U.S. patent application number 13/148868 was filed with the patent office on 2012-04-26 for medical device and cartridge.
This patent application is currently assigned to NOVO NORDISK A/S. Invention is credited to Bo Erik Lennart Berggren, Henrik Rasmussen, Bodo von Munchow.
Application Number | 20120101470 13/148868 |
Document ID | / |
Family ID | 40902733 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120101470 |
Kind Code |
A1 |
Rasmussen; Henrik ; et
al. |
April 26, 2012 |
MEDICAL DEVICE AND CARTRIDGE
Abstract
A cartridge is engageable with a medical device, the cartridge
comprising an ordered arrangement of N electrical components (540)
each with different respective values of an electrical property,
and an ordered arrangement of N conductors (522, 524, 526) operably
coupled to the ordered arrangement of the N electrical components.
A medical device is arranged to receive a cartridge and comprises
for each of N conductors on the cartridge, at least a first
respective contact arranged to electrically couple with the
corresponding conductor when the cartridge is engaged with the
medical device; the medical device also comprises an evaluation
means operable to evaluate the different respective values of an
electrical property of N electrical components on the cartridge,
wherein the N electrical components form an ordered arrangement
which is operably coupled to the N conductors on the cartridge, and
a switching arrangement operable to selectively electrically couple
a respective pair of contacts to said evaluation means.
Inventors: |
Rasmussen; Henrik;
(Fredensborg, DK) ; Berggren; Bo Erik Lennart;
(Lund, SE) ; von Munchow; Bodo; (Lyngby,
DK) |
Assignee: |
NOVO NORDISK A/S
BAGSVAERD
DK
|
Family ID: |
40902733 |
Appl. No.: |
13/148868 |
Filed: |
February 12, 2010 |
PCT Filed: |
February 12, 2010 |
PCT NO: |
PCT/EP10/51804 |
371 Date: |
January 11, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61155174 |
Feb 25, 2009 |
|
|
|
Current U.S.
Class: |
604/404 ;
29/592.1; 40/299.01; 604/403 |
Current CPC
Class: |
A61M 5/24 20130101; A61M
2005/2492 20130101; A61M 5/31533 20130101; A61M 2005/2488 20130101;
A61M 2207/00 20130101; G06K 19/067 20130101; A61M 2205/6027
20130101; G09F 3/0291 20130101; A61M 5/31525 20130101; Y10T
29/49002 20150115 |
Class at
Publication: |
604/404 ;
40/299.01; 604/403; 29/592.1 |
International
Class: |
A61J 1/14 20060101
A61J001/14; H05K 13/00 20060101 H05K013/00; G09F 3/02 20060101
G09F003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2009 |
EP |
09152862.0 |
Claims
1. A cartridge engageable with a medical device, the cartridge
comprising: an ordered arrangement of N electrical components each
with different respective values of an electrical property; and an
ordered arrangement of N conductors operably coupled to the ordered
arrangement of the N electrical components.
2. A cartridge according to claim 1, wherein each of the N
components has a value of the electrical property selected from a
respective one of N non-overlapping sets of M possible values of
the electrical property.
3. A cartridge according to claim 2, wherein within the ordered
arrangement of N electrical components, the order of the N
electrical components is arranged with respect to the ordered
arrangement of N conductors to encode information.
4. A cartridge according to claim 1, wherein each of the N
components has a first electrical contact and a second electrical
contact; the first electrical contact of each of the N electrical
components share a common connection; and the second electrical
contact of each respective one of the N electrical components is
connected to a respective one of the N conductors.
5. A cartridge according to claim 1, wherein each of the N
components has a first electrical contact and a second electrical
contact; the first electrical contact of each respective one of the
N electrical components is connected to the second electrical
contact of a respective other of the N electrical components to
form N links; and each respective one of the N links is connected
to a respective one of the N conductors.
6. A cartridge according to claim 1, wherein the electrical
property is impedance.
7. A cartridge according to claim 1, wherein all of the N
electrical components are one selected from the list consisting of:
i. resistors; ii. capacitors; iii. inductors; and iv. diodes.
8. A cartridge according to claim 1, comprising a further conductor
separate to the ordered arrangement of N conductors and not
electrically coupled to the ordered arrangement of N electrical
components on the cartridge.
9. A cartridge according to claim 1, wherein the conductors and the
ordered arrangement of N electrical components are mounted on an
outer surface of the cartridge.
