Abstract:
A pulse oximetry user interface has a display and a plurality of views each configured to occupy the display. Each of the views are adapted to present data responsive to a physiological signal. A plurality of icons are configured to occupy a portion of the views and adapted to designate the content of the views. Further, a plurality of keys are proximate to the display and correspond to the icons so as to select the icons. One of the views is a pleth view that presents a pulse waveform. Another one of the views is a trend view that presents a trend graph. At least one of the icons can be selected so as to switch the display between the pleth view and the trend view.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims a priority benefit under 35 U.S.C. §120 from, and is a continuation-in-part of U.S. patent application Ser. No. 09/641,542, filed Aug. 18, 2000, entitled “Dual-Mode Pulse Oximeter,” No. 09/516,110, filed Mar. 1, 2000, now U.S. Pat. No. 6,584,336 entitled “Universal/Upgrading Pulse Oximeter,” and No. 09/491,175, filed Jan. 25, 2000 now ABN, entitled “Universal/Upgrading Pulse Oximeter.” This application also claims a priority benefit under 35 U.S.C. §119(e) from U.S. Provisional Patent Application No. 60/268,207, filed Feb. 12, 2001, entitled “Pulse Oximetry User Interface,” No. 60/161,565, filed Oct. 26, 1999, entitled “Improved Universal/Upgrading Pulse Oximeter, and No. 60/117,097, filed Jan. 25, 1999, entitled “Universal/Upgrading Pulse Oximeter.” Each of the foregoing applications are incorporated by reference herein. For reference, the &#39;542 patent application is also a continuation-in-part of the &#39;175 patent application, the &#39;110 patent application is a continuation of the &#39;175 patent application, and the &#39;175 patent application claims priority to the &#39;565 and &#39;097 provisional patent applications. 
    
    
     BACKGROUND OF THE INVENTION 
     Pulse oximetry is a continuous and non-invasive method of measuring the level of arterial oxygen saturation in blood. The measurement is taken by placing a sensor on a patient, usually on the fingertip for adults and the hand or foot for neonates. The sensor is connected to a pulse oximetry instrument with a patient cable. The sensor collects signal data from the patient and sends it to the instrument. A pulse oximetry instrument typically displays the calculated data as a percent value for arterial oxygen saturation (SpO 2 ), as a pulse rate (PR) and as a plethysmographic waveform. 
     Pulse oximetry is governed by a several principles. Oxyhemoglobin (oxygenated blood) and deoxyhemoglobin (non-oxygenated blood) differ in their absorption of red and infrared light (spectrophotometry). Also, the amount of arterial blood in tissue changes with an arterial pulse (photoplethysography). Therefore, the amount of light absorbed by the varying quantities of arterial blood changes as well. 
     A typical pulse oximeter uses a two-wavelength pulsatile system to distinguish between oxygenated and deoxygenated blood. Signal data is obtained by passing red and infrared light through a capillary bed (for example a fingertip, a hand, a foot) and measuring changes in light absorption during the pulsatile cycle. A typical pulse oximeter utilizes a sensor with red and infrared light-emitting diodes (LEDs) that pass light through the site to a photodiode (photodetector). The photodetector receives the light, converts it into an electronic signal and sends it, via a patient cable, to the pulse oximeter for calculation. 
     A pulse oximeter measures and displays functional saturation, which is the amount of oxygenated hemoglobin expressed as a percentage of the hemoglobin that can transport oxygen. This is not a measure of fractional saturation, i.e. oxygenated hemoglobin expressed as a percentage of all measured hemoglobin, including measured dysfunctional hemoglobin such as carboxyhemoglobin or methemoglobin. 
     Oxygen saturation measurements obtained from a pulse oximeter are commonly compared to saturations calculated from the partial pressure of oxygen (PO 2 ) obtained from an arterial blood gas sample. The calculated value obtained from the blood gas sample, however, may differ from the SpO 2  measurement of the pulse oximeter. Different results are usually obtained from the blood gas sample if the calculated saturation is not appropriately corrected for the effects of variables that shift the relationship between PO 2  and saturation, such as pH, temperature, the partial pressure of carbon dioxide (PCO 2 ), and fetal hemoglobin. Also, as blood gas samples are usually taken over a period of 20 seconds (the time it takes to draw blood) a meaningful comparison can only be achieved if the core oxygen saturation of the patient is stable and not changing over the period of time that the blood gas sample is taken. 
     Embodiments of the present invention seeks to overcome some or al of these and other problems. 
     SUMMARY OF THE INVENTION 
     One aspect of a pulse oximetry user interface is a display and a plurality of views each configured to occupy at least a portion of the display. Each of the views are adapted to present data responsive to a physiological signal. A plurality of icons are configured to occupy a portion of the views and adapted to designate the content of the views. Further, a plurality of keys are proximate to the display and are associated with or otherwise correspond to the icons such that selection of key corresponds to selection of an icon. One of the views is a pleth view that presents a pulse waveform. Another one of the views is a trend view that presents a trend graph. At least one of the icons can be selected so as to switch the display between the pleth view and the trend view. 
