Contoured protrusion for improving spectroscopic measurement of blood constituents

A noninvasive physiological sensor for measuring one or more physiological parameters of a medical patient can include a bump interposed between a light source and a photodetector. The bump can be placed in contact with body tissue of a patient and thereby reduce a thickness of the body tissue. As a result, an optical pathlength between the light source and the photodetector can be reduced. In addition, the sensor can include a heat sink that can direct heat away from the light source. Moreover, the sensor can include shielding in the optical path between the light source and the photodetector. The shielding can reduce noise received by the photodetector.

BACKGROUND

The standard of care in caregiver environments includes patient monitoring through spectroscopic analysis using, for example, a pulse oximeter. Devices capable of spectroscopic analysis generally include a light source(s) transmitting optical radiation into or reflecting off a measurement site, such as, body tissue carrying pulsing blood. After attenuation by tissue and fluids of the measurement site, a photodetection device(s) detects the attenuated light and outputs a detector signal(s) responsive to the detected attenuated light. A signal processing device(s) process the detector(s) signal(s) and outputs a measurement indicative of a blood constituent of interest, such as glucose, oxygen, met hemoglobin, total hemoglobin, other physiological parameters, or other data or combinations of data useful in determining a state or trend of wellness of a patient.

In noninvasive devices and methods, a sensor is often adapted to position a finger proximate the light source and light detector. For example, noninvasive sensors often include a clothespin-shaped housing that includes a contoured bed conforming generally to the shape of a finger. The contoured bed positions the finger for measurement and attempts to stabilize it.

Unfortunately, this type of contour cannot be ideal, especially for measuring blood constituents like glucose.

SUMMARY

This disclosure describes embodiments of noninvasive methods, devices, and systems for measuring a blood analyte, such as oxygen, carbon monoxide, methemoglobin, total hemoglobin, glucose, proteins, glucose, lipids, a percentage thereof (e.g., saturation) or for measuring many other physiologically relevant patient characteristics. These characteristics can relate, for example, to pulse rate, hydration, trending information and analysis, and the like. In certain embodiments, a noninvasive sensor interfaces with tissue at a measurement site and deforms the tissue in a way that increases signal gain in certain desired wavelengths. In an embodiment, a protrusion can be provided in a finger bed of a noninvasive sensor for a patient's finger. The protrusion can reduce tissue thickness, thereby sometimes increasing signal gain by tens of times or even more. This protrusion can include different sizes and shapes depending on the tissue site and the desired blood analyte to be measured.

In disclosed embodiments, the protrusion is employed in noninvasive sensors to assist in measuring and detecting various analytes. The disclosed noninvasive sensor can also include, among other things, emitters and detectors positioned to produce multi-stream sensor information. The noninvasive sensor can have different architectures and can include or be coupled to other components, such as a display device, a network interface, and the like. The protrusion can be employed in any type of noninvasive sensor.

In certain embodiments, a noninvasive physiological sensor for measuring one or more physiological parameters of a medical patient can include a bump interposed between a light source and a photodetector. The bump can be placed in contact with body tissue of a patient and thereby reduce a thickness of the body tissue. As a result, an optical pathlength between the light source and the photodetector can be reduced. In addition, the sensor can include a heat sink that can direct heat away from the light source. Moreover, the sensor can include shielding in the optical path between the light source and the photodetector. The shielding can reduce noise received by the photodetector.

DETAILED DESCRIPTION

The present disclosure generally relates to non-invasive medical devices. In an embodiment, a physiological sensor includes a detector housing that can be coupled to a measurement site, such as a patient's finger. The sensor housing can include a curved bed that can generally conform to the shape of the measurement site. In addition, the curved bed can include a protrusion shaped to increase an amount of light radiation from the measurement site. In an embodiment, the protrusion is used to thin out the measurement site. This allows the light radiation to pass through less tissue, and accordingly is attenuated less. In an embodiment, the protrusion can be used to increase the area from which attenuated light can be measured. In an embodiment, this is done through the use of a lens which collects attenuated light exiting the measurement site and focuses onto one or more detectors. The protrusion can advantageously include plastic, including a hard opaque plastic, such as a black or other colored plastic, helpful in reducing light noise. In an embodiment, such light noise includes light that would otherwise be detected at a photodetector that has not been attenuated by tissue of the measurement site of a patient sufficient to cause the light to adequately included information indicative of one or more physiological parameters of the patient. Such light noise includes light piping.

In an embodiment, the protrusion can be formed from the curved bed, or can be a separate component that is positionable with respect to the bed. In an embodiment, a lens made from any appropriate material is used as the protrusion. The protrusion can be convex in shape. The protrusion can also be sized and shaped to conform the measurement site into a flat or relatively flat surface. The protrusion can also be sized to conform the measurement site into a rounded surface, such as, for example, a concave or convex surface. The protrusion can include a cylindrical or partially cylindrical shape. The protrusion can be sized or shaped differently for different types of patients, such as an adult, child, or infant. The protrusion can also be sized or shaped differently for different measurement sites, including, for example, a finger, toe, hand, foot, ear, forehead, or the like. The protrusion can thus be helpful in any type of noninvasive sensor. The external surface of the protrusion can include one or more openings or windows. The openings can be made from glass to allow attenuated light from a measurement site, such as a finger, to pass through to one or more detectors. Alternatively, some of all of the protrusion can be a lens, such as a partially cylindrical lens.

The sensor can also include a shielding, such as a metal enclosure as described below or embedded within the protrusion to reduce noise. The shielding can be constructed from a conductive material, such as copper, in the form of a metal cage or enclosure, such as a box. The shielding can include a second set of one or more openings or windows. The second set of openings can be made from glass and allow light that has passed through the first set of windows of the external surface of the protrusion to pass through to one or more detectors that can be enclosed, for example, as described below.

In various embodiments, the shielding can include any substantially transparent, conductive material placed in the optical path between an emitter and a detector. The shielding can be constructed from a transparent material, such as glass, plastic, and the like. The shielding can have an electrically conductive material or coating that is at least partially transparent. The electrically conductive coating can be located on one or both sides of the shielding, or within the body of the shielding. In addition, the electrically conductive coating can be uniformly spread over the shielding or may be patterned. Furthermore, the coating can have a uniform or varying thickness to increase or optimize its shielding effect. The shielding can be helpful in virtually any type of noninvasive sensor that employs spectroscopy.

In an embodiment, the sensor can also include a heat sink. In an embodiment, the heat sink can include a shape that is functional in its ability to dissipate excess heat and aesthetically pleasing to the wearer. For example, the heat sink can be configured in a shape that maximizes surface area to allow for greater dissipation of heat. In an embodiment, the heat sink includes a metalicized plastic, such as plastic including carbon and aluminum to allow for improved thermal conductivity and diffusivity. In an embodiment, the heat sink can advantageously be inexpensively molded into desired shapes and configurations for aesthetic and functional purposes. For example, the shape of the heat sink can be a generally curved surface and include one or more fins, undulations, grooves or channels, or combs.

In the present disclosure, a sensor can measure various blood analytes noninvasively using multi-stream spectroscopy. In an embodiment, the multi-stream spectroscopy can employ visible, infrared and near infrared wavelengths. As disclosed herein, the sensor is capable of noninvasively measuring blood analytes or percentages thereof (e.g., saturation) based on various combinations of features and components.

The sensor can include photocommunicative components, such as an emitter, a detector, and other components. The emitter can include a plurality of sets of optical sources that, in an embodiment, are arranged together as a point source. The various optical sources can emit a sequence of optical radiation pulses at different wavelengths towards a measurement site, such as a patient's finger. Detectors can then detect optical radiation from the measurement site. The optical sources and optical radiation detectors can operate at any appropriate wavelength, including, as discussed herein, infrared, near infrared, visible light, and ultraviolet. In addition, the optical sources and optical radiation detectors can operate at any appropriate wavelength, and such modifications to the embodiments desirable to operate at any such wavelength will be apparent to those skilled in the art. In certain embodiments, multiple detectors are employed and arranged in a spatial geometry. This spatial geometry provides a diversity of path lengths among at least some of the detectors and allows for multiple bulk and pulsatile measurements that are robust. Each of the detectors can provide a respective output stream based on the detected optical radiation, or a sum of output streams can be provided from multiple detectors. In some embodiments, the sensor can also include other components, such as one or more heat sinks and one or more thermistors.

The sensor can be coupled to one or more monitors that process and/or display the sensor's output. The monitors can include various components, such as a sensor front end, a signal processor, a display, etc.

The sensor can be integrated with a monitor, for example, into a handheld unit including the sensor, a display and user controls. In other embodiments, the sensor can communicate with one or more processing devices. The communication can be via wire(s), cable(s), flex circuit(s), wireless technologies, or other suitable analog or digital communication methodologies and devices to perform those methodologies. Many of the foregoing arrangements allow the sensor to be attached to the measurement site while the device is attached elsewhere on a patient, such as the patient's arm, or placed at a location near the patient, such as a bed, shelf or table. The sensor or monitor can also provide outputs to a storage device or network interface.

Reference will now be made to the Figures to discuss embodiments of the present disclosure.

FIG. 1illustrates an example of a data collection system100. In certain embodiments, the data collection system100noninvasively measure a blood analyte, such as oxygen, carbon monoxide, methemoglobin, total hemoglobin, glucose, proteins, glucose, lipids, a percentage thereof (e.g., saturation) or for measuring many other physiologically relevant patient characteristics. The system100can also measure additional blood analytes and/or other physiological parameters useful in determining a state or trend of wellness of a patient.

The data collection system100can be capable of measuring optical radiation from the measurement site. For example, in some embodiments the data collection system100can employ photodiodes defined in terms of area. In an embodiment, the area is from about 1 mm2-5 mm2(or higher) that are capable of detecting about 100 nanoamps (nA) or less of current resulting from measured light at full scale. In addition to having its ordinary meaning, the phrase “at full scale” can mean light saturation of a photodiode amplifier (not shown). Of course, as would be understood by a person of skill in the art from the present disclosure various other sizes and types of photodiodes can be used with the embodiments of the present disclosure.

The data collection system100can measure a range of approximately about 2 nA to about 100 nA full scale. The data collection system100can also include sensor front-ends that are capable of processing and amplifying current from the detector(s) at signal-to-noise ratios (SNRs) of about 100 decibels (dB) or more, such as about 120 dB in order to measure various desired analytes. The data collection system100can operate with a lower SNR if less accuracy is desired for an analyte like glucose.

