Abstract:
A physiological sensor combination has a flexible substrate configured to attach to a tissue site. Multiple sensors are disposed on the substrate, which generate physiological signals. Each of the signals is responsive to a different physiological parameter. Conductors are carried on the substrate and routed between the sensors and at least one connector. The connector is configured to communicate the physiological signals to at least one monitor, which derives measurements of the parameters.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application relates to and claims the benefit of prior U.S. Provisional Patent Application No. 60/347,047 entitled Physiological Sensor Combination, filed Jan. 8, 2002, which is incorporated by reference herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Pulse oximetry is a widely accepted noninvasive procedure for measuring the oxygen saturation level of arterial blood, an indicator of a person&#39;s oxygen supply. Early detection of low blood oxygen level is important in the medical field, for example in critical care and surgical applications, because an insufficient supply of oxygen can result in brain damage and death in a matter of minutes. A pulse oximetry system consists of a sensor applied to a patient, a pulse oximeter, and a patient cable connecting the sensor and the pulse oximeter. The pulse oximeter typically provides a numerical readout of the patient&#39;s oxygen saturation, a numerical readout of pulse rate, and an audible indication of each pulse. In addition, the pulse oximeter may display the patient&#39;s plethysmograph, which provides a visual indication of the patient&#39;s pulse contour and pulse rate.  
           [0003]    Measuring a biopotential signal, such as an electroencephalogram (EEG) is also a widely accepted procedure for patient monitoring and diagnostic tests. An EEG measures cortical activity of the brain, which can reflect changes in cortical or subcortical cellular function due to insufficient oxygen or drugs, to name a few. For example, changes in EEG bandwidth and power can provide a measure of the effects of anesthetics on the brain. A biopotential measurement system consists of a bipotential sensor, a monitor and a patient cable connecting the sensor to the monitor. For example, an EEG monitor measures the potential difference between at least two well-spaced electrodes, using a separate ground electrode, and displays the resulting signal.  
         SUMMARY OF THE INVENTION  
         [0004]    A physiological sensor combination has a flexible substrate configured to attach to a tissue site. Multiple sensors are disposed on the substrate, which generate physiological signals. Each of the signals is responsive to a different physiological parameter. Conductors are carried on the substrate and routed between the sensors and at least one connector. The connector is configured to communicate the physiological signals to at least one monitor, which derives measurements of the parameters. In one embodiment, the sensors comprise multiple electrodes disposed on the substrate. Each of the electrodes are adapted to be in electrical communication with the tissue site and electrically connect to at least one of the conductors. Further, an emitter and a detector are mounted to the substrate and electrically connected to at least one of the conductors. The emitter is adapted to transmit light into the tissue site, and the detector is adapted to receive reflected light from the tissue site.  
           [0005]    In a particular embodiment, the substrate has a first side adapted to face toward the tissue site and a second side adapted to face away from the tissue site, where the conductors and the electrodes are disposed on the first side and the emitter and the detector are mounted to the first side. The substrate may comprise a fold-over portion having a circuit side corresponding to the first side, where the fold-over portion is adapted to fold so that the circuit side is proximate the second side. Further, the emitter and the detector may be mounted to the a fold-over portion. The substrate may define at least one aperture configured so that the emitter and the detector each align with a corresponding aperture when the foldover is in a folded position.  
           [0006]    In another particular embodiment, the physiological sensor combination comprises a plurality of biopotential sensor pinouts corresponding to the electrodes, a plurality of optical sensor pinouts corresponding to the emitter and the detector, and a common connector extending from the substrate. The biopotential sensor pinouts and said optical sensor pinouts are each disposed on the common connector.  
