Abstract
The invention refers to a device for attachment to a portable liquid injection device, wherein said device is designed to enclose the drug reservoir of the injection device completely. Further, said device has at least one wave guide enabling a radio frequency wave to be applied along the drug reservoir of the injection device. In particular, the portable liquid injection device is a so-called insulin pen, i.e. a portable liquid injection device which is used to inject insulin for the treatment of diabetes. The inventive device preferably is in the form of a cap, in particular in the form of a cap of an insulin pen.
Claims
1. A device for attachment to a portable liquid injection device, in particular for attachment to a so-called insulin pen, wherein said device is designed to enclose the drug reservoir of the injection device completely, and wherein said device has at least one wave guide enabling a radio frequency wave, preferably with a wavelength larger than 1 mm to be travelling along an axis preferably a longitudinal axis of the drug reservoir.
2. The device according to claim 1, characterized in that the wave guide comprises a conductive surface, in particular a cylindrical conductive surface, wherein preferably the axis of said surface is provided to be parallel with a longitudinal axis of the injection device, in particular parallel with the longitudinal axis of an insulin pen.
3. The device according to claim 1, characterized in that at least one antenna is provided coupling a radio frequency wave into the wave guide and to measure real and imaginary components of transmission/reflectance of said wave.
4. The device according to claim 1, characterized in that the device is in the form of a sleeve or in the form of a cap, in particular in the form of a cap of an insulin pen.
5. The device according to claim 1, characterized in that the device is removable.
6. The device according to claim 1, characterized in that the device comprises an electric circuitry, to which inter alia the antennas are connected.
7. The device according to claim 1, characterized in that the device contains a radio wave generator and preferably a wave analyzer.
8. The device according to claim 1, characterized in that the device comprises at least one power source, in particular a battery.
9. The device according to claim 1, characterized in that the device comprises a transmission/reflectance measurement circuitry.
10. The device according to claim 1, characterized in that the device comprises a flexible printed circuit board (PCB), preferably a flexible PCB wound-up to a cylindrical shape.
11. The device according to claim 10, characterized in that said flexible PCB is adapted to a sleeve-like or a cap-like component, wherein preferably said flexible PCB is molded or mounted into said sleeve-like or cap-like component.
12. The device according to claim 1, characterized in that the device comprises at least one means for data processing and data transmission.
13. The device according to claim 1, characterized in that the device is designed to substitute at least one existing cap of an existing insulin pen.
14. A portable liquid injection device, in particular insulin pen, comprising a device according to claim 1, wherein preferably said device is attached to the injection device, in particular to the insulin pen.
Description
[0097] The drawings merely serve for illustration and better understanding of the invention and are not to be understood as in any way limiting the invention.
[0098] The figures schematically show:
[0099] FIG. 1 an insulin pen and its cap according to the state of the art,
[0100] FIG. 2 the drug reservoir of a portable liquid injection device with a cylindrical conductive surface integrated into the drug reservoir as a wave guide,
[0101] FIG. 3 a schematic representation of some transmission modes in cylindrical waveguides, and
[0102] FIG. 4 an insulin pen and its cap with keylock mechanism which can be implemented with an inventive device.
[0103] FIG. 5 the electric and magnetic field of a coaxial resonantor stub generated according to the invention,
[0104] FIG. 6 an embodiment with a radio wave generator coupled to a coaxial resonator stub,
[0105] FIG. 7 an inventive device acting as a transmission line stub with a length of the stub ,
[0106] FIG. 8 a display of reflection coefficient and phase shifts on a Smith Chart, and
[0107] FIG. 9 the relative reflected power spectrum in a S11 plot.
[0108] In FIG. 1, a typical insulin pen 1 according to the state of the art is shown. As mentioned earlier, an insulin pen is used to inject insulin for the treatment of diabetes. As is well-known, insulin is a hormone produced by the pancreas. It is important for regulating carbohydrate and fat metabolism in the body.
[0109] Insulin pen 1 according to FIG. 1 has a needle 2 at its one end and a button 3 for actuating the injection at the other end. Further, in FIG. 1, a dosage knob 4 and a dose window 5 are shown.
[0110] Further, insulin pen 1 has a drug reservoir 6 containing the insulin to be injected into the patient. It is the filling level/filling state of this drug reservoir which shall be monitored according to the present invention.
[0111] The insulin pen 1 according to FIG. 1 also has a cap 7 which is used according to the prior art to cover the part of the pen comprising the needle and the drug reservoir.
[0112] FIG. 2 shows an embodiment of a liquid injection device 11 (e.g. an insulin pen) in which a conductive layer acting as a wave guide 12 encloses a drug reservoir 13 which is at least partly filled with a drug 14 in liquid form with the drug solution 14 being the bulk of the dielectric material inside the wave guide (12).
