. 4depicts a bottom view of the patient attachment unit110showing the internal components and structures therein, with the housing removed. Specifically, the bottom portion of the housing110a, to which the attachment interface116is secured, has been removed. These internal components and structures correspond generally to the micro-fluidic circuit250, discussed inFIG. 3. The components and structures in the patient attachment unit110may be disposed in or connected to a flow manifold300, which serves as a mounting platform for the various components. Note that not all conduits and flow components are depicted inFIG. 4, as some components may be secured to the opposite side of the manifold300or formed therein.

As described above with regard toFIG. 3, insulin in the bolus flowpath264(the bolus flowpath264, inFIG. 4, is downstream of the labeled arrow) of the micro-fluidic circuit250is delivered from the elastomer reservoir252, filtered through the filter260, and stored in the variable-volume bolus reservoir256. In certain embodiment, the elastomer reservoir252may have a total volume of about 3200 microliters; the variable-volume bolus reservoir256may have a total volume of about 180 microliters to about 260 microliters. Other volumes of the various components are also contemplated. When the fluid pressure in the elastomer reservoir252is greater than the fluid pressure in the variable-volume reservoir256, the variable-volume reservoir256will continue to fill, subject to the flow rate dictated at least by flow restrictor274C in the bolus flowpath264. Downstream of the variable-volume bolus reservoir256is the bolus displacement chamber270, which may store a single dose of insulin (e.g., about 5, about 10, about 20, or about 25, or greater than about 25 microliters of insulin, in various embodiments). A check valve258allows for free flow of insulin from the variable-volume bolus reservoir256to the bolus displacement chamber270. The check valve258prevents backflow during a bolus stroke (i.e., actuation of the bolus button268).

Actuating the bolus button268opens the two valves272(SeeFIG. 3) and empties the entire contents of the bolus displacement chamber270. Audible, visual, and/or tactile feedback may be provided to the patient to signal that a bolus has been delivered. Releasing the bolus button268closes the two downstream valves272. The displacement chamber270is then refilled with insulin from the variable-volume bolus reservoir256, which is, in turn, filled with insulin from the reservoir252. The bolus flow rate is controlled with a fixed volume-per-stroke of bolus stimulus, i.e., a predetermined volume of insulin-per-stroke. In another embodiment, the bolus flow control rate also may be controlled by a bolus rate flow restrictor. Also, downstream of the filter260is the basal flowpath262(the basal flowpath262, inFIG. 4, is downstream of the labeled arrow) of the micro-fluidic circuit250. The flow restrictors274A,274B are located on opposite sides of a pressure sensor chamber302.

In various embodiments, each flow restrictor274A,274B has a length in a range of about 18 mm to about 35 mm. Other lengths of the flow restrictors are also contemplated, for example, from about 10 mm to about 20 mm. The various channels284in the manifold300may be formed by, for example, laser cutting, and the flow restrictors274A,274B may be placed therein. The flow restrictors274A,274B may be glued or fused into the channels, though other methods of retention are also contemplated. Exemplary flow restrictors are described in U.S. Patent Application Publication No. 2006/0054230, the disclosure of which is hereby incorporated by reference herein in its entirety. The flow restrictors274A,274B are connected to and in fluidic communication with a pressure sensor chamber302that includes a flexible member or sensor membrane302a(SeeFIG. 7) disposed thereon. The sensor membrane302amay be generally coterminous with a mating mounting platform404(SeeFIG. 7) of the patient attachment unit110, as described in more detail below. As the insulin in the basal flowpath262flows into the chamber302, pressure of the insulin within the basal flowpath262displaces the sensor membrane302a. This displacement is sensed by the pressure sensor266A, as described below. In this manner, the pressure sensor266A may sense the pressure of the insulin in the basal flowpath via movement of the sensor membrane302a.

