Abstract:
An embodiment of the present disclosure provides a noninvasive optical sensor or probe including disposable and reusable components. The assembly of the disposable and reusable components is straightforward, along with the disassembly thereof. During application to a measurement site, the assembled sensor is advantageously secured together while the componentry is advantageously properly positioned.

Description:
PRIORITY CLAIM 
       [0001]    The present application claims priority benefit under 35 U.S.C. §120 to, and is a continuation to U.S. patent application Ser. No. 13/563,541, filed Jul. 31, 2012, entitled “Optical Sensor Including Disposable and Reusable Elements,” which is a continuation of U.S. patent application Ser. No. 11/606,455, filed Nov. 29, 2006, entitled “Optical Sensor Including Disposable and Reusable Elements,” which claims priority benefit under 35 U.S.C. §119(e) from U.S. Provisional Application No. 60/740,541, filed Nov. 29, 2005, entitled “Optical Sensor Including Disposable and Reusable Elements.” The present application incorporates the foregoing disclosures herein by reference. 
       REFERENCE TO RELATED APPLICATIONS 
       [0002]    This application also relates to U.S. Pat. No. 6,920,345, filed on Jan. 24, 2003 and issued on Jul. 19, 2005, entitled “Optical Sensor Including Disposable And Reusable Elements.” The present application also incorporates the foregoing disclosure herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Disclosure 
         [0004]    The present disclosure relates to noninvasive optical sensors capable of detecting light attenuated by body tissue. More specifically, the disclosure relates to the combination of reusable and disposable components of such sensors. 
         [0005]    2. Description of the Related Art 
         [0006]    Early detection of low blood oxygen is important in a wide range of applications, including patient monitoring, the fitness industry, home care and the like. Noninvasive oximetry was developed to study and to measure, among other things, the oxygen status of blood. Pulse oximetry—a noninvasive, widely accepted form of oximetry—relies on a sensor attached externally to a patient to output signals indicative of various physiological parameters, such as a patient&#39;s blood oxygen saturation. 
         [0007]    A pulse oximeter sensor generally includes one or more energy emission devices, such as specific wavelength emitting LEDs, and one or more energy detection devices. The sensor is generally attached to a measurement site such as a patient&#39;s finger, ear, ankle, or the like, using an attachment mechanism such as a disposable tape, reusable housing, a plastic or hook-and-loop fastening strap, or the like. The attachment mechanism positions the emitters and detector proximal to the measurement site such that the emitters project energy into the blood vessels and capillaries of the measurement site, which in turn attenuate the energy. The detector then detects that attenuated energy. The detector communicates at least one signal indicative of the detected attenuated energy to a signal processing device such as an oximeter. The oximeter generally calculates, among other things, one or more physiological parameters of the measurement site. 
         [0008]    Noninvasive oximetry sensors can be disposable, reusable, or some combination thereof. Reusable sensors offer advantages of superior cost savings. However, reusable sensors are often available in a limited number of sizes even though patient measurement sites, such as fingers or toes, can have a much larger size distribution. Therefore, sometimes reusable sensors do not readily conform to each patient&#39;s measurement site. Disposable sensors on the other hand offer superior conformance to the measurement area. However, disposable sensors are generally more costly due to limited use of the relatively expensive sensor components which could otherwise last for repeated uses. 
         [0009]    Faced with the drawbacks of reusable and disposable sensors, manufacturers began designing a number of middle-ground sensors. For example, some manufacturers offer a reusable detector portion that couples to a disposable emitter portion. After a single use, the disposable emitter portion is detached from the reusable detector portion and discarded. While this design reuses some of the expensive electronic components, obviously others are still discarded. 
         [0010]    Another example of a middle-ground sensor includes a reusable “Y” type sensor, where a reusable emitter portion connects to one branch of the “Y” while a reusable detector portion connects to the other branch. A disposable tape positions the two branches on a measurement site. In this design, the electronics are reusable; however, the multiple wires tend to be somewhat difficult to properly attach, especially with a moving patient. 
