Abstract:
A finger-placement sensor fixture aligns and removably secures a finger to a sensor pad of a reusable finger-clip optical sensor so as to assure the finger is repeatably aligned between the sensors emitters and detectors and that the finger stays aligned during a test procedure. The sensor fixture has a sensor pad configured to removably install within a sensor clip. The sensor pad has a sensor cavity custom molded to the shape of an individual&#39;s fingertip. A plurality of metal strips are embedded within the sensor pad. A plurality of magnets are embedded within the sensor clip. The sensor pad metal strips are configured to align with the sensor clip magnets so that the sensor pad can be removed, disposed of, replaced and consistently aligned with the sensor clip.

Description:
PRIORITY CLAIM TO RELATED PROVISIONAL APPLICATION 
       [0001]    The present application claims priority benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/785,487 filed Mar. 14, 2013, titled Finger-Placement Sensor Fixture. The above-cited provisional patent application is hereby incorporated in its entirety by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Noninvasive physiological monitoring systems for measuring constituents of circulating blood have advanced from basic pulse oximeters capable of measuring blood oxygen saturation to advanced blood parameter monitors capable of measuring various blood constituents. A basic pulse oximeter typically includes an optical sensor, a monitor for processing sensor signals and displaying results and a cable electrically interconnecting the sensor and the monitor. A basic pulse oximetry sensor typically has a red wavelength light emitting diode (LED), an infrared (IR) wavelength LED and a photodiode detector. The LEDs and detector are attached to a patient tissue site, such as a finger. The cable transmits drive signals from the monitor to the LEDs, and the LEDs respond to the drive signals to transmit light into the tissue site. The detector generates a photoplethysmograph signal responsive to the emitted light after attenuation by pulsatile blood flow within the tissue site. The cable transmits the detector signal to the monitor, which processes the signal to provide a numerical readout of oxygen saturation (SpO 2 ) and pulse rate, along with an audible pulse indication of the person&#39;s pulse. The photoplethysmograph waveform may also be displayed. 
         [0003]    Conventional pulse oximetry assumes that arterial blood is the only pulsatile blood flow in the measurement site. During patient motion, venous blood also moves, which causes errors in conventional pulse oximetry. Advanced pulse oximetry processes the venous blood signal so as to report true arterial oxygen saturation and pulse rate under conditions of patient movement. Advanced pulse oximetry also functions under conditions of low perfusion (small signal amplitude), intense ambient light (artificial or sunlight) and electrosurgical instrument interference, which are scenarios where conventional pulse oximetry tends to fail. 
         [0004]    Advanced pulse oximetry is described in at least U.S. Pat. Nos. 6,770,028; 6,658,276; 6,157,850; 6,002,952; 5,769,785 and 5,758,644, which are assigned to Masimo Corporation (“Masimo”) of Irvine, Calif. and are incorporated in their entirety by reference herein. Corresponding low noise optical sensors are disclosed in at least U.S. Pat. Nos. 6,985,764; 6,813,511; 6,792,300; 6,256,523; 6,088,607; 5,782,757 and 5,638,818, which are also assigned to Masimo and are also incorporated in their entirety by reference herein. Advanced pulse oximetry systems including Masimo SET® low noise optical sensors and read through motion pulse oximetry monitors for measuring SpO 2 , pulse rate (PR) and perfusion index (PI) are available from Masimo. Optical sensors include any of Masimo LNOP®, LNCS®, SofTouch™ and Blue™ adhesive or reusable sensors. Pulse oximetry monitors include any of Masimo Rad-8®, Rad-5®, Rad®-5v or SatShare® monitors. 
         [0005]    Advanced blood parameter measurement systems are capable of measuring various blood parameters in addition to SpO 2 , such as total hemoglobin and carboxyhemoglobin to name a few. Advanced blood parameters measurement systems are described in at least U.S. Pat. No. 7,647,083, filed Mar. 1, 2006, titled Multiple Wavelength Sensor Equalization; U.S. Pat. No. 7,729,733, filed Mar. 1, 2006, titled Configurable Physiological Measurement System; U.S. Pat. No. 7,957,780, filed Mar. 1, 2006, titled Physiological Parameter Confidence Measure and U.S. Pat. No. 8,224,411, filed Mar. 1, 2006, titled Noninvasive Multi-Parameter Patient Monitor, all assigned to Cercacor Laboratories, Inc., Irvine, Calif. (“Cercacor”) and all incorporated in their entirety by reference herein. An advanced parameter measurement system that includes acoustic monitoring is described in U.S. Pat. Pub. No. 2010/0274099, filed Dec. 21, 2009, titled Acoustic Sensor Assembly, assigned to Masimo and incorporated in its entirety by reference herein. 
