Abstract:
An arm mountable portable patient monitoring device configured to receive physiological information from a plurality of sensors attached to a patient via wired connections for on-patient monitoring of parameter measurements and wireless transmission of parameter measurements to separate monitoring devices. The arm mountable portable patient monitoring device includes a housing, a strap, a display, a first sensor port positioned on a first side of the housing configured to face toward a hand of the patient when the housing is secured to the arm of the patient, second and third sensor ports configured to receive signals from additional sensor arrangements via a wired connections, one or more signal processing arrangements configured to cause to be displayed measurements of oxygen saturation and pulse rate, and a transmitter configured to wirelessly transmit information indicative of the measurements of oxygen saturation and pulse rate to a separate monitoring device.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 14/815232, filed on Jul. 31, 2015, entitled “Physiological Measurement Communications Adapter,” which is a continuation of U.S. patent application Ser. No. 14/217,788, filed on Mar. 18, 2014, entitled “Wrist-Mounted Physiological Measurement Device,” now U.S. Pat. No. 9,113,832, which is a continuation of U.S. patent application Ser. No. 14/037,137, filed on Sep. 25, 2013, entitled “Physiological Measurement Communications Adapter,” now U.S. Pat. No. 9,113,831, which is a continuation of U.S. patent application Ser. No. 12/955,826, filed on Nov. 29, 2010, entitled “Physiological Measurement Communications Adapter,” now U.S. Pat. No. 8,548,548, which is a continuation of U.S. patent application Ser. No. 11/417,006, filed on May 3, 2006, entitled “Physiological Measurement Communications Adapter,” now U.S. Pat. No. 7,844,315, which claims priority benefit under 35 U.S.C. §120 to, and is a continuation of, U.S. patent application Ser. No. 11/048,330, filed Feb. 1, 2005, entitled “Physiological Measurement Communications Adapter,” now U.S. Pat. No. 7,844,314, which is a continuation of U.S. patent application Ser. No. 10/377,933, entitled “Physiological Measurement Communications Adapter,” now U.S. Pat. No. 6,850,788, which claims priority benefit under 35 U.S.C. §119(e) from U.S. Provisional Application No. 60/367,428, filed Mar. 25, 2002, entitled “Physiological Measurement Communications Adapter.” The present application also incorporates the foregoing utility disclosures herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Patient vital sign monitoring may include measurements of blood oxygen, blood pressure, respiratory gas, and EKG among other parameters. Each of these physiological parameters typically requires a sensor in contact with a patient and a cable connecting the sensor to a monitoring device. For example,  FIGS. 1-2  illustrate a conventional pulse oximetry system  100  used for the measurement of blood oxygen. As shown in  FIG. 1 , a pulse oximetry system has a sensor  110 , a patient cable  140  and a monitor  160 . The sensor  110  is typically attached to a finger  10  as shown. The sensor  110  has a plug  118  that inserts into a patient cable socket  142 . The monitor  160  has a socket  162  that accepts a patient cable plug  144 . The patient cable  140  transmits an LED drive signal  252  ( FIG. 2 ) from the monitor  160  to the sensor  110  and a resulting detector signal  254  ( FIG. 2 ) from the sensor  110  to the monitor  160 . The monitor  160  processes the detector signal  254  ( FIG. 2 ) to provide, typically, a numerical readout of the patient&#39;s oxygen saturation, a numerical readout of pulse rate, and an audible indicator or “beep” that occurs in response to each arterial pulse. 
         [0003]    As shown in  FIG. 2 , the sensor  110  has both red and infrared LED emitters  212  and a photodiode detector  214 . The monitor  160  has a sensor interface  271 , a signal processor  273 , a controller  275 , output drivers  276 , a display and audible indicator  278 , and a keypad  279 . The monitor  160  determines oxygen saturation by computing the differential absorption by arterial blood of the two wavelengths emitted by the sensor emitters  212 , as is well-known in the art. The sensor interface  271  provides LED drive current  252  which alternately activates the red and IR LED emitters  212 . The photodiode detector  214  generates a signal  254  corresponding to the red and infrared light energy attenuated from transmission through the patient finger  10  ( FIG. 1 ). The sensor interface  271  also has input circuitry for amplification, filtering and digitization of the detector signal  254 . The signal processor  273  calculates a ratio of detected red and infrared intensities, and an arterial oxygen saturation value is empirically determined based on that ratio. The controller  275  provides hardware and software interfaces for managing the display and audible indicator  278  and keypad  279 . The display and audible indicator  278  shows the computed oxygen status, as described above, and provides the pulse beep as well as alarms indicating oxygen desaturation events. The keypad  279  provides a user interface for setting alarm thresholds, alarm enablement, and display options, to name a few. 