         [0011]    Other examples of middle-ground sensors include a disposable tape sandwich where a reusable flexible circuit housing an emitter portion and a detector portion, are “sandwiched” between adhesive layers. Separation of such disposable tape sandwiches can be cumbersome. In yet another example of a middle-ground sensor, the Assignee of the present application disclosed a reusable flexible circuit that is snapped into a disposable tape. In an embodiment of that disclosure, small pegs on the flexible circuit snap into mechanically mating elements on the disposable tape. Grooves allow some longitudinal travel between the reusable portion and the disposable portion, thereby allowing for some self adjustment between components to account for differences in radial attachment requirements. 
       SUMMARY OF THE DISCLOSURE 
       [0012]    However, even with the advances discussed in the foregoing, there continues to be a need for a commercially viable, straightforward, middle-ground solution that offers reusability of expensive electronic components while maintaining some of the advantages of disposable attachment. 
         [0013]    Accordingly, one aspect of an embodiment of the present disclosure is to provide a sensor having reusable and disposable components. In an embodiment, the sensor advantageously includes a disposable component structured to provide a locking feature capable of reducing a chance that the disposable and reusable components can separate when attached or otherwise in close proximity to the body. In an embodiment, a locking mechanism takes advantage of longitudinal displacement and engages when the reusable and disposable portions of the sensor are curved around the measurement site (such as a finger). Separation of the reusable portion from the disposable portion is then advantageously complicated until the sensor is removed from the patient and the displacement is reversed. 
         [0014]    A further aspect of an embodiment of this disclosure is that the tip of the reusable sensor component slides angularly into the front housing component on the disposable portion before sitting flat in a slot or guide. The slot or guide includes a rubber stop that in an embodiment advantageously provides a fluid-tight or at least fluid resistant contact. 
         [0015]    In a further embodiment, a memory device or information element is provided as part of the disposable housing. An electrical contact is made between the memory device and the reusable components to, for example, ensure quality control in the disposable housing, provide information to the patient monitor about the type of sensor, type of patient, type of attachment mechanism or attachment position, information about operating characteristics of the sensor, product manufacture or sale history, distributor history, amount of use, combinations of the same or the like. 
         [0016]    For purposes of summarizing the disclosure, certain aspects, advantages and novel features of the disclosure have been described herein. Of course, it is to be understood that not necessarily all such aspects, advantages or features will be embodied in any particular embodiment of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The following drawings and the associated descriptions are provided to illustrate embodiments of the present disclosure and do not limit the scope of the claims. 
           [0018]      FIG. 1  illustrates an exemplary block diagram of an oximeter system including a sensor and a monitoring instrument, according to embodiments of the disclosure. 
           [0019]      FIG. 2  illustrates a perspective view of the sensor of  FIG. 1 , where reusable and disposable components of the sensor are separated according to an embodiment of the disclosure. 
           [0020]      FIGS. 3A-3B  illustrate perspective views of the sensor of  FIG. 2 , where the components are connected in an assembly/disassembly position, according to an embodiment of the disclosure. 
           [0021]      FIG. 4  illustrates a perspective side view of the sensor of  FIG. 2 , where the components are in an attached position, according to an embodiment of the disclosure. 
           [0022]      FIG. 5A-5B  illustrate top and bottom perspective views of a detector casing or housing of the reusable component, according to an embodiment of the disclosure. 
           [0023]      FIG. 6A-6B  illustrate top and bottom perspective views of an emitter casing or housing of the reusable component, according to an embodiment of the disclosure. 
           [0024]      FIG. 7  illustrates a perspective view of a front holding clip of the disposable component, the clip being capable of mechanically mating with the detector casing of  FIG. 5 , according to an embodiment of the disclosure. 
           [0025]      FIG. 8  illustrates a perspective view of the assembly/disassembly clip of the disposable component, the clip being capable of mechanically mating with the emitter casing of  FIG. 6 , according to an embodiment of the disclosure. 
           [0026]      FIG. 9  illustrates a top planar view of the disposable component including the front holding clip and the assembly/disassembly clip of  FIGS. 7-8 , according to an embodiment of the disclosure. 
           [0027]      FIG. 10A  illustrates an exploded view of the disposable component, according to an embodiment of the disclosure. 
           [0028]      FIG. 10B  illustrates an exploded view of the reusable component, according to an embodiment of the disclosure. 
           [0029]      FIG. 11  illustrates top planar and side views of component placement of conventional sensors. 