FIG. 5depicts a schematic perspective view of the indicator unit120with the top exterior housing120aremoved.FIG. 6shows an exploded view of the indicator unit120depicted inFIG. 5. As discussed herein, the indicator unit120may, in certain embodiments, detect changes in pressure within the micro-fluidic circuit250contained in the patient attachment unit110, and perform other tests to ensure proper operation of the medicine delivery device100. The patient may be alerted as necessary via audible, visual, and/or tactile (e.g., vibration) signals. The components to detect pressure changes, process information, and generate signals or alerts to the patient are contained within the indicator unit120.

The internal components of the separate indicator unit120are mounted, either directly or indirectly, to a mounting platform350, which, in one embodiment, may be the bottom surface of the indicator unit120. Partially shown extending from the underside of the indicator unit120is at least one circular mating projection352, which is configured to mate with the patient attachment unit110, as described below. Mounting arms354defining hollow interiors are disposed at or near the edges of the mounting platform350. The mounting arms354correspond to and connect to the top exterior housing120awith screw, snap-fit, press or other types of connections. Also disposed on the mounting platform350are a supercapacitor358, a vibrating motor360, and two wells362,364. Each well362,364defines a hollow geometrical structure, e.g., a cylinder. Overlaid on at least the wells362,364is a printed circuit board (PCB)366, which may include one or more processors, as well as a test switch368disposed thereon. Several apertures370formed in the PCB366correspond to and align with extensions370afrom the mounting platform350. The extensions370amay be melted during manufacturing to secure the PCB366thereto. The indicator button122aligns vertically over the test switch368. A piezoelectric sounder374or other sound-generating component is located proximate the PCB366. One or more battery holder solder pins376also penetrate the PCB. An activation switch378interacts with an activation button380, which contacts an activation projection428(FIG. 7) on the patient attachment unit110.

FIG. 7depicts the patient attachment unit110andFIG. 8depicts the underside of the indicator unit120. The elements that allow for the connection and communication between both units110,120are described below. Indicator unit120has a contoured surface400that mates with a matching surface402of the patient attachment unit110. The surfaces may be of a undulating curved shape, as shown. Alternative embodiments may utilize crescent, linear, or other shaped surfaces. In another embodiment of the present invention, the contoured surface400of the indicator unit120may have a vertically-graded slope. The mating shapes of the leading surface400and the matching surface402assist in properly securing and aligning the indicator unit120to the patient attachment unit110and help prevent inadvertent detachment of the two units. Further, the complementary shapes of the contoured surface400and the matching surface402direct the indicator unit120to move in and out of a locking position, to connect and disconnect the indicator unit120from the patient attachment unit110while ensuring proper alignment of the operative components.

Proximate the matching surface402of the patient attachment unit110is a mating mounting platform404. Multiple apertures406,408, and410in the mounting platform404are configured to receive corresponding mating projections416,414,352extending from a bottom surface120bof the indicator unit120to secure the two units. The apertures406,408, and410may have a polygon, oblong, or other shape. Alternative configurations, shapes, and orientations of the apertures406,408,410and the mating projections416,414,352are contemplated. The wells362,364are formed in and are substantially coterminous with the bottom surface120bof the indicator unit120. In addition, a raised lip412circumscribes the well362and projects above the bottom surface120b. The well362and the lip412are oriented to substantially align with the sensor membrane302awhen the patient attachment unit110and indicator unit120are connected. The sensor membrane302ais substantially coterminous with the mating mounting platform404, and is the top surface of the pressure chamber302, described above. A pressure equalizing membrane426also may be substantially coterminous with the mating mounting platform404. The function of the pressure equalizing membrane426is described below. The activation projection428contacts the activation button380when the patient attachment unit110is connected to the indicator unit120.