       SUMMARY OF THE INVENTION 
       [0004]    Conventional physiological measurement systems are limited by the patient cable connection between sensor and monitor. A patient must be located in the immediate vicinity of the monitor. Also, patient relocation requires either disconnection of monitoring equipment and a corresponding loss of measurements or an awkward simultaneous movement of patient equipment and cables. Various devices have been proposed or implemented to provide wireless communication links between sensors and monitors, freeing patients from the patient cable tether. These devices, however, are incapable of working with the large installed base of existing monitors and sensors, requiring caregivers and medical institutions to suffer expensive wireless upgrades. It is desirable, therefore, to provide a communications adapter that is plug-compatible both with existing sensors and monitors and that implements a wireless link replacement for the patient cable. 
         [0005]    An aspect of a physiological measurement communications adapter comprises a sensor interface configured to receive a sensor signal. A transmitter modulates a first baseband signal responsive to the sensor signal so as to generate a transmit signal. A receiver demodulates a receive signal corresponding to the transmit signal so as to generate a second baseband signal corresponding to the first baseband signal. Further, a monitor interface is configured to communicate a waveform responsive to the second baseband signal to a sensor port of a monitor. The waveform is adapted to the monitor so that measurements derived by the monitor from the waveform are generally equivalent to measurements derivable from the sensor signal. The communications adapter may further comprise a signal processor having an input in communications with the sensor interface, where the signal processor is operable to derive a parameter responsive to the sensor signal and where the first baseband signal is responsive to the parameter. The parameter may correspond to at least one of a measured oxygen saturation and a pulse rate. 
         [0006]    One embodiment may further comprise a waveform generator that synthesizes the waveform from a predetermined shape. The waveform generator synthesizes the waveform at a frequency adjusted to be generally equivalent to the pulse rate. The waveform may have a first amplitude and a second amplitude, and the waveform generator may be configured to adjusted the amplitudes so that measurements derived by the monitor are generally equivalent to a measured oxygen saturation. 
         [0007]    In another embodiment, the sensor interface is operable on the sensor signal to provide a plethysmograph signal output, where the first baseband signal is responsive to the plethysmograph signal. This embodiment may further comprise a waveform modulator that modifies a decoded signal responsive to the second baseband signal to provide the waveform. The waveform modulator may comprise a demodulator that separates a first signal and a second signal from the decoded signal, an amplifier that adjusts amplitudes of the first and second signals to generate a first adjusted signal and a second adjusted signal, and a modulator that combines the first and second adjusted signals into the waveform. The amplitudes of the first and second signals may be responsive to predetermined calibration data for the sensor and the monitor. 
         [0008]    An aspect of a physiological measurement communications adapter method comprises the steps of inputting a sensor signal at a patient location, communicating patient data derived from the sensor signal between the patient location and a monitor location, constructing a waveform at the monitor location responsive to the sensor signal, and providing the waveform to a monitor via a sensor port. The waveform is constructed so that the monitor calculates a parameter generally equivalent to a measurement derivable from the sensor signal. 
         [0009]    In one embodiment, the communicating step may comprise the substeps of deriving a conditioned signal from the sensor signal, calculating a parameter signal from the conditioned signal, and transmitting the parameter signal from the patient location to the monitor location. The constructing step may comprise the substep of synthesizing the waveform from the parameter signal. In an alternative embodiment, the communicating step may comprise the substeps of deriving a conditioned signal from said sensor signal and transmitting the conditioned signal from the patient location to the monitor location. The constructing step may comprise the substeps of demodulating the conditioned signal and re-modulating the conditioned signal to generate the waveform. The providing step may comprise the substeps of inputting a monitor signal from an LED drive output of the sensor port, modulating the waveform in response to the monitor signal, and outputting the waveform on a detector input of the sensor port. 
         [0010]    Another aspect of a physiological measurement communications adapter comprises a sensor interface means for inputting a sensor signal and outputting a conditioned signal, a transmitter means for sending data responsive to the sensor signal, and a receiver means for receiving the data. The communications adapter further comprises a waveform processor means for constructing a waveform from the data so that measurements derived by a monitor from the waveform are generally equivalent to measurements derivable from the sensor signal, and a monitor interface means for communicating the waveform to a sensor port of the monitor. The communications adapter may further comprise a signal processor means for deriving a parameter signal from the conditioned signal, where the data comprises the parameter signal. The waveform processor means may comprise a means for synthesizing the waveform from the parameter signal. The data may comprise the conditioned signal, and the waveform processor means may comprise a means for modulating the conditioned signal in response to the monitor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an illustration of a prior art pulse oximetry system; 
           [0012]      FIG. 2  is a functional block diagram of a prior art pulse oximetry system; 
           [0013]      FIG. 3  is an illustration of a physiological measurement communications adapter; 
           [0014]      FIGS. 4A-B  are illustrations of communications adapter sensor modules; 
           [0015]      FIGS. 5A-C  are illustrations of communications adapter monitor modules; 
           [0016]      FIG. 6  is a functional block diagram of a communications adapter sensor module; 
           [0017]      FIG. 7  is a functional block diagram of a communications adapter monitor module; 
           [0018]      FIG. 8  is a functional block diagram of a sensor module configured to transmit measured pulse oximeter parameters; 
           [0019]      FIG. 9  is a functional block diagram of a monitor module configured to received measured pulse oximeter parameters; 
           [0020]      FIG. 10  is a functional block diagram of a sensor module configured to transmit a plethysmograph; 
           [0021]      FIG. 11  is a functional block diagram of a monitor module configured to receive a plethysmograph; 
           [0022]      FIG. 12  is a functional block diagram of a waveform modulator; 
           [0023]      FIG. 13  is a functional block diagram of a sensor module configured for multiple sensors; and 
           [0024]      FIG. 14  is a functional block diagram of a monitor module configured for multiple sensors. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Overview 
       [0025]      FIG. 3  illustrates one embodiment of a communications adapter.  FIGS. 4-5  illustrate physical configurations for a communications adapter. In particular,  FIGS. 4A-B  illustrate sensor module configurations and  FIGS. 5A-C  illustrate monitor module configurations.  FIGS. 6-14  illustrate communications adapter functions. In particular,  FIGS. 6-7  illustrate general functions for a sensor module and a monitor module, respectively.  FIGS. 8-9  functionally illustrate a communications adapter where derived pulse oximetry parameters, such as saturation and pulse rate are transmitted between a sensor module and a monitor module. Also,  FIGS. 10-12  functionally illustrate a communications adapter where a plethysmograph is transmitted between a sensor module and a monitor module.  FIGS. 13-14  functionally illustrate a multiple-parameter communications adapter. 