         [0006]    Advanced blood parameter measurement systems include Masimo Rainbow® SET, which provides measurements in addition to SpO 2 , such as total hemoglobin (SpHb™), oxygen content (SpOC™), methemoglobin (SpMet®), carboxyhemoglobin (SpCO®) and PVI®. Advanced blood parameter sensors include Masimo Rainbow® adhesive, ReSposable™ and reusable sensors. Advanced blood parameter monitors include Masimo Radical-7™, Rad-87™ and Rad-7™ and Rad-57™ monitors, all available from Masimo. Advanced parameter measurement systems may also include acoustic monitoring such as acoustic respiration rate (RRa™) using a Rainbow Acoustic Sensor™ and Rad-87™ monitor, available from Masimo. Such advanced pulse oximeters, low noise sensors and advanced parameter systems have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios. 
       SUMMARY OF THE INVENTION 
       [0007]    A finger-placement sensor repeatably aligns a finger within a reusable finger-clip optical sensor and in particular between the sensor emitters and detectors so as to obtain consistent blood parameter test results. Consistent finger-sensor alignment is particularly advantageous when making noninvasive blood glucose measurements with an optical sensor. The sensor fixture integrates a custom finger mold for each individual. In an embodiment, the custom mold is repeatably aligned within an optical sensor clip using metal tabs embedded in the mold and corresponding rare earth magnets disposed within the sensor clip. 
         [0008]    One aspect of a finger-placement sensor is a fixture that aligns and removably secures a finger to a sensor pad of a reusable finger-clip optical sensor so as to assure the finger is repeatably aligned between the sensors emitters and detectors and that the finger stays aligned during a test procedure. The sensor fixture comprises a custom sensor pad configured to removably install within a sensor clip and the sensor pad has a sensor cavity that conforms to the shape of an individual&#39;s fingertip. In various embodiments, the finger-placement sensor fixture has a top sensor pad that conforms to the fingernail-side of a selected finger of the individual. Metal strips are embedded within the top sensor pad so as to aid the alignment of the top sensor pad within an emitter shell of the sensor clip. Magnets are embedded within the emitter shell so as to align the metal strips with respect to the magnets. A bottom sensor pad conforms to the finger pad-side of the selected finger. A second plurality of magnets are embedded with a detector shell of the sensor clip. A second plurality of metal strips are embedded within the bottom sensor pad so as to aid the alignment of the bottom sensor pad within the detector shell of the sensor clip. 
         [0009]    Another aspect of a finger-placement sensor is a method for consistently aligning a fingertip within a reusable optical sensor that removably clips onto the fingertip so as to noninvasively measure constituents of blood flow within the fingertip. The method comprises physically analyzing potential measurement sites as suitable for optical sensor measurements, manufacturing a sensor fixture and evaluating the sensor fixture. In various embodiments, physically analyzing comprises eliminating finger sites that have congenital defects, prior injuries or unusual shapes and sizes. Manufacturing a sensor fixture comprises generating at least one of a hand mold or an optical scan finger image. Evaluating the sensor fixture comprises comparing a series of optical sensor measurements utilizing the sensor fixture with test strip measurements taken over a predetermined period of time and determining if the variance of the optical sensor measurements compared with the test strip measurements are within predetermined limits. Manufacturing a sensor fixture further comprises creating an injection mold based upon the at least one of a hand mold or an optical scan finger image. Manufacturing a sensor fixture further comprises molding a sensor pad from the injection mold and embedding at least one metal alignment strip within the sensor pad. 