Each of the projections416,414,352of the indicator unit120mate with the corresponding apertures406,408, and410of the patient attachment unit110to form the complete assembled fluid medicament delivery device100. Specifically, the guiding projection416mates with the guiding aperture406; the aligning projections414mate with the aligning apertures408; and the circular mating projections352mate with the asymmetrically oblong apertures410. Each mating pair has corresponding shapes and corresponding orientations to secure the indicator unit120to the patient attachment unit110. Each of the circular mating projection352includes an enlarged end352a, which is enlarged relative to an extension352bthat projects from the exposed bottom surface120bof the indicator unit120. The enlarged end352ais configured and sized to fit within the enlarged portion410aof aperture410. When completely installed, as described below, the extension352bis partially surrounded by a constricted portion410bof the oblong aperture410.

The patient attachment unit110and the indicator unit120may be secured to and detached from one another as depicted inFIGS. 9A-9D. First, from the initial position depicted inFIG. 9A, the indicator unit120is inverted (Step 1) such that the bottom surface120bis arranged substantially opposite the mounting platform404, as depicted inFIG. 9B. The indicator unit120is then placed (Step 2) in close proximity to the patient attachment unit110, such that the enlarged ends352aof the circular mating projections352are aligned with and pass through the enlarged portions410aof the apertures410. To completely secure the indicator unit120to the patient attachment unit110, the patient slides (Step 3) the indicator unit120in an chordal direction, so that the extensions352bof the mating projections352are located within the constricted portion410bof the apertures410. The enlarged ends352aprevent the indicator unit120from being inadvertently dislodged from the patient attachment unit110. To disconnect the indicator unit120from the patient attachment unit110, the patient slides (Step 4) the indicator unit120in a direction opposite the direction of Step3. Textured edge124may provide a gripping surface to facilitate this step. The enlarged ends352aare again aligned with the enlarged portions410aof the apertures410, and the two units110,120may be separated.

The indicator unit120may be disconnected from the patient attachment unit110in response to an occlusion event in the patent attachment unit110, or due to an electronics failure or low battery charge within the indicator unit120. Additionally, the two units110,120may be disconnected because insulin in the patient attachment unit110may be exhausted or functionally depleted after prolonged use. In general, this may occur after a period of time defined at least in part by the volume of the elastomer reservoir252or the amount of insulin introduced to the reservoir252during filling. In certain embodiments, the elastomer reservoir, when fully filled with insulin, may contain sufficient insulin to dispense as needed for about 24, about 48, about 72, or greater than about 72 hours. Other times are also contemplated, based on the type of medicament being delivered, elastomer reservoir size, delivery schedule, etc. The separate indicator unit120alerts the patient when insufficient levels of insulin remain in the patient attachment unit110. When the insulin supply in the elastomer reservoir252is exhausted or functionally depleted, the indicator unit120may be disconnected from the patient attachment unit110and the patient attachment unit110may be disposed of. Another patient attachment unit110may be obtained, filled with insulin and connected to the separate indicator unit120, which may be re-used as long as it has sufficient battery power. Alternatively, the exhausted or functionally depleted patient attachment unit110may be refilled via the fill port252.

Depicted inFIG. 10is a cross-sectional view of the assembled fluid medicament delivery device100, depicting a number of internal components, including the piezoelectric sounder374, the PCB366, the battery356, and the wells362,364. For clarify, many of the various conduits and components contained within the patient attachment unit110are not depicted. This figure is used to show the general mating relationship between the two units110,120. When the indicator unit120is secured to the patient attachment unit110, the bottom surface120bof the indicator unit120is in close proximity but slightly spaced from the mounting platform404, with the exception of the raised lip412of the well362. The raised lip412of the well362contacts the sensor membrane302aof the patient attachment unit110. In alternative embodiments, other portions of the bottom surface120bmay contact the mounting platform404. The pressure sensors266A,266B are mounted to the PCB366and disposed in the wells362,364, respectively. Each well is filled with a substance to transmit effectively pressure, for example, a solid resilient gel362a,364amanufactured of silicone gel, for example, as manufactured by Dow Corning Corporation as product no. 3-4241. In general, silicone gels having a shore hardness of about 60 Shore 00 will produce satisfactory results. Other gels may also be utilized. During manufacture, to prevent leakage of the gel at the interface of the PCB366and wall of the wells362,364, a portion of the gel362ais placed in each well362,364, and allowed to solidify. The remainder of the wells362,364is then completely filled with the gel362a, which is, in turn, allowed to harden. A meniscus422of the gel362ain the well362extends to the edge of the raised lip412. Accordingly, when the patient attachment unit110and the indicator unit120are connected, the meniscus422of the gel362acontacts the sensor membrane302a. The contact between the gel362aand sensor membrane302aallows both to move in relation to one another. As fluid pressure increases within the pressure chamber302, the sensor membrane302ais forced against the meniscus422. This pressure is transmitted through the gel362ato the sensor266A. In an alternative manufacturing process, the wells362may be inverted and filled from the underside, with the PCB366placed on the wells362prior to curing of the gel.