The data collection system100can measure analyte concentrations, including glucose, at least in part by detecting light attenuated by a measurement site102. The measurement site102can be any location on a patient's body, such as a finger, foot, ear lobe, or the like. For convenience, this disclosure is described primarily in the context of a finger measurement site102. However, the features of the embodiments disclosed herein can be used with other measurement sites102.

In the depicted embodiment, the system100includes an optional tissue thickness adjuster or tissue shaper105, which can include one or more protrusions, bumps, lenses, or other suitable tissue-shaping mechanisms. In certain embodiments, the tissue shaper105is a flat or substantially flat surface that can be positioned proximate the measurement site102and that can apply sufficient pressure to cause the tissue of the measurement site102to be flat or substantially flat. In other embodiments, the tissue shaper105is a convex or substantially convex surface with respect to the measurement site102. Many other configurations of the tissue shaper105are possible. Advantageously, in certain embodiments, the tissue shaper105reduces thickness of the measurement site102while preventing or reducing occlusion at the measurement site102. Reducing thickness of the cite can advantageously reduce the amount of attenuation of the light because the there is less tissue through which the light must travel. Shaping the tissue in to a convex (or alternatively concave) surface can also provide more surface area from which light can be detected.

The embodiment of the data collection system100shown also includes an optional noise shield103. In an embodiment, the noise shield103can be advantageously adapted to reduce electromagnetic noise while increasing the transmittance of light from the measurement site102to one or more detectors106(described below). For example, the noise shield103can advantageously include a conductive coated glass or metal grid electrically communicating with one or more other shields of the sensor101. In an embodiment where the noise shield103includes conductive coated glass, the coating can advantageously include indium tin oxide. In an embodiment, the indium tin oxide includes a surface resistivity ranging from approximately from 30 ohms per square inch to 500 ohms per square inch. In an embodiment, the resistivity is approximately 30, 200, or 500 ohms per square inch. As would be understood by a person of skill in the art from the present disclosure, other resistivities can also be used which are less than 30 ohms or more than 500 ohms. Other conductive materials transparent or substantially transparent to light can be used instead.

In some embodiments, the measurement site102is somewhere along a non-dominant arm or a non-dominant hand, e.g., a right-handed person's left arm or left hand. In some patients, the non-dominant arm or hand can have less musculature and higher fat content, which can result in less water content in that tissue of the patient. Tissue having less water content can provide less interference with the particular wavelengths that are absorbed in a useful manner by blood analytes like glucose. Accordingly, in some embodiments, the data collection system100can be used on a person's non-dominant hand or arm.

The data collection system100can include a sensor101(or multiple sensors) that is coupled to a processing device or physiological monitor109. In an embodiment, the sensor101and the monitor109are integrated together into a single unit. In another embodiment, the sensor101and the monitor109are separate from each other and communicate one with another in any suitable manner, such as via a wired or wireless connection. The sensor101and monitor109can be attachable and detachable from each other for the convenience of the user or caregiver, for ease of storage, sterility issues, or the like. The sensor101and the monitor109will now be further described.

In the depicted embodiment shown inFIG. 1, the sensor101includes an emitter104, a tissue shaper105, a set of detectors106, and a front-end interface108. The emitter104can serve as the source of optical radiation transmitted towards measurement site102. As will be described in further detail below, the emitter104can include one or more sources of optical radiation, such as LEDs, laser diodes, incandescent bulbs with appropriate frequency-selective filters, combinations of the same, or the like. In an embodiment, the emitter104includes sets of optical sources that are capable of emitting visible and near-infrared optical radiation.

In some embodiments, the emitter104is used as a point optical source, and thus, the one or more optical sources of the emitter104can be located within a close distance to each other, such as within about a 2 mm to about 4 mm. The emitters104can be arranged in an array, such as is described in U.S. Publication No. 2006/0211924, filed Sep. 21, 2006, titled “Multiple Wavelength Sensor Emitters,” the disclosure of which is hereby incorporated by reference in its entirety. In particular, the emitters104can be arranged at least in part as described in paragraphs [0061] through [0068] of the aforementioned publication, which paragraphs are hereby incorporated specifically by reference. Other relative spatial relationships can be used to arrange the emitters104.

For analytes like glucose, currently available non-invasive techniques often attempt to employ light near the water absorbance minima at or about 1600 nm. Typically, these devices and methods employ a single wavelength or single band of wavelengths at or about 1600 nm. However, to date, these techniques have been unable to adequately consistently measure analytes like glucose based on spectroscopy.

In contrast, the emitter104of the data collection system100can emit, in certain embodiments, combinations of optical radiation in various bands of interest. For example, in some embodiments, for analytes like glucose, the emitter104can emit optical radiation at three (3) or more wavelengths between about 1600 nm to about 1700 nm. In particular, the emitter104can emit optical radiation at or about 1610 nm, about 1640 nm, and about 1665 nm. In some circumstances, the use of three wavelengths within about 1600 nm to about 1700 nm enable sufficient SNRs of about 100 dB, which can result in a measurement accuracy of about 20 mg/DL or better for analytes like glucose.

In other embodiments, the emitter104can use two (2) wavelengths within about 1600 nm to about 1700 nm to advantageously enable SNRs of about 85 dB, which can result in a measurement accuracy of about 25-30 mg/DL or better for analytes like glucose. Furthermore, in some embodiments, the emitter104can emit light at wavelengths above about 1670 nm. Measurements at these wavelengths can be advantageously used to compensate or confirm the contribution of protein, water, and other non-hemoglobin species exhibited in measurements for analytes like glucose conducted between about 1600 nm and about 1700 nm. Of course, other wavelengths and combinations of wavelengths can be used to measure analytes and/or to distinguish other types of tissue, fluids, tissue properties, fluid properties, combinations of the same or the like.

For example, the emitter104can emit optical radiation across other spectra for other analytes. In particular, the emitter104can employ light wavelengths to measure various blood analytes or percentages (e.g., saturation) thereof. For example, in one embodiment, the emitter104can emit optical radiation in the form of pulses at wavelengths about 905 nm, about 1050 nm, about 1200 nm, about 1300 nm, about 1330 nm, about 1610 nm, about 1640 nm, and about 1665 nm. In another embodiment, the emitter104can emit optical radiation ranging from about 860 nm to about 950 nm, about 950 nm to about 1100 nm, about 1100 nm to about 1270 nm, about 1250 nm to about 1350 nm, about 1300 nm to about 1360 nm, and about 1590 nm to about 1700 nm. Of course, the emitter104can transmit any of a variety of wavelengths of visible or near-infrared optical radiation.

Due to the different responses of analytes to the different wavelengths, certain embodiments of the data collection system100can advantageously use the measurements at these different wavelengths to improve the accuracy of measurements. For example, the measurements of water from visible and infrared light can be used to compensate for water absorbance that is exhibited in the near-infrared wavelengths.

As briefly described above, the emitter104can include sets of light-emitting diodes (LEDs) as its optical source. The emitter104can use one or more top-emitting LEDs. In particular, in some embodiments, the emitter104can include top-emitting LEDs emitting light at about 850 nm to 1350 nm.

The emitter104can also use super luminescent LEDs (SLEDs) or side-emitting LEDs. In some embodiments, the emitter104can employ SLEDs or side-emitting LEDs to emit optical radiation at about 1600 nm to about 1800 nm. Emitter104can use SLEDs or side-emitting LEDs to transmit near infrared optical radiation because these types of sources can transmit at high power or relatively high power, e.g., about 40 mW to about 100 mW. This higher power capability can be useful to compensate or overcome the greater attenuation of these wavelengths of light in tissue and water. For example, the higher power emission can effectively compensate and/or normalize the absorption signal for light in the mentioned wavelengths to be similar in amplitude and/or effect as other wavelengths that can be detected by one or more photodetectors after absorption. Alternatively, the emitter104can use other types of sources of optical radiation, such as a laser diode, to emit near-infrared light into the measurement site102.

In addition, in some embodiments, in order to assist in achieving a comparative balance of desired power output between the LEDs, some of the LEDs in the emitter104can have a filter or covering that reduces and/or cleans the optical radiation from particular LEDs or groups of LEDs. For example, since some wavelengths of light can penetrate through tissue relatively well, LEDs, such as some or all of the top-emitting LEDs can use a filter or covering, such as a cap or painted dye. This can be useful in allowing the emitter104to use LEDs with a higher output and/or to equalize intensity of LEDs.

The data collection system100also includes a driver111that drives the emitter104. The driver111can be a circuit or the like that is controlled by the monitor109. For example, the driver111can provide pulses of current to the emitter104. In an embodiment, the driver111drives the emitter104in a progressive fashion, such as in an alternating manner. The driver111can drive the emitter104with a series of pulses of about 1 milliwatt (mW) for some wavelengths that can penetrate tissue relatively well and from about 40 mW to about 100 mW for other wavelengths that tend to be significantly absorbed in tissue. A wide variety of other driving powers and driving methodologies can be used in various embodiments.

The driver111can be synchronized with other parts of the sensor101and can minimize or reduce jitter in the timing of pulses of optical radiation emitted from the emitter104. In some embodiments, the driver111is capable of driving the emitter104to emit optical radiation in a pattern that varies by less than about 10 parts-per-million.

The detectors106capture and measure light from the measurement site102. For example, the detectors106can capture and measure light transmitted from the emitter104that has been attenuated or reflected from the tissue in the measurement site102. The detectors106can output a detector signal107responsive to the light captured or measured. The detectors106can be implemented using one or more photodiodes, phototransistors, or the like.

In addition, the detectors106can be arranged with a spatial configuration to provide a variation of path lengths among at least some of the detectors106. That is, some of the detectors106can have the substantially, or from the perspective of the processing algorithm, effectively, the same path length from the emitter104. However, according to an embodiment, at least some of the detectors106can have a different path length from the emitter104relative to other of the detectors106. Variations in path lengths can be helpful in allowing the use of a bulk signal stream from the detectors106.

The front end interface108provides an interface that adapts the output of the detectors106, which is responsive to desired physiological parameters. For example, the front end interface108can adapt a signal107received from one or more of the detectors106into a form that can be processed by the monitor109, for example, by a signal processor110in the monitor109. The front end interface108can have its components assembled in the sensor101, in the monitor109, in connecting cabling (if used), combinations of the same, or the like. The location of the front end interface108can be chosen based on various factors including space desired for components, desired noise reductions or limits, desired heat reductions or limits, and the like.

The front end interface108can be coupled to the detectors106and to the signal processor110using a bus, wire, electrical or optical cable, flex circuit, or some other form of signal connection. The front end interface108can also be at least partially integrated with various components, such as the detectors106. For example, the front end interface108can include one or more integrated circuits that are on the same circuit board as the detectors106. Other configurations can also be used.