           [0030]      FIG. 12  illustrates top planar and side views of component placement according to an embodiment of the disclosure. 
           [0031]      FIG. 13  illustrates a top down planar view of a disposable sensor, according to an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    An embodiment of the present disclosure is a sensor with a reusable component and a disposable component. The reusable component generally includes reusable expensive electronic components of a sensor, including, for example, the emitters and detector. In an embodiment, the emitters and the detector are located in respective casings connected by a short flexible circuit. In an embodiment, a disposable component includes mechanically matable portions adapted to mechanically mate with the casings of the reusable component. In an embodiment, the casings of the reusable component mate with the disposable component in a manner that provides an assembly/disassembly state, and an attached state. During the assembly/disassembly state, a caregiver can readily and straightforwardly assemble the sensor by aligning the casings on the reusable component and the mechanical housings of the disposable component and snapping them together. In an embodiment, the alignment is generally vertical in nature and the snapping occurs by lightly pressing on the components while on a flat surface or supported from underneath by, for example, the hand of the assembler. Each detector housing generally vertically accepts the casings; however, one of the casings, such as, for example, the forward housing or clip accepts the casing in such a way as to keep the forward casing generally immobile. 
         [0033]    Disassembly is equally as straightforward, as the caregiver may advantageously lift on the reusable component wire, and the rearward casing extracts from the mechanically mated housing of the disposable element. Continual lifting then similarly extracts the forward casing from the mechanically mated housing of the disposable element. In an embodiment, the flexible circuit between the forward and rearward casing may be reinforced in order to withstand multiple disassembly stresses or forces occurring from the lifting of the reusable wire. In an embodiment, pressing the disposable portion onto a flat surface while lifting the reusable portion aids in the disassembly process. 
         [0034]    The disposable portion includes structures designed to attach the sensor to a measurement site. In an embodiment, the disposable portion comprises a flexible tape having an adhesive side capable of removably adhering to the measurement site. In an embodiment where the disposable portion wraps around a measurement site, the act of bending the flexible circuit advantageously causes the assembly/disassembly clip to recess into the mechanically mated portion of the disposable housing, thereby reducing the likelihood of disassembly during application to a measurement site. In an embodiment, the sensor components are locked together through the longitudinal displacement of the clip with respect to the disposable housing. In such an embodiment, a stop diminishes the capacity of the clip to move vertically, thereby locking it into place. In this embodiment, removing the adhesive from the measurement site and straightening the sensor components unlocks the reusable and disposable components. 
         [0035]    In an embodiment, assembly also necessarily electrically connects electronic components of the disposable portion with those of the reusable portion. In an embodiment, then disposable portion includes an information element or memory device, such as, for example, a resistor, a single wire addressable memory device, such as those EPROMs or EEPROMs commercially available from Dallas Semiconductor, other memory or processing devices, combinations of the same, or the like. The information element may include data accessibly by an attached patient monitor to accomplish quality control, monitor configuration, sensor use monitoring, combinations of the same, or the like. 
         [0036]    Still other advantages of embodiments of the present disclosure include proportionally positioning of the mechanically mating housings to provide for optical alignment between the emitters and detector. Moreover, in embodiments including the disposable tape, the tape may advantageously be scored to assist the caregiver in proper alignment with the body tissue at the measurement site. 
         [0037]    To facilitate a complete understanding of the disclosure, the remainder of the detailed description describes the disclosure with reference to the drawings. Corresponding parts refer to corresponding elements and the leading digit indicates the figure in which that element first appears. 
         [0038]    General Design 
         [0039]      FIG. 1  presents an exemplary block diagram of the components generally found in an oximeter sensor, according to an embodiment of the invention. For example,  FIG. 1  shows as oximeter system  100  including sensor  102 , cable  170 , and monitor  172 . The sensor  102  includes one or more emitters  174  for irradiating body tissue with light, and one or more detectors  176  capable of detecting the light after attenuation by the tissue. The sensor  102  also includes an information element  136  such as an EPROM. The sensor  102  also includes a plurality of conductors communicating signals; including emitter drive signal conductors  180 , detector composite signal conductors  182 , and EPROM conductors  184 . According to an embodiment, the sensor conductors  180 ,  182 ,  184  communicate their signals to and from the monitor  172  through cable  170 . 