     Another aspect of a pulse oximetry user interface is a method comprising the steps of deriving a pulse waveform responsive to a physiological signal, calculating a data trend responsive to the physiological signal and providing the pulse waveform in a first display view. Other steps include presenting at least a portion of the data trend in a second display view, selecting a first icon accessible from the first display view to switch to the second display view, and selecting a second icon accessible from the second display view to switch to the first display view. 
     Yet another aspect of a pulse oximetry user interface is a view means for presenting to a user data responsive to a physiological signal, a main menu means for choosing display related categories, and a category menu means for choosing display related parameters. The parameters determine the characteristic of the view means. The user interface also includes an icon means for designating the view means, accessing the menu means and altering the parameters. The interface further includes a soft key means for selecting the icon means. 
     For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention have been described herein. Of course, it is to be understood that not necessarily all such aspects, advantages or features will be embodied in any particular embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements. In addition, the first digit of each reference number indicates the figure in which the element first appears. 
     FIGS. 1A-C are perspective views of a three-in-one pulse oximeter; 
     FIGS. 2A-C are illustrations of a pulse oximeter user interface; 
     FIG. 3 is a hierarchical chart of a pulse oximeter user interface; 
     FIGS. 4-6 are illustrations of display views; 
     FIG. 4 illustrates a pleth only view; 
     FIGS. 5A-B illustrate horizontal and vertical formats, respectively, of a pleth and signal quality view; 
     FIG. 6 illustrates a numeric view; 
     FIGS. 7A-D are graphs of pleth auto-scaling and auto-clipping characteristics; 
     FIGS. 8A-B are hierarchical charts of soft key icons; 
     FIGS. 9A-B illustrate horizontal and vertical formats, respectively, of a main menu; 
     FIG. 10 is an illustration of a trend view; 
     FIGS. 11-18 are illustrations of submenus and screens accessible from the main menu; 
     FIGS. 11A-B illustrate horizontal and vertical formats, respectively, of an alarm menu; 
     FIG. 12 is an illustration of a display menu; 
     FIG. 13 is an illustration of a general menu; 
     FIG. 14 is an illustration of a clock menu; 
     FIG. 15 is an illustration of an about screen; 
     FIG. 16 is an illustration of an output menu; 
     FIG. 17 is an illustration of a service menu; 
     FIG. 18 is an illustration of a password screen; 
     FIGS. 19-21 are illustrations of trend-related menus and screens accessible from the trend view; 
     FIG. 19 is an illustration of a trend setup menu; 
     FIG. 20 is an illustration of a histogram screen; and 
     FIG. 21 is an illustration of a clear confirmation screen. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A-C illustrate an instrument that provides the functionality of three pulse oximeters in one. FIG. 1A illustrates a full-featured handheld pulse oximeter  101 . FIG. 1B illustrates a full-featured standalone pulse oximeter  105 . FIG. 1C illustrates an upgrading pulse oximeter  109 . 
     As shown in FIG. 1A, the handheld  101  contains the majority of the pulse oximeter features. Pulse oximetry measurement information, as well as instrument status data is displayed to a user on a handheld LCD screen  210  (FIG.  2 A). User input is handled through control keys  220 - 260  (FIG. 2A) on a front panel. User input and displays are controlled by the handheld  101 . A sensor cable  10  connects into a swivel connector  20  on the handheld  100 . The handheld  101  is battery powered and can be used either as a transport monitor or as a handheld pulse oximeter for spot checks. A handheld release button  30  is pressed to pull the handheld  101  out of a docking station  103  (FIG.  1 B). 
     As shown in FIG. 1B, the handheld  101  snaps into the docking station  103  to provide the standalone pulse oximeter  105 . The docking station  103  connects to AC power for standalone operation or handheld battery charging. In one embodiment, a docking station battery is also available. The standalone pulse oximeter  105  features an analog output/nurse call and a serial output that interfaces to, for example, a printer or computer. 
     As shown in FIG. 1C, utilizing an interface cable  107 , the standalone  105  also interfaces to the sensor port of an SpO 2  module of a validated multiparameter patient monitor or other pulse oximeter monitor so as to upgrade conventional pulse oximetry to advanced pulse oximetry. The interface cable  107  attaches to the back of the docking station  105 . 