The front end interface108can be implemented using one or more amplifiers, such as transimpedance amplifiers, that are coupled to one or more analog to digital converters (ADCs) (which can be in the monitor109), such as a sigma-delta ADC. A transimpedance-based front end interface108can employ single-ended circuitry, differential circuitry, and/or a hybrid configuration. A transimpedance-based front end interface108can be useful for its sampling rate capability and freedom in modulation/demodulation algorithms. For example, this type of front end interface108can advantageously facilitate the sampling of the ADCs being synchronized with the pulses emitted from the emitter104.

The ADC or ADCs can provide one or more outputs into multiple channels of digital information for processing by the signal processor110of the monitor109. Each channel can correspond to a signal output from a detector106.

In some embodiments, a programmable gain amplifier (PGA) can be used in combination with a transimpedance-based front end interface108. For example, the output of a transimpedance-based front end interface108can be output to a PGA that is coupled with an ADC in the monitor109. A PGA can be useful in order to provide another level of amplification and control of the stream of signals from the detectors106. Alternatively, the PGA and ADC components can be integrated with the transimpedance-based front end interface108in the sensor101.

In another embodiment, the front end interface108can be implemented using switched-capacitor circuits. A switched-capacitor-based front end interface108can be useful for, in certain embodiments, its resistor-free design and analog averaging properties. In addition, a switched-capacitor-based front end interface108can be useful because it can provide a digital signal to the signal processor110in the monitor109.

As shown inFIG. 1, the monitor109can include the signal processor110and a user interface, such as a display112. The monitor109can also include optional outputs alone or in combination with the display112, such as a storage device114and a network interface116. In an embodiment, the signal processor110includes processing logic that determines measurements for desired analytes, such as glucose, based on the signals received from the detectors106. The signal processor110can be implemented using one or more microprocessors or subprocessors (e.g., cores), digital signal processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), combinations of the same, and the like.

The signal processor110can provide various signals that control the operation of the sensor101. For example, the signal processor110can provide an emitter control signal to the driver111. This control signal can be useful in order to synchronize, minimize, or reduce jitter in the timing of pulses emitted from the emitter104. Accordingly, this control signal can be useful in order to cause optical radiation pulses emitted from the emitter104to follow a precise timing and consistent pattern. For example, when a transimpedance-based front end interface108is used, the control signal from the signal processor110can provide synchronization with the ADC in order to avoid aliasing, cross-talk, and the like. As also shown, an optional memory113can be included in the front-end interface108and/or in the signal processor110. This memory113can serve as a buffer or storage location for the front-end interface108and/or the signal processor110, among other uses.

The user interface112can provide an output, e.g., on a display, for presentation to a user of the data collection system100. The user interface112can be implemented as a touch-screen display, an LCD display, an organic LED display, or the like. In addition, the user interface112can be manipulated to allow for measurement on the non-dominant side of patient. For example, the user interface112can include a flip screen, a screen that can be moved from one side to another on the monitor109, or can include an ability to reorient its display indicia responsive to user input or device orientation. In alternative embodiments, the data collection system100can be provided without a user interface112and can simply provide an output signal to a separate display or system.

A storage device114and a network interface116represent other optional output connections that can be included in the monitor109. The storage device114can include any computer-readable medium, such as a memory device, hard disk storage, EEPROM, flash drive, or the like. The various software and/or firmware applications can be stored in the storage device114, which can be executed by the signal processor110or another processor of the monitor109. The network interface116can be a serial bus port (RS-232/RS-485), a Universal Serial Bus (USB) port, an Ethernet port, a wireless interface (e.g., WiFi such as any 802.1x interface, including an internal wireless card), or other suitable communication device(s) that allows the monitor109to communicate and share data with other devices. The monitor109can also include various other components not shown, such as a microprocessor, graphics processor, or controller to output the user interface112, to control data communications, to compute data trending, or to perform other operations.

Although not shown in the depicted embodiment, the data collection system100can include various other components or can be configured in different ways. For example, the sensor101can have both the emitter104and detectors106on the same side of the measurement site102and use reflectance to measure analytes. The data collection system100can also include a sensor that measures the power of light emitted from the emitter104.

FIGS. 2A through 2Dillustrate example monitoring devices200in which the data collection system100can be housed. Advantageously, in certain embodiments, some or all of the example monitoring devices200shown can have a shape and size that allows a user to operate it with a single hand or attach it, for example, to a patient's body or limb. Although several examples are shown, many other monitoring device configurations can be used to house the data collection system100. In addition, certain of the features of the monitoring devices200shown inFIGS. 2A through 2Dcan be combined with features of the other monitoring devices200shown.

Referring specifically toFIG. 2A, an example monitoring device200A is shown, in which a sensor201aand a monitor209aare integrated into a single unit. The monitoring device200A shown is a handheld or portable device that can measure glucose and other analytes in a patient's finger. The sensor201aincludes an emitter shell204aand a detector shell206a. The depicted embodiment of the monitoring device200A also includes various control buttons208aand a display210a.

The sensor201acan be constructed of white material used for reflective purposes (such as white silicone or plastic), which can increase usable signal at the detector106by forcing light back into the sensor201a. Pads in the emitter shell204aand the detector shell206acan contain separated windows to prevent or reduce mixing of light signals, for example, from distinct quadrants on a patient's finger. In addition, these pads can be made of a relatively soft material, such as a gel or foam, in order to conform to the shape, for example, of a patient's finger. The emitter shell204aand the detector shell206acan also include absorbing black or grey material portions to prevent or reduce ambient light from entering into the sensor201a.

In some embodiments, some or all portions of the emitter shell204aand/or detector shell206acan be detachable and/or disposable. For example, some or all portions of the shells204aand206acan be removable pieces. The removability of the shells204aand206acan be useful for sanitary purposes or for sizing the sensor201ato different patients. The monitor209acan include a fitting, slot, magnet, or other connecting mechanism to allow the sensor201cto be removably attached to the monitor209a.

The monitoring device200aalso includes optional control buttons208aand a display210athat can allow the user to control the operation of the device. For example, a user can operate the control buttons208ato view one or more measurements of various analytes, such as glucose. In addition, the user can operate the control buttons208ato view other forms of information, such as graphs, histograms, measurement data, trend measurement data, parameter combination views, wellness indications, and the like. Many parameters, trends, alarms and parameter displays could be output to the display210a, such as those that are commercially available through a wide variety of noninvasive monitoring devices from Masimo® Corporation of Irvine, Calif.

Furthermore, the controls208aand/or display210acan provide functionality for the user to manipulate settings of the monitoring device200a, such as alarm settings, emitter settings, detector settings, and the like. The monitoring device200acan employ any of a variety of user interface designs, such as frames menus, touch-screens, and any type of button.

FIG. 2Billustrates another example of a monitoring device200B. In the depicted embodiment, the monitoring device200B includes a finger clip sensor201bconnected to a monitor209bvia a cable212. In the embodiment shown, the monitor209bincludes a display210b, control buttons208band a power button. Moreover, the monitor209bcan advantageously includes electronic processing, signal processing, and data storage devices capable of receiving signal data from said sensor201b, processing the signal data to determine one or more output measurement values indicative of one or more physiological parameters of a monitored patient, and displaying the measurement values, trends of the measurement values, combinations of measurement values, and the like.

The cable212connecting the sensor201band the monitor209bcan be implemented using one or more wires, optical fiber, flex circuits, or the like. In some embodiments, the cable212can employ twisted pairs of conductors in order to minimize or reduce cross-talk of data transmitted from the sensor201bto the monitor209b. Various lengths of the cable212can be employed to allow for separation between the sensor201band the monitor209b. The cable212can be fitted with a connector (male or female) on either end of the cable212so that the sensor201band the monitor209bcan be connected and disconnected from each other. Alternatively, the sensor201band the monitor209bcan be coupled together via a wireless communication link, such as an infrared link, radio frequency channel, or any other wireless communication protocol and channel.

The monitor209bcan be attached to the patient. For example, the monitor209bcan include a belt clip or straps (see, e.g.,FIG. 2C) that facilitate attachment to a patient's belt, arm, leg, or the like. The monitor209bcan also include a fitting, slot, magnet, LEMO snap-click connector, or other connecting mechanism to allow the cable212and sensor201bto be attached to the monitor209B.

The monitor209bcan also include other components, such as a speaker, power button, removable storage or memory (e.g., a flash card slot), an AC power port, and one or more network interfaces, such as a universal serial bus interface or an Ethernet port. For example, the monitor209bcan include a display210bthat can indicate a measurement for glucose, for example, in mg/dL. Other analytes and forms of display can also appear on the monitor209b.

In addition, although a single sensor201bwith a single monitor209bis shown, different combinations of sensors and device pairings can be implemented. For example, multiple sensors can be provided for a plurality of differing patient types or measurement sites or even patient fingers.

FIG. 2Cillustrates yet another example of monitoring device200C that can house the data collection system100. Like the monitoring device200B, the monitoring device200C includes a finger clip sensor201cconnected to a monitor209cvia a cable212. The cable212can have all of the features described above with respect toFIG. 2B. The monitor209ccan include all of the features of the monitor200B described above. For example, the monitor209cincludes buttons208cand a display210c. The monitor209cshown also includes straps214cthat allow the monitor209cto be attached to a patients limb or the like.

FIG. 2Dillustrates yet another example of monitoring device200D that can house the data collection system100. Like the monitoring devices200B and200C, the monitoring device200D includes a finger clip sensor201dconnected to a monitor209dvia a cable212. The cable212can have all of the features described above with respect toFIG. 2B. In addition to having some or all of the features described above with respect toFIGS. 2B and 2C, the monitoring device200D includes an optional universal serial bus (USB) port216and an Ethernet port218. The USB port216and the Ethernet port218can be used, for example, to transfer information between the monitor209dand a computer (not shown) via a cable. Software stored on the computer can provide functionality for a user to, for example, view physiological data and trends, adjust settings and download firmware updates to the monitor209b, and perform a variety of other functions. The USB port216and the Ethernet port218can be included with the other monitoring devices200A,200B, and200C described above.

FIGS. 3A through 3Cillustrate more detailed examples of embodiments of a sensor301a. The sensor301ashown can include all of the features of the sensors100and200described above.

Referring toFIG. 3A, the sensor301ain the depicted embodiment is a clothespin-shaped clip sensor that includes an enclosure302afor receiving a patient's finger. The enclosure302ais formed by an upper section or emitter shell304a, which is pivotably connected with a lower section or detector shell306a. The emitter shell304acan be biased with the detector shell306ato close together around a pivot point303aand thereby sandwich finger tissue between the emitter and detector shells304a,306a.

