Patent Application
20150202385
The present invention relates generally to infusion pumps for controlled delivery of liquid food and medications to patients. More specifically, the present invention relates to a sensor system in an infusion pump for detecting the presence or absence of a cassette by which an administration tubing set is operatively connected to the pump.
Programmable infusion pumps are used to carry out controlled delivery of liquid food for enteral feeding and medications for various purposes, for example pain management. In a common arrangement, an infusion pump receives a disposable administration set comprising a cassette removably received by the pump and flexible tubing connected to the cassette for providing a fluid delivery path through the pump.
The cassette itself may be intended for use with a particular infusion pump model or models, and/or with tubing having predetermined properties. In this regard, the cassette may include safety features that are designed and manufactured according to specifications determined at least in part by the intended infusion pump model and/or administration set tubing. The safety features of the cassette may cooperate with corresponding features on the matching pump, and may be manufactured according to size tolerances related to tubing diameter and flexibility. For example, the cassette may have an anti-free flow mechanism for protecting the patient from uncontrolled fluid delivery. The anti-free flow mechanism may take the form of an external pinch clip occluder actuated when the cassette is properly loaded in the pump and a door of the pump is closed. Alternatively, the anti-free flow mechanism may take the form of an internal “in-line occluder” that resides within the flow passage of the tubing, wherein a flow passage is only opened when the cassette is properly loaded in the pump and the pump door is closed.
The cassette may provide additional safety features beyond free flow protection. For example, the cassette may be matched to the pump to maintain a desired volumetric accuracy of the pump, and to ensure correct function of occlusion and air-in-line sensors used to trigger safety alarms.
In view of the safety importance of the cassette, it is desirable to provide means to detect whether or not a matching cassette is properly loaded in the pump as a precondition to enabling pump operation.
In accordance with the present invention, an infusion pump in which an administration set is removably received is provided with an optical detection system for determining whether or not a cassette of the administration set is properly loaded in the pump. In an embodiment of the present invention, operation of the pump is disabled if a cassette is not properly loaded in the pump.
The optical cassette detection system generally comprises an optical emitter and a corresponding photosensitive detector each mounted to the pump, and a window carried by the cassette that includes at least one fluorophore. The optical emitter is arranged to emit an excitation light beam directed along an optical axis, wherein the excitation light beam is in an excitation wavelength band chosen to excite the at least one fluorophore in the window. The window intersects the optical axis at a location between the optical emitter and the photosensitive detector when the cassette is properly loaded in the pump so that the at least one fluorophore is exposed to the excitation light beam and emits light in an emission wavelength band distinct from the excitation wavelength band. The photosensitive detector is arranged along the optical axis to receive light in the emission wavelength band exiting the window. The photosensitive detector is configured to detect light within the emission wavelength band, and generates a detector signal representing an intensity of light in the emission wavelength band which it receives.
The detector signal is evaluated by signal evaluation electronics to determine if the detector signal level is above a predetermined threshold, indicating that a cassette is properly loaded in the pump. The signal evaluation electronics may be in communication with a pump controller, wherein the pump controller is programmed to disable pump operation unless a cassette is loaded as determined by the optical cassette detection system.
In an embodiment of the invention, the window includes a light entry surface and a light exit surface parallel to the light entry surface, and the window is integrally formed with the cassette in a one-piece molded part made of transparent plastic or translucent plastic that is doped with one or more fluorophores.
The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:
In the illustrated embodiment, pump 10 is a rotary peristaltic pump having a rotor 30, wherein pumping segment 28 is wrapped around rotor 30 and is engaged by angularly spaced rollers on rotor 30 as the rotor rotates to provide peristaltic pumping action forcing liquid through the tubing of administration set 12. As may be understood by reference to
Cassette 14 may include an in-line occluder 32 which may be incorporated into downstream loop connector 20. In-line occluder 32 prevents flow when pump door 34 is open. An actuator 36 on an underside of pump door 34 engages pumping segment 28 in a manner which opens a flow path around occluder 32 when door 34 is closed.