     A handheld pulse oximeter, docking station, standalone pulse oximeter and interface cable are described in U.S. patent application Ser. No. 09/516,110 filed Mar. 1, 2000 entitled “Universal/Upgrading Pulse Oximeter,” assigned to the assignee of the present invention and incorporated by reference herein. Pulse oximeters having handheld, docking stations and standalone features include those commercially available from, for example, Masimo Corporation of Irvine, Calif., under the Radical™ brand. An associated publication entitled “Radical, Signal Extraction Pulse Oximeter, Operator&#39;s Manual,” ©2001 Masimo Corporation is incorporated by reference herein. Interface cables are also available from, for example, Masimo Corporation under the SatShare™ brand. 
     Handheld Pulse Oximeter 
     FIGS. 2A-C generally illustrate a pulse oximeter user interface. FIG. 2A illustrates a handheld user interface having the display  210 , the fixed function keys  220 - 240 , programmable function keys (“soft keys”)  260 , associated soft key icons  270  and a loudspeaker  280 . The loudspeaker  280  provides an audio indication of alarms, which are described with respect to FIGS. 11A-B, below. The display  210  is described with respect to FIGS. 4-6, below. The four soft keys  260  are pressed to select a corresponding one of the soft key icons  270 . The soft key icons  270  indicate the software menu items that can be selected through the soft keys  260 . Pressing a soft key  260  next to an icon  270  selects the option. The soft keys  260  and soft key icons  270  are described with respect to FIGS. 8A-B, below. 
     As shown in FIG. 2A, the fixed function keys  220 - 240  include a power/standby button  220 , an alarm silence button  230  and a backlight/contrast button  240 . The power/standby button  220  is pressed to turn the instrument on, and it is held down for more than 2 seconds and then released to turn the instrument off. 
     The alarm silence button  230  is pressed to temporarily silence patient alarms. Also, the alarm silence button  230  is pressed when SENSOR OFF or NO SENSOR messages are flashing, such as when the sensor is removed from the patient, to acknowledge the end of monitoring. In these states, all further alarms are suspended until the pulse oximeter starts measuring oxygen saturation (i.e. SpO 2 ) and pulse rate again. System fault alarms can be silenced by pressing the power/standby button  220  or the alarm silence button  230 . 
     The backlight/contrast button  240  is pressed to change the illumination level of the backlight. With the AC line power connected, four levels of illumination are available in addition to a no illumination level. In the handheld mode, three levels of illumination are available in addition to a no illumination level. The lowest illumination is used for the most efficient battery usage. The backlight/contrast button  240  is also used to change the contrast of the LCD display by pressing and holding it for longer than two seconds to begin the contrast change and releasing it at the desired contrast setting. 
     Standalone Pulse Oximeter 
     FIG. 2B illustrates a standalone user interface having LED indicators  290  in addition to some or all of the interface features of the handheld, described above. When the handheld is placed into the docking station, the handheld can become a full-featured standalone pulse oximeter. The standalone acts as a battery charger for the handheld and has AC power connection capabilities. The standalone can also interface to serial devices, nurse call or analog output devices, and multiparameter patient monitors through an interface cable. 
     FIG. 2C illustrates the standalone LED indicators  290  including a docking station battery charging indicator  292 , a handheld battery charging indicator  294 , a visual alarm indicator  295 , an AC power indicator  297  and a docking indicator  299 . The docking station battery charging indicator  292  is illuminated when the docking station battery is charging. The handheld battery charging indicator  294  also is illuminated when the handheld battery is charging. Both charging indicators  292 ,  294  blink just prior to charging. Neither charging indicator  294  illuminates when a battery is fully charged or when a battery is not present. The visual alarm indicator  295  is illuminated when an alarm condition is active and the alarm status indicator is shown. The AC power indicator  297  is illuminated when the docking station is plugged into AC line power. The docking indicator  299  is illuminated when the handheld is turned on and is properly interfaced to a docking station. When the standalone is turned on at start up, all indicator LEDs initially turn on and off. 
     User Interface Details 
     FIG. 3 provides a hierarchical overview  300  of the content of the user display  210  (FIG. 2A) having display views  310 , display view soft key icons  320 , main menu and trend view  330 , submenus  340 , trend soft key icons  350  and trend-related screens  360 . There are three display views  310  including a pleth only view  400 , described with respect to FIG. 4, a pleth and signal quality view  500 , described with respect to FIGS. 5A-C, and a numeric view, described with respect to FIG.  6 . 
     As shown in FIG. 3, there are two pages of soft key icons  320  that appear in the display views  310 . A first page of icons  801  includes a main menu icon  814  (FIG. 8A) that, when selected, provides a main menu  900 . The main menu  900  includes soft key icons  820  (FIG. 8A) that allow selection of the submenus  340 . A second page of icons  802  include a trend icon  864  (FIG. 8B) that, when selected, provides a trend view  1000 . The trend view  1000  includes three pages of trend soft key icons  350 . One of the trend soft key icon pages  350  provides for the selection of the trend-related screens  360 . The display view icons  320 , main menu icons  820  (FIG.  8 A), and trend icons  350  are described with respect to FIGS. 8A-B, below. The main menu  900  is described with respect to FIGS. 9A-B, below, and the trend view  1000  is described with respect to FIG. 10, below. The submenus  340  are described with respect to FIGS. 11-17, below. The general submenu  1300  provides for the selection of a home mode and associated password screen  1800 , described with respect to FIG.  13  and FIG. 18, below. 