           [0007]    Another aspect of a physiological sensor combination is a substrate means for combining a first sensor and a second sensor, a connector means for communicating signals from the first sensor and the second sensor to at least one monitor, and an identifying means of conveying information about each of the first sensor and the second sensor to the monitor. The physiological sensor combination may further comprise a fold-over means for positioning sensor components so as to extend away from a tissue site. The physiological sensor combination may additionally comprise an aperture means for providing light communications between sensor components and the tissue site. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is an illustration of a physiological sensor combination applied to a patient and having a patient cable connected near the patient&#39;s forehead;  
         [0009]    [0009]FIG. 2 is an illustration of a physiological sensor combination applied to a patient and having a patient cable connected near the patient&#39;s temple;  
         [0010]    FIGS.  3 A-B are perspective views of a circuit substrate and an assembled sensor, respectively, for a physiological sensor combination having a single-sided circuit substrate and a shared connector;  
         [0011]    [0011]FIG. 4 is a schematic diagram of a physiological sensor combination showing the location of applied sensor components;  
         [0012]    [0012]FIG. 5 is a layout diagram of a single-sided circuit for a physiological sensor combination;  
         [0013]    [0013]FIG. 6 is a perspective view of a physiological sensor combination having a single-sided circuit substrate and dual connectors; and  
         [0014]    [0014]FIG. 7 is a perspective view of a physiological sensor combination having a double-sided circuit substrate and dual connectors. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    FIGS.  1 - 2  show a physiological sensor combination applied to a patient. FIGS.  3 - 5  illustrate a physiological sensor combination having a biopotential sensor and an optical sensor configured on a single-sided flexible circuit substrate with a shared patient cable connector. FIG. 6 illustrates a physiological sensor combination also having a biopotential sensor and an optical sensor configured on a single-sided flexible circuit substrate. The biopotential sensor and the optical sensor, however, each have separate patient cable connectors. FIG. 7 illustrates a physiological sensor combination having a biopotential sensor and an optical sensor configured on a double-sided circuit substrate, each sensor also having separate patient cable connectors.  
         [0016]    FIGS.  1 - 2  illustrate a physiological sensor combination applied to the forehead and temple areas of a patient. A patient cable  130  connects the physiological sensor combination  100  (FIG. 1),  101  (FIG. 2) to one or more monitoring devices (not shown). As shown in FIG. 1, the patient cable  130  may connect near the patient&#39;s forehead. As shown in FIG. 2, the patient cable  130  may alternatively connect near the patient&#39;s temple. The biopotential sensor  110  and optical sensor  120  may share a common connector  140 . Alternatively, the biopotential sensor  110  and optical sensor  120  may each have a dedicated patient cable connector, as described in further detail with respect to FIGS.  6 - 7 , below. The biopotential sensor  110  may be an EEG sensor for depth of consciousness monitoring, as described above. The optical sensor  120  may be a pulse oximetry reflectance sensor for oxygen saturation monitoring, also described above  
         [0017]    FIGS.  3 A-B illustrate a physiological sensor combination  100  having a biopotential sensor  110  and an optical sensor  120  configured on a flexible circuit substrate  500 . As shown in FIG. 3A, the flexible circuit  500  is single-sided, having a blank side  501  and a circuit side  502  with printed conductive traces  510  on the circuit side  502 . The biopotential sensor  110  has electrodes  410  (not visible and shown as dashed lines) printed on the circuit side  502 . The electrodes  410  are configured so that one electrode is applied to the temple area and two electrodes are applied to the forehead, as further described with respect to FIGS.  4 - 5 , below.  