Also shown inFIG. 10is an ambient air channel420, which is formed when the indicator unit120is attached to the patient attachment unit110. Since the mounting platform404and the bottom surface120bare generally not in contact, ambient air pressure may be transmitted freely into an interstitial space420abetween the two units110,120. This exposes both a surface or meniscus424of the gel364ain the well364and the pressure equalizing membrane426to ambient air pressure P external to the device100. This allows the device100to sense changes in ambient air pressure, as described below.

FIG. 11depicts an enlarged inverted cross-sectional view of the well362. The pressure sensor266A is mounted on the PCB366at the base of the well362. As described above, the gel362ais filled to the edge of the raised lip412. Three dashed lines422A,422B, and422C illustrate the meniscus422of the gel362aaccording to various conditions. Line422A illustrates over-filling of the gel362a; line422B illustrates desired filling of the gel362a; line422C illustrates under-filling of the gel362a. When the gel362ais filled to the desired level (i.e., coplanar with the raised lip412) the meniscus422B is proximate with the sensor membrane302a, while transferring little or no force between the two elements. Force transmission remains minimal or nonexistent until fluid fills the pressure chamber302. The raised lip412minimizes the initial distance between the meniscus422B and the sensor membrane302a. If the gel362ahas been over-filled, the meniscus422A may exert force on the sensor membrane302a, which may lead to inaccurate sensing. If the gel362ahas been under-filled, the sensor membrane302amay not contact the meniscus422C, again leading to inaccurate sensing.

FIG. 12depicts a simplified, schematic view of the fluid medicament delivery device100to illustrate the interrelationships between, as well as the functionality of, the various components according to one embodiment of the device100. The patient attachment unit110includes a simplified, schematic version of the micro-fluidic circuit depicted inFIG. 3, contained within the housing110a. The flexible pressure equalizing membrane426is disposed within and substantially coterminous with the mounting platform404. The patient attachment unit110includes the reservoir252, for example, an elastomer bladder. The fill port254may be used to introduce insulin into the reservoir252. Insulin displaced from the reservoir252fills the basal flowpath262and the bolus flowpath264. Insulin flows through the bolus flowpath264and into the patient via the cannula282when the bolus button268is actuated. Insulin in the basal flowpath262flows through the pressure sensor chamber302, which includes a sensor membrane302a, which is substantially coterminous with the top portion of the mounting platform404of the patient attachment unit110. Insulin from the basal flowpath262and bolus flowpath264is introduced subcutaneously into the patient via the cannula282.

The simplified, schematic version of the indicator unit120includes the PCB366, which is powered by the battery352. The piezoelectric sounder374and/or a light, such as a LED, is connected to the PCB366. Also mounted on the PCB366are the pressure sensors266A,266B, which are each disposed in the wells362,364, respectively. The well364depicted on the right inFIG. 12includes the raised lip412. Each well362,364is filled with the gel362a,364a, such that the meniscus422,424is formed thereon.