         [0026]      FIG. 3  illustrates a communications adapter  300  having a sensor module  400  and a monitor module  500 . The communications adapter  300  communicates patient data derived from a sensor  310  between the sensor module  400 , which is located proximate a patient  20  and the monitor module  500 , which is located proximate a monitor  360 . A wireless link  340  is provided between the sensor module  400  and the monitor module  500 , replacing the conventional patient cable, such as a pulse oximetry patient cable  140  ( FIG. 1 ). Advantageously, the sensor module  400  is plug-compatible with a conventional sensor  310 . In particular, the sensor connector  318  connects to the sensor module  400  in a similar manner as to a patient cable. Further, the sensor module  400  outputs a drive signal to the sensor  310  and inputs a sensor signal from the sensor  310  in an equivalent manner as a conventional monitor  360 . The sensor module  400  may be battery powered or externally powered. External power may be for recharging internal batteries or for powering the sensor module during operation or both. 
         [0027]    As shown in  FIG. 3 , the monitor module  500  is advantageously plug-compatible with a conventional monitor  360 . In particular, the monitor&#39;s sensor port  362  connects to the monitor module  500  in a similar manner as to a patient cable, such as a pulse oximetry patient cable  140  ( FIG. 1 ). Further, the monitor module  500  inputs a drive signal from the monitor  360  and outputs a corresponding sensor signal to the monitor  360  in an equivalent manner as a conventional sensor  310 . As such, the combination sensor module  400  and monitor module  500  provide a plug-compatible wireless replacement for a patient cable, adapting an existing wired physiological measurement system into a wireless physiological measurement system. The monitor module  500  may be battery powered, powered from the monitor, such as by tapping current from a monitor&#39;s LED drive, or externally powered from an independent AC or DC power source. 
         [0028]    Although a communications adapter  300  is described herein with respect to a pulse oximetry sensor and monitor, one of ordinary skill in the art will recognize that a communications adapter may provide a plug-compatible wireless replace for a patient cable that connects any physiological sensor and corresponding monitor. For example, a communications adapter  300  may be applied to a biopotential sensor, a non-invasive blood pressure (NIBP) sensor, a respiratory rate sensor, a glucose sensor and the corresponding monitors, to name a few. 
       Sensor Module Physical Configurations 
       [0029]      FIGS. 4A-B  illustrate physical embodiments of a sensor module  400 .  FIG. 4A  illustrates a wrist-mounted module  410  having a wrist strap  411 , a case  412  and an auxiliary cable  420 . The case  412  contains the sensor module electronics, which are functionally described with respect to  FIG. 6 , below. The case  412  is mounted to the wrist strap  411 , which attaches the wrist-mounted module  410  to a patient  20 . The auxiliary cable  420  mates to a sensor connector  318  and a module connector  414 , providing a wired link between a conventional sensor  310  and the wrist-mounted module  410 . Alternatively, the auxiliary cable  420  is directly wired to the sensor module  400 . The wrist-mounted module  410  may have a display  415  that shows sensor measurements, module status and other visual indicators, such as monitor status. The wrist-mounted module  410  may also have keys (not shown) or other input mechanisms to control its operational mode and characteristics. In an alternative embodiment, the sensor  310  may have a tail (not shown) that connects directly to the wrist-mounted module  410 , eliminating the auxiliary cable  420 . 