         [0018]    Further shown in FIG. 3A, the optical sensor  120  includes a fold-over  540 , an emitter  420 , a detector  430  and an information element  440 . The emitter  420 , detector  430  and information element  440  are each mounted to the circuit side  502  on the fold-over  540  and electrically connected to traces  510 , as described in detail with respect to FIGS.  4 - 5 , below. The optical sensor  120  is configured so that emitter  420  and a detector  430  are applied over the forehead, also described with respect to FIGS.  4 - 5 , below. The fold-over  540  is such that each of the emitter  420  and detector  430  align with corresponding apertures  520  (FIG. 5) so that light transmitted from the emitter  420  passes through an aperture  520  (FIG. 5) and into a patient&#39;s skin and that reflected light passes out of a patient&#39;s skin, through an aperture  520  (FIG. 5) and is received by the detector  430 . The substrate  500  has a stub  530  that contains pinouts  532  (FIG. 5), which connect to the electrodes  410  and also to the emitter  420 , detector  430  and information element  440 , also described in detail with respect to FIGS.  4 - 5 , below. Emitters and a detector for a pulse oximetry sensor are described in detail in U.S. Pat. No. 6,256,523 entitled “Low Noise Optical Probe,” which is assigned to Masimo Corporation and incorporated by reference herein. An information element for a pulse oximetry sensor is described in detail in U.S. Pat. No. 6,001,986 entitled “Manual And Automatic Probe Calibration,” which is assigned to Masimo Corporation and incorporated by reference herein.  
         [0019]    As shown in FIG. 3B, the biopotential sensor  110  has an adhesive foam layer  310  disposed around the electrodes  410  on the circuit side  502 . The foam layer  310  has an adhesive for patient skin attachment and cushions the biopotential sensor  110  against the skin. Further, the foam layer  310  forms cavities around the electrodes  410  that are filled with a conductive gel for electrical communication between a tissue site and the electrodes  410 . Printed electrode indicators  370  facilitate sensor application on a tissue site. Electrodes printed on a substrate, an associated foam layer, and gel-filled foam cavities are described in detail in U.S. Pat. No. 6,032,064 entitled “Electrode Array System For Measuring Electrophysiological Signals,” assigned to Aspect Medical Systems, Inc. and incorporated by reference herein. One of ordinary skill in the art will recognize that various electrode configurations may be utilized as the biopotential sensor  110 .  
         [0020]    Also shown in FIG. 3B, the optical sensor  120  has a face tape  330  and a base tape  340  that envelop the fold-over  540  along with the fold-over mounted components  420 - 440 . In one embodiment, the face tape  330  and base tape  340  attach together and to the fold-over  540  with PSA. Further, the base tape  340  has a backing (not shown) that is removed to expose an adhesive for skin attachment. The face tape  330  also secures the detector  430  within an optical cavity and cover  350 . A printed emitter indicator  390  facilitates sensor application on a tissue site. Emitters, detectors, optical cavities and corresponding covers are described in detail in U.S. Pat. No. 6,256,523, referenced above.  
         [0021]    Further shown in FIG. 3B, the physiological sensor combination  100  has a tab  320  that attaches to the stub  530  (FIG. 3A) to complete the connector  140 . In one embodiment, the attachment is accomplished with pressure sensitive adhesive (PSA) between the tab  320  and stub  530 . The tab  320  provides a stiffener for the pinouts  532  (FIG. 5) and an insertion and locking mechanism for a mating patient cable connector, as described in U.S. Pat. No. 6,152,754 entitled “Circuit Board Based Cable Connector” and U.S. Pat. No. 6,280,213 entitled “Patient Cable Connector,” each assigned to Masimo Corporation and incorporated by reference herein.  
         [0022]    The physiological sensor combination  100  is described above with respect to a fold-over that positions the optical sensor components  420 - 440  so that they extend away from the tissue site. This advantageously allows a smooth surface to be positioned against the tissue site for patient comfort. In another embodiment, however, there is no fold-over  540  and the components  420 - 440  extend from the substrate toward the tissue site. In yet another embodiment, there is no fold-over and the components  420  are mounted on the substrate side opposite the conductors and utilize substrate feed-throughs to connect with the flex circuit traces  510 . Further, the fold-over  540  is described above as positioning the emitter  420  and detector  430  over substrate apertures  520  (FIG. 5). In an alternative embodiment, the fold-over  540  is skewed so that the emitter  420  and detector  430  are positioned away from the substrate so that no apertures are necessary.  