     The content of the user display  210  (FIG. 2A) can appear as a horizontal format or a vertical format. The content of the user display  210  (FIG. 2A) can rotate between display formats as the handheld  101  (FIG. 1A) or standalone  105  (FIG. 1B) are physically moved to corresponding horizontal or vertical positions. Alternatively, the display content can rotate between horizontal and vertical formats by selection of a rotate soft key icon  868  (FIG.  8 B), described below. Horizontal and vertical format pairs are illustrated in FIGS. 5A-B,  9 A-B, and  11 A-B. A rotatable format display is described in U.S. patent application Ser. No. 09/516,110, referenced above. 
     Display Views 
     Pleth View 
     FIG. 4 illustrates a pleth only view  400  having an oxygen saturation  412 , a pulse rate  414 , a perfusion index  418  and a pulse waveform  422 . The oxygen saturation  412  displays a functional arterial hemoglobin oxygen saturation measurement in units of percentage SpO 2 . When a sensor is not connected to a patient and during pulse search, the display will show dashed lines. The oxygen saturation  412  is calculated and the display is updated at a frequency of once per second. The pulse rate  414  displays a patient&#39;s pulse rate in beats per minute. The pulse rate  414  is calculated and the display is updated at a frequency of once per second. 
     The pulse waveform  422  displays the acquired plethysmograph (“pleth”). The pulse waveform  422  is scaled with signal strength, as described in detail with respect to FIGS. 7A-D, below. The pulse waveform  422  is updated at a frequency of 31.25 times per second. The perfusion index  418  displays the percentage of pulsatile signal to non-pulsatile signal. 
     As shown in FIG. 4, the pleth view  400  also has saturation limits  432 , pulse rate limits  434  and an alarm status indicator  436 . The saturation limits  432  display the upper and lower saturation alarm limits. The saturation limits  432  are displayed next to the oxygen saturation  412 . The pulse rate limits  434  display the upper and lower pulse rate alarm limits. The pulse rate limits  434  are displayed next to the pulse rate  414 . When a measured value reaches or exceeds an alarm limit  432 ,  434  the associated number display  412 ,  414  and the corresponding violated limit  432 ,  434  flash. 
     The alarm status indicator  436  is a bell symbol that can be shown with or without a slash. It flashes when an alarm condition is present. When the alarm is silenced using the alarm silence button  230  (FIG.  2 A), an alarm status indicator  436  with a slash and a timer is shown to indicate that the alarm is temporarily silenced. When the alarm is silenced through an “all mute” menu selection, which is permanent until power is cycled or deselected using menu, an alarm status indicator  436  with a slash is shown to indicate that alarm has been silenced. 
     Also shown in FIG. 4, the pleth view  400  has status messages  442 - 448  and indicators  460 - 480 . The status messages include an advanced signal processing message (“Masimo SET”)  442  when such processing is active, a fast signal processing message (“FastSat”)  444  when operating in that mode, and a maximum sensitivity message (“Max”)  448  when operating in that mode. The advance signal processing can include advanced pulse oximetry such as that commercially available from Masimo Corporation of Irvine, Calif. under the Masimo SET® brand. Fast signal processing is described in U.S. patent application Ser. No. 09/586,845 entitled “Variable Mode Averager,” assigned to the assignee of the present invention and incorporated by reference herein. 
     The indicators include battery status indicators  460 , time and date indicators  470  and an output mode indicator  480 . Battery status indicators  460  show the capacity of the handheld and optional docking station batteries. An indicator  460  flashes when less than 15 minutes of battery life is left and the battery needs to be recharged. The docking station battery status indicator is not shown when the optional docking station battery is not present. The time and date indicators  470  display the current time and date. The date and time are displayed in dd/mm/yyyy or mm/dd/yyyy format. The date and time display format is selected in the clock menu  1400  (FIG.  14 ). The output mode indicator  480  displays the output mode selected by the user. The output mode indicator  480  also displays the type of interface cable. In are embodiment, the output mode indicator  480  is only displayed when the instrument actively outputs data other than ASCII text or interfaces with a monitor through the interface cable. 