         [0040]    Although disclosed with reference to the cable  170 , a skilled artisan will recognize from the disclosure herein that the communication to and from the sensor  106  may advantageously include a wide variety of cables, cable designs, public or private communication networks or computing systems, wired or wireless communications, combinations of the same, or the like. 
         [0041]    The information element  136  may comprise an EPROM, an EEPROM, combinations of the same, or the like. In general, the information element  136  may include a read-only device or a read and write device. The information element may advantageously also comprise a resistor, an active network, or any combination of the foregoing. The remainder of the present disclosure will refer to such possibilities as simply an information element for ease of disclosure. 
         [0042]    The information element  136  may advantageously store some or all of a wide variety of data and information, including, for example, information on the type or operation of the sensor  104 , type of patient or body tissue, buyer or manufacturer information, sensor characteristics including the number of wavelengths capable of being emitted, emitter specifications, emitter drive requirements, demodulation data, calculation mode data, calibration data, software such as scripts, executable code, or the like, sensor electronic elements, sensor life data indicating whether some or all sensor components have expired and should be replaced, encryption information, or monitor or algorithm upgrade instructions or data. The information element  136  may advantageously configure or activate the monitor, monitor algorithms, monitor functionality, or the like based on some or all of the foregoing information. For example, without authorized data accessibly on the information element  136 , quality control functions may inhibit functionality of the monitor. Likewise, particular data may activate certain functions while keeping others inactive. For example, the data may indicate a number of emitter wavelengths available, which in turn may dictate the number and/or type of physiological parameters that can be monitored or calculated. 
         [0043]      FIG. 1  also shows the monitor  172  comprising one or more processing boards  186  communicating with one or more host instruments  188 . According to an embodiment, the board  186  comprises processing circuitry arranged on one or more printed circuit boards capable of being installed in specialized monitoring equipment or distributed as an OEM component for a wide variety of patient monitoring equipment. As shown in  FIG. 1 , the board  186  includes a front end signal conditioner  190 , a sensor controller  194 , a digital signal processor or microcontroller  192 , and a memory reader  1102 . In an embodiment, the processor  192  instructs the sensor controller  194  to output one or more drive signals capable of causing the emitters  174  to activate. The front end  190  receives detector output indicating of light from the emitters  174  attenuated by body tissue of the measurement site. The front end  190  conditions the signal and outputs the signal and/or signal data to the processor  192 . The processor  192  executes calculations adapted to determine values and/or indications or physiological parameters, trends of the parameters, alarms based on the parameters or the trends or combinations of trends and/or parameters, or the like. In addition, the reader  1102  is capable of retrieving information stored on information element  136 . The reader  1102  or the processor  192  may advantageously decrypt such information to the extent desired. 
         [0044]    In an embodiment, the host instrument  188 , communicates with the processor  192  to receive signals indicative of the physiological parameter information calculated by the processor  192 . The host instrument preferably includes one or more display devices  196  capable of providing indicia representative of the calculated physiological parameters of the tissue at the measurement site. Such display devices  196  may be controlled by a monitor controller  198  that accepts signals from processor  192 . In an embodiment, monitor controller  198  may also accept signals from user interface  1100 . Such signals may be indicative of various display options for configuring the output to display  196 . In an embodiment, the host instrument  188  may advantageously be capable of displaying one or more of a pulse rate, plethysmograph data, perfusion quality, signal or measurement quality, values of blood constituents in body tissue, including for example, SpCO, functional or fractional SpO.sub.2, or the like. In other embodiments, the host instrument  188  is capable of displaying values for one or more of SpMet, HbO.sub.2, Hb, HbCO, HbMet, Hct, blood glucose, bilirubin, or the like. In still additional embodiments, the host instrument  188  is capable of displaying trending data for one or more of the foregoing measured or determined data. Moreover an artisan will realize from the disclosure herein many display options for the data are available. 
         [0045]    In an embodiment, the host instrument  188  includes audio or visual alarms that alert caregivers that one or more physiological parameters are falling below predetermined safe thresholds, and may include indications of the confidence a caregiver should have in the displayed data. In further embodiment, the host instrument  188  may advantageously include circuitry capable of determining the expiration or overuse of components of the sensor  102 , including for example, reusable elements, disposable elements, or combinations of the same. 