         [0023]    [0023]FIG. 4 illustrates a circuit diagram for a physiological sensor combination  100  having a biopotential sensor circuit  401  and an optical sensor circuit  402 . The biopotential sensor circuit  401  has an electrode array  410 , which is placed on well-separated skin areas. In one embodiment, a first electrode  414  is placed on a temple area  492  and a second electrode  418  is placed on a forehead area  494 . A ground electrode  412  is also placed on the forehead area  494  near the second electrode  418 . Each electrode of the array  410  provides a pinout to a connector  140 . The connector  140  provides sensor input to a monitor. The electrodes placed on the patient&#39;s head transmit EEG signals to a monitor, which may include a separate digitizer located near the patient to reduce electrical noise. The difference in potential between the first electrode  414  and second electrode  418  reflects primarily a far-field electrical source, i.e. the EEG from the distant brain cortex, and not a near-field electrical source, such as transdermal nervous stimulation of muscle. The monitor filters the EEG data, analyzes it for artifact and extracts characteristic features from the complex signal to provide pattern recognition of changes over time.  
         [0024]    Also shown in FIG. 4, the optical sensor circuit  402  has an emitter  420 , a detector  430  and an information element  440 . The emitter  420  includes both a red LED (light emitting diode) and an infrared (IR) LED in a back-to-back arrangement. In alternative embodiments, the red and IR LEDs are arranged in three-wire, common anode or common cathode configurations, as is well-known in the art. The detector  430  is a photodiode. The LEDs  420  and photodiode  430  are located on the skin in close proximity, such as on a forehead area  498 . In this manner, the LEDs emit light into the blood vessels and capillaries underneath the skin, and the photodiode  430  is positioned to detect the LED emitted light reflected from the skin tissues. The emitter  420  and detector  430  provide pinouts to the connector  140 , which provides a sensor input to a monitor. The monitor determines oxygen saturation by computing the differential absorption by arterial blood of the two wavelengths of light projected into the skin from the emitter  420 , as is well-known in the art. The monitor provides LED drive current, which alternately activates the red and IR LEDs. The detector  430  uses a single photodiode that responds to both the red and infrared emitted light and generates a time-division-multiplexed (“modulated”) output signal to the monitor, corresponding to the red and infrared light energy attenuated by absorption and reflection from the patient&#39;s tissue. The monitor has front-end circuitry for amplification, filtering and digitization of the detector signal. The monitor also has a signal processor that calculates a ratio of detected red and infrared intensities, and an arterial oxygen saturation value is empirically determined based on that ratio.  
         [0025]    Further shown in FIG. 4, the optical sensor circuit  402  may have an information element  440 , such as a resistor configured in parallel with the emitter  420  LEDs. The information element  440  can be read by the monitor and used to determine such things as LED wavelength, sensor type or manufacturer. Information elements and monitor reading of information elements are described in U.S. Pat. No. 6,011,986, referenced above. Advantageously, although associated with the optical sensor circuit  402 , the information element  440  can be used to designate information regarding the biopotential sensor portion of the physiological sensor combination  100 . For example, the information element  440  can specify the number of electrodes as well as the electrode locations on the head.  
         [0026]    [0026]FIG. 5 illustrates a flexible circuit  500  for a physiological sensor combination  100 . The flexible circuit  500  has a substrate  504 , traces  510 , electrodes  410 , pinouts  530  and apertures  520 . Conductors are deposited and/or etched on a circuit side  502  of the substrate  504  in a pattern to form the traces  510 , electrodes  410  and pinouts  532 , as is well known in the art. In one embodiment, the substrate  504  is a flexible polyester film and the conductors are silver/silver-chloride. In another embodiment, the conductors are copper. The components  420 - 440  attach to the flexible circuit  500  and are electrically connected to the traces  510 , such as with solder. The fold-over  540  is configured so that the emitter  420  and detector  430  align with the corresponding apertures  520 .  