10. A cartridge according to claim 1, wherein the conductors and
the ordered arrangement of N electrical components are mounted on a
label; the label is affixed to an outer surface of the cartridge;
and the label extends around the cartridge and overlaps itself to
cover the ordered arrangement of N electrical components.
11. A cartridge according to claim 1, further comprising a
non-conductive protective layer applied over at least the N
conductors.
12. A label for attachment to a cartridge, the cartridge being
engageable with a medical device, the label comprising: an ordered
arrangement of N electrical components each with different
respective values of an electrical property; and an ordered
arrangement of N conductors operably coupled to the ordered
arrangement of the N electrical components.
13. A medical device arranged to receive a cartridge according to
claim 1, further comprising: for each of N conductors on the
cartridge, at least a first respective contact arranged to
electrically couple with the corresponding conductor when the
cartridge is engaged with the medical device; an evaluation means
operable to evaluate the different respective values of an
electrical property of N electrical components on the cartridge,
wherein the N electrical components form an ordered arrangement
which is operably coupled to the N conductors on the cartridge; and
a switching arrangement operable to selectively electrically couple
a respective pair of contacts to said evaluation means.
14. A medical device according to claim 13, wherein the switching
arrangement is operable to short-circuit all but one component that
is electrically in parallel with a first component currently
electrically coupled to said evaluation means.
15. A method of manufacturing a cartridge engageable with a medical
device, the method comprising: selecting a code, responsive to the
intended contents of the cartridge; selecting a respective one of M
possible values of an electrical property from each of N
non-overlapping sets; associating with the cartridge an ordered
arrangement of N electrical components operably coupled to an
ordered arrangement of N conductors, wherein each component
embodies a respective one of the selected values of the electrical
property; and selecting a particular order of the N electrical
components with respect to the ordered arrangement of N conductors,
wherein the selected of values of electrical properties together
with the selected order with respect to the N conductors of the N
electrical components embodying these values signify in combination
the selected code.
Description
[0001] The present invention relates to a medical device and
cartridge.
[0002] Many medical devices are arranged to use detachable
cartridges that carry consumable materials. These devices include
systems such as pumps, injectors and nebulisers that deliver
consumables such as anaesthetics, steroids or other drugs or fluids
to a patient.
[0003] Clearly, where a range of possible consumable materials is
available in similar cartridges (for example different
concentrations of a drug) it is important that a cartridge
including the appropriate consumable material for the situation is
used. Typically this is achieved by selection of the appropriate
cartridge by a qualified medical practitioner.
[0004] However, for patient-operated medical devices such as
personal insulin injection systems, such qualified medical
supervision is not regularly available and so use of the medical
device and the selection of suitable consumable materials for it
depends upon the patient themselves. Thus for example there is the
potential for a patient to administer the wrong type, or wrong
dose, of a drug into their body.
[0005] Prior art systems disclose mechanisms for marking such
cartridges so that the medical device can evaluate the cartridge's
content independently of the user. Such systems include barcodes on
the cartridges (U.S. Pat. No. 6,859,673); binary patterns encoded
by metallic or wirelessly inductive strips on the cartridge (U.S.
Pat. No. 6,110,152, WO0213133, WO1992017231 or WO2007107562), or
data represented by the value of one or more resistors (DE4020522,
U.S. Pat. No. 6,743,202).
[0006] However, for very small, lightweight and cheap medical
devices such as personal insulin injection systems, and similarly
for small, lightweight and cheap containers such as insulin
cartridges used by such personal insulin injections systems, the
prior art discloses mechanisms that are either overly complex,
require excessive space on the cartridge or are susceptible to
damage or contamination (for example by a spillage of insulin,
which is electrically conductive).
[0007] Therefore there is a requirement for an improved system
comprising a machine-identifiable cartridge for use with a medical
device.
[0008] In a first aspect, a cartridge is engageable with a medical
device, the cartridge comprising an ordered arrangement of N
electrical components each with different respective values of an
electrical property, and an ordered arrangement of N conductors
operably coupled to the ordered arrangement of the N electrical
components.
[0009] Such an ordered arrangement may take the form of a
topologically triangular or deltoid arrangement wherein each of the
N components has a first electrical contact and a second electrical
contact, the first electrical contact of each respective one of the
N electrical components being connected to the second electrical
contact of a respective other of the N electrical components to
form N links, and each respective one of the N links is connected
to a respective one of the N conductors.