Reference is now made to
Pump 10 includes an optical cassette detection system 50 operable to detect whether or not cassette 14 is properly loaded in pump 10 with cassette tab 38 present in slot 42. Cassette detection system 50 includes an optical emitter 52, which may be mounted to pump 10 on one side of slot 42, and a photosensitive detector 54, which may be mounted to pump 10 on an opposite side of slot 42. In the illustrated embodiment, detector 54 is aligned with emitter 52 along an optical axis 58 passing through slot 42, however detector 54 may be arranged so that it is not aligned with emitter 52 along optical axis 58. Cassette detection system 50 further includes a window 55 carried by cassette 14. Window 55 is arranged on cassette 14 to intersect optical axis 58 at a location between optical emitter 52 and photosensitive detector 54 when cassette 14 is properly loaded in pump 10. Cassette detection system 50 may also include signal processing electronics 56 connected to photosensitive detector 54 for receiving an electronic signal generated by detector 54 and evaluating the signal. Signal processing electronics 56 may be in communication with a pump controller 60, whereby operation of pump 10 may be controlled based on an evaluation of the detector signal.
In accordance with the present invention, window 55 includes at least one fluorophore 59, and optical emitter 52 is arranged to emit an excitation light beam directed along optical axis 58. The excitation light beam is in an excitation wavelength band chosen to excite the fluorophore(s) 59, whereby the fluorophore(s) emit light in an emission wavelength band distinct from the excitation wavelength band in response to absorption of excitation beam energy. In the present specification, reference to the emission wavelength band being “distinct from” the excitation wavelength band means that the emission wavelength band and the excitation wavelength band are respectively centered about two different wavelengths that are distinguishable from one another. Emitter 52 may be a light-emitting diode (LED) or other light source. Emitter 52 may be a narrow band emitter, for example a laser LED, emitting light in the excitation wavelength band. Alternatively, emitter 52 may emit light in a relatively wide wavelength band, and a wavelength filter (no shown) may be arranged after the emitter to filter the light by passing only light in the excitation wavelength band.
Photosensitive detector 54 may be configured to detect light within the emission wavelength band. For example, detector 54 may have a spectral responsivity that is substantially confined to the emission wavelength band or some spectral portion thereof, and that drops off significantly for the excitation wavelength band. Alternatively, or in addition, detector 54 may be configured with a wavelength filter (not shown) that filters out light in the excitation wavelength band and passes light in the emission wavelength band or in some portion of the emission wavelength band for detection. Photosensitive detector 54 generates a detector signal, for example a current or voltage signal, having a level corresponding to the intensity of light in the emission wavelength band received by the detector. Photosensitive detector 54 may be a photodiode or other photosensitive element capable of generating an electrical signal in response to incident light.
In the embodiment shown herein, emitter 52 and photosensitive detector 54 are each mounted in pump 10 adjacent to slot 42, and window 55 is part of tab 38, however other configurations and arrangements are possible. While not shown, emitter 52 and detector 54 may have lenses, fiber optics, or other optical elements associated therewith for collimating, focusing, and/or directing the beam.
As best seen in
When cassette 14 is not loaded in pump 10, the excitation light beam from emitter 52 passes directly to detector 54. Because detector 54 is configured to detect light in the emission wavelength band, and not light in the excitation wavelength band, the level of the signal generated by detector 54 will remain below a predetermined threshold level when cassette 14 is not loaded. When cassette 14 is properly loaded in pump 10, the at least one fluorophore 59 in window 55 absorbs light in the excitation wavelength band and emits light in the emission wavelength band. Some of the light in the emission wavelength band is received by detector 54. Consequently, when cassette 14 is loaded in pump 10, the level of the signal generated by detector 54 will rise above the threshold level.
Signal processing electronics 56 evaluates the signal from detector 54 to determine if cassette 14 is properly loaded in pump 10. The signal processing and evaluation may be completely analog, or the detector signal level may be converted to a digital value and compared to a threshold in a digital comparator circuit. As illustrated in
Tab 38 on cassette 14 provides structure that may be used for carrying window 55 and positioning the window in optical cassette detection system 50. A wide variety of tab arrangements and optical detection system configurations are of course possible. The centered arrangement of a thin tab 38 on the underside of cassette 14, and the use of a thin slot 42 in pump 10, takes advantage of the tab and slot as a means for guiding and centering the cassette 14 during installation. Moreover, the cassette detection system 50 is hidden within the pump and is inconspicuous to users. Emitter 52 and detector 54 may be recessed slightly from the surface of slot 42 behind respective transparent barriers (not shown) to keep dirt and fluid away from the emitter and detector.
While the invention has been described in connection with exemplary embodiments, the detailed description is not intended to limit the scope of the invention to the particular forms set forth. The invention is intended to cover such alternatives, modifications and equivalents of the described embodiment as may be included within the spirit and scope of the invention.