         [0030]      FIG. 4B  illustrates a clip-on module  460  having a clip  461 , a case  462  and an auxiliary cable  470 . The clip  461  attaches the clip-on module  460  to patient clothing or objects near a patient  20 , such as a bed frame. The auxiliary cable  470  mates to the sensor connector  318  and functions as for the auxiliary cable  420  ( FIG. 4A ) of the wrist-mounted module  410  ( FIG. 4A ), described above. The clip-on module  460  may have a display  463  and keys  464  as for the wrist-mounted module  410  ( FIG. 4A ). Either the wrist-mounted module  410  or the clip-on module  460  may have other input or output ports (not shown) that download software, configure the module, or provide a wired connection to other measurement instruments or computing devices, to name a few examples. 
       Monitor Module Physical Configurations 
       [0031]      FIGS. 5A-C  illustrate physical embodiments of a monitor module  500 .  FIG. 5A  illustrates a direct-connect module  510  having a case  512  and an integrated monitor connector  514 . The case  512  contains the monitor module electronics, which are functionally described with respect to  FIG. 7 , below. The monitor connector  514  mimics that of the monitor end of a patient cable, such as a pulse oximetry patient cable  140  ( FIG. 1 ), and electrically and mechanically connects the monitor module  510  to the monitor  360  via the monitor&#39;s sensor port  362 . 
         [0032]      FIG. 5B  illustrates a cable-connect module  540  having a case  542  and an auxiliary cable  550 . The case  542  functions as for the direct-connect module  510  ( FIG. 5A ), described above. Instead of directly plugging into the monitor  360 , the cable-connect module  540  utilizes the auxiliary cable  550 , which mimics the monitor end of a patient cable, such as a pulse oximetry patient cable  140  ( FIG. 1 ), and electrically connects the cable-connect module  540  to the monitor sensor port  362 . 
         [0033]      FIG. 5C  illustrates a plug-in module  570  having a plug-in case  572  and an auxiliary cable  580 . The plug-in case  572  is mechanically compatible with the plug-in chassis of a multiparameter monitor  370  and may or may not electrically connect to the chassis backplane. The auxiliary cable  580  mimics a patient cable and electrically connects the plug-in module  570  to the sensor port  372  of another plug-in device. A direct-connect module  510  ( FIG. 5A ) or a cable-connect module  540  ( FIG. 5B ) may also be used with a multiparameter monitor  370 . 
         [0034]    In a multiparameter embodiment, such as described with respect to  FIGS. 13-14 , below, a monitor module  500  may connect to multiple plug-in devices of a multiparameter monitor  370 . For example, a cable-connect module  540  ( FIG. 5B ) may have multiple auxiliary cables  550  ( FIG. 5B ) that connect to multiple plug-in devices installed within a multiparameter monitor chassis. Similarly, a plug-in module  570  may have one or more auxiliary cables  580  with multiple connectors for attaching to the sensor ports  372  of multiple plug-in devices. 
       Communications Adapter Functions 
       [0035]      FIGS. 6-7  illustrate functional embodiments of a communications adapter.  FIG. 6  illustrates a sensor module  400  having a sensor interface  610 , a signal processor  630 , an encoder  640 , a transmitter  650  and a transmitting antenna  670 . A physiological sensor  310  provides an input sensor signal  612  at the sensor connector  318 . Depending on the sensor  310 , the sensor module  400  may provide one or more drive signals  618  to the sensor  310 . The sensor interface  610  inputs the sensor signal  612  and outputs a conditioned signal  614 . The conditioned signal  614  may be coupled to the transmitter  650  or further processed by a signal processor  630 . If the sensor module configuration utilizes a signal processor  630 , it derives a parameter signal  632  responsive to the sensor signal  612 , which is then coupled to the transmitter  650 . Regardless, the transmitter  650  inputs a baseband signal  642  that is responsive to the sensor signal  612 . The transmitter  650  modulates the baseband signal  642  with a carrier to generate a transmit signal  654 . The transmit signal  654  may be derived by various amplitude, frequency or phase modulation schemes, as is well known in the art. The transmit signal  654  is coupled to the transmit antenna  670 , which provides wireless communications to a corresponding receive antenna  770  ( FIG. 7 ), as described below. 
         [0036]    As shown in  FIG. 6 , the sensor interface  610  conditions and digitizes the sensor signal  612  to generate the conditioned signal  614 . Sensor signal conditioning may be performed in the analog domain or digital domain or both and may include amplification and filtering in the analog domain and filtering, buffering and data rate modification in the digital domain, to name a few. The resulting conditioned signal  614  is responsive to the sensor signal  612  and may be used to calculate or derive a parameter signal  632 . 
         [0037]    Further shown in  FIG. 6 , the signal processor  630  performs signal processing on the conditioned signal  614  to generate the parameter signal  632 . The signal processing may include buffering, digital filtering, smoothing, averaging, adaptive filtering and frequency transforms to name a few. The resulting parameter signal  632  may be a measurement calculated or derived from the conditioned signal, such as oxygen saturation, pulse rate, blood glucose, blood pressure and EKG to name a few. Also, the parameter signal  632  may be an intermediate result from which the above-stated measurements may be calculated or derived. 