[0010] In a specific form, the conductors and the ordered
arrangement of N electrical components are mounted on a label that
is affixed to an outer surface of the cartridge. The label may
extend around the cartridge so that it overlaps itself. The
conductors may be formed so as to extend around the cartridge
circumferentially. In some embodiments, the ordered arrangement of
N electrical components is positioned substantially at one end of
the ordered arrangement of N conductors. By forming the label to
overlap itself, a continuous or substantial continuos loop of
conductors may be formed so as to cover the ordered arrangement of
N electrical components. In embodiments where the number of N
electrical components are larger than two, this ensures that the
loop of conductors extend with no or only a slight gap in the
circumferential direction, without the need for making a multilayer
structure to provide the necessary connections to the N
components.
[0011] In another aspect, a medical device arranged to receive a
cartridge comprises for each of N conductors on the cartridge at
least a first respective contact arranged to electrically couple
with the corresponding conductor when the cartridge is engaged with
the medical device; the medical device also comprises an evaluation
means operable to evaluate the different respective values of an
electrical property of N electrical components on the cartridge,
wherein the N electrical components form an ordered arrangement
which is operably coupled to the N conductors on the cartridge, and
a switching arrangement operable to selectively electrically couple
a respective pair of contacts to said evaluation means.
[0012] In a further aspect, a method of manufacturing a cartridge
engageable with a medical device, comprising the steps of selecting
a code, responsive to the intended contents of the cartridge,
selecting a respective one of M possible values of an electrical
property from each of N non-overlapping sets, associating with the
cartridge an ordered arrangement of N electrical components
operably coupled to an ordered arrangement of N conductors, wherein
each component embodies a respective one of the selected values of
the electrical property, and selecting a particular order of the N
electrical components with respect to the ordered arrangement of N
conductors, wherein the selected of values of electrical properties
together with the selected order with respect to the N conductors
of the N electrical components embodying these values signify in
combination the selected code.
[0013] Further respective aspects and features of the invention are
defined in the appended claims.
[0014] Embodiments of the present invention will now be described
by way of example with reference to the accompanying drawings, in
which:
[0015] FIG. 1 is a schematic diagram of a medical device and a
cartridge in accordance with an embodiment of the present
invention.
[0016] FIGS. 2A and 2B are schematic diagrams of ordered
arrangements of components in accordance with embodiments of the
present invention.
[0017] FIG. 3 is a schematic diagram of a labelled cartridge in
accordance with an embodiment of the present invention.
[0018] FIGS. 4A, 4B and 4C are schematic diagrams of electrical
contact engagement means in accordance with embodiments of the
present invention.
[0019] FIG. 5 is a schematic diagram of a switching arrangement in
accordance with an embodiment of the present invention.
[0020] FIG. 6 is a schematic diagram of an oscillator circuit in
accordance with an embodiment of the present invention.
[0021] FIG. 7 is a flow diagram of a method of manufacture of a
cartridge in accordance with an embodiment of the present
invention.
[0022] A medical device and cartridge are disclosed. In the
following description, a number of specific details are presented
in order to provide a thorough understanding of the embodiments of
the present invention. It will be apparent, however, to a person
skilled in the art that these specific details need not be employed
to practise the present invention. Conversely, specific details
known to the person skilled in the art are omitted for the purposes
of clarity where appropriate.
[0023] As a non-limiting example, a summary embodiment of the
present invention comprises a pen-style personal insulin injector
arranged to receive a pre-filled medicament cartridge, attached to
which are three resistors, a first contact of each sharing a common
connection and the second contact of each being connected to a
respective conductive strip. The conductive strips are accessible
by the injector when the cartridge is properly engaged with it.
Each resistor is chosen to have a resistance value selected from a
respective one of three non-overlapping sets of possible values, so
that each resistor has a different value and that value is unique
to its respective set. The selection of a value from a set is used
to encode information relating to the contents of the cartridge.
Likewise, the placement of each resistor within an ordered
arrangement (for example, which resistor is connected to which
conductive strip) is also chosen to convey information relating to
the contents of the cartridge, as the use of distinct values from
non-overlapping sets enables the relative positions of each
resistor with respect to the conducting strips to be evaluated.
[0024] In this way a robust encoding of information about the
contents of the cartridge can be conveyed in a compact manner.