In an embodiment, the pivot point303aadvantageously includes a pivot capable of adjusting the relationship between the emitter and detector shells304a,306ato effectively level the sections when applied to a tissue site. In another embodiment, the sensor301aincludes some or all features of the finger clip described in U.S. Publication No. 2006/0211924, incorporated above, such as a spring that causes finger clip forces to be distributed along the finger. Paragraphs through [0105], which describe this feature, are hereby specifically incorporated by reference.

The emitter shell304acan position and house various emitter components of the sensor301a. It can be constructed of reflective material (e.g., white silicone or plastic) and/or can be metallic or include metalicized plastic (e.g., including carbon and aluminum) to possibly serve as a heat sink. The emitter shell304acan also include absorbing opaque material, such as, for example, black or grey colored material, at various areas, such as on one or more flaps307a, to reduce ambient light entering the sensor301a.

The detector shell306acan position and house one or more detector portions of the sensor301a. The detector shell306acan be constructed of reflective material, such as white silicone or plastic. As noted, such materials can increase the usable signal at a detector by forcing light back into the tissue and measurement site (seeFIG. 1). The detector shell306acan also include absorbing opaque material at various areas, such as lower area308a, to reduce ambient light entering the sensor301a.

Referring toFIGS. 3B and 3C, an example of finger bed310is shown in the sensor301b. The finger bed310includes a generally curved surface shaped generally to receive tissue, such as a human digit. The finger bed310includes one or more ridges or channels314. Each of the ridges314has a generally convex shape that can facilitate increasing traction or gripping of the patients finger to the finger bed. Advantageously, the ridges314can improve the accuracy of spectroscopic analysis in certain embodiments by reducing noise that can result from a measurement site moving or shaking loose inside of the sensor301a. The ridges314can be made from reflective or opaque materials in some embodiments to further increase SNR. In other implementations, other surface shapes can be used, such as, for example, generally flat, concave, or convex finger beds310.

Finger bed310can also include an embodiment of a tissue thickness adjuster or protrusion305. The protrusion305includes a measurement site contact area370(seeFIG. 3C) that can contact body tissue of a measurement site. The protrusion305can be removed from or integrated with the finger bed310. Interchangeable, different shaped protrusions305can also be provided, which can correspond to different finger shapes, characteristics, opacity, sizes, or the like.

Referring specifically toFIG. 3C, the contact area370of the protrusion305can include openings or windows320,321,322, and323. When light from a measurement site passes through the windows320,321,322, and323, the light can reach one or more photodetectors (seeFIG. 3E). In an embodiment, the windows320,321,322, and323mirror specific detector placements layouts such that light can impinge through the protrusion305onto the photodetectors. Any number of windows320,321,322, and323can be employed in the protrusion305to allow light to pass from the measurement site to the photodetectors.

The windows320,321,322, and323can also include shielding, such as an embedded grid of wiring or a conductive glass coating, to reduce noise from ambient light or other electromagnetic noise. The windows320,321,322, and323can be made from materials, such as plastic or glass. In some embodiments, the windows320,321,322, and323can be constructed from conductive glass, such as indium tin oxide (ITO) coated glass. Conductive glass can be useful because its shielding is transparent, and thus allows for a larger aperture versus a window with an embedded grid of wiring. In addition, in certain embodiments, the conductive glass does not need openings in its shielding (since it is transparent), which enhances its shielding performance. For example, some embodiments that employ the conductive glass can attain up to an about 40% to about 50% greater signal than non-conductive glass with a shielding grid. In addition, in some embodiments, conductive glass can be useful for shielding noise from a greater variety of directions than non-conductive glass with a shielding grid.

Turning toFIG. 3B, the sensor301acan also include a shielding315a, such as a metal cage, box, metal sheet, perforated metal sheet, a metal layer on a non-metal material, or the like. The shielding315ais provided in the depicted embodiment below or embedded within the protrusion305to reduce noise. The shielding315acan be constructed from a conductive material, such as copper. The shielding315acan include one or more openings or windows (not shown). The windows can be made from glass or plastic to thereby allow light that has passed through the windows320,321,322, and323on an external surface of the protrusion305(seeFIG. 3C) to pass through to one or more photodetectors that can be enclosed or provided below (seeFIG. 3E).

In an embodiment, the photodetectors can be positioned within or directly beneath the protrusion305(seeFIG. 3E). In such cases, the mean optical path length from the emitters to the detectors can be reduced and the accuracy of blood analyte measurement can increase. For example, in one embodiment, a convex bump of about 1 mm to about 3 mm in height and about 10 mm2to about 60 mm2was found to help signal strength by about an order of magnitude versus other shapes. Of course other dimensions and sizes can be employed in other embodiments. Depending on the properties desired, the length, width, and height of the protrusion305can be selected. In making such determinations, consideration can be made of protrusion's305effect on blood flow at the measurement site and mean path length for optical radiation passing through openings320,321,322, and323. Patient comfort can also be considered in determining the size and shape of the protrusion.

In an embodiment, the protrusion305can include a pliant material, including soft plastic or rubber, which can somewhat conform to the shape of a measurement site. Pliant materials can improve patient comfort and tactility by conforming the measurement site contact area370to the measurement site. Additionally, pliant materials can minimize or reduce noise, such as ambient light. Alternatively, the protrusion305can be made from a rigid material, such as hard plastic or metal.

Rigid materials can improve measurement accuracy of a blood analyte by conforming the measurement site to the contact area370. The contact area370can be an ideal shape for improving accuracy or reducing noise. Selecting a material for the protrusion305can include consideration of materials that do not significantly alter blood flow at the measurement site. The protrusion305and the contact area370can include a combination of materials with various characteristics.

The contact area370serves as a contact surface for the measurement site. For example, in some embodiments, the contact area370can be shaped for contact with a patient's finger. Accordingly, the contact area370can be sized and shaped for different sizes of fingers. The contact area370can be constructed of different materials for reflective purposes as well as for the comfort of the patient. For example, the contact area370can be constructed from materials having various hardness and textures, such as plastic, gel, foam, and the like.

The formulas and analysis that follow with respect toFIG. 5provide insight into how selecting these variables can alter transmittance and intensity gain of optical radiation that has been applied to the measurement site. These examples do not limit the scope of this disclosure.

Referring toFIG. 5, a plot500is shown that illustrates examples of effects of embodiments of the protrusion305on the SNR at various wavelengths of light. As described above, the protrusion305can assist in conforming the tissue and effectively reduce its mean path length. In some instances, this effect by the protrusion305can have significant impact on increasing the SNR.

According to the Beer Lambert law, a transmittance of light (I) can be expressed as follows: I=Io*e−m*b*c, where Iois the initial power of light being transmitted, m is the path length traveled by the light, and the component “b*c” corresponds to the bulk absorption of the light at a specific wavelength of light. For light at about 1600 nm to about 1700 nm, for example, the bulk absorption component is generally around 0.7 mm−1. Assuming a typical finger thickness of about 12 mm and a mean path length of 20 mm due to tissue scattering, then I=Io*e(−20*0.7).

In an embodiment where the protrusion305is a convex bump, the thickness of the finger can be reduced to 10 mm (from 12 mm) for some fingers and the effective light mean path is reduced to about 16.6 mm from 20 mm (see box510). This results in a new transmittance, I1=Io*e(−16.6*0.7). A curve for a typical finger (having a mean path length of 20 mm) across various wavelengths is shown in the plot500ofFIG. 5. The plot500illustrates potential effects of the protrusion305on the transmittance. As illustrated, comparing I and I1results in an intensity gain of e(−16.6*0.7)/e(−20*0.7), which is about a 10 times increase for light in the about 1600 nm to about 1700 nm range. Such an increase can affect the SNR at which the sensor can operate. The foregoing gains can be due at least in part to the about 1600 nm to about 1700 nm range having high values in bulk absorptions (water, protein, and the like), e.g., about 0.7 mm−1. The plot500also shows improvements in the visible/near-infrared range (about 600 nm to about 1300 nm).

The contribution of a the protrusion305to increased SNR cannot have been previously recognized by persons having ordinary skill in the art at least in part because currently available devices can have been concerned primarily with conforming to the measurement site for patient comfort. In addition, for light in the visible range and infrared range, or in other words, at the wavelengths of many previous devices, the bulk absorption of light component in the finger is generally much lower at around 0.1 mm−1. Therefore, the same change in thickness increases intensity by, for example, e(−16.6*0.1)/e(−20*0.1), which results in about a 1.5 times increase. In currently available devices, such an impact cannot have been significant enough to warrant overriding other considerations, such as patient comfort. It should be noted, however, that the various protrusion305designs disclosed herein can increase SNR while also preserving patient comfort.

Turning again toFIGS. 3A through 3C, an example heat sink350ais also shown. The heat sink350acan be attached to, or protrude from an outer surface of, the sensor301a, thereby providing increased ability for various sensor components to dissipate excess heat. By being on the outer surface of the sensor301ain certain embodiments, the heat sink350acan be exposed to the air and thereby facilitate more efficient cooling. In an embodiment, one or more of the emitters (seeFIG. 1) generate sufficient heat that inclusion of the heat sink350acan advantageously allows the sensor301ato remain safely cooled. The heat sink350acan include one or more materials that help dissipate heat, such as, for example, aluminum, steel, copper, carbon, combinations of the same, or the like. For example, in some embodiments, the emitter shell304acan include a heat conducting material that is also readily and relatively inexpensively moldable into desired shapes and forms.

In some embodiments, the heat sink350aincludes metalicized plastic. The metalicized plastic can include aluminum and carbon, for example. The material can allow for improved thermal conductivity and diffusivity, which can increase commercial viability of the heat sink. In some embodiments, the material selected to construct the heat sink350acan include a thermally conductive liquid crystalline polymer, such as CoolPoly® D5506, commercially available from Cool Polymers®, Inc. of Warwick, R.I. Such a material can be selected for its electrically non-conductive and dielectric properties so as, for example, to aid in electrical shielding. In an embodiment, the heat sink350aprovides improved heat transfer properties when the sensor301ais active for short intervals of less than a full day's use. In an embodiment, the heat sink350acan advantageously provide improved heat transfers in about three (3) to about four (4) minute intervals, for example, although a heat sink350acan be selected that performs effectively in shorter or longer intervals.

Moreover, the heat sink350acan have different shapes and configurations for aesthetic as well as for functional purposes. In an embodiment, the heat sink is configured to maximize heat dissipation, for example, by maximizing surface area. In an embodiment, the heat sink350ais molded into a generally curved surface and includes one or more fins, undulations, grooves, or channels. The example heat sink350ashown includes fins351a(seeFIG. 3A).