         [0046]    Although disclosed with reference to particular embodiment, an artisan will recognize from the disclosure herein many variations of the instrument  172 . For example, in a broad sense, the instrument  172  accepts data from the sensor  102 , determines values for one or more parameters, trends, alarms or the like, and outputs them to an interface such as a display. 
         [0047]    Sensor Configuration 
         [0048]      FIG. 2  illustrates an embodiment of sensor  102 , having reusable component  204  and disposable component  206 . The components are shown detached.  FIG. 3  shows a very similar perspective drawing, but with reusable component  204  and disposable component  206  in their attached, in their assembled state. Returning to  FIG. 2 , the reusable component  204  comprises an emitter casing  208 , a detector casing  210 , and a flexible circuit  212 . The emitter casing  208  comprises one or more emission devices operable to emit light at multiple wavelengths, such as red and infrared. Detector casing  210  houses one or more detectors, such as a photodiode detector. In an embodiment, a flexible circuit connects the emitter casing  208  and detector casing  210 . In a preferred embodiment, the flexible circuit is housed in a protective cover and extends beyond the emitter casing  208 . An artisan will understand from the disclosure herein that the emitter and detector electrical components may advantageously be housed in the casings disclosed or simply reversed from the foregoing disclosure. In an embodiment, the flexible circuit  212  and/or cabling extends significantly beyond the casings to advantageously remove any cable attachment mechanisms from the proximity of the tissue site. 
         [0049]      FIG. 2  also shows the disposable component  206  including a base  214 , an assembly/disassembly clip  216  and a front holding clip  218 , the clips each adapted to accept the emitter casing  208  and detector casing  210 , respectively. In the preferred embodiment, front holding clip  218  includes a front stop  220 . Front stop  220  is advantageous for a number of reasons. It helps reduce the likelihood that the reusable component  102 , and in particular detector casing  210 , will slide forward in the front holding clip  218  during assembly or use. In addition, in an embodiment where the stop  220  comprises rubber or other liquid resistant material, the stop  220  provides a liquid resistant connection between the detector casing  210  and front holding clip  218 , reducing the likelihood of sensor contamination and electrical shorts. Rubber or a similar material may be used in an embodiment to compose such a front stop  220 . 
         [0050]      FIG. 3A  shows detector casing  210  clipped or snapped into front holding clip  218  with a tip of the casing slid below a portion of the front stop  220 . This allows the front stop  220  to reduce not only horizontal movement of the detector casing  210 , but also helps reduce vertical release of the detector casing unless pulled from, for example, the cable.  FIG. 3  also shows the front stop  220  with a generally rounded shape providing a relatively soft material with few, if any, sharp edges. Such an embodiment advantageously reduces damage to a patient or the sensor if the patient tries to scratch body tissue using the edges of the assembled sensor, or if the sensor is dropped, banged against something while worn, or the like. This is particularly useful when used with burn victims or other patients whose skin may damage easily. 
         [0051]      FIG. 3B  highlights the ease of assembly. The disposable portion  206  is set on a surface or held in the one hand. The caregiver then aligns a front tip of casing  210  and guides it into front holding clip  218 . This is more a vertical alignment with the front tip snapping below stop  220 . The casing  210  including rounded wings  531  ( FIG. 5 ) that mechanically associate with rounded side walls  739  ( FIG. 7 ). These mechanical structures allow the tip of casing  210  to slide below stop  220 , and snap down into place. Once casing  210  is in place, casing  208  aligns vertically and simply slides down, with tabs  262  ( FIG. 6 ) located sliding into slots  222  ( FIG. 8 ) on either side of assembly/disassembly clip  216 . In an embodiment, the flexible circuit portion  212  between the casings  208  and  210  may bulge slightly. 