Complementary measures to mitigate against contamination include a
non-conductive protective layer over the conductors that is
punctured by contacts in the injector when the cartridge is
engaged, an exposed conductor not connected to the components that
indicates contamination if a subsequent electrical connection is
found, and the use of components with complex impedance
(resistance) such as capacitors, whose complex impedance is
measured at an oscillating frequency where the electrical
properties of the presumed contaminant (here, insulin) are less
likely to affect measurement.
[0025] Referring now to FIG. 1, in an embodiment of the present
invention a medical device in the form of a personal insulin
injector 100 comprises a main body 120 housing a dosing mechanism
(not shown), a dose setting interface 122, and a user interface 124
for displaying information such as the currently set dosage.
[0026] The injector also comprises a detachable cartridge holder
130, into which a cartridge 150 may be inserted. The holder is then
engaged with the injector housing, causing the cartridge to be
engaged with the injector dosing mechanism of the injector. The
cartridge 150 may be of the so-called `plunger` type illustrated in
FIG. 1, or may equally be a flexible or collapsible reservoir or
any other suitable form.
[0027] A needle assembly 140 may then be attached to the cartridge
and holder by the screw thread 154 of the cartridge, causing a
rear-facing end of the needle to puncture a sealed aperture in the
cartridge, thereby enabling a flow of insulin into the needle under
the control of the dosing mechanism.
[0028] In addition, the cartridge comprises an encoding circuit 152
that embodies a code that can be evaluated by the injector.
[0029] Referring now to FIGS. 2A and 2B, the encoding circuit
comprises an ordered arrangement 540A, 540B of three electrical
components (A, B and C), each having a particular and different
value of an electrical property such as impedance (or complex
impedance). Possible components include resistors, capacitors
and/or inductances, or diodes (which have non-linear
impedance).
[0030] FIG. 2A shows the three components arranged in a so-called
`star` configuration, in which one contact of each component shares
a common connection.
[0031] FIG. 2B show the three components arranged in a polygonal
(here triangular) configuration, in which a first contact of each
component is connected to the second contact of one of the other
components to form a closed chain.
[0032] In both configurations, three conductor strips (522, 524 and
526) are electrically coupled to the arrangement of components. In
the star configuration, each conductor strip connects to the free
contact of a respective component. In the triangular configuration,
each conductor strip connects to a respective link between the
first and second contacts of a pair of components. The conducting
strips then typically form an ordered sequence of rings around some
or all of the circumference of the cartridge 150.
[0033] Advantageously, this arrangement avoids the use of a common
or ground conductor, thereby reducing the number of conductors
required and hence both costs and the risk of such a common
conductor becoming contaminated and compromising measurements of
all the component values.
[0034] Data is encoded using the components in the following
manner. Each of the three components (A, B and C) has a particular
value of an electrical property that is selected from a respective
one of three sets of possible values, and these sets do not
overlap. As a non-limiting example, possible values of impedance
may be as given as follows in Table 1:
TABLE-US-00001 TABLE 1 Three non-overlapping sets of three possible
impedance values Component A B C Value 1 (Ohms) 100 400 1600 Value
2 (Ohms) 200 800 3200 Value 3 (Ohms) 300 1200 4800
[0035] This gives 3.sup.3=27 possible unique combinations of values
for the arrangements of A, B and C seen in FIG. 2A or 2B.
[0036] Notably, the possible values held by the components A, B or
C are uniquely characteristic of those components (or the value
sets with which the components are associated).
[0037] Consequently, therefore, the order in which the components
are arranged with respect to the conductor strips (522, 524 and
526) can also be uniquely identified. For example, using successive
conductor strips on a cartridge to test the impedances may result
in values 100, 800, 1600 being evaluated (using example values from
Table 1), meaning the components are arranged as A, B and C with
respect to the conductors (for example as seen in FIGS. 2A and 2B).
Meanwhile, testing of a different cartridge in the same way may
result in values 800, 100, 1600, meaning the components are
arranged as B, A and C with respect to the conductors.
[0038] Therefore the ordering of the components A, B and C with
respect to the series of conducting strips can also be used to
convey information. For three components, the respective order can
be rotated three ways: (A, B, C), (C, A, B), (B, C, A), and these
rotations can also be mirrored: (C, B, A), (B, A, C), (A, C,
B).