When the indicator unit120is attached to the patient attachment unit110, the ambient air channel420and the interstitial space420ais formed therebetween. Note that the various connecting elements are not depicted. Both the meniscus424of the gel364aand the flexible pressure equalizing membrane426of the patient attachment unit110are exposed to the ambient pressure PAin the interstitial space420a.

As insulin in the basal flowpath262flows through the pressure sensor chamber302, when insulin pressure is greater than ambient pressure, the insulin in the filled pressure sensor chamber302will flex the sensor membrane302aoutwards. This outward deflection will, in turn, apply pressure to the meniscus422of the gel362a, thus transmitting that pressure to pressure sensor266A. The PCB366interprets the pressure increase and, if required, alerts the patient, e.g., via the piezoelectric sounder374and/or the light.

Changes in pressure conditions in the basal flowpath that may occur for at least several reasons: (1) due to an occlusion or partial occlusion downstream of the pressure sensor chamber302; (2) due to an occlusion or partial occlusion upstream of the pressure sensor chamber302; or (3) due to a pressure spike inherent in the last phase of contraction of the elastomer reservoir252. An occlusion or partial occlusion causes the basal flow to stop or partially stop. A pressure spike from the elastomer reservoir252occurs when the reservoir252is approaching the limit of the reservoir's ability to continue the flow of insulin. During contraction, the elastomer reservoir252maintains a substantially constant pressure on the insulin delivered via the basal flowpath262. However, as the reservoir252nears its fully contracted state, the wall applies move force to the insulin, temporarily increasing the pressure until the wall achieves a final rest condition and the insulin pressure equalizes with that of the subcutaneous pressure of the patient. These pressure relationships are described in more detail below.

The indicator unit120may be programmed to conduct a pressure reading periodically, for example, about every 30 minutes, to monitor the function of the fluid medicament delivery device100. This allows for low power consumption and provides for longer life of the battery352. Periodic pressure readings allow the indicator unit120to alert the patient to, and differentiate between, a change in fluid pressure caused by occlusions/partial occlusions and a change in fluid pressure caused by the last contraction phase of the elastomer reservoir252. As described in more detail below, the electronic components contained within the indicator unit120may determine that a change in pressure during the early operational life of the device100is due to an occlusion (e.g., a blocked cannula282). Further, the indicator unit120may determine that a change in pressure during the late stages of operation of the device100is due to the last contraction phase of the elastomer reservoir252. Regardless, upon detection of a pressure change of a predetermined threshold valve, the patient will be alerted that the device100is not working properly and that the patient attachment unit110needs to be replaced.

The fluid medicament delivery device100may operate properly in various external pressure environments, for example, while a patient is at sea-level, at elevated pressure conditions (i.e., below sea-level), and at decreased pressure conditions (i.e., above sea-level). Additionally, due to the functionality described below, the components contained within the indicator unit120are able to distinguish pressure changes caused by occlusions from those caused by changes in ambient pressure. The fluid medicament delivery device100will continue operating normally in various external pressure environments and, thus, alert the patient to changes in pressure that are only due to conditions that require attention to the device100(e.g., an occlusion, a partial occlusion, or a near-empty condition of the elastomer bladder252).

As described above, the indicator unit120includes two pressure sensors266A,266B that are both absolute pressure sensors. When the indicator unit120and patient attachment unit110are connected, the pressure sensor266B is exposed to ambient air pressure PA. Table 1 depicts known conditions for ambient pressure PA, subcutaneous (below the skin surface S) pressure PSof a human body, and reservoir pressure PR. These pressures are given at sea-level, 1 meter below sea-level, and 3000 meters above sea-level. As an initial matter, due to the presence of the pressure equalizing membrane426, the ambient pressure PAequals the device internal pressure PI. The human body is also pressurized relative to the ambient air pressure PA, such that the subcutaneous pressure Psof the human body may be calculated as a combination of the ambient pressure and about 10 mbar. The reservoir pressure PRexerted against the fluid contained therein may be calculated as the combination of the internal device pressure PIand about 820 mbar (i.e., the pressure exerted directly against the fluid by the elastomer bladder material). The pressure exerted by the elastomer bladder material may be greater than or less thank 820 mbar, depending on the material used.