     Further shown in FIG. 4, the pleth view  400  has system messages generated by the instrument that are displayed in a system message area  450 . Each message and its meaning are described immediately below. An “AMBIENT LIGHT” message indicates that too much light is on the patient (sensor). A “DEFECTIVE SENSOR” message indicates that the oximeter cannot identify the connected sensor or the sensor has failed, which, for example, may be caused by a broken sensor cable wire, inoperative LEDs, an unauthorized sensor, or a faulty detector. An “INTERFERENCE” message indicates that an outside signal or energy is preventing a reading. An “INVALID SENSOR” message indicates the oximeter cannot identify the connected sensor, which again can be due to a broken sensor cable wire, inoperative LEDs, an unauthorized sensor, or a faulty detector. A “LOW BATTERY” message indicates that the battery charge is low, signaling that the handheld be placed into the docking station to be powered with AC line power or that the battery be replaced. A “LOW PERFUSION” message indicates that the signal is too small. A “LOW SIGNAL IQ” message indicates a low signal quality, and is discussed further with respect to FIGS. 5A-C, below. A “NO SENSOR” message indicates that a sensor is not fully inserted into the connector, which may be due to an incorrect sensor, or a defective sensor or cable, or that the sensor is inserted upside down. A “PULSE SEARCH” message indicates that the instrument is searching for patient&#39;s pulse. A “SENSOR OFF” message indicates that a sensor is off the patient and should be reattached. A “SERVICE REQUIRED” message indicates an internal failure and that the instrument requires service. The “SERVICE REQUIRED” message fills the entire display. 
     As shown in FIG. 4, the pleth view  400  has soft key icons  270  as described with respect to FIG. 2A, above. In the display views  400 - 600  (FIG.  3 ), including the pleth view  400 , the soft key icons  270  can be page  1  display view icons  810  (FIG. 8A) or page  2  display view icons  860  (FIG.  8 B), described below. 
     Pleth And Signal Quality View 
     FIGS. 5A-B illustrate a pleth and signal quality view  500 , in horizontal and vertical format, respectively, having the features of the pleth only view  400  (FIG. 4) in addition to a signal quality waveform  510 . The signal quality waveform  510  provides a visual indicator of the plethysmogram signal quality. In particular, the signal quality waveform  510  displays the acquired signal quality and the timing of a patient&#39;s pulse by a series of vertical lines  512 . With motion, the plethysmographic waveform is often distorted and may be obscured by one or more artifacts. The vertical lines  512  coincide with peaks of an arterial pulsation. Even with a plethysmographic waveform obscured by artifacts, the instrument locates the arterial pulsation. A pulse tone generated by the loudspeaker  280  (FIG.  2 ), when enabled, coincides with the vertical lines  512 . The height of a particular vertical line of the signal quality waveform  510  indicates the quality of the measured signal. A generally large vertical line indicates that the SpO 2  measurement is based on a good quality signal. A generally small vertical line indicates that the SpO 2  measurement is based on data with low signal quality. When the signal quality is very low the accuracy of the SpO 2  measurement may be compromised and the “LOW SIGNAL IQ” system message  450  (FIG. 4) is displayed, as described above. The signal quality waveform  510  is updated at a frequency of 31.25 times per second. Signal quality may also be shown as a single, pulsating bar  610  (FIG.  6 ), as described with respect to the numeric view  600  (FIG.  6 ), below. Signal quality is described in U.S. patent application Ser. No. 09/858,114 entitled “Pulse Oximetry Data Confidence Indicator,” assigned to the assignee of the present invention and incorporated by reference herein. 
     Low signal quality may be due to various factors, such as improper sensor application, misalignment of the sensor&#39;s emitter and detector resulting in smaller signals, extreme changes in the patient&#39;s physiology and blood flow at the monitoring site, such as an inflated blood pressure cuff, a squeezing motion, sampling of an arterial blood specimen from the hand containing the pulse oximetry sensor, severe hypotension, peripheral vasoconstriction in response to hypothermia, medications, or a spell of Raynaud&#39;s syndrome. With neonates or infants, the peripheral blood flow to the sensor site may occur as the result of lifting or crossing of their legs, such as during a diaper change. 
     Numeric View 
     FIG. 6 illustrates a numeric view  600  having the features of the pleth view  400  (FIG. 4) without the pulse waveform  422  (FIG.  4 ). In particular, the numeric view prominently displays oxygen saturation  412  and pulse rate  414 . Further, the numeric view  600  features a signal quality bar  610  having a pulsating height that is responsive to the patient&#39;s arterial pulse and to signal quality. Signal quality is described with respect to FIGS. 5A-B, above. Specifically, the bar height pulses coincide with peaks of an arterial pulsation and the bar height indicates signal quality, with a generally small bar height corresponding to low signal quality and a generally large bar height corresponding to high signal quality. 