         [0052]      FIG. 3B  shows the emitter casing  208  after it has been slid onto assembly/disassembly clip  216 . With the reusable sensor component  204  and the disposable sensor component  206  in a generally flat position, the emitter casing  208  remains vertically mobile in slots  222  of assembly/disassembly clip  216 . When the sensor  102  is wrapped around a measurement site  426 , such as a finger, as shown in  FIG. 4 , emitter casing  208  slides forward in assembly/disassembly clip  216  due to the tension from flexible circuit  212  and detector casing  210  being substantially immobile in front holding clip  218 . Tabs  262  ( FIG. 6 ) slide away from slots  222  ( FIG. 8 ) and under holding elements  224  ( FIG. 8 ). Holding elements  224  prevent emitter casing  208  from moving vertically or further forward by restricting tabs  262 . As stated before, the tension from flexible circuit  212  when it is wrapped around a measurement site  426  prevents the emitter casing  208  from moving horizontally backwards. The immobility of casing  210 , combined with the tabs  262  sliding out of alignment with slots  222 , effectively secure the reusable sensor component  204  with respect to disposable component  206 , with the emitters appropriately position with respect to the detector. Thus, realignment through release of tension, i.e., removing the sensor from an attachment site and straightening it out, ensure straightforward disassembly of the sensor components. Although shown using tabs  262  and slots  222 , a skilled artisan will recognize from the disclosure herein a wide variety of mechanical mechanisms that ensure reliable attachability when the sensor is applied to the tissue site and straightforward assembly/disassembly when the sensor is removed. For example, one or more detents that snap closed beyond a catch and are released through pinching could be used to secure the reusable portion  104  to the disposable portion  106 . 
         [0053]    As alluded to previously,  FIG. 4  depicts sensor  102  as would be seen when in use on a measurement site  426 . In this case, the measurement site is a finger, but other sites such as a toe, ear, wrist or ankle may also work. Disposable component  206  and reusable component  204  are attached, and reusable component  204  is in the assembled and attached position. Longitudinal tension on the flexible circuit  212  from the differing radius between the tape and the circuit has pulled the emitter casing  208  forward, placing tabs  262  under holding elements  224 .  FIG. 4  shows that, in an embodiment, emitter casing  208  is rearward with respect to assembly/disassembly clip  216  when in the unattached position ( FIG. 3B ), but the front of emitter casing  208  is forward and in an embodiment, generally flush with assembly/disassembly clip  216  when in the attached position ( FIG. 4 ). 
         [0054]      FIGS. 5A-5B  show close up top and bottom perspective views of an embodiment of the detector casing  210 . Electrical contact acceptors  528  are shown as insets on the sides of detector casing  210 . In an embodiment, electrical contact acceptors  528  are located on either side of the detector casing  210  and include conductive material that would be connected to a wire in flexible circuit  212 . Buttons  530  found on either side of the detector casing  210  are, in the preferred embodiment, generally hemispherical protrusions adapted to sit in depressions  738  found on front holding clip  218  (see  FIG. 7 ). 
         [0055]      FIG. 7  shows a close up perspective view of an embodiment of the front holding clip  218 , again to show detail less easily seen in smaller figures. While most of the front sensor clip  218  may be made of plastic or some other rigid material, the preferred embodiment has front stop  220  made of rubber as has been discussed. Opening  732  is also shown here and may be a hole through front holding clip  218  or may just be of a generally transparent material that will allow light from the LEDs to enter the tissue at the measurement site and allow light energy to be read by the photodiode. Having window  732  be transparent material will allow the sensor to obtain readings while keeping the LEDs and photodiode from becoming contaminated. Other optical filters or the like could also be housed in window  732 . 
         [0056]    Located inside front stop  220  are conducting prongs  734 . Conducting prongs  734  are adapted to fit into electrical contact acceptors  528 . In an embodiment, the conducting prongs  734  close the circuit with the information element  136 . When the detector casing  210  clips into front holding clip  218 , the conducting prongs  734  slide into electrical contact with acceptors  528 . The completed circuit allows the sensor  102 , and in turn an oximeter, to communicate with information element  136 . Depressions  738  are located on the interior of front holding clip  218 . They are preferably generally hemispherical depressions similar in size to buttons  530 , so as to accept buttons  530 , and hold detector casing  210  in a substantially immobile position relative to front holding clip  218 . Thus, a straightforward snap-in snap-out friction fit is accomplished using buttons  520  and depressions  738 . 