[0039] The total number of possible unique combinations with
respect to a fixed set of conductors for three components is
therefore 27.times.6 or 162.
[0040] More generally, the set of six arrangements of A, B and C
above are achieved by swapping successive pairs of components with
respect to the three conductors, as follows:
##STR00001##
[0041] This approach may then be generalised to more than N=3
components. For example, in the case of four components (A, B, C,
D) in a star or square formation analogous to those in FIGS. 2A and
2B, with a corresponding four sets of non-overlapping values and
four conductors, a total of 24 unique orderings with respect to the
four conductors can be generated by successively swapping pairs of
components in the above fashion. Notably, for four non-overlapping
sets each of three values, there are 3.sup.4=81 possible unique
combinations of values for any one arrangement of components A, B,
C and D. Therefore the total number of possible unique combinations
is 81.times.24=1,944.
[0042] It will be appreciated that optionally more than M=3
electrical property values may be available in each set, thereby
further increasing the possible number of unique combinations.
[0043] Alternatively, fewer values may be used. Using fewer values
simplifies evaluation, reduces requirements for component value
tolerance and measurement accuracy, and/or improves robustness to
contamination. For example, using four components with four
non-overlapping sets each only having two possible electrical
property values (e.g. as shown in the non-limiting example of Table
2 below), then there are 2.sup.4=16.times.24=384 unique
combinations.
TABLE-US-00002 TABLE 2 N = 4 non-overlapping sets of M = 2 possible
impedance values Component A B C D Value 1 (Ohms) 100 400 1200 3200
Value 2 (Ohms) 200 800 1600 4800
[0044] In addition, it will be appreciated that unlike a system
where each component may take any value from a single, larger set
of possible values (for example where components A, B, C and D
could each take any one of the eight values shown in Table 2,
thereby giving 576 possible combinations), in embodiments of the
present invention if one component value (or values for a pair of
components) are affected by contamination, then identification of
the other component values provides information about the
contaminated component values by a process of elimination (e.g. if
values 800, 1200 and 4800 are read accurately, then the final
reading must either correspond to 100 or 200 for component A). This
assists any attempt to resolve the value of the contaminated
component, thereby making the code more robust to
contamination.
[0045] Robustness may be further improved by the use of a redundant
coding scheme. For example, in the case of the above arrangement of
four components seen in Table 2, the values of components A and C
may be correlated, as may those of B and D. In this way if any one
component is compromised and returns a value outside the expected
range of its set, the information is still available from the
corresponding other component. The correlation of non-adjacent
components (and by extension, non-adjacent conductors) reduces the
risk of a contaminating spillage compromising both components or
conductors of a correlated pair.
[0046] It will be appreciated that other coding schemes may also be
apparent to the person skilled in the art.
[0047] Referring now to FIG. 3, in an embodiment of the present
invention an ordered arrangement of components 540 (encompassing a
star arrangement 540A or a polygonal arrangement such as a triangle
or square 540B) is mounted on (e.g. affixed to) a label 510 using
known techniques is and is appropriately connected to an ordered
arrangement of conductors (522, 524, 526) that extend across the
width of the label.
[0048] Optionally, the width of the label is such that it is
greater than the circumference of the cartridge, so that when the
label is wrapped around the cartridge an overlapping portion
extends to cover the components and their connections to the
conductor strips, thereby providing a degree of protection to the
components from contamination or damage due to handling. This
configuration has the additional benefit that the conducting strips
then substantially encircle the cartridge, thereby removing the
requirement for rotational alignment of the cartridge with
electrical contacts in the medical device.
[0049] Alternatively, if the label does not overlap then the
components may be covered by a non-conductive protective layer, and
the conductors then also extended over this layer, thereby again
substantially encircling the cartridge to the extent that the label
encircles it. In this case connections to the conductors would be
provided that extend out from under the protective layer to connect
the components to the conductive strip.
[0050] Alternatively or in addition, the arrangement of components
540 may all be clustered, grouped or otherwise positioned at or
near one end of the conductor strips, so that only a small
proportion of the circumference of the cartridge corresponding to
the components does not feature the conductors, as seen in FIG.
3.
[0051] It will be appreciated that consequently in an embodiment of
the present invention the label 510 alone, comprising the encoding
circuitry and conductors, may be provided separately to
conventional cartridges, and only subsequently applied to such
cartridges for example at a packaging plant at a later date.