Further, the fluid pressure PFis sensed at pressure sensor266A because the meniscus422of the gel362acontacts the sensor membrane302aof the pressure sensor chamber302through which the insulin flows. Table 2 depicts fluid pressures PFat sea-level, 1 meter below sea-level, and 3000 meters above sea-level. Under Normal (i.e., unblocked) conditions, the fluid pressure PFat the pressure sensor266A is the average of the subcutaneous pressure Psand the reservoir pressure PR. Table 2 also depicts fluid pressure PFat complete occlusion and partial occlusion (so-called “half-blocking”) conditions both upstream and downstream of the pressure sensor chamber302. Half-blocking conditions may occur when a flow channel or a flow restrictor has a partial occlusion, allowing passage of inclusion at only one-half of its rated flow rate.

Table 3 depicts pressure differentials ΔP at sea-level, 1 meter below sea-level, and 3000 meters above sea-level. Generally, a Normal pressure differential ΔP may be about 450 mbar +/−about 15%. In one embodiment, a pressure differential ΔP between fluid pressure PFand ambient pressure PAfrom about 344 mbar to about 517 mbar at, below, or above sea-level, is considered normal. A pressure differential ΔP below about 344 mbar is considered a first failure state, generally caused by an upstream (of the pressure sensor chamber302) occlusion, partial occlusion, or near-empty elastomer bladder condition. A pressure differential ΔP above about 517 mbar is considered a second failure state, generally caused by a downstream (of the pressure sensor chamber302) occlusion or partial occlusion. The uniform pressure differentials for each failure condition (i.e., upstream and downstream occlusion, upstream and downstream half-blocking) allow the device to differentiate between the various failure conditions. Information regarding the various failure conditions may be stored in the components within the indicator unit120, for later download to a computer for device-diagnostic or other purposes.

The pressure-equalizing membrane426allows the device to accurately sense pressures and analyze the various pressure conditions during operation, either at, above, or below sea-level. Consider a proposed insulin infusion device that lacks a pressure equalizing membrane (depicted as426inFIG. 12). Table 4 depicts known conditions for ambient pressure PA, internal device pressure PI, subcutaneous pressure PSof a human, and reservoir pressure PR. These pressures are given at sea-level, 1 meter below sea-level, and 3000 meters above sea-level. Since a pressure equalizing membrane is not utilized, the internal device pressure PIremains constant (in this case, at the environmental pressure at which the device was manufactured, e.g., sea-level). In certain devices, the internal pressure PImay be elevated, if the device was manufactured in a clean room, for example, which typically has a pressure higher than the ambient pressure of the location where the clean room is contained. Regardless, this constant internal pressure PIhas a direct effect on the reservoir pressure PR, as shown in Table 4.

Table 5 depicts fluid pressures PFat sea-level, 1 meter below sea-level, and 3000 meters above sea-level, for a device lacking a pressure-equalizing membrane. Fluid pressure PFat complete occlusion and partial occlusion conditions upstream and downstream of the pressure sensor chamber302are also depicted in Table 5.

Table 6 depicts pressure differentials ΔP at sea-level, 1 meter below sea-level, and 3000 meters above sea-level. As described above, a Normal pressure differential ΔP may be defined as about 450 mbar +/−about 15%. That is, a pressure differential ΔP from about 344 mbar to about 517 mbar at, below, or above sea-level is considered normal. A pressure differential ΔP below about 344 mbar is considered a first failure state; a pressure differential ΔP above about 517 mbar is considered a second failure state. The pressure differentials depicted in Table 6 show the advantages provided by a infusion device that includes a pressure-equalizing membrane, such as that used with the device described herein. Absence of the pressure equalizing membrane may cause at least three types of problems. First, pressure differentials under Normal (i.e., unblocked) conditions may register as a failure condition (where a failure condition is defined as a pressure differential in excess of 517 mbar). See, for example, the Normal condition pressure at 3000 meters altitude, which is an operational altitude for an airplane. In such a case, the device is operating normally, but the device interprets the pressure differential as a failure condition. The device would signal the patient that the device is not operating properly, which may cause the patient to remove and replace a device that is otherwise operating properly.