     Stability of the oxygen saturation  412  readings may be a good indicator of signal validity. Although stability is a relative term, experience provides a good feeling for changes that are artifactual or physiological and the speed, timing, and behavior of each. The stability of the oxygen saturation  412  readings over time is affected by the averaging mode being used. The longer the averaging time, the more stable the readings tend to become. This is due to a dampened response as the signal is averaged over a longer period of time than during shorter averaging times. However, longer averaging times delay the response of the oximeter and reduce the measured variations of SpO 2  and pulse rate (PR). Inaccurate measurements may be caused by significant levels of dysfunctional hemoglobin (e.g., carboxyhemoglobin or methemoglobin), intravascular dyes such as indocyanine green or methylene blue, venous pulsations at the frequency of the patient&#39;s arterial pulse and very low hemoglobin levels. 
     The displayed pulse rate  414  may differ slightly from the heart rate displayed on ECG monitors due to differences in averaging times. There may also be a discrepancy between cardiac electrical activity and peripheral arterial pulsation. Significant differences may indicate a problem with the signal quality due to physiological changes in the patient or one of the instruments or application of the sensor or patient cable. The pulsations from intra-aortic balloon support can be additive to the pulse rate displayed on the pulse oximeter. 
     Pleth Auto-Scaling And Auto-Clipping 
     FIGS. 7A-D illustrate auto-scaling and auto-clipping characteristics for the pulse waveform  422  (FIG. 4) available on the pleth view  400  (FIG. 4) or pleth and signal quality view  500  (FIGS.  5 A-C). The measured signal strength can vary quite widely. However, in a preferred embodiment, the signal strength can vary from 0% to 100%. In a more preferred embodiment, the signal strength can vary from 02% to 20%. The challenge is to display a measured waveform having three orders of magnitude dynamic range in a meaningful way. FIG. 7A illustrates an auto-scale/auto-clip graph  701  having a display target axis  710  in units of percentage of full-scale and a signal strength axis  720  in units of percentage of DC. Plotted on the graph  701  is a scaling/clipping curve  730 , which illustrates the display characteristics for the pulse waveform  422  (FIG. 4) at various measured signal levels. FIG. 7B illustrates an expanded graph  702  corresponding to FIG. 7A for values along the signal strength axis  720  in a range from about 0 to 0.2%. FIGS. 7A-B illustrate one auto-scaling and auto-clipping embodiment, where the measured pulse waveform is scaled to about a 90% full-scale value for all signal strength values above about 0.02% and clipped to about 0 for all signal strength values below about 0.02%. 
     FIG. 7C illustrates an auto-scale/auto-clip graph  703  similar to  701  (FIG.  7 A). Plotted on the graph  703  is a scaling/clipping curve  750 , which illustrates the display characteristics for the pulse waveform  422  (FIG. 4) at various measured signal levels. FIG. 7D illustrates an expanded graph  704  corresponding to FIG. 7C for values along the signal strength axis  720  in a range from about 0 to 0.5%. FIGS. 7C-D illustrate another auto-scaling and auto-clipping embodiment where the measured pulse waveform is scaled to between about 15% and 90% full-scale in a piecewise linear fashion for signal strength values above about 0.02% and clipped to about 0 for all signal strength values below about 0.02%. In this manner, the displayed pulse waveform  422  (FIG. 4) advantageously conveys to the user meaningful information about the measured signal strength. Specifically, for signal strength in the range of about 10%-20%, the pulse waveform  422  (FIG. 4) is scaled to about 90% full-scale. For signal strength in the range of about 2% to 10%, the pulse waveform  422  (FIG. 4) is scaled linearly to a corresponding range of about 60% to 90% full-scale. For signal strength in the range of about 0.5% to 2%, the pulse waveform  422  (FIG. 4) is scaled linearly to a corresponding range of about 15% to 60% full-scale. For signal strength in the range of about 0.02% to 0.5%, the pulse waveform  422  (FIG. 4) is scaled to about 15% full-scale. For signal strength in the range of about 0 to 0.02%, the pulse waveform  422  (FIG. 4) is clipped to about 0. 
     Soft Keys 
     FIGS. 8A-B are hierarchical charts of soft key icons corresponding to the soft key buttons  260  (FIG.  2 A). A soft key icon is selected by pressing and releasing the soft key button to the right of the icon (horizontal display) or underneath the icon (vertical display). Four icons are shown on the right side or bottom of the display. FIG. 8A illustrates a first set of soft key icons  801 , including the first page of display view icons  810 , menu icons  820 , category icons  830  and parameter icons  840 . FIG. 8B illustrates a second set of soft key icons  802 , including the second page of display view icons  860  and trend-related icons  870 - 890 . The display view icons  810  (FIG.  8 A),  860  (FIG. 8B) are those icons initially shown on the three views  400  (FIG.  4 ),  500  (FIGS.  5 A-B),  600  (FIG.  6 ), described above. The menu icons  820  (FIG. 8A) are those icons shown on the main menu  900  (FIGS.  9 A-B). The category  830  and parameter  840  icons are those shown on the submenus  1100 - 1700  (FIGS.  11 - 17 ). The trend-related icons  870 - 890  (FIG. 8B) are those icons shown on the trend view  1000  (FIG. 10) and on the trend-related menus and screens  1900 - 2100  (FIGS.  19 - 21 ). 