         [0038]    As described above, the sensor interface  610  performs mixed analog and digital pre-processing of an analog sensor signal and provides a digital output signal to the signal processor  630 . The signal processor  630  then performs digital post-processing of the front-end processor output. In alternative embodiments, the input sensor signal  612  and the output conditioned signal  614  may be either analog or digital, the front-end processing may be purely analog or purely digital, and the back-end processing may be purely analog or mixed analog or digital. 
         [0039]    In addition,  FIG. 6  shows an encoder  640 , which translates a digital word or serial bit stream, for example, into the baseband signal  642 , as is well-known in the art. The baseband signal  642  comprises the symbol stream that drives the transmit signal  654  modulation, and may be a single signal or multiple related signal components, such as in-phase and quadrature signals. The encoder  640  may include data compression and redundancy, also well-known in the art. 
         [0040]      FIG. 7  illustrates a monitor module  500  having a receive antenna  770 , a receiver  710 , a decoder  720 , a waveform processor  730  and a monitor interface  750 . A receive signal  712  is coupled from the receive antenna  770 , which provides wireless communications to a corresponding transmit antenna  670  ( FIG. 6 ), as described above. The receiver  710  inputs the receive signal  712 , which corresponds to the transmit signal  654  ( FIG. 6 ). The receiver  710  demodulates the receive signal to generate a baseband signal  714 . The decoder  720  translates the symbols of the demodulated baseband signal  714  into a decoded signal  724 , such as a digital word stream or bit stream. The waveform processor  730  inputs the decoded signal  724  and generates a constructed signal  732 . The monitor interface  750  is configured to communicate the constructed signal  732  to a sensor port  362  of a monitor  360 . The monitor  360  may output a sensor drive signal  754 , which the monitor interface  750  inputs to the waveform processor  730  as a monitor drive signal  734 . The waveform processor  730  may utilize the monitor drive signal  734  to generate the constructed signal  732 . The monitor interface  750  may also provide characterization information  758  to the waveform processor  730 , relating to the monitor  360 , the sensor  310  or both, that the waveform processor  730  utilizes to generate the constructed signal  732 . 
         [0041]    The constructed signal  732  is adapted to the monitor  360  so that measurements derived by the monitor  360  from the constructed signal  732  are generally equivalent to measurements derivable from the sensor signal  612  ( FIG. 6 ). Note that the sensor  310  ( FIG. 6 ) may or may not be directly compatible with the monitor  360 . If the sensor  310  ( FIG. 6 ) is compatible with the monitor  360 , the constructed signal  732  is generated so that measurements derived by the monitor  360  from the constructed signal  732  are generally equivalent (within clinical significance) with those derivable directly from the sensor signal  612  ( FIG. 6 ). If the sensor  310  ( FIG. 6 ) is not compatible with the monitor  360 , the constructed signal  732  is generated so that measurements derived by the monitor  360  from the constructed signal  732  are generally equivalent to those derivable directly from the sensor signal  612  ( FIG. 6 ) using a compatible monitor. 
       Wireless Pulse Oximetry 
       [0042]      FIGS. 8-11  illustrate pulse oximeter embodiments of a communications adapter.  FIGS. 8-9  illustrate a sensor module and a monitor module, respectively, configured to communicate measured pulse oximeter parameters.  FIG. 10-11  illustrate a sensor module and a monitor module, respectively, configured to communicate a plethysmograph signal. 
       Parameter Transmission 
       [0043]      FIG. 8  illustrates a pulse oximetry sensor module  800  having a sensor interface  810 , signal processor  830 , encoder  840 , transmitter  850 , transmitting antenna  870  and controller  890 . The sensor interface  810 , signal processor  830  and controller  890  function as described with respect to  FIG. 2 , above. The sensor interface  810  communicates with a standard pulse oximetry sensor  310 , providing an LED drive signal  818  to the LED emitters  312  and receiving a sensor signal  812  from the detector  314  in response. The sensor interface  810  provides front-end processing of the sensor signal  812 , also described above, providing a plethysmograph signal  814  to the signal processor  830 . The signal processor  830  then derives a parameter signal  832  that comprises a real time measurement of oxygen saturation and pulse rate. The parameter signal  832  may include other parameters, such as measurements of perfusion index and signal quality. In one embodiment, the signal processor is an MS-5 or MS-7 board available from Masimo Corporation, Irvine, Calif. 
         [0044]    As shown in  FIG. 8 , the encoder  840 , the transmitter  850  and the transmitting antenna  870  function as described with respect to  FIG. 6 , above. For example, the parameter signal  832  may be a digital word stream that is serialized into a bit stream and encoded into a baseband signal  842 . The baseband signal  842  may be, for example, two bit symbols that drive a quadrature phase shift keyed (QPSK) modulator in the transmitter  850 . Other encodings and modulations are also applicable, as described above. The transmitter  850  inputs the baseband signal  842  and generates a transmit signal  854  that is a modulated carrier having a frequency suitable for short-range transmission, such as within a hospital room, doctor&#39;s office, emergency vehicle or critical care ward, to name a few. The transmit signal  854  is coupled to the transmit antenna  870 , which provides wireless communications to a corresponding receive antenna  970  ( FIG. 9 ), as described below. 