[0052] Alternatively, the components and/or the conductors can be
mounted (e.g. affixed) directly on the cartridge in a similar
manner, again using known techniques. In this case again the
components may be clustered at or near one end of the conductor
strips, or may be covered by a protective layer over which the
conductors extend.
[0053] In the case of mounting the circuitry and conductors on
either the label or directly on the cartridge, in an embodiment of
the present invention the components may be discrete components or
may be part of an integrated circuit, or may be printed onto the
label or cartridge (for example using resistive inks).
[0054] Likewise in the case of mounting the circuitry and
conductors on either the label or directly on the cartridge, in an
embodiment of the present invention a non-conductive protective
layer or coating is then applied over the conductors, and
optionally over the components. The coating serves to shield the
conductors (and optionally components) from electrically conductive
contamination such as a spillage of insulin forming a connection
between two conductors and thereby affecting the measurement of the
electrical properties of the components. In use, the corresponding
measurement reading contacts in the medical device push or scrape
through this layer to make electrical contact as the cartridge is
engaged with the medical device, as explained later herein.
[0055] In an embodiment of the present invention, an additional
so-called `verification conductor` is provided that is not
electrically coupled to the ordered arrangement of components, and
is not covered by a protective layer. In the medical device an
additional corresponding contact is also provided. The medical
device can then determine whether there is any electrical
connection between the additional contact and any of the
measurement reading contacts in the medical device, thereby
indicating whether a conductive contaminant may be on the surface
of the cartridge or have impregnated the label, if present.
[0056] The medical device can then alert the user and/or prevent
full engagement of the cartridge (for example by actuation of a
blocking mechanism), enabling the user to remove the cartridge and
attempt to clean off the contaminant.
[0057] Notably, in the case that the other conductors corresponding
to the ordered arrangement of components are covered by a
protective coating, such an electrical connection can be arranged
to occur before the contacts of the medical device puncture the
coating (as the contaminant will lie upon the coating), thereby
allowing detection and removal of the contaminant before the
protection of the coating is compromised.
[0058] In the medical device, measurement reading contacts are
aligned to correspond with the conductors on the cartridge and make
an electrical connection when the cartridge is engaged.
[0059] As noted previously, in the case that the conductors
connected to the ordered arrangement of components are covered by a
protective layer, the corresponding measurement reading contacts
push through the protective layer to make electrical contact.
[0060] Referring now to FIG. 4A, where during engagement of the
cartridge the motion of the cartridge holder retaining the
cartridge is primarily axial with respect to the aperture that
receives the cartridge, a bridging contact 470' mounted on the
holder (similar, for example, to a relay contact) is arranged to
encounter a protrusion 472' in the body of the medical device as
the holder is pushed into place, so forcing the bridging contact
470' through the protective layer (not shown) to the conductor 526
below. The protrusion 472' comprises the measurement reading
electrical contact, thereby making electrical contact with the
conductor on the cartridge 150 via the bridging contact 470'. It
will be appreciated that only one contact arrangement is shown in
FIG. 4A for the purposes of clarity, and is not limiting.
[0061] Referring now to FIG. 4B, where during engagement of the
cartridge the motion of the cartridge holder retaining the
cartridge is primarily rotational with respect to the aperture that
receives the cartridge, a bridging contact 470'' within the
cartridge holder (such as, for example, a circle or arc of wire
that has protrusions towards and away from the cartridge 150) is
arranged to encounter a protrusion 472'' in the body of the medical
device as the holder is rotated, so forcing a portion of the
bridging contact 470'' through the protective layer (not shown) to
the conductor 526 below. The protrusion 472'' comprises the
measurement reading electrical contact, thereby making electrical
contact with the conductor of the cartridge 150 via the bridging
contact 470''. It will be appreciated that only one contact
arrangement is shown in FIG. 4B for the purposes of clarity and is
not limiting.
[0062] Alternatively, in a medical device that does not use a
cartridge holder or where it is undesirable to use bridging
contacts, other mechanisms to drive the measurement reading
contacts thought the protective coating on the conductor strips of
the cartridge will be apparent to the person skilled in the
art.
[0063] For example referring now to FIG. 4C, a measurement reading
contact 474 is pivotally mounted within the medical device such
that axial engagement of the cartridge with the medical device
forces the measurement reading contact 474 through the protective
layer (not shown) to the conductor 526 below. It will be
appreciated again that only one contact arrangement is shown in
FIG. 4C for the purposes of clarity and is not limiting.