     As shown in FIG. 8A, the first page of display view icons  810  include next page  812 , menu access  814 , increase loudness  816  and decrease loudness  818 . Next page  812  is selected to access the second page of display view icons  860  (FIG.  8 B). Menu access  814  is selected to enter the main menu  900  (FIGS.  9 A-B). Increase loudness  816  is selected to increase the volume of the pulse beep. In one embodiment, there are seven levels of volume available. Decrease loudness  818  is selected to decrease the volume of the pulse beep. The lowest volume level will silence the pulse beep and the decrease loudness  818  icon will appear with a slash through it. 
     As shown in FIG. 8B, the second page of display view icons  860  include next page  862 , trend display  864 , sensitivity  866  and rotate display  868 . Next page  862  is selected to return to the first page of display view icons  810  (FIG.  8 A). Trend display  864  is selected to show the trend view  1000  (FIG.  10 ). Sensitivity  866  is selected to toggle between normal and maximum sensitivity modes. Normal sensitivity is used for normal patient monitoring purposes. Maximum sensitivity is used for improved sensitivity performance on patients with extremely low perfusion. With the maximum sensitivity setting, the SENSOR OFF detection performance may be compromised. In one embodiment, the instrument automatically retains a sensitivity setting after a power cycle, and in another embodiment, the instrument does not retain a sensitivity setting after a power cycle. Rotate display  868  is selected to reconfigure the display contents in a vertical or horizontal format. The display contents rotate clockwise in 90 degree increments, accordingly. 
     Main Menu 
     FIGS. 9A-B illustrate horizontal and vertical formats, respectively, of a main menu  900 . When the main menu  900  is accessed, the plethysmograph and signal quality waveform displays are replaced with main menu categories  910 . The display view soft key icons  810  (FIG.  8 A),  860  (FIG. 8B) are also replaced by the main menu soft key icons  820  (FIG.  8 A). When the main menu  900  is accessed the instrument remains functional and the saturation and pulse rate numbers will continue to be displayed. 
     As shown in FIG. 8A, the main menu  900  (FIGS. 9A-B) uses the four main menu icons  820 , including exit  822 , select category  824 , previous  826  and next  828 . Exit  822  is selected to exit the main menu  900  (FIGS. 9A-B) and return to the original display view. Select category  824  is selected to choose a highlighted menu category  910  (FIGS. 9A-B) and display the corresponding submenu  1100 - 1700  (FIGS.  11 - 17 ). Previous  826  is selected to scroll through the menu categories  910  (FIGS.  9 A-B), highlighting categories without selecting them. Next  828  is selected to scroll through the menu categories  910  (FIGS.  9 A-B), in a direction opposite from previous  826 , also highlighting categories without selecting them. Once a menu category  910  (FIGS. 9A-B) is highlighted, the chosen submenu  1100 - 1700  (FIGS. 11-17) is displayed with a select category  824  selection. 
     Also shown in FIG. 8A, a submenu  1100 - 1700  (FIGS. 11-17) is displayed with a set of category icons  830 , including exit  832 , edit parameter  834 , previous  836  and next  838 . Exit  832  is selected to exit the category submenu  1100 - 1700  (FIGS. 11-17) and return to the main menu  900  (FIGS.  9 A-B). Edit parameter  834  is selected to choose a highlighted parameter in a submenu for editing. Previous  836  and next  838  function in a similar manner as described above to highlight parameters without selecting them. Once a parameter is highlighted, the parameter is edited by selecting edit parameter  834 . 
     Further shown in FIG. 8A, once a parameter has been selected for editing, a set of parameter icons  840  are displayed, including exit  842 , accept  844 , previous  846  and next  848 . Exit  842  is selected to exit a parameter without making any new selections permanent. Accept  844  is selected to save any changes. Previous  846  is selected to increase or toggle a parameter settings. Next  848  is selected to decrease or toggle a parameter settings. Submenus and associated parameters are described in more detail with respect to FIGS. 11-17, below. 
