Patent Publication Number: US-2010125188-A1

Title: Motion correlated pulse oximetry

Description:
BACKGROUND 
     Blood oxygenation can be determined using pulse oximetry. In some environments, pulse oximetry accuracy is insufficient to allow proper treatment or diagnosis of a patient. Current technology for pulse oximetry is inadequate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIG. 1  includes a block diagram of a system according to one example. 
         FIG. 2  includes a pictorial representation of a system according to one example. 
         FIG. 3  includes a flow chart of a method according to one example. 
         FIG. 4  includes a motion sensor with a coordinate system. 
     
    
    
     DETAILED DESCRIPTION 
     By way of overview, an example of the present subject matter includes a motion compensated physiological sensor. In one example, the physiological sensor includes a pulse oximetry sensor. Motion detected by the motion sensor can be used to compensate or correct the pulse oximetry data provided by the pulse oximetry sensor. In one example, motion detected by the motion sensor is used to generate a notification. The notification can be a signal provided to the user, a physician, or other caregiver or the notification can be stored in a memory or other storage device. 
     In one example, the motion sensor is configured to be worn by the user. For example, the motion sensor can include an accelerometer. The accelerometer can have one or more axes of sensitivity. The accelerometer can be attached to a selected body portion of the user. For example, a torso-worn accelerometer can be used in a sleep study or used to detect vibrations or movement of a user during transit from one location to another. As another example, a wrist-worn or ankle-worn accelerometer can detect limb movement of the user. Movement artifacts detected during a sleep study, for example, can be correlated to measured oximetry or pulse data. 
     In one example, the present subject matter includes a body worn pulse oximetry sensor that is coupled by a wired connection to a body worn accelerometer. 
     The sensor can be configured to detect pulse oximetry using an optical detector coupled to a finger, a toe, an ear lobe, a forehead, or other tissue. The sensor can be configured for long term monitoring or short term monitoring. 
     In addition to a pulse oximetry sensor, other types of physiological sensors are also contemplated. For example, the sensor can include a sensor configured to measure pulse rate, measure oxygen saturation, or arterial hemoglobin. 
       FIG. 1  includes a block diagram of system  10 A according to one example. In the example shown in the figure, system  10 A includes local unit  100 A coupled by link  150 A to remote unit  200 A. 
     Local unit  100 A includes motion sensor  110 A. Motion sensor  110 A can include an accelerometer or other device for detecting acceleration or motion. Motion sensor  110 A can be sensitive to motion along a single-axis or along multiple axes. Motion sensor  110 A provides an electrical output signal corresponding to a detected magnitude and direction of acceleration. 
     Local unit  100 A includes physiological sensor  120 A. Physiological sensor  120 A can include a pulse oximetry sensor having a light emitter (source) and having a light detector. A pulse oximetry sensor provides an electrical output signal corresponding to a measure of blood oxygenation. According to one example, blood oxygenation is based on modulation of light detected by the light detector. 
     An output from motion sensor  10 A is provided to processor  130 A by link  112  and an output from physiological sensor  120 A is provided to processor  130 A by link  122 A. Link  112  can be wired or wireless and in the example shown, includes interface  115 . In a similar manner, link  122 A can be wired or wireless and in the example shown, includes interface  125 . 
     An example of a wired link can include a copper conductor. Examples of a wireless link can include an optical communication link or a radio frequency communication link. According to one example, a radio frequency communication link can include a Bluetooth communication link. Bluetooth is a wireless protocol utilizing short-range communications technology. 
     Interface  115  or interface  125  can include a radio frequency transceiver or other telemetry unit. In one example, interface  115  or interface  125  includes a driver, an analog-to-digital (ADC) converter, or other circuitry to interface processor  130 A to motion sensor  110 A and physiological sensor  120 A. 
     Link  112 , interface  115 , link  122 A, or interface  125  can be unidirectional or bidirectional. In other words, processor  130 A can both receive and transmit data between either one or both of motion sensor  110 A and physiological sensor  120 A. 
     Processor  130 A can include a digital data processor (such as a central processing unit or a microprocessor), an analog processor, or a mixed signal processor. In the example shown, processor  130 A is coupled to memory  135 . Memory  135  can provide storage for instructions to control operation of processor  130 A. Memory  135  can provide data storage for processor  130 A. 