[0064] In a conventional system that used a common ground
connection, the electrical property of each component would be
determined by switchably selecting between the components
individually and measuring with respect to the ground connection.
However to mitigate against contamination or damage to such a
ground connection, in embodiments of the present invention there is
no such common ground connection. As a result the values of the
components must be evaluated by measuring components in
combination.
[0065] Referring back to FIG. 2A, and using impedance as a
non-limiting example, sequential measurements of impedance between
conductors 522 and 524, 524 and 526, and finally 526 and 522 result
in measurement of the series impedances of components A+B, B+C and
C+A. Since impedances in series add together it is possible to
calculate from these three measurements the individual impedances
of components A, B and C.
[0066] Similarly, referring back to FIG. 2B, and again using
impedance as a non-limiting example of electrical property,
sequential measurements of impedance between conductors 522 and
524, 524 and 526, and finally 526 and 522 result in measurement of
the impedance of component A in parallel with the series impedance
of components B+C (i.e. A.parallel.(B+C)), then B.parallel.(C+A)
and finally C.parallel.(A+B). Again in principle these values can
then be used to calculate the individual values of A, B and C.
[0067] Referring now to FIG. 5, this second calculation can be
simplified by a switching arrangement that short-circuits one of
the impedances in the series. For example, by closing switches
SW.sub.2 and SW.sub.3, component C is short circuited, and a
measurement of A.parallel.B can then be made by closing (i.e.
measuring across) switches SW.sub.4 and SW.sub.5 (or alternatively
by measuring across switches SW.sub.5 and SW.sub.6, which gives the
commutative and hence equivalent measurement B.parallel.A).
Measurement of B.parallel.C is achieved by closing switches
SW.sub.1 and SW.sub.2 to short circuit component A and measuring
across switches SW.sub.5 and SW.sub.6 or SW.sub.4 and SW.sub.6,
whilst C.parallel.A can be measured by closing switches SW.sub.1
and SW.sub.3 to short circuit component B and measuring across
switches SW.sub.4 and SW.sub.5 or SW.sub.4 and SW.sub.6. From the
measured values of A.parallel.B, B.parallel.C and C.parallel.A, the
individual values of A, B and C can be calculated.
[0068] This simplified calculation is less sensitive to component
tolerances and measurement accuracy, and hence also to any residual
contamination.
[0069] In addition, because each combined component value
(A.parallel.B, etc) can be measured using two possible switch
combinations, contamination between adjacent conductors can be
mitigated by using the alternatively available pair of switches
(and hence alternative pair of conductors). Such contamination can
be inferred, for example, if the difference between a measured
value and each of the possible values in the corresponding value
set falls outside a preset tolerance.
[0070] It will be appreciated that the above switching arrangement
can be extended to four or more components, and so more generally
measures values in a triangular, square or other polygonal
arrangement of components by measuring across switches connected
across a first component whilst short-circuiting all other
components except a predetermined one in a series that is parallel
to that first component.
[0071] Referring now to FIG. 6, in an embodiment of the present
invention the components used have complex impedances (for example
capacitors or inductors, rather than resistors). To measure the
impedances (for example in the form of A.parallel.B, as described
above), each component is connected to an electronic integrator
(U1)/comparator (U2) circuit, so forming an oscillator as seen in
FIG. 6.
[0072] In FIG. 6 the generated frequency is determined primarily by
resistor R.sub.4 and the combined capacitor presented to the
circuit by the switching arrangement C.sub.XY (such as, for
example, A.parallel.B). R.sub.KX (is the comparatively small
contact resistance, whilst C.sub.PXY and R.sub.PXY are the
capacitive and resistive characteristics of any contaminants.
[0073] Notably, the dielectric properties of insulin (a likely
contaminant) are not constant with frequency. Therefore by careful
selection of the value of resistor R4 and optionally of the values
in the N non-overlapping value sets used by the N components, a
suitable range of resultant frequencies can be generated that occur
where the dielectric properties of the insulin (or other cartridge
payload if applicable) are substantially at their lowest, so
further mitigating against the effects of contamination.
[0074] The frequencies so generated are measured at point P in FIG.
6, and may then be used to determine the presented combined
component value (such as A.parallel.B), and from a plurality of
such measurements in sequence the individuals values of A, B C, etc
can be obtained.