         [0045]      FIG. 9  illustrates a monitor module  900  having a receive antenna  970 , a receiver  910 , a decoder  920 , a waveform generator  930  and an interface cable  950 . The receive antenna  970 , receiver  910  and decoder  920  function as described with respect to  FIG. 7 , above. In particular, the receive signal  912  is coupled from the receive antenna  970 , which provides wireless communications to a corresponding transmit antenna  870  ( FIG. 8 ). The receiver  910  inputs the receive signal  912 , which corresponds to the transmit signal  854  ( FIG. 8 ). The receiver  810  demodulates the receive signal  912  to generate a baseband signal  914 . Not accounting for transmission errors, the baseband signal  914  corresponds to the sensor module baseband signal  842  ( FIG. 8 ), for example a symbol stream of two bits each. The decoder  920  assembles the baseband signal  914  into a parameter signal  924 , which, for example, may be a sequence of digital words corresponding to oxygen saturation and pulse rate. Again, not accounting for transmission errors, the monitor module parameter signal  924  corresponds to the sensor module parameter signal  832  ( FIG. 8 ), derived by the signal processor  830  ( FIG. 8 ). 
         [0046]    Also shown in  FIG. 9 , the waveform generator  930  is a particular embodiment of the waveform processor  730  ( FIG. 7 ) described above. The waveform generator  930  generates a synthesized waveform  932  that the pulse oximeter monitor  360  can process to calculate SpO 2  and pulse rate values or exception messages. In the present embodiment, the waveform generator output does not reflect a physiological waveform. In particular, the synthesized waveform is not physiological data from the sensor module  800 , but is a waveform synthesized from predetermined stored waveform data to cause the monitor  360  to calculate oxygen saturation and pulse rate equivalent to or generally equivalent (within clinical significance) to that calculated by the signal processor  830  ( FIG. 8 ). The actual intensity signal from the patient received by the detector  314  ( FIG. 8 ) is not provided to the monitor  360  in the present embodiment. Indeed, the waveform provided to the monitor  360  will usually not resemble a plethysmographic waveform or other physiological data from the patient to whom the sensor module  800  ( FIG. 8 ) is attached. 
         [0047]    The synthesized waveform  932  is modulated according to the drive signal input  934 . That is, the pulse oximeter monitor  360  expects to receive a red and IR modulated intensity signal originating from a detector, as described with respect to  FIGS. 1-2 , above. The waveform generator  930  generates the synthesized waveform  932  with a predetermined shape, such as a triangular or sawtooth waveform stored in waveform generator memory or derived by a waveform generator algorithm. The waveform is modulated synchronously with the drive input  934  with first and second amplitudes that are processed in the monitor  360  as red and IR portions of a sensor signal. The frequency and the first and second amplitudes are adjusted so that pulse rate and oxygen saturation measurements derived by the pulse oximeter monitor  360  are generally equivalent to the parameter measurements derived by the signal processor  830  ( FIG. 8 ), as described above. One embodiment of a waveform generator  930  is described in U.S. Patent Application No. 60/117,097 entitled “Universal/Upgrading Pulse Oximeter,” assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein. Although the waveform generator  930  is described above as synthesizing a waveform that does not resemble a physiological signal, one of ordinary skill will recognize that another embodiment of the waveform generator  930  could incorporate, for example, a plethysmograph simulator or other physiological signal simulator. 
         [0048]    Further shown in  FIG. 9 , the interface cable  950  functions in a manner similar to the monitor interface  750  ( FIG. 7 ) described above. The interface cable  950  is configured to communicate the synthesized waveform  932  to the monitor  360  sensor port and to communicate the sensor drive signal  934  to the waveform generator  930 . The interface cable  950  may include a ROM  960  that contains monitor and sensor characterization data. The ROM  960  is read by the waveform generator  930  so that the synthesized waveform  932  is adapted to a particular monitor  360 . For example, the ROM  960  may contain calibration data of red/IR versus oxygen saturation, waveform amplitude and waveform shape information. An interface cable is described in U.S. Patent Application No. 60/117,092, referenced above. Monitor-specific SatShare™ brand interface cables are available from Masimo Corporation, Irvine, Calif. In an alternative embodiment, such as a direct connect monitor module as illustrated in  FIG. 5A , an interface cable  950  is not used and the ROM  960  may be incorporated within the monitor module  900  itself. 
       Plethysmograph Transmission 
       [0049]      FIG. 10  illustrates another pulse oximetry sensor module  1000  having a sensor interface  1010 , encoder  1040 , transmitter  1050 , transmitting antenna  1070  and controller  1090 , which have the corresponding functions as those described with respect to  FIG. 8 , above. The encoder  1040 , however, inputs a plethysmograph signal  1014  rather than oxygen saturation and pulse rate measurements  832  ( FIG. 8 ). Thus, the sensor module  1000  according to this embodiment encodes and transmits a plethysmograph signal  1014  to a corresponding monitor module  1100  ( FIG. 11 ) in contrast to derived physiological parameters, such as oxygen saturation and pulse rate. The plethysmograph signal  1014  is illustrated in  FIG. 10  as being a direct output from the sensor interface  1010 . In another embodiment, the sensor module  1000  incorporates a decimation processor, not shown, after the sensor interface  1010  so as to provide a plethysmograph signal  1014  having a reduced sample rate. 