         [0010]    A further aspect of a finger-placement sensor fixture attachable within at least one shell portion of a reusable optical sensor is a sensor pad means for clamping a fingertip within an optical sensor, a finger mold means for conforming the sensor pad to the shape of the fingertip and a magnetic means for aligning the sensor pad within the optical sensor. In various embodiments, the sensor pad means comprises a top sensor pad means for stabilizing the fingernail side of a fingertip within an optical sensor. The finger mold means comprises at least one of an injection mold means or an optical scan means for capturing a specific size and shape of a particular patient&#39;s fingertip. The magnetic means comprises a rare earth magnetic means for creating an first alignment object within a sensor clip shell and a metal strip means for creating a second alignment object within the sensor pad. A bottom sensor pad means stabilizes the fingertip side of a fingertip within the optical sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective illustration of a finger-placement sensor fixture attachable to a sensor clip so as to establish and maintain repeatable finger placement within a reusable optical sensor; 
           [0012]      FIG. 2  is a flow diagram of a customized reusable sensor process for a diabetic patient; 
           [0013]      FIGS. 3A-B  are wire-frame illustrations of an optical finger scan for creating a finger-placement sensor fixture; 
           [0014]      FIGS. 4A-D  are top, side, front and perspective views, respectively, of an injection mold for creating a finger-placement sensor fixture; 
           [0015]      FIGS. 5A-C  are perspective views of three individualized finger-placement sensor fixtures; and 
           [0016]      FIG. 6  an exploded side view of a optical sensor embodiment having a finger-placement sensor fixture. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]      FIG. 1  generally illustrates a physiological monitoring system  100  that utilizes a finger-placement sensor fixture  501 . The monitoring system  100  includes a blood parameter monitor  110  and an optical sensor  120  configured to noninvasively measure and display a patient&#39;s blood glucose level among other parameters. In an embodiment, the sensor  120  attaches to a person&#39;s finger  1  so as to illuminate the finger with optical radiation, which is detected after attenuation by fingertip blood flow. The sensor communicates these optical measurements of blood attenuation, along with other sensor data such as sensor position and temperature, to the monitor  110 . The monitor  110  calculates and displays blood parameter measurements  112  accordingly. A physiological monitoring system is described in U.S. patent application Ser. No. 13/308,461 titled Handheld Processing Device Including Medical Applications For Minimally And Non Invasive Glucose Measurements, filed Nov. 30, 2011, assigned to Cercacor Laboratories Inc. (“Cercacor”), and incorporated in its entirety by reference herein. A reusable optical sensor is described in U.S. patent application Ser. No. 13/473,477 titled Personal Health Device, filed May 16, 2012, assigned to Cercacor and incorporated in its entirety by reference herein. 
         [0018]    As shown in  FIG. 1 , and in particular inset  5  therein, optical sensor measurements as described above are sensitive to finger placement between top and bottom sensor pads. A finger-placement sensor fixture  501  is attachable within a sensor clip  122  so as to establish and maintain repeatable finger placement within a reusable optical sensor  120 . In an embodiment, the finger-placement sensor fixture  501  replaces one or both of generic top and bottom sensor pads with a customized pad specifically molded to an individual&#39;s finger so as to advantageously improve finger placement repeatability. 
         [0019]      FIG. 2  illustrates a customized reusable sensor process  200  for a diabetic patient or other user. A patient initially visits a physician office  210 , such as an endocrinologist or an internal medicine specialist. The physician conducts an exam  212  and various tests. Based upon the exam  212  and test results, the physician makes a diagnosis  214  that the patient has type 1 or type 2 diabetes or other conditions requiring regular or frequent blood constituent monitoring. As a result, the physician informs the patient that they need to frequently monitor their blood glucose levels or other blood parameters as part of a regime for controlling those levels. Accordingly, the physician prescribes noninvasive monitoring technology  216  as an alternative to frequent blood sampling with lances and test strips. 
         [0020]    As shown in  FIG. 2 , following the initial visit  210 , the physician or a trained member of the physician&#39;s staff conducts a site analysis  220 . First, during a site evaluation  222 , the physician/staff member identifies areas of the patient&#39;s fingers or hands that are potential measurement sites  222 . This may involve close physical examination of those patient areas and optical sensor measurements to name a few. For example, some finger sites may be unsuitable for optical sensor measurements due to congenital defects, prior injuries, unusual sizes and shapes, etc. Next, the chosen measurement site is characterized  224  by using photographic techniques, optical scanning (visible/IR) or by taking a physical mold of the measurement site or sites. 
         [0021]    Also shown in  FIG. 2 , the physician site analysis  220  results are then transmitted to a manufacturer  230  so as to create sensor fixtures  232 . The sensor fixtures are then shipped back to the requesting physician  234 . In particular, the manufacturer  230  uses the physician&#39;s scans or molds to create a supply of low-cost, patient-customized, disposable sensor fixtures  232  that each perfectly fit a particular measurement site of a specific patient. 