An alternative shape of a sensor301band heat sink350bis shown inFIG. 3D. The sensor301bcan include some or all of the features of the sensor301a. For example, the sensor301bincludes an enclosure302bformed by an emitter shell304band a detector shell306b, pivotably connected about a pivot303a. The emitter shell304bcan also include absorbing opaque material on one or more flaps307b, and the detector shell306acan also include absorbing opaque material at various areas, such as lower area308b.

However, the shape of the sensor301bis different in this embodiment. In particular, the heat sink350bincludes comb protrusions351b. The comb protrusions351bare exposed to the air in a similar manner to the fins351aof the heat sink350a, thereby facilitating efficient cooling of the sensor301b.

FIG. 3Eillustrates a more detailed example of a detector shell306bof the sensor301b. The features described with respect to the detector shell306bcan also be used with the detector shell306aof the sensor301a.

As shown, the detector shell306bincludes detectors316. The detectors316can have a predetermined spacing340from each other, or a spatial relationship among one another that results in a spatial configuration. This spatial configuration can purposefully create a variation of path lengths among detectors316and the emitter discussed above.

In the depicted embodiment, the detector shell316can hold multiple (e.g., two, three, four, etc.) photodiode arrays that are arranged in a two-dimensional grid pattern. Multiple photodiode arrays can also be useful to detect light piping (e.g., light that bypasses measurement site102). In the detector shell316, walls can be provided to separate the individual photodiode arrays to prevent or reduce mixing of light signals from distinct quadrants. In addition, the detector shell316can be covered by windows of transparent material, such as glass, plastic, or the like, to allow maximum or increased transmission of power light captured. In various embodiments, the transparent materials used can also be partially transparent or translucent or can otherwise pass some or all of the optical radiation passing through them. As noted, this window can include some shielding in the form of an embedded grid of wiring, or a conductive layer or coating.

As further illustrated byFIG. 3E, the detectors316can have a spatial configuration of a grid. However, the detectors316can be arranged in other configurations that vary the path length. For example, the detectors316can be arranged in a linear array, a logarithmic array, a two-dimensional array, or the like. Furthermore, any number of the detectors316can be employed in certain embodiments.

FIG. 3Fillustrates another embodiment of a sensor301f. The sensor301fcan include some or all of the features of the sensor301aofFIG. 3Adescribed above. For example, the sensor301fincludes an enclosure302fformed by an upper section or emitter shell304f, which is pivotably connected with a lower section or detector shell306faround a pivot point303f. The emitter shell304fcan also include absorbing opaque material on various areas, such as on one or more flaps307f, to reduce ambient light entering the sensor301f. The detector shell306fcan also include absorbing opaque material at various areas, such as a lower area308f. The sensor301falso includes a heat sink350f, which includes fins351f.

In addition to these features, the sensor301fincludes a flex circuit cover360, which can be made of plastic or another suitable material. The flex circuit cover360can cover and thereby protect a flex circuit (not shown) that extends from the emitter shell304fto the detector shell306f. An example of such a flex circuit is illustrated in U.S. Publication No. 2006/0211924, incorporated above (seeFIG. 46and associated description, which is hereby specifically incorporated by reference). The flex circuit cover360is shown in more detail below inFIG. 17.

FIGS. 4A through 4Cillustrate example arrangements of a protrusion405, which is an embodiment of the protrusion305described above. In an embodiment, the protrusion405can include a measurement site contact area470. The measurement site contact area470can include a surface that molds body tissue of a measurement site, such as a finger, into a flat or relatively flat surface.

The protrusion405can have dimensions that are suitable for a measurement site such as a patient's finger. As shown, the protrusion405can have a length400, a width410, and a height430. The length400can be from about 9 to about 11 millimeters, e.g., about 10 millimeters. The width410can be from about 7 to about 9 millimeters, e.g., about 8 millimeters. The height430can be from about 0.5 millimeters to about 3 millimeters, e.g., about 2 millimeters. In an embodiment, the dimensions400,410, and430can be selected such that the measurement site contact area470includes an area of about 80 square millimeters although larger and smaller areas can be used for different sized tissue for an adult, an adolescent, or infant, or for other considerations.

The measurement site contact area470can also include differently shaped surfaces that conform the measurement site into different shapes. For example, the measurement site contact area470can be generally curved and/or convex with respect to the measurement site. The measurement site contact area470can be other shapes that reduce or even minimize air between the protrusion405and or the measurement site. Additionally, the surface pattern of the measurement site contact area470can vary from smooth to bumpy, e.g., to provide varying levels of grip.

InFIGS. 4A and 4C, openings or windows420,421,422, and423can include a wide variety of shapes and sizes, including for example, generally square, circular, triangular, or combinations thereof. The windows420,421,422, and423can be of non-uniform shapes and sizes. As shown, the windows420,421,422, and423can be evenly spaced out in a grid like arrangement. Other arrangements or patterns of arranging the windows420,421,422, and423are possible. For example, the windows420,421,422, and423can be placed in a triangular, circular, or linear arrangement. In some embodiments, the windows420,421,422, and423can be placed at different heights with respect to the finger bed310ofFIG. 3. The windows420,421,422, and423can also mimic or approximately mimic a configuration of, or even house, a plurality of detectors.

FIGS. 6A through 6Dillustrate another embodiment of a protrusion605that can be used as the tissue shaper105described above or in place of the protrusions305,405described above. The depicted protrusion605is a partially cylindrical lens having a partial cylinder608and an extension610. The partial cylinder608can be a half cylinder in some embodiments; however, a smaller or greater portion than half of a cylinder can be used. Advantageously, in certain embodiments, the partially cylindrical protrusion605focuses light onto a smaller area, such that fewer detectors can be used to detect the light attenuated by a measurement site.

FIG. 6Aillustrates a perspective view of the partially cylindrical protrusion605.FIG. 6Billustrates a front elevation view of the partially cylindrical protrusion605.FIG. 6Cillustrates a side view of the partially cylindrical protrusion605.FIG. 6Dillustrates a top view of the partially cylindrical protrusion605.

Advantageously, in certain embodiments, placing the partially cylindrical protrusion605over the photodiodes in any of the sensors described above adds multiple benefits to any of the sensors described above. In one embodiment, the partially cylindrical protrusion605penetrates into the tissue and reduces the pathlength of the light traveling in the tissue, similar to the protrusions described above.

The partially cylindrical protrusion605can also collect light from a large surface and focus down the light to a smaller area. As a result, in certain embodiments, signal strength per area of the photodiode can be increased. The partially cylindrical protrusion605can therefore facilitate a lower cost sensor because, in certain embodiments, less photodiode area can be used to obtain the same signal strength. Less photodiode area can be realized by using smaller photodiodes or fewer photodiodes (see, e.g.,FIG. 14). If fewer or smaller photodiodes are used, the partially cylindrical protrusion605can also facilitate an improved SNR of the sensor because fewer or smaller photodiodes can have less dark current.

The dimensions of the partially cylindrical protrusion605can vary based on, for instance, a number of photodiodes used with the sensor. Referring toFIG. 6C, the overall height of the partially cylindrical protrusion605(measurement “a”) in some implementations is about 1 to about 3 mm. A height in this range can allow the partially cylindrical protrusion605to penetrate into the pad of the finger or other tissue and reduce the distance that light travels through the tissue. Other heights, however, of the partially cylindrical protrusion605can also accomplish this objective. For example, the chosen height of the partially cylindrical protrusion605can be selected based on the size of the measurement site, whether the patient is an adult or child, and so on. In an embodiment, the height of the protrusion605is chosen to provide as much tissue thickness reduction as possible while reducing or preventing occlusion of blood vessels in the tissue.

Referring toFIG. 6D, the width of the partially cylindrical protrusion605(measurement “b”) can be about 3 to about 5 mm. In one embodiment, the width is about 4 mm. In one embodiment, a width in this range provides good penetration of the partially cylindrical protrusion605into the tissue to reduce the pathlength of the light. Other widths, however, of the partially cylindrical protrusion605can also accomplish this objective. For example, the width of the partially cylindrical protrusion605can vary based on the size of the measurement site, whether the patient is an adult or child, and so on. In addition, the length of the protrusion605could be about 10 mm, or about 8 mm to about 12 mm, or smaller than 8 mm or greater than 12 mm.

In certain embodiments, the focal length (f) for the partially cylindrical protrusion605can be expressed as:

f=Rn-1,
where R is the radius of curvature of the partial cylinder608and n is the index of refraction of the material used. In certain embodiments, the radius of curvature can be between about 1.5 mm and about 2 mm. In another embodiment, the partially cylindrical protrusion605can include a material, such as nBK7 glass, with an index of refraction of around 1.5 at 1300 nm, which can provide focal lengths of between about 3 mm and about 4 mm.

A partially cylindrical protrusion605having a material with a higher index of refraction such as nSF11 glass (e.g., n=1.75 at 1300 nm) can provide a shorter focal length and possibly a smaller photodiode chip, but can also cause higher reflections due to the index of refraction mismatch with air. Many types of glass or plastic can be used with index of refraction values ranging from, for example, about 1.4 to about 1.9. The index of refraction of the material of the protrusion605can be chosen to improve or optimize the light focusing properties of the protrusion605. A plastic partially cylindrical protrusion605could provide the cheapest option in high volumes but can also have some undesired light absorption peaks at wavelengths higher than 1500 nm. Other focal lengths and materials having different indices of refraction can be used for the partially cylindrical protrusion605.

Placing a photodiode at a given distance below the partially cylindrical protrusion605can facilitate capturing some or all of the light traveling perpendicular to the lens within the active area of the photodiode (seeFIG. 14). Different sizes of the partially cylindrical protrusion605can use different sizes of photodiodes. The extension610added onto the bottom of the partial cylinder608is used in certain embodiments to increase the height of the partially cylindrical protrusion605. In an embodiment, the added height is such that the photodiodes are at or are approximately at the focal length of the partially cylindrical protrusion605. In an embodiments, the added height provides for greater thinning of the measurement site. In an embodiment, the added height assists in deflecting light piped through the sensor. This is because light piped around the sensor passes through the side walls of the added height without being directed toward the detectors. The extension610can also further facilitate the protrusion605increasing or maximizing the amount of light that is provided to the detectors. In some embodiments, the extension610can be omitted.

FIG. 6Eillustrates another view of the sensor301fofFIG. 3F, which includes an embodiment of a partially cylindrical protrusion605b. Like the sensor301A shown inFIGS. 3B and 3C, the sensor301fincludes a finger bed310f. The finger bed310fincludes a generally curved surface shaped generally to receive tissue, such as a human digit. The finger bed310falso includes the ridges or channels314described above with respect toFIGS. 3B and 3C.