[0075] It will be appreciated that a similar measurement scheme may
be used for the case where the electrical property of the
components is itself a resonant or natural oscillating frequency.
For example, the components may comprise crystals (such a quartz or
another suitable piezoelectric crystal), each with a tuned
frequency, or alternatively or in addition component pairs such as
resistor/capacitor or inductor/capacitor giving rise to a natural
oscillating frequency. In this latter case such frequency
generating circuits may be treated as a single functional component
for the purposes of the coding scheme described herein.
[0076] The information provided by the codes may vary in quantity
and type. In the previous example herein of table 1, where three
components and three associated non-overlapping sets each comprise
three possible electrical property values, the total number of
possible unique arrangements was 162. As a non-limiting example, a
1:1 redundancy in the coding may be applied (for example using
component value correlation, as described previously), resulting in
81 usable codes.
[0077] 64 of these codes may then be interpreted for example as a
set of five binary flags, indicating the type of insulin and its
concentration. Alternatively each code may be related to a look-up
table held in a memory of the medical device, for example by using
the code as part of a memory address, to give up to 81 different
species of cartridge payload.
[0078] Finally, the medical device can act upon the information
obtained using the code and inform the user of the species of
payload within the cartridge. This may take the form of any
suitable user interface, including alphanumeric text or an
indicator light on the device, or wireless communication to a base
unit, etc. Optionally the medical device may also evaluate whether
the payload satisfies a usage condition; for example whether the
payload has passed a sell-by date, or is the wrong concentration or
type for the time of day or for a sequenced drug regime managed by
the device. If the evaluation indicates that the payload is
inapplicable, it may communicate a warning to the user via a
suitable user interface, and/or may prevent administration of the
payload to the user or require an explicit override from the user
to do so.
[0079] Referring now to FIG. 7, a method of manufacturing a
cartridge engageable with a medical device comprises: [0080] in a
first step (10), selecting a code, responsive to the intended
contents of the cartridge; [0081] in a second step (20), selecting
a respective one of M possible values of an electrical property
from each of N non-overlapping sets; [0082] in a third step (30),
associating with the cartridge an ordered arrangement of N
electrical components operably coupled to an ordered arrangement of
N conductors, wherein each component embodies a respective one of
the selected values of the electrical property; and [0083] in a
fourth step (40), selecting a particular order of the N electrical
components with respect to the ordered arrangement of N conductors,
wherein [0084] the selected of values of electrical properties
together with the selected order with respect to the N conductors
of the N electrical components embodying these values signify in
combination the selected code.
[0085] It will be apparent to a person skilled in the art that
variations in the above method corresponding to manufacture of the
various embodiments of the apparatus described above are considered
within the scope of the present invention, including but not
limited to: [0086] i. the components being arranged in a star or
polygon topology; [0087] ii. the arrangement of components being
positioned substantially at one end of the arrangement of
conductors; [0088] iii. the electrical property being impedance;
[0089] iv. the components used being one of resistors, capacitors,
inductors, diodes or any component suitable to embody a specific
value of the chosen electrical property; [0090] v. coating the
conductors in an insulating, non-porous layer; [0091] vi. including
a further conductor to detect contamination; [0092] vii.
associating the components and conductors with the cartridge by use
of glue or other fixing means, or alternatively [0093] viii.
mounting the components and conductors on a label, and in this
latter case [0094] ix. associating the components and conductors
with the cartridge by affixing the label to the cartridge as a
further step of manufacture, optionally so that the label overlaps
itself to protect the (suitably positioned) components.
[0095] It will be appreciated that the apparatus disclosed herein
may operate in part using conventional hardware suitably adapted as
applicable by software instruction or by the inclusion or
substitution of dedicated hardware.
[0096] Thus the required adaptation to existing parts of a
conventional equivalent device may be implemented in the form of a
computer program product comprising processor implementable
instructions stored on a data carrier such as a floppy disk,
optical disk, hard disk, PROM, RAM, flash memory or any combination
of these or other storage media, or transmitted via data signals on
a network such as an Ethernet, a wireless network, the Internet, or
any combination of these of other networks, or realised in hardware
as an ASIC (application specific integrated circuit) or an FPGA
(field programmable gate array) or other configurable circuit
suitable to use in adapting the conventional equivalent device.
* * * * *