     Processor  130 A of local unit  100 A communicates with processor  230  of remote unit  200 A using link  150 A. Link  150 A can be wired or wireless. Processor  130 A is coupled to link  150 A by interface  140 . Interface  140  can include a transceiver, a driver, or other circuit to communicate using link  150 A. In one example, interface  140  includes an electrical connector. 
     In the example shown, remote unit  200 A includes interface  240 , processor  230 , memory  235 , and interface  260 . 
     Interface  240 , like interface  140 , can include a transceiver or other circuit to provide or receive a signal using link  150 A. Processor  230  can include a digital data processor, an analog processor, or a mixed signal processor, and in the example shown, can execute instructions stored using memory  235 . Interface  260  is coupled to output port  262  which provides a coupling to externalities such as computer  265 , printer  270 , database  275 , and network  280 . 
     Motion detected by motion sensor  110 A can be used to correlate or compensate the data generated by physiological sensor  120 A. Various algorithms or techniques can be implemented using any of processor  130 A, processor  230 A, or other processor (such as a processor of computer  265 ). For example, processor  130 A can be configured to execute instructions to generate a processor output based on a signal received from motion sensor  110 A and physiological sensor  120 A. The instructions can use the detected motion to adjust weighting of the data from the physiological sensor  120 A. In one example, motion data is used to subtract or nullify portions of the data generated by physiological sensor  120 A. In one example, a processor executes instructions to compensate for periodic movement arising from ambulance travel or other motion. 
     Interface  260  can include a wireless transceiver. For example, interface  260  can include a radio frequency transceiver (such as a Bluetooth transceiver) to allow wireless telemetry to a remote computer. 
     In the example shown, computer  265  has a display and can include a desktop or laptop computer or other processor. Printer  270  can include a laser printer. Database  275  can include, for example, a storage device or other structure to store data corresponding to motion and physiological parameters of the user. Network  280  can include a local area network (LAN) such as an Ethernet or a wide area network (WAN) such as the internet. 
     Local unit  100 A can include a battery or other power supply. Remote unit  200 A can include a battery or other power supply. 
       FIG. 2  includes a pictorial representation of system  10 B according to one example. In the example shown, system  10 B includes local unit  100 B and remote unit  200 B. Local unit  100 B includes physiological sensor  120 B, and in the example shown, sensor  120 B includes a pulse oximetry sensor configured for use on a finger of a user. A pulse oximetry sensor as shown in the figure includes optical emitter  80  and optical detector  85 . An output signal from optical detector  85  corresponds to the blood oxygenation of the user at the sensor site. In one example, local unit  100 B includes a battery power supply as part of one or both of device  94  and sensor  120 B. Local unit  100 B is configured for lightweight, portable use and affords mobility for the user. 
     The output signal from physiological sensor  120 B is communicated by link  122 B to device  94 . Link  122 B can include a wired or wireless communication channel. Device  94 , in the example shown, is configured for wearing on a wrist or ankle of the user. Device  94  includes straps  92  configured to encircle and to hold housing  90  in close contact with the user. Sensor  110 B is affixed to housing  90  and includes an accelerometer. Sensor  110 B can be sensitive to motion along one axis or multiple axes (such as two, three, or more). Housing  90  also includes processor  130 B. In one example, processor  130 B includes a digital processor to generate a processor output using a signal detected by physiological sensor  120 B and motion sensor  110 B. In various examples, device  94  includes a display and user-operable controls. 
     Housing  90  also includes other circuitry such as interface  115 , interface  125 , interface  140 , and memory  135 . In one example, housing  90  includes a transceiver configured to communicate wirelessly with remote unit  200 B. 
     Remote unit  200 B, in the example shown, includes an antenna to communicate wirelessly with local unit  100 B via link  150 B. In addition, remote unit  200 B includes a connector for coupling, via port  262 B, with externalities. 
     System  10 A, as shown in  FIG. 1 , depicts a general view in which local unit  100 A includes motion sensor  110 A, physiological sensor  120 A, and processor  130 A. System  10 A can be configured in various combinations of one, two, or three housings with separate housings coupled by various communication channels. A housing can be fabricated of plastic, metal, or other material. 