         [0050]      FIG. 11  illustrates another pulse oximetry monitor module  1100  having a receive antenna  1170 , a receiver  1110 , a decoder  1120  and an interface cable  1150 , which have the corresponding functions as those described with respect to  FIG. 9 , above. This monitor module embodiment  1100 , however, has a waveform modulator  1200  rather than a waveform generator  930  ( FIG. 9 ), as described above. The waveform modulator  1200  inputs a plethysmograph signal from the decoder  1120  rather than oxygen saturation and pulse rate measurements, as described with respect to  FIG. 9 , above. Further, the waveform modulator  1200  provides an modulated waveform  1132  to the pulse oximeter monitor  360  rather than a synthesized waveform, as described with respect to  FIG. 9 . The modulated waveform  1132  is a plethysmographic waveform modulated according to the monitor drive signal input  1134 . That is, the waveform modulator  1200  does not synthesize a waveform, but rather modifies the received plethysmograph signal  1124  to cause the monitor  360  to calculate oxygen saturation and pulse rate generally equivalent (within clinical significance) to that derivable by a compatible, calibrated pulse oximeter directly from the sensor signal  1012  ( FIG. 10 ). The waveform modulator  1200  is described in further detail with respect to  FIG. 12 , below. 
         [0051]      FIG. 12  shows a waveform modulator  1200  having a demodulator  1210 , a red digital-to-analog converter (DAC)  1220 , an IR DAC  1230 , a red amplifier  1240 , an IR amplifier  1250 , a modulator  1260 , a modulator control  1270 , a look-up table (LUT)  1280  and a ratio calculator  1290 . The waveform modulator  1200  demodulates red and IR plethysmographs (“pleths”) from the decoder output  1124  into a separate red pleth  1222  and IR pleth  1232 . The waveform modulator  1200  also adjusts the amplitudes of the pleths  1222 ,  1232  according to stored calibration curves for the sensor  310  ( FIG. 10 ) and the monitor  360  ( FIG. 11 ). Further, the waveform modulator  1200  re-modulates the adjusted red pleth  1242  and adjusted IR pleth  1252 , generating a modulated waveform  1132  to the monitor  360  ( FIG. 11 ). 
         [0052]    As shown in  FIG. 12 , the demodulator  1210  performs the demodulation function described above, generating digital red and IR pleth signals  1212 ,  1214 . The DACs  1220 ,  1230  convert the digital pleth signals  1212 ,  1214  to corresponding analog pleth signals  1222 ,  1232 . The amplifiers  1240 ,  1250  have variable gain control inputs  1262 ,  1264  and perform the amplitude adjustment function described above, generating adjusted red and IR pleth signals  1242 ,  1252 . The modulator  1260  performs the re-modulation function described above, combining the adjusted red and IR pleth signals  1242 ,  1252  according to a control signal  1272 . The modulator control  1270  generates the control signal  1272  synchronously with the LED drive signal(s)  1134  from the monitor  360 . 
         [0053]    Also shown in  FIG. 12 , the ratio calculator  1290  derives a red/IR ratio from the demodulator outputs  1212 ,  1214 . The LUT  1280  stores empirical calibration data for the sensor  310  ( FIG. 10 ). The LUT  1280  also downloads monitor-specific calibration data from the ROM  1160  ( FIG. 11 ) via the ROM output  1158 . From this calibration data, the LUT  1280  determines a desired red/IR ratio for the modulated waveform  1132  and generates red and IR gain outputs  1262 ,  1264  to the corresponding amplifiers  1240 ,  1250 , accordingly. A desired red/IR ratio is one that allows the monitor  360  ( FIG. 11 ) to derive oxygen saturation measurements from the modulated waveform  1132  that are generally equivalent to that derivable directly from the sensor signal  1012  ( FIG. 10 ). 
         [0054]    One of ordinary skill in the art will recognize that some of the signal processing functions described with respect to  FIGS. 8-11  may be performed either within a sensor module or within a monitor module. Signal processing functions performed within a sensor module may advantageously reduce the transmission bandwidth to a monitor module at a cost of increased sensor module size and power consumption. Likewise, signal processing functions performed within a monitor module may reduce sensor module size and power consumption at a cost of increase transmission bandwidth. 