         [0022]    Further shown in  FIG. 2 , the physician provides each patient with a physiological measurement system  100  and a supply of customized disposable sensor fixtures  232  to install as needed within an optical sensor  120 . These sensor fixtures  501  ( FIG. 1 ), when installed within an optical sensor, advantageously allow highly repeatable sensor placement on each specific patient, allowing very accurate and repeatable noninvasive measurements, such as blood glucose, to be taken in lieu of frequent and painful lancing and blood draws necessary for test strip measurements. In an embodiment, these patient-customized, disposable sensor fixtures  501  ( FIG. 1 ) are used in combination with an optically neutral gel placed on the patient measurement site to further enhance the repeatability and accuracy of noninvasive optical sensor measurements of blood glucose. 
         [0023]      FIGS. 3-5  illustrate various specific aspects and embodiments of site analysis  220  ( FIG. 2 ) and manufacture  230  ( FIG. 2 ), as described with respect to  FIG. 2 , above.  FIGS. 3A-B  illustrate wire-frame finger images  300  generated with an optical scan (video camera, stereo camera or snapshot camera imaging) or a physical mold of a patient&#39;s hand performed at a physician&#39;s office during an initial physician visit. 
         [0024]      FIGS. 4A-D  illustrate an injection mold  400  generated from an optical scan or hand mold for creating a finger-placement sensor fixture. The injection mold  400  is a negative of a selected finger generated from the optical scan finger images  300  (FIGS. A-B). A particular one of a patient&#39;s fingers may be selected for the injection mold process based upon the physician&#39;s site analysis  220  ( FIG. 2 ). In this example, the injection mold is for a top sensor pad  501  ( FIG. 1 ) that fits the fingernail side of a patient&#39;s finger. In other embodiments, an injection mold is made for a bottom sensor pad fitting the finger-pad side of a patient&#39;s finger, or for both top and bottom pads. 
         [0025]      FIGS. 5A-C  illustrate finger-placement sensor fixtures  500  for three different individuals, where each sensor fixture  500  is configured as a top sensor pad of an optical sensor  120  ( FIG. 1 ). Advantageously, each sensor fixture  500  is configured to closely conform to the size and shape of a particular individual&#39;s finger so that each time that individual takes a sensor measurement, their finger is repeatably positioned within the sensor relative to the optical sensor emitters and detectors each time glucose or other physiological parameter is noninvasively measured. In an embodiment, small metal strips are embedded in the sensor fixture  500  corresponding to small rare earth magnets embedded in the sensor clip so that the disposable sensor fixtures can be replaced in a repeatable and consistent position within the sensor clip  122  ( FIG. 1 ). 
         [0026]      FIG. 6  illustrates a sensor  600  having one or more sensor pads  601 ,  602  advantageously configured as customized finger-placement sensor fixtures. The sensor  600  has an emitter section  610  that is pivotably connected with a detector section  620  around hinge pins  680 , which capture a hinge spring (not shown) that urges the sensor  600  to a closed position. Together, a top grip  622  and a bottom grip  642  form clip grips that press-to-open and release-to-close. The emitter section  610  has a heat sink  615 , an emitter shell  620  and a top sensor pad  601 . The detection section  620  has a detector shell  640  and a bottom sensor pad  602 . A bend relief  660  is captured between the emitter shell  620  and top sensor pad  601  and receives a sensor cable (not shown). 
         [0027]    As shown in  FIG. 6 , advantageously, the top sensor pad  601  removably attaches to the emitter shell  620 , and the bottom sensor pad  602  removably attaches to the detector shell  640 . In this manner, either the top sensor pad  601 , the bottom sensor pad  602  or both may be customized as finger-placement sensor fixtures, as described above. 
         [0028]    Further shown in  FIG. 6 , a pair of top magnets  603  are imbedded on both sides of and within the emitter shell  620 . A pair of bottom magnets  606  are imbedded on both sides of and within the detector shell  640 . A pair of top metal strips  604  are imbedded on both sides of and within the top sensor pad  601  so as to generally align with the top magnets  603 . A pair of bottom metal strips  606  are imbedded on both sides of and within the bottom sensor pad  602  so as to generally align with the bottom magnets  606 . Advantageously, the shell magnets  603 ,  605  strongly attract the sensor pad metal strips  604 ,  606  so as to consistently align the sensor pads  604 ,  606  within the sensor  600 , allowing these finger-placement sensor fixtures, e.g.  501  ( FIG. 1 ) to maintain consistent finger placement with respect to the sensor emitters and detectors. 
         [0029]    A finger-placement sensor fixture has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in art will appreciate many variations and modifications.