The example of finger bed310fshown also includes the protrusion605b, which includes the features of the protrusion605described above. In addition, the protrusion605balso includes chamfered edges607on each end to provide a more comfortable surface for a finger to slide across (see alsoFIG. 14D). In another embodiment, the protrusion605bcould instead include a single chamfered edge607proximal to the ridges314. In another embodiment, one or both of the chamfered edges607could be rounded.

The protrusion605balso includes a measurement site contact area670that can contact body tissue of a measurement site. The protrusion605bcan be removed from or integrated with the finger bed310f. Interchangeable, differently shaped protrusions605bcan also be provided, which can correspond to different finger shapes, characteristics, opacity, sizes, or the like.

FIGS. 7A and 7Billustrate block diagrams of sensors701that include example arrangements of conductive glass or conductive coated glass for shielding. Advantageously, in certain embodiments, the shielding can provide increased SNR. The features of the sensors701can be implemented with any of the sensors101,201,301described above. Although not shown, the partially cylindrical protrusion605ofFIG. 6can also be used with the sensors701in certain embodiments.

For example, referring specifically toFIG. 7A, the sensor701aincludes an emitter housing704aand a detector housing706. The emitter housing704aincludes LEDs104. The detector housing706aincludes a tissue bed710awith an opening or window703a, the conductive glass730a, and one or more photodiodes for detectors106provided on a submount707a.

During operation, a finger102can be placed on the tissue bed710aand optical radiation can be emitted from the LEDs104. Light can then be attenuated as it passes through or is reflected from the tissue of the finger102. The attenuated light can then pass through the opening703ain the tissue bed710a. Based on the received light, the detectors106can provide a detector signal107, for example, to the front end interface108(seeFIG. 1).

In the depicted embodiment, the conductive glass730is provided in the opening703. The conductive glass730can thus not only permit light from the finger to pass to the detectors106, but it can also supplement the shielding of the detectors106from noise. The conductive glass730can include a stack or set of layers. InFIG. 7A, the conductive glass730ais shown having a glass layer731proximate the finger102and a conductive layer733electrically coupled to the shielding790a.

In an embodiment, the conductive glass730acan be coated with a conductive, transparent or partially transparent material, such as a thin film of indium tin oxide (ITO). To supplement electrical shielding effects of a shielding enclosure790a, the conductive glass730acan be electrically coupled to the shielding enclosure790a. The conductive glass730acan be electrically coupled to the shielding704abased on direct contact or via other connection devices, such as a wire or another component.

The shielding enclosure790acan be provided to encompass the detectors106to reduce or prevent noise. For example, the shielding enclosure790acan be constructed from a conductive material, such as copper, in the form of a metal cage. The shielding or enclosure a can include an opaque material to not only reduce electrical noise, but also ambient optical noise.

Referring toFIG. 7B, another block diagram of an example sensor701bis shown. A tissue bed710bof the sensor701bincludes a protrusion705b, which is in the form of a convex bump. The protrusion705bcan include all of the features of the protrusions or tissue shaping materials described above. For example, the protrusion705bincludes a contact area370that comes in contact with the finger102and which can include one or more openings703b. One or more components of conductive glass730bcan be provided in the openings703. For example, in an embodiment, each of the openings703can include a separate window of the conductive glass730b. In an embodiment, a single piece of the conductive glass730bcan used for some or all of the openings703b. The conductive glass730bis smaller than the conductive glass730ain this particular embodiment.

A shielding enclosure790bis also provided, which can have all the features of the shielding enclosure790a. The shielding enclosure790bis smaller than the shielding enclosure790a; however, a variety of sizes can be selected for the shielding enclosures790.

FIGS. 8A through 8Dillustrate a perspective view, side views, and a bottom elevation view of the conductive glass described above with respect to the sensors701a,701b. As shown in the perspective view ofFIG. 8Aand side view ofFIG. 8B, the conductive glass730includes the electrically conductive material733described above as a coating on the glass layer731described above to form a stack. In an embodiment where the electrically conductive material733includes indium tin oxide, surface resistivity of the electrically conductive material733can range approximately from 30 ohms per square inch to 500 ohms per square inch, or approximately 30, 200, or 500 ohms per square inch. As would be understood by a person of skill in the art from the present disclosure, other resistivities can also be used which are less than 30 ohms or more than 500 ohms. Other transparent, electrically conductive materials can be used as the material733.

Although the conductive material733is shown spread over the surface of the glass layer731, the conductive material733can be patterned or provided on selected portions of the glass layer731. Furthermore, the conductive material733can have uniform or varying thickness depending on a desired transmission of light, a desired shielding effect, and other considerations.

InFIG. 8C, a side view of a conductive glass830ais shown to illustrate an embodiment where the electrically conductive material733is provided as an internal layer between two glass layers731,835. Various combinations of integrating electrically conductive material733with glass are possible. For example, the electrically conductive material733can be a layer within a stack of layers. This stack of layers can include one or more layers of glass731,835, as well as one or more layers of conductive material733. The stack can include other layers of materials to achieve desired characteristics.

InFIG. 8D, a bottom perspective view is shown to illustrate an embodiment where a conductive glass830bcan include conductive material837that occupies or covers a portion of a glass layer839. This embodiment can be useful, for example, to create individual, shielded windows for detectors106, such as those shown inFIG. 3C. The conductive material837can be patterned to include an area838to allow light to pass to detectors106and one or more strips841to couple to the shielding704ofFIG. 7.

Other configurations and patterns for the conductive material can be used in certain embodiments, such as, for example, a conductive coating lining periphery edges, a conductive coating outlaid in a pattern including a grid or other pattern, a speckled conductive coating, coating outlaid in lines in either direction or diagonally, varied thicknesses from the center out or from the periphery in, or other suitable patterns or coatings that balance the shielding properties with transparency considerations.

FIG. 9depicts an example graph900that illustrates comparative results obtained by an example sensor having components similar to those disclosed above with respect toFIGS. 7 and 8. The graph900depicts the results of the percentage of transmission of varying wavelengths of light for different types of windows used in the sensors described above.

A line915on the graph900illustrates example light transmission of a window made from plain glass. As shown, the light transmission percentage of varying wavelengths of light is approximately 90% for a window made from plain glass. A line920on the graph900demonstrates an example light transmission percentage for an embodiment in which a window is made from glass having an ITO coating with a surface resistivity of 500 ohms per square inch. A line925on the graph900shows an example light transmission for an embodiment in which a window is made from glass that includes a coating of ITO oxide with a surface resistivity of 200 ohms per square inch. A line930on the graph900shows an example light transmission for an embodiment in which a window is made from glass that includes a coating of ITO oxide with a surface resistivity of 30 ohms per square inch.

The light transmission percentage for a window with currently available embedded wiring can have a light transmission percentage of approximately 70%. This lower percentage of light transmission can be due to the opacity of the wiring employed in a currently available window with wiring. Accordingly, certain embodiments of glass coatings described herein can employ, for example, ITO coatings with different surface resistivity depending on the desired light transmission, wavelengths of light used for measurement, desired shielding effect, and other criteria.

FIGS. 10A through 10Billustrate comparative noise floors of example implementations of the sensors described above. Noise can include optical noise from ambient light and electromagnetic noise, for example, from surrounding electrical equipment. InFIG. 10A, a graph1000depicts possible noise floors for different frequencies of noise for an embodiment in which one of the sensors described above included separate windows for four (4) detectors106. One or more of the windows included an embedded grid of wiring as a noise shield. Symbols1030-1033illustrate the noise floor performance for this embodiment. As can be seen, the noise floor performance can vary for each of the openings and based on the frequency of the noise.

InFIG. 10B, a graph1050depicts a noise floor for frequencies of noise1070for an embodiment in which the sensor included separate openings for four (4) detectors106and one or more windows that include an ITO coating. In this embodiment, a surface resistivity of the ITO used was about 500 ohms per square inch. Symbols1080-1083illustrate the noise floor performance for this embodiment. As can be seen, the noise floor performance for this embodiment can vary less for each of the openings and provide lower noise floors in comparison to the embodiment ofFIG. 10A.

FIG. 11illustrates an example structure for configuring the set of optical sources of the emitters described above. As shown, an emitter1104can include a driver1111, a thermistor1120, a set of top-emitting LEDs1102for emitting red and/or infrared light, a set of side-emitting LEDs1104for emitting near infrared light, and a submount1106.

The thermistor1120can be provided to compensate for temperature variations. For example, the thermistor1120can be provided to allow for wavelength centroid and power drift of LEDs1102and1104due to heating. In addition, other thermistors (not shown) can be employed, for example, to measure a temperature of a measurement site. Such a temperature can be helpful in correcting for wavelength drift due to changes in water absorption, which can be temperature dependent, thereby providing more accurate data useful in detecting blood analytes like glucose.

The driver1105can provide pulses of current to the emitter1104. In an embodiment, the driver1105drives the emitter1104in a progressive fashion for example, in an alternating manner based on a control signal from, for example, a processor (e.g., the processor110). For example, the driver1105can drive the emitter1104with a series of pulses to about 1 milliwatt (mW) for visible light to light at about 1300 nm and from about 40 mW to about 100 mW for light at about 1600 nm to about 1700 nm. However, a wide number of driving powers and driving methodologies can be used. The driver1105can be synchronized with other parts of the sensor and can minimize or reduce any jitter in the timing of pulses of optical radiation emitted from the emitter1104. In some embodiments, the driver1105is capable of driving the emitter1104to emit an optical radiation in a pattern that varies by less than about 10 parts-per-million; however other amounts of variation can be used.

The submount1106provides a support structure in certain embodiments for aligning the top-emitting LEDs1102and the side-emitting LEDs1104so that their optical radiation is transmitted generally towards the measurement site. In some embodiments, the submount1106is also constructed of aluminum nitride (AlN) or beryllium oxide (BEO) for heat dissipation, although other materials or combinations of materials suitable for the submount1106can be used.

FIG. 12illustrates a detector submount1200having photodiode detectors that are arranged in a grid pattern on the detector submount1200to capture light at different quadrants from a measurement site. One detector submount1200can be placed under each window of the sensors described above, or multiple windows can be placed over a single detector submount1200. The detector submount1200can also be used with the partially cylindrical protrusion605described above with respect toFIG. 6.

The detectors include photodiode detectors1-4that are arranged in a grid pattern on the submount1200to capture light at different quadrants from the measurement site. As noted, other patterns of photodiodes, such as a linear row, or logarithmic row, can also be employed in certain embodiments.