         [0027]    [0027]FIG. 6 illustrates a physiological sensor combination  600  having a biopotential sensor  610  and an optical sensor  660 . The biopotential sensor  610  is configured as described with respect to FIGS.  3 - 5 , above, except that the physiological sensor combination  600  has a connector  620  that is dedicated to the biopotential sensor  610  rather than being shared with the optical sensor  660 . The optical sensor  660  also is configured as described with respect to FIGS.  3 - 5 , above, except that a connector  670  is dedicated to the optical sensor  660  rather than being shared with the biopotential sensor  610 . Further, the optical sensor  660  has a single fold-over (not visible) on which is mounted the emitter  420  (FIG. 4) and detector  430  (FIG. 4) rather than having a separate fold-over  540  (FIG. 3A) for each.  
         [0028]    [0028]FIG. 7 illustrates a physiological sensor combination  700  having a biopotential sensor  710  and an optical sensor  760 . The biopotential sensor  710  is configured as described with respect to FIG. 6, above. The optical sensor  760  also is configured as described with respect to FIG. 6, above, except that the flexible circuit  500  (FIG. 5) is double-sided, i.e. the traces  510  (FIG. 5) associated with the biopotential sensor  710  are on the side facing the patient&#39;s skin when applied, and the traces  510  (FIG. 5) associated with the optical sensor  760  are on the side away from the patient&#39;s skin when applied. As a result, the connector  770  is dedicated to the optical sensor  760  and has pinouts  772  facing away from the patient&#39;s skin when applied. Further, the optical sensor  760  does not have a fold-over  540  (FIG. 3A). Rather, the optical sensor components  420 - 440  (FIG. 4) are mounted on the flexible circuit side away from the patient&#39;s skin.  
         [0029]    A physiological sensor combination is described above with either a shared patient cable connector or a patient cable connector dedicated to each sensor. One of ordinary skill will recognize that either connector configuration will allow the sensor to communicate with a single monitor that analyzes and displays multiple physiological parameters or, alternatively, multiple monitors that are dedicated to analyzing only related physiological parameters, such as oxygen saturation and pulse rate.  
         [0030]    The physiological sensor combination as described above can be cost effectively manufactured, advantageously allowing disposable use. One of ordinary skill in the art will recognize that, however, that the physiological sensor combination as disclosed herein can be similarly applied to construct a reusable sensor combination.  
         [0031]    The physiological sensor combination was also described above with respect to a shared substrate. One of ordinary skill in the art will recognize that a physiological sensor combination can be constructed from, for example, a biopotential sensor configured on a first substrate and an optical sensor configured on a second substrate, where the first substrate and the second substrate are joined together during the manufacturing process to form a multilayer substrate or an otherwise integrated substrate incorporating multiple sensors.  
         [0032]    Although a physiological sensor combination is described above with respect to a biopotential sensor combined with an optical sensor applied to a patient&#39;s head, one of ordinary skill in the art will recognize that a physiological sensor combination may be applied to other tissue sites and utilize other sensor combinations, where there is a need to combine two or more sensors in one to accommodate sensors competing for the same tissue site. For example, a physiological sensor combination may include a noninvasive blood pressure (NIBP) sensor and a pulse oximetry sensor or a NIBP sensor and a respiration rate sensor for monitoring on the forearm or the wrist. As another example, a physiological sensor combination may include two optical sensors and one biopotential sensor applied to the forehead and configured as a pulse oximetry sensor and a EEG sensor, as described above, in addition to a near infrared spectroscopy sensor for measuring cerebral tissue oxygenation.  
         [0033]    A biopotential sensor as described above could be used in conjunction with a depth of anesthesia monitor that uses not just passive EEG, but also active EEG. That is an Evoked Potential EEG can be used, where some kind of sound is played and changes in EEG are observed as the patient goes into consciousness.  
         [0034]    A physiological sensor combination 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 the art will appreciate many variations and modifications.