Second, a condition that should be interpreted as a failure condition may be overlooked. See, for example, the Upstream Half-blocking condition pressure at 3000 meters altitude. There, the pressure differential falls within the normal range of about 344 mbar to 517 mbar. Thus, the device would not alert the patient to a failure conditions, even though there is blockage within the fluid circuit. This may cause a serious medical condition. Third, as can be seen, the pressure differentials are not consistent across the same failure conditions, which would prevent the particular failure condition from being subsequently identified during diagnostics.

FIG. 13Adepicts a perspective view of a fluid medicament delivery device100in accordance with an embodiment of the invention.FIGS. 13B-13Cdepict a procedure for using the fluid medicament delivery device100. The fluid medicament delivery device100includes the patient attachment unit110and the separate indicator unit120. A housing for the cannula insertion device450and the bolus button268are disposed on the patient attachment unit110. An adhesive tape452for adhering the device100to the skin of a patient is disposed on the underside of the patient attachment unit110. A liner454is included to cover the adhesive tape452before the device100is attached to the patient.

The device100is first removed its packaging (Step500) which keeps the device100clean during storage and transport, prior to use. The separate indicator unit120is mounted to the patient attachment unit100(Step502), for example, in the manner described above and shown inFIGS. 9A-9C. To fill the device100with insulin (Step504), an insulin pen254ais connected to a fill port254on the underside of the patient attachment unit110. Insulin is then dispensed from the pen254ato fill the insulin reservoir (Step506). Once full, the insulin pen254ais disconnected from the device100and discarded (Step508). The liner454is then removed from the device100to expose the adhesive tape (Step510). The patient attachment unit100is then adhered to an appropriate portion of the patient's skin S (Step512). Acceptable locations include, but are not limited to, the abdominal area, the area above the buttocks, or the area proximate the triceps muscle. The patient then actuates the cannula insertion device450to insert the cannula into the body (Step514). The patient disconnects the housing of the cannula insertion device450from the patient attachment unit110(Step516). The device100is now operational and may be worn by the patient during normal, everyday activities. When the device100needs to be removed (either due to a failure state or depletion of insulin), the patient peels the device100from the skin S (Step518). As shown in Step520, the patient may then detach the indicator unit120from the patient attachment unit110, as described above with regard toFIG. 9D. The indicator unit120may then be attached to a new patient attachment unit110′. In this way, the comparatively more-expensive indicator unit120may be reused, while the less-expensive patient attachment unit110may be disposed of.

The various components utilized in the device described herein may be metal, glass, and/or any type of polymer suitable for sterilization and useful for delivering insulin or other medicaments subcutaneously. Polyurethane, polypropylene, PVC, PVDC, EVA, and others, are contemplated for use, as are stainless steel and other medical-grade metals. More specifically, medical-grade plastics may be utilized for the cannula itself, as well as other components that contact or otherwise penetrate the body of the patient. Needles and springs made from medical-grade stainless steel are also desirable, to prevent failure associated with use.

While there have been described herein what are to be considered exemplary and preferred embodiments of the present invention, other modifications of the invention will become apparent to those skilled in the art from the teachings herein without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive. The particular methods of manufacture and geometries disclosed herein are exemplary in nature and are not to be considered limiting. It is therefore desired to be secured in the appended claims all such modifications as fall within the spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent is the invention as defined and differentiated in the following claims, and all equivalents.