FIG. 13illustrates an example multi-stream process1300. The multi-stream process1300can be implemented by the data collection system100and/or by any of the sensors described above. As shown, a control signal from a signal processor1310controls a driver1305. In response, an emitter1304generates a pulse sequence1303from its emitter (e.g., its LEDs) into a measurement site or sites1302. As described above, in some embodiments, the pulse sequence1303is controlled to have a variation of about 10 parts per million or less. Of course, depending on the analyte desired, the tolerated variation in the pulse sequence1303can be greater (or smaller).

In response to the pulse sequence1300, detectors1to n (n being an integer) in a detector1306capture optical radiation from the measurement site1302and provide respective streams of output signals. Each signal from one of detectors1-n can be considered a stream having respective time slots corresponding to the optical pulses from emitter sets1-n in the emitter1304. Although n emitters and n detectors are shown, the number of emitters and detectors need not be the same in certain implementations.

A front end interface1308can accept these multiple streams from detectors1-n and deliver one or more signals or composite signal(s) back to the signal processor1310. A stream from the detectors1-n can thus include measured light intensities corresponding to the light pulses emitted from the emitter1304.

The signal processor1310can then perform various calculations to measure the amount of glucose and other analytes based on these multiple streams of signals. In order to help explain how the signal processor1310can measure analytes like glucose, a primer on the spectroscopy employed in these embodiments will now be provided.

Spectroscopy is premised upon the Beer-Lambert law. According to this law, the properties of a material, e.g., glucose present in a measurement site can be deterministically calculated from the absorption of light traveling through the material. Specifically, there is a logarithmic relation between the transmission of light through a material and the concentration of a substance and also between the transmission and the length of the path traveled by the light. As noted, this relation is known as the Beer-Lambert law.

The Beer-Lambert law is usually written as:
AbsorbanceA=m*b*c, where:
m is the wavelength-dependent molar absorptivity coefficient (usually expressed in units of M−1cm−1);

b is the mean path length; and

c is the analyte concentration (e.g., the desired parameter).

In spectroscopy, instruments attempt to obtain the analyte concentration (c) by relating absorbance (A) to transmittance (T). Transmittance is a proportional value defined as:
T=I/Io, where:

I is the light intensity measured by the instrument from the measurement site; and

Iois the initial light intensity from the emitter.

Absorbance (A) can be equated to the transmittance (T) by the equation:
A=−logT

In view of this relationship, spectroscopy thus relies on a proportional-based calculation of −log (I/Io) and solving for analyte concentration (c).

Typically, in order to simplify the calculations, spectroscopy will use detectors that are at the same location in order to keep the path length (b) a fixed, known constant. In addition, spectroscopy will employ various mechanisms to definitively know the transmission power (Io), such as a photodiode located at the light source. This architecture can be viewed as a single channel or single stream sensor, because the detectors are at a single location.

However, this scheme can encounter several difficulties in measuring analytes, such as glucose. This can be due to the high overlap of absorption of light by water at the wavelengths relevant to glucose as well as other factors, such as high self-noise of the components.

Embodiments of the present disclosure can employ a different approach that in part allows for the measurement of analytes like glucose. Some embodiments can employ a bulk, non-pulsatile measurement in order to confirm or validate a pulsatile measurement. In addition, both the non-pulsatile and pulsatile measurements can employ, among other things, the multi-stream operation described above in order to attain sufficient SNR. In particular, a single light source having multiple emitters can be used to transmit light to multiple detectors having a spatial configuration.

A single light source having multiple emitters can allow for a range of wavelengths of light to be used. For example, visible, infrared, and near infrared wavelengths can be employed. Varying powers of light intensity for different wavelengths can also be employed.

Secondly, the use of multiple-detectors in a spatial configuration allow for a bulk measurement to confirm or validate that the sensor is positioned correctly. This is because the multiple locations of the spatial configuration can provide, for example, topology information that indicates where the sensor has been positioned. Currently available sensors do not provide such information. For example, if the bulk measurement is within a predetermined range of values, then this can indicate that the sensor is positioned correctly in order to perform pulsatile measurements for analytes like glucose. If the bulk measurement is outside of a certain range or is an unexpected value, then this can indicate that the sensor should be adjusted, or that the pulsatile measurements can be processed differently to compensate, such as using a different calibration curve or adjusting a calibration curve. This feature and others allow the embodiments to achieve noise cancellation and noise reduction, which can be several times greater in magnitude that what is achievable by currently available technology.

In order to help illustrate aspects of the multi-stream measurement approach, the following example derivation is provided. Transmittance (T) can be expressed as:
T=e−m*b*c

In terms of light intensity, this equation can also be rewritten as:
I/Io=e−m*b*c

Or, at a detector, the measured light (I) can be expressed as:
I=Io*e−m*b*c

As noted, in the present disclosure, multiple detectors (1to n) can be employed, which results in I1. . . Instreams of measurements. Assuming each of these detectors have their own path lengths, b1. . . bn, from the light source, the measured light intensities can be expressed as:
I1=Io*e−m*bn*c

The measured light intensities at any two different detectors can be referenced to each other. For example:
I1/In=(Io*e−mb1c)/(Io*e−mbnc)

As can be seen, the terms, Io, cancel out and, based on exponent algebra, the equation can be rewritten as:
I1/In=e−m(b1−bn)c

From this equation, the analyte concentration (c) can now be derived from bulk signals I1. . . Inand knowing the respective mean path lengths b1and bn. This scheme also allows for the cancelling out of Io, and thus, noise generated by the emitter1304can be cancelled out or reduced. In addition, since the scheme employs a mean path length difference, any changes in mean path length and topological variations from patient to patient are easily accounted. Furthermore, this bulk-measurement scheme can be extended across multiple wavelengths. This flexibility and other features allow embodiments of the present disclosure to measure blood analytes like glucose.

For example, as noted, the non-pulsatile, bulk measurements can be combined with pulsatile measurements to more accurately measure analytes like glucose. In particular, the non-pulsatile, bulk measurement can be used to confirm or validate the amount of glucose, protein, etc. in the pulsatile measurements taken at the tissue at the measurement site(s)1302. The pulsatile measurements can be used to measure the amount of glucose, hemoglobin, or the like that is present in the blood. Accordingly, these different measurements can be combined to thus determine analytes like blood glucose.

FIG. 14Aillustrates an embodiment of a detector submount1400apositioned beneath the partially cylindrical protrusion605ofFIG. 6(or alternatively, the protrusion605b). The detector submount1400aincludes two rows1408aof detectors1410a. The partially cylindrical protrusion605can facilitate reducing the number and/or size of detectors used in a sensor because the protrusion605can act as a lens that focuses light onto a smaller area.

To illustrate, in some sensors that do not include the partially cylindrical protrusion605, sixteen detectors can be used, including four rows of four detectors each. Multiple rows of detectors can be used to measure certain analytes, such as glucose or total hemoglobin, among others. Multiple rows of detectors can also be used to detect light piping (e.g., light that bypasses the measurement site). However, using more detectors in a sensor can add cost, complexity, and noise to the sensor.

Applying the partially cylindrical protrusion605to such a sensor, however, could reduce the number of detectors or rows of detectors used while still receiving the substantially same amount of light, due to the focusing properties of the protrusion605(seeFIG. 14B). This is the example situation illustrated in FIG.14—two rows1408aof detectors1410aare used instead of four. Advantageously, in certain embodiments, the resulting sensor can be more cost effective, have less complexity, and have an improved SNR, due to fewer and/or smaller photodiodes.

In other embodiments, using the partially cylindrical protrusion605can allow the number of detector rows to be reduced to one or three rows of four detectors. The number of detectors in each row can also be reduced. Alternatively, the number of rows might not be reduced but the size of the detectors can be reduced. Many other configurations of detector rows and sizes can also be provided.

FIG. 14Bdepicts a front elevation view of the partially cylindrical protrusion605(or alternatively, the protrusion605b) that illustrates how light from emitters (not shown) can be focused by the protrusion605onto detectors. The protrusion605is placed above a detector submount1400bhaving one or more detectors1410bdisposed thereon. The submount1400bcan include any number of rows of detectors1410, although one row is shown.

Light, represented by rays1420, is emitted from the emitters onto the protrusion605. These light rays1420can be attenuated by body tissue (not shown). When the light rays1420enter the protrusion605, the protrusion605acts as a lens to refract the rays into rays1422. This refraction is caused in certain embodiments by the partially cylindrical shape of the protrusion605. The refraction causes the rays1422to be focused or substantially focused on the one or more detectors1410b. Since the light is focused on a smaller area, a sensor including the protrusion605can include fewer detectors to capture the same amount of light compared with other sensors.

FIG. 14Cillustrates another embodiment of a detector submount1400c, which can be disposed under the protrusion605b(or alternatively, the protrusion605). The detector submount1400cincludes a single row1408cof detectors1410c. The detectors are electrically connected to conductors1412c, which can be gold, silver, copper, or any other suitable conductive material.

The detector submount1400cis shown positioned under the protrusion605bin a detector subassembly1450illustrated inFIG. 14D. A top-down view of the detector subassembly1450is also shown inFIG. 14E. In the detector subassembly1450, a cylindrical housing1430is disposed on the submount1400c. The cylindrical housing1430includes a transparent cover1432, upon which the protrusion605bis disposed. Thus, as shown inFIG. 14D, a gap1434exists between the detectors1410cand the protrusion605b. The height of this gap1434can be chosen to increase or maximize the amount of light that impinges on the detectors1410c.

The cylindrical housing1430can be made of metal, plastic, or another suitable material. The transparent cover1432can be fabricated from glass or plastic, among other materials. The cylindrical housing1430can be attached to the submount1400cat the same time or substantially the same time as the detectors1410cto reduce manufacturing costs. A shape other than a cylinder can be selected for the housing1430in various embodiments.

In certain embodiments, the cylindrical housing1430(and transparent cover1432) forms an airtight or substantially airtight or hermetic seal with the submount1400c. As a result, the cylindrical housing1430can protect the detectors1410cand conductors1412cfrom fluids and vapors that can cause corrosion. Advantageously, in certain embodiments, the cylindrical housing1430can protect the detectors1410cand conductors1412cmore effectively than currently-available resin epoxies, which are sometimes applied to solder joints between conductors and detectors.

In embodiments where the cylindrical housing1430is at least partially made of metal, the cylindrical housing1430can provide noise shielding for the detectors1410c. For example, the cylindrical housing1430can be soldered to a ground connection or ground plane on the submount1400c, which allows the cylindrical housing1430to reduce noise. In another embodiment, the transparent cover1432can include a conductive material or conductive layer, such as conductive glass or plastic. The transparent cover1432can include any of the features of the noise shields790described above.