     For example,  FIG. 2  illustrates system  10 B in which a first housing includes physiological sensor  120 B and a second housing includes motion sensor  110 B and processor  130 B. The first housing and the second housing communicate using link  122 B. Motion sensor  10 B can be a micromachined or nanofabricated device and mounted on a printed wire board (PWB) or other substrate along with processor  130 B or other elements. 
     In one example, motion sensor  110 A is integrated in a first housing and a second housing includes processor  130 A and physiological sensor  120 A. For example, processor  130 A and optical elements of physiological sensor  120 A can be affixed to a flexible circuit substrate. The substrate can include an aperture for an optical element of a pulse oximetry sensor. 
     In one example, a first housing include motion sensor  110 A and physiological sensor  120 A and a second housing includes processor  130 A. 
     In one example, a first housing includes motion sensor  110 A, a second housing includes physiological sensor  120 A, and a third housing includes processor  130 A, and the various housings are in communication with wired communication links or wireless communication links. In one example, a wired communication link includes an electrical connector such as a zero-insertion force (ZIF) connector. Examples of a wireless communication link include a radio frequency transceiver and an optical communication system (such as fiber optic bundle). 
       FIG. 3  includes a flow chart of method  300  according to one example. At  310 , method  300  includes generating a first signal corresponding to a physiological parameter at a first site of a user. For example, the physiological parameter can correspond to blood oxygenation as measured by a pulse oximetry sensor coupled to a user. The sensor can be affixed to a toe, a finger, an ear lobe, or other tissue of a user. In one example, the physiological parameter can correspond to tissue oxygenation as measured by a suitable sensor coupled to a user. 
     At  320 , method  300  includes generating a second signal using a user-worn sensor, the second signal corresponding to movement of the user. The second signal can correspond to movement of a portion of the user that differs from that of the site used for measuring the physiological parameter. For example, the physiological parameter can be derived from a toe measurement and the user movement can correspond to motion of the user&#39;s arm. The first signal and the second signal can correspond to the same portion of the user, such as a torso. 
     At  330 , method  300  includes using a communication link to couple the first signal and the second signal. The communication link, in one example, includes a physical link such as a wired connection or an optical fiber. 
     At  340 , method  300  includes wirelessly communicating data corresponding to the first signal and the second signal to a remote device. The data can be wirelessly communicated using, for example, a radio frequency transceiver, an optical coupling or other means. 
     A processor executing instructions can be used to receive the data and identify motion artifacts in the data from a physiological sensor. A motion artifact can be classified according to magnitude, direction, or other parameter. In addition, a motion artifact can be correlated with the data from the physiological sensor. Correlating can include classifying data according to a scaling criteria based on data reliability, accuracy, or other parameter. 
       FIG. 4  includes motion sensor  110 C with a coordinate system. Motion sensor  110 C can generate an output signal corresponding to motion that can be described as pitch  405  (movement or rotation about the x-axis), roll  410  (about the y-axis), and yaw  415  (about the z-axis). 
     The relative alignment of an optical sensor (as part of physiological sensor  120 A, for example) and an axis of sensitivity of motion sensor  110 C can be selected according to a particular application. For example, the optical sensor can be aligned so that a direction of light emission from a light emitting diode (LED) is aligned with a z-axis. 
     For a limb-worn device having an accelerometer with one axis of sensitivity (z-axis), the LED can be aligned to emit along the z-axis. In this configuration, for example, a toe-worn physiological sensor can be correlated with movement of a leg during flexion and extension of a knee joint. A one axis accelerometer may be suitable for an ambulatory user. 
     For a limb-worn device having an accelerometer with two axes of sensitivity (x-axis and y-axis), the LED can be aligned to emit along the z-axis. This configuration allows, for example, detection of limb rotation in which the palm is rotated to face up or face down (supination, pronation) and bending of the elbow (flexion, extension). A two axes accelerometer may be suitable for sleep study analysis. 
     For a limb-worn device having an accelerometer with three axes of sensitivity (x-axis, y-axis, and z-axis), the LED can be aligned to emit along any particular axis. This configuration allows, for example, detection of patient movement such as during transportation in an ambulance or wheel chair. 
     A particular motion sensor can be configured to detect gross movements of a user. A gross movement relates to use of the large muscles of the human body, such as those in the legs, arms, and abdomen. 
     Additional Notes 
     The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown and described. However, the present inventors also contemplate examples in which only those elements shown and described are provided. 
     All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. 
     In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
     Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like. 
     The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.