         [0057]      FIGS. 6A-6B  show close up top and bottom perspective views of emitter casing  208 . Rear pegs  660  are located on either side of emitter casing  208 . When tabs  262  slide down slots  222  of assembly/disassembly clip  216 , rear alignment pegs  660  slide down behind assembly/disassembly clip  216 . Rear pegs  660  provide further restriction from forward movement, and structural support integrity, once emitter casing  208  has slid into a locking position by hitting rear stops  840  in assembly/disassembly clip  216  (See  FIG. 8 ). 
         [0058]      FIG. 8  illustrates a close-up perspective view of a assembly/disassembly clip  216  according to the preferred embodiment. As discussed emitter casing  208 , slides down into assembly/disassembly clip  216  with tabs  262  passing through slots  222  and rear pegs  660  passing behind assembly/disassembly clip  216 . As emitter casing  208  slides forward due to pull from application to a user, tabs  262  generally restrict over-forward movement or any vertical movement by abutting holding elements  224 . Rear pegs  660  also generally abut rear stops  840 . Assembly/disassembly clip  216  also has a window  842  that is substantially similar to window  732  on the front holding clip  218 . 
         [0059]      FIG. 9  shows a top down view of the disposable sensor element. As shown in  FIG. 9 , the assembly/disassembly clip  216  and the slots  222  that allow vertical entry of the tabs  262  and the emitter casing  208 . Moreover,  FIG. 9  shows windows  842  and  732  in assembly/disassembly clip  216  and front holding clip  218 , respectively.  FIG. 9  also shows windows  944  and  946 . Windows  944 ,  946  are included in the base  214 . Like the openings  732 ,  842 , windows  944 ,  946  may either be holes through base  214 , or they may be of a material allowing free light transmission. Windows  944 ,  946  generally align with openings  732  and  842  to provide optical access to the measurement site for the emitters and detectors of the sensor.  FIG. 9  also shows the contact prongs  734  on the insides of front holding clip  218 . The contact prongs  734  connect the reusable sensor component  204  to information element  136 , which may be variously utilized such as for storing information relating to the sensor&#39;s manufacturer or the like. 
         [0060]    Manufacture 
         [0061]      FIG. 10A  illustrates an exploded view of an embodiment of disposable sensor component  206 . As shown in  FIG. 10A , disposable sensor component  206  comprises a plurality of layers. For example, disposable sensor component  206  includes a base tape  1038 . This base tape  1038  is preferably transparent polyethylene approximately 0.001 inches thick. Such material can be purchased from various sources, such as Product Number 3044 from Avery Dennison Medical of 7100 Lindsey Dr., Mentor, Ohio, 44060. As with all dimension recitations herein, an artisan will recognize from the disclosure herein that the dimensions of a particular layer may advantageously be redesigned according to various design desires or needs, and layers may be added or combined without departing from the scope of the present disclosure. 
         [0062]    A second layer comprises a tape or web layer  1040 . This layer is preferably white polypropylene also approximately 0.001 inches thick. One potential source for this material is Scapa North America, 540 North Oak Street, Inglewood, Calif., 90302, specifically product number P-341. Tape layer  1040  also has windows  1054  that allow light energy emanating from the sensor emitters to pass through this layer to the measurement site  426  and also allows the light to pass through to the detector. The windows  1054  may be holes, transparent material, optical filters, or the like. In the preferred embodiment, base tape  1038  does not have windows  1054 . Base tape  1038  is preferably generally clear as discussed above. This allows light to pass through the tape from the sensor, while also generally reducing contamination of the sensor components. Disposable component  206  also includes clip  218  and assembly/disassembly clip  216 . In an embodiment, information element  136  resides in a depression or slot within clip  218 , preferably affixed in place by adhesives and/or mechanical structure. In an embodiment, a polyester film layer  1042  sandwiches the clips  216 ,  218  in place. In an embodiment the polyester film layer  1042  is generally clear and approximately 0.003 inches thick. Polyester film layer  1042  also includes slots  1044  to allow the vertical elements of assembly/disassembly clip  216  and front holding clip  218  to protrude therefrom and to allow polyester film layer  1042  to sit relatively flatly against the bases of assembly/disassembly clip  216  and front holding clip  218 . Front stop  220  may be connected to the vertical elements of front holding clip  218  with polyester film layer  1042  therebetween. 