[0113] According to FIG. 2 the waveguide 12 is in the form of a cylindrical conductive surface lining or coating the inner surface of the cylindrical device 11 and therefore enclosing the drug reservoir 13 completely. As explained earlier, said cylindrical conductive surface forming the waveguide 12 can be provided by a sleeve inserted or integrated into the device, preferably into the cap. The cylindrical conductive surface can also be provided by a coating or even by the inner surface of the device/cap itself. Preferably the conductive surface is made from a metal or a metal alloy.
[0114] Further, FIG. 2 shows an antenna 15 protruding into the device. This antenna 15 is coupled to a RF (radio frequency) transceiver (not shown in FIG. 2).
[0115] According to a preferred embodiment the radio wave emitted by the antenna 15 travels along the waveguide 12 and is fully reflected at opening 16 of the device 11 because of the impedance change. As a consequence, antenna 15 receives the reflected wave.
[0116] In another preferred embodiment, a second antenna (not shown in FIG. 2) is placed close to opening 16 inside the waveguide 12. Therefore, in those embodiments there are two antennas for emitting and/or receiving the radio wave(s).
[0117] In another preferred embodiment, only exemplified in this description of FIG. 2, a wavelength of the radio wave (RF wave) is chosen that lies about the cut-off wavelength (frequency) of the waveguide. In another preferred embodiment a wavelength is chosen corresponding to a TMx or TEx transfer mode.
[0118] In FIG. 3 some transmission modes in cylindrical waveguides are shown. In correspondence with the above definitions of TE waves and TM waves the electric (E) and magnetic (H) field lines are sketched.
[0119] Further, in FIG. 4 an insulin pen and its cap is shown in which a key-lock mechanism as already described above is implemented. Such a key-lock mechanism comprises two parts which match with each other or fit together like a key and its lock so that e.g. confounding two pens with different types of insulin is excluded. Such a key-lock mechanism can be implemented with all embodiments of the already described inventive device.
[0120] For the sake of simplicity the insulin pen and its cap have the same reference numbers as the insulin pen and its cap according to FIG. 1. As a consequence, FIG. 4 shows an insulin pen 1 and its cap 7, wherein insulin pen 1 has a needle 2 at its one end and a button 3 for actuating the injection at the other end. Further, in FIG. 4 a dosage knob 4 and a dose window 5 are shown. The drug reservoir of insulin pen 1 is shown with reference number 6.
[0121] According to FIG. 4 cap 7 has a characteristic form at its open end at the right side. This characteristic form 7 matches with the characteristic form of a ring or sleeve 8 which is permanently located on insulin pen 1. Only if the characteristic form of the open end of cap 7 fits into the corresponding characteristic form of sleeve 8 on cap 1, it is possible to attach cap 7 according to FIG. 4 on insulin pen 1 according to FIG. 4. If there is no fit or match, the user of the insulin cap will realize that he or she obviously uses the wrong cap for the corresponding insulin pen.
[0122] FIG. 5 shows the radial electric (solid lines) and magnetic (dashed circles) field in a coaxial stub or resonator, as explained earlier in the description with reference to FIG. 5.
[0123] FIG. 6 shows a radio wave generator (17) coupled to the coaxial resonator stub capacitively (18) and/or inductively using a coil (19), in a preferred embodiment a toroid shaped coil. At the end of the central water/drug solution cylinder, which is being formed by the sliding plunger (20) ejecting the drug solution (21), the impedance of said stub undergoes a strong discontinuity. This causes reflection of the radio wave. The wave analyzer (22) can now determine phase shift and/or resonance frequency and/or impedance changes. The data processing and transmission unit (23) controls the wave generator (17) and the wave analyzer (22), measuring the phase shift, transmittance, impedance, and reflection coefficient at either a single fixed wavelength or different variable wavelengths.
[0124] FIG. 7 shows a pen cap acting as a transmission line stub using a wavelength where the length of the stub is smaller or equal to a quarter of the wavelength. The electric component of the wave is plotted above the schematic drawing, showing both the emitted and reflected waves as well as the phase shift. FIG. 7 A shows a full injection pen, FIG. 7 B a partially emptied injection pen where the length of the stub is smaller or equal to a quarter of the wavelength. FIG. 7 C shows a full pen where the length of the stub is equal or larger than the wavelength.
[0125] FIG. 8 shows the reflection coefficient and the phase shifts for different lengths of the drug solution column plotted on a Smith chart.
[0126] FIG. 9 shows the relative reflected power spectrum in a S11 plot where the resonance frequencies are visibly changed by changes in the length of the water column thereby allowing determination of the remaining volume and dose in the pen.