The protrusion605bincludes the chamfered edges607described above with respect toFIG. 6E. These chamfered edges607can allow a patient to more comfortably slide a finger over the protrusion605bwhen inserting the finger into the sensor301f.

FIG. 14Fillustrates a portion of the detector shell306f, which includes the detectors1410con the substrate1400c. The substrate1400cis enclosed by a shielding enclosure1490, which can include the features of the shielding enclosures790a,790bdescribed above (see alsoFIG. 17). The shielding enclosure1490can be made of metal. The shielding enclosure1490includes a window1492aabove the detectors1410c, which allows light to be transmitted onto the detectors1410c.

A noise shield1403is disposed above the shielding enclosure1490. The noise shield1403, in the depicted embodiment, includes a window1492acorresponding to the window1492a. Each of the windows1492a,1492bcan include glass, plastic, or can be an opening without glass or plastic. In some embodiments, the windows1492a,1492bmay be selected to have different sizes or shapes from each other.

The noise shield1403can include any of the features of the conductive glass described above. In the depicted embodiment, the noise shield1403extends about three-quarters of the length of the detector shell306f. In other embodiments, the noise shield1403could be smaller or larger. The noise shield1403could, for instance, merely cover the detectors1410c, the submount1400c, or a portion thereof. The noise shield1403also includes a stop1413for positioning a measurement site within the sensor301f. Advantageously, in certain embodiments the noise shield1403can reduce noise caused by light piping.

A thermistor1470is also shown. The thermistor1470is attached to the submount1400cand protrudes above the noise shield1403. As described above, the thermistor1470can be employed to measure a temperature of a measurement site. Such a temperature can be helpful in correcting for wavelength drift due to changes in water absorption, which can be temperature dependent, thereby providing more accurate data useful in detecting blood analytes like glucose.

In the depicted embodiment, the detectors1410care not enclosed in the cylindrical housing1430. In an alternative embodiment, the cylindrical housing1430encloses the detectors1410cand is disposed under the noise shield1403. In another embodiment, the cylindrical housing1430encloses the detectors1410cand the noise shield1403is not used. If both the cylindrical housing1403and the noise shield1403are used, either or both can have noise shielding features.

FIG. 14Gillustrates the detector shell306fofFIG. 14F, with the finger bed310fdisposed thereon.FIG. 14Hillustrates the detector shell306fofFIG. 14G, with the protrusion605bdisposed in the finger bed310f.

FIG. 14Iillustrates a cutaway view of the sensor301f. Not all features of the sensor301fare shown, such as the protrusion605b. Features shown include the emitter and detector shells304f,306f, the flaps307f, the heat sink350fand fins351f, the finger bed310f, and the noise shield1403.

In addition to these features, emitters1404are depicted in the emitter shell304f. The emitters1404are disposed on a submount1401, which is connected to a circuit board1419. The emitters1404are also enclosed within a cylindrical housing1480. The cylindrical housing1480can include all of the features of the cylindrical housing1430described above. For example, the cylindrical housing1480can be made of metal, can be connected to a ground plane of the submount1401to provide noise shielding, and can include a transparent cover1482.

The cylindrical housing1480can also protect the emitters1404from fluids and vapors that can cause corrosion. Moreover, the cylindrical housing1480can provide a gap between the emitters1404and the measurement site (not shown), which can allow light from the emitters1404to even out or average out before reaching the measurement site.

The heat sink350f, in addition to including the fins351f, includes a protuberance352fthat extends down from the fins351fand contacts the submount1401. The protuberance352fcan be connected to the submount1401, for example, with thermal paste or the like. The protuberance352fcan sink heat from the emitters1404and dissipate the heat via the fins351f.

FIGS. 15A and 15Billustrate embodiments of sensor portions1500A,1500B that include alternative heat sink features to those described above. These features can be incorporated into any of the sensors described above. For example, any of the sensors above can be modified to use the heat sink features described below instead of or in addition to the heat sink features of the sensors described above.

The sensor portions1500A,1500B shown include LED emitters1504; however, for ease of illustration, the detectors have been omitted. The sensor portions1500A,1500B shown can be included, for example, in any of the emitter shells described above.

The LEDs1504of the sensor portions1500A,1500B are connected to a substrate or submount1502. The submount1502can be used in place of any of the submounts described above. The submount1502can be a non-electrically conducting material made of any of a variety of materials, such as ceramic, glass, or the like. A cable1512is attached to the submount1502and includes electrical wiring1514, such as twisted wires and the like, for communicating with the LEDs1504. The cable1512can correspond to the cables212described above.

Although not shown, the cable1512can also include electrical connections to a detector. Only a portion of the cable1512is shown for clarity. The depicted embodiment of the cable1512includes an outer jacket1510and a conductive shield1506disposed within the outer jacket1510. The conductive shield1506can be a ground shield or the like that is made of a metal such as braided copper or aluminum. The conductive shield1506or a portion of the conductive shield1506can be electrically connected to the submount1502and can reduce noise in the signal generated by the sensor1500A,1500B by reducing RF coupling with the wires1514. In alternative embodiments, the cable1512does not have a conductive shield. For example, the cable1512could be a twisted pair cable or the like, with one wire of the twisted pair used as a heat sink.

Referring specifically toFIG. 15A, in certain embodiments, the conductive shield1506can act as a heat sink for the LEDs1504by absorbing thermal energy from the LEDs1504and/or the submount1502. An optional heat insulator1520in communication with the submount1502can also assist with directing heat toward the conductive shield1506. The heat insulator1520can be made of plastic or another suitable material. Advantageously, using the conductive shield1506in the cable1512as a heat sink can, in certain embodiments, reduce cost for the sensor.

Referring toFIG. 15B, the conductive shield1506can be attached to both the submount1502and to a heat sink layer1530sandwiched between the submount1502and the optional insulator1520. Together, the heat sink layer1530and the conductive shield1506in the cable1512can absorb at least part of the thermal energy from the LEDs and/or the submount1502.

FIGS. 15C and 15Dillustrate implementations of a sensor portion1500C that includes the heat sink features of the sensor portion1500A described above with respect toFIG. 15A. The sensor portion1500C includes the features of the sensor portion1500A, except that the optional insulator1520is not shown.FIG. 15Dis a side cutaway view of the sensor portion1500C that shows the emitters1504.

The cable1512includes the outer jacket1510and the conductive shield1506. The conductive shield1506is soldered to the submount1502, and the solder joint1561is shown. In some embodiments, a larger solder joint1561can assist with removing heat more rapidly from the emitters1504. Various connections1563between the submount1502and a circuit board1519are shown. In addition, a cylindrical housing1580, corresponding to the cylindrical housing1480ofFIG. 14I, is shown protruding through the circuit board1519. The emitters1504are enclosed in the cylindrical housing1580.

FIGS. 15E and 15Fillustrate implementations of a sensor portion1500E that includes the heat sink features of the sensor portion1500B described above with respect toFIG. 15B. The sensor portion1500E includes the heat sink layer1530. The heat sink layer1530can be a metal plate, such as a copper plate or the like. The optional insulator1520is not shown.FIG. 15Fis a side cutaway view of the sensor portion1500E that shows the emitters1504.

In the depicted embodiment, the conductive shield1506of the cable1512is soldered to the heat sink layer1530instead of the submount1502. The solder joint1565is shown. In some embodiments, a larger solder joint1565can assist with removing heat more rapidly from the emitters1504. Various connections1563between the submount1502and a circuit board1519are shown. In addition, the cylindrical housing1580is shown protruding through the circuit board1519. The emitters1504are enclosed in the cylindrical housing1580.

FIGS. 15G and 15Hillustrate embodiments of connector features that can be used with any of the sensors described above with respect toFIGS. 1 through 15F. Referring toFIG. 15G, the circuit board1519includes a female connector1575that mates with a male connector1577connected to a daughter board1587. The daughter board1587includes connections to the electrical wiring1514of the cable1512. The connected boards1519,1587are shown inFIG. 15H. Also shown is a hole1573that can receive the cylindrical housing1580described above.

Advantageously, in certain embodiments, using a daughter board1587to connect to the circuit board1519can enable connections to be made more easily to the circuit board1519. In addition, using separate boards can be easier to manufacture than a single circuit board1519with all connections soldered to the circuit board1519.

FIGS. 16A and 16Billustrate embodiments of disposable optical sensors1600. In an embodiment, any of the features described above, such as protrusion, shielding, and/or heat sink features, can be incorporated into the disposable sensors1600shown. For instance, the sensors1600can be used as the sensors101in the system100described above with respect toFIG. 1. Moreover, any of the features described above, such as protrusion, shielding, and/or heat sink features, can be implemented in other disposable sensor designs that are not depicted herein.

The sensors1600include an adult/pediatric sensor1610for finger placement and a disposable infant/neonate sensor1602configured for toe, foot or hand placement. Each sensor1600has a tape end1610and an opposite connector end1620electrically and mechanically interconnected via a flexible coupling1630. The tape end1610attaches an emitter and detector to a tissue site. Although not shown, the tape end1610can also include any of the protrusion, shielding, and/or heat sink features described above. The emitter illuminates the tissue site and the detector generates a sensor signal responsive to the light after tissue absorption, such as absorption by pulsatile arterial blood flow within the tissue site.

The sensor signal is communicated via the flexible coupling1630to the connector end1620. The connector end1620can mate with a cable (not shown) that communicates the sensor signal to a monitor (not shown), such as any of the cables or monitors shown above with respect toFIGS. 2A through 2D. Alternatively, the connector end1620can mate directly with the monitor.

FIG. 17illustrates an exploded view of certain of the components of the sensor301fdescribed above. A heat sink1751and a cable1781attach to an emitter shell1704. The emitter shell attaches to a flap housing1707. The flap housing1707includes a receptacle1709to receive a cylindrical housing1480/1580(not shown) attached to an emitter submount1702, which is attached to a circuit board1719.

A spring1787attaches to a detector shell1706via pins1783,1785, which hold the emitter and detector shells1704,1706together. A support structure1791attaches to the detector shell1706, which provides support for a shielding enclosure1790. A noise shield1713attaches to the shielding enclosure1790. A detector submount1700is disposed inside the shielding enclosure1790. A finger bed1710attaches to the noise shield1703. A partially cylindrical protrusion1705is disposed in the finger bed1710. Moreover, a flex circuit cover1706attaches to the pins1783,1785. Although not shown, a flex circuit can also be provided that connects the circuit board1719with the submount1700(or a circuit board to which the submount1700is connected).