         [0063]    The disposable portion  204  also includes light-blocking layer  1046 , preferably made of metalized polypropylene approximately 0.002 inches thick. This is a commercially available product available, for example, as Bioflex™ RX48P. Light-blocking layer  1046  has cut-outs  1048  adapted to accept assembly/disassembly clip  216  and front holding clip  218 . Light-blocking layer  1046  increases the likelihood of accurate readings by preventing the penetration to the measurement site of any ambient light energy (light blocking) and the acquisition of nonattenuated light from the emitters (light piping). Above light blocking layer  1046  is an opaque branding layer  1047  also having cut-outs  1048 . This branding layer may advantageously comprise manufacturer&#39;s logos, instructions or other markings. Disposable sensor component  206  also comprises face tape  1050 . This face tape  1050  is preferably a clear film approximately 0.003 inches thick and may be obtained commercially through companies such as 3M (product number 1527ENP), located in St. Paul, Minn., 55144. Face tape  1050  has cut-outs  1052  adapted to accept assembly/disassembly clip  216  and front holding clip  218 . 
         [0064]    Additional Advantages 
         [0065]      FIG. 11  illustrates a disposable sensor highlighting issues relating to sensor positioning. Generally, when applying the sensor of  FIG. 11 , a caregivers will split the center portion between the emitter and detector around, for example, a finger or toe. This may not be ideal, because as shown, it places the emitter  174  and detector  176  in a position where the optical alignment may be slightly or significantly off. 
         [0066]      FIG. 12  illustrates an embodiment of the disposable component  206  including scoring line  1258 . Scoring line  1258  is particularly advantageous, because it aids in quick and proper placement of the sensor on a measurement site  426 . Scoring line  1258  lines up with the tip of a fingernail or toenail in at least some embodiments using those body parts as the measurement site.  FIG. 12  also illustrates the disposable component  206  where the distance between the windows  944 ,  946  is purposefully off center. For example, in an embodiment, the clips  216  and  218  will position the sensor components off center by an approximate 40%-60% split. A scoring line  1258  preferably marks this split, having about 40% of the distance from window  946  to window  944  as the distance between window  946  and the scoring line  1258 . This leaves the remaining approximately 60% of the distance between the two windows  944 ,  946  as the distance between scoring line  1258  and window  944 . 
         [0067]    Scoring line  1258  preferably lines up with the tip of the nail. The approximately 40% distance sits atop a measurement site  426 , such as the figure shown in a generally flat configuration. The remaining approximately 60% of the distance, that from the scoring line  1258  to window  944 , curves around the tip of the measurement site  426  and rests on the underside of the measurement site. This allows windows  944 ,  946 —and thus in turn detector  176  and emitter  174 —to optically align across measurement site  426 . Scoring line  1258  aids in providing a quick and yet typically more precise guide in placing a sensor on a measurement site  426  than previously disclosed sensors. While disclosed with reference to a 40%-60% split, the off center positioning may advantageously comprise a range from an about 35%—about 65% split to an about 45%—about 55% split. In a more preferred embodiment, window  944  to scoring line  1258  would comprise a distance of between about 37.5% and about 42.5% of the total distance between window  944  and  946 . In the most preferred embodiment, the distance between window  944  and scoring line  1258  would be approximately 40% of the total distance between window  944  and window  946 , as is illustrated in  FIG. 12 . With a general 40%-60% split in this manner, the emitter and detector should generally align for optimal emission and detection of energy through the measurement site. 
         [0068]      FIG. 13  illustrates a disposable sensor containing many of the features discussed in this disclosure. Based on the disclosure herein, one of ordinary skill in the art may advantageously fix the components discussed herein to form a disposable sensor without moving beyond the scope of the present disclosure. 
         [0069]    Although the sensor disclosed herein with reference to preferred embodiments, the disclosure is not intended to be limited thereby. Rather, a skilled artisan will recognize from the disclosure herein a wide number of alternatives for the sensor. For example, the emitter and detector locations may be in the opposite housings from what was discussed here. It is also possible that the assembly/disassembly clip and sensor clip would be reversed in relation to the casings into which they clip. Additionally, other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Accordingly, the present disclosure is not intended to be limited by the reaction of the preferred embodiments, but is to be defined by reference to the appended claims. 
         [0070]    Additionally, all publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.