         [0055]    For example, a monitor module embodiment  900  ( FIG. 9 ) described above receives measured pulse oximeter parameters, such as oxygen saturation and pulse rate, and generates a corresponding synthesized waveform. In that embodiment, the oxygen saturation and pulse rate computations are performed within a sensor module  800  ( FIG. 8 ). Another monitor module embodiment  1100  ( FIG. 11 ), also described above, receives a plethysmograph waveform and generates a remodulated waveform. In that embodiment, minimal signal processing is performed within a sensor module  1000  ( FIG. 10 ). In yet another embodiment, not shown, a sensor module transmits a plethysmograph waveform or a decimated plethysmograph waveform having a reduced sample rate. A corresponding monitor module has a signal processor, such as described with respect to  FIG. 8 , in addition to a waveform generator, as described with respect to  FIG. 9 . The signal processor computes pulse oximeter parameters and the waveform generator generates a corresponding synthesized waveform, as described above. In this embodiment, minimal signal processing is performed within the sensor module, and the monitor module functions are performed on the pulse oximeter parameters computed within the monitor module. 
       Wireless Multiple Parameter Measurements 
       [0056]      FIGS. 13-14  illustrate a multiple parameter communications adapter.  FIG. 13  illustrates a multiple parameter sensor module  1300  having sensor interfaces  1310 , one or more signal processors  1330 , a multiplexer and encoder  1340 , a transmitter  1350 , a transmitting antenna  1370  and a controller  1390 . One or more physiological sensors  1301  provide input sensor signals  1312  to the sensor module  1300 . Depending on the particular sensors  1301 , the sensor module  1300  may provide one or more drive signals  1312  to the sensors  1301  as determined by the controller  1390 . The sensor interfaces  1310  input the sensor signals  1312  and output one or more conditioned signals  1314 . The conditioned signals  1314  may be coupled to the transmitter  1350  or further processed by the signal processors  1330 . If the sensor module configuration utilizes signal processors  1330 , it derives multiple parameter signals  1332  responsive to the sensor signals  1312 , which are then coupled to the transmitter  1350 . Regardless, the transmitter  1350  inputs a baseband signal  1342  that is responsive to the sensor signals  1312 . The transmitter  1350  modulates the baseband signal  1342  with a carrier to generate a transmit signal  1354 , which is coupled to the transmit antenna  1370  and communicated to a corresponding receive antenna  1470  ( FIG. 14 ), as described with respect to  FIG. 6 , above. Alternatively, there may be multiple baseband signals  1342 , and the transmitter  1350  may transmit on multiple frequency channels, where each channel coveys data responsive to one or more of the sensor signals  1314 . 
         [0057]    As shown in  FIG. 13 , the sensor interface  1310  conditions and digitizes the sensor signals  1312  as described for a single sensor with respect to  FIG. 6 , above. The resulting conditioned signals  1314  are responsive to the sensor signals  1312 . The signal processors  1330  perform signal processing on the conditioned signals  1314  to derive parameter signals  1332 , as described for a single conditioned signal with respect to  FIG. 6 , above. The parameter signals  1332  may be physiological measurements such as oxygen saturation, pulse rate, blood glucose, blood pressure, EKG, respiration rate and body temperature to name a few, or may be intermediate results from which the above-stated measurements may be calculated or derived. The multiplexer and encoder  1340  combines multiple digital word or serial bit streams into a single digital word or bit stream. The multiplexer and encoder also encodes the digital word or bit stream to generate the baseband signal  1342 , as described with respect to  FIG. 6 , above. 
         [0058]      FIG. 14  illustrates a multiple parameter monitor module  1400  having a receive antenna  1470 , a receiver  1410 , a demultiplexer and decoder  1420 , one or more waveform processors  1430  and a monitor interface  1450 . The receiver  1410  inputs and demodulates the receive signal  1412  corresponding to the transmit signal  1354  ( FIG. 13 ) to generate a baseband signal  1414  as described with respect to  FIG. 7 , above. The demultiplexer and decoder  1420  separates the symbol streams corresponding to the multiple conditioned signals  1314  ( FIG. 13 ) and/or parameter signals  1332  ( FIG. 13 ) and translates these symbol streams into multiple decoded signals  1422 , as described for a single symbol stream with respect to  FIG. 7 , above. Alternatively, multiple frequency channels are received to generate multiple baseband signals, each of which are decoded to yield multiple decoded signals  1422 . The waveform processors  1430  input the decoded signals  1422  and generate multiple constructed signals  1432 , as described for a single decoded signal with respect to  FIGS. 7-12 , above. The monitor interface  1450  is configured to communicate the constructed signals  1432  to the sensor ports of a multiple parameter monitor  1401  or multiple single parameter monitors, in a manner similar to that for a single constructed signal, as described with respect to  FIGS. 7-12 , above. In particular, the constructed signals  1432  are adapted to the monitor  1401  so that measurements derived by the monitor  1401  from the constructed signals  1432  are generally equivalent to measurements derivable directly from the sensor signals  1312  ( FIG. 13 ). 
         [0059]    A physiological measurement communications adapter is described above with respect to wireless communications and, in particular, radio frequency communications. A sensor module and monitor module, however, may also communicate via wired communications, such as telephone, Internet or fiberoptic cable to name a few. Further, wireless communications can also utilize light frequencies, such as IR or laser to name a few. 
         [0060]    A physiological measurement communications adapter has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only. One of ordinary skill in the art will appreciate many variations and modifications of a physiological measurement communications adapter within the scope of the claims that follow.