     Trend View 
     FIG. 10 illustrates a trend view  1000  having a first line of information  1010 , a second line of information  1020 , an oxygen saturation trend graph  1030 , a low signal quality indicator  1040 , and a pulse rate trend graph  1050 . The first line  1010  on the trend view  1000  shows the time scale of the trend graph, followed by the starting date, starting time and end time of the data set that is displayed on the screen. The second line  1020  of the trend view  1000  shows the minimum, average, and maximum SpO 2  and pulse rate measurements contained in the displayed data set (excluding zero measurements). The oxygen saturation trend graph  1030  shows the SpO 2  measurements displayed versus time. The pulse rate trend graph  1050  shows the pulse rate measurements displayed versus time. A dark line  1032 ,  1034  on the trend graphs  1030 ,  1050  indicates averaged data, while grayed-out data points show minimum and maximum values. The low signal quality indicator  1040  appears as a grayed-out box, line or other designation located on the bottom axis or other portion of the oxygen saturation trend graph  1030  and indicates a period of time for which the “LOW SIGNAL IQ” message was active. During this time, the signal quality was very low and the accuracy of the measurement may have been compromised. The vertical scale of the oxygen saturation  1030  and pulse rate  1050  graphs can be set in the trend setup screen  1900  (FIG.  19 ). 
     Once the trend display icon  864  (FIG. 8B) is selected, the trend data is shown on the trend view  1000 . The instrument stores one data set of oxygen saturation, pulse rate and system messages in a dedicated memory area. Depending on the trend period, a setting for how often the data is stored in the trend memory, the instrument can store between 72 hours and 30 days worth of trend data. The instrument also employs data compression. The actual amount of trend data that is stored is dependent on the type of data that is collected. The instrument only stores data in the trend memory while the instrument is turned on, and the trend data remains in memory until the memory fills up or is cleared by the user. Changing the date and time of the system clock or changing the trend period will also clear the data in the trend memory. The trend capacity for a trend period setting of 2 seconds is a minimum of 72 hours (3 days). For a trend period setting of 10 seconds, the trend memory capacity is typically 720 hours (30 days). 
     By default, the trend view  1000  automatically refreshes at a rate of once every 10 seconds, to show the latest measured SpO 2  and pulse rate data. This feature is only available while the trend view is 2 hours or less and the latest measured data is shown. If the user scrolls through the data set to display previously recorded trend data or if the trend scale is greater than 2 hours, the trend view will time out after 1 minute of inactivity (i.e. the user does not press any of the soft key buttons) and the previous display view will be shown. 
     As shown in FIG. 8B, in the trend view there are a total of 12 soft key icon selections  870 - 890  on 3 pages. The first page has next menu  872 , exit  874 , scroll left  876  and scroll right  878  icons. Next menu  872  is selected to access the next page of menu selections. Exit  874  is selected to return to the previous display view. Scroll left  876  is selected to scroll through the data set in the backward time direction. Scroll right  878  is selected to scroll through the data set in the forward time direction. The display scrolls by ½ the selected time scale. For example, if a 2 hr display view is selected, then selecting scroll left  876  or scroll right  878  will scroll the displayed data by 1 hr to the left or right, respectively. 
     Also shown in FIG. 8B, the second page has next menu  882 , zoom  884 , zoom from left  886 , and zoom from right  888  icons. Next menu  882  is selected to access the next page of icons. Zoom  884  is selected to change the time scale of the trend view. The available time scales are 24 hrs, 12 hrs, 8 hrs, 4 hrs, 2 hrs, 1 hr, 30 minutes, 10 minutes, 1 minute and 20 seconds. Zoom  884  uses the last recorded data point as the zoom reference point. In other words, the last recorded data point is always shown as the right-most data point on the display. Zoom from left  886  is selected to zoom into the data set while keeping the data point that is shown on the right side of the trend graph as the zoom reference point. Zoom from right  888  is selected to zoom into the data set while keeping the data point that is shown on the left side of the trend graph as the zoom reference point. 
     Further shown in FIG. 8B, the third page has next menu  882 , trend setup  884 , histogram  896  and clear trend data  898  icons. Next menu  882  is selected to return to the first page of icons. Trend setup  884  is selected to enter the trend setup screen  1900  (FIG.  19 ). Histogram  896  is selected to display the selected data set (the data set shown in the trend view) in histogram format  2000  (FIG.  20 ). Clear trend data  898  is selected to clear the data stored in the trend memory, which is verified via a confirmation screen  2100  (FIG.  21 ). 
     FIGS. 11A-B illustrate an alarms menu  1100  in horizontal and vertical formats, respectively, having a high SpO 2  alarm limit  1110 , a low SpO 2  alarm limit  1120 , a high pulse rate alarm limit  1130 , and a low pulse rate alarm limit  1140 . Alarm limit settings are typically checked each time the pulse oximeter is used to ensure that they are appropriate for the patient being monitored. An audible alarm and a flashing alarm status indicator  432  (FIG. 4) will occur when an alarm limit is met or exceeded. 
     The SpO 2  high alarm limit  1110  can be set anywhere between 2% and 100%, with a 1% step size. In the “—” (off) setting, the alarm can be turned off completely. The SpO 2  low alarm limit  1120  can be set anywhere between 1% and 100%, with a 1% step size. The pulse rate high alarm limit  1130  can be set anywhere between 30 BPM and 240 BPM, with a 5 BPM step size. The pulse rate low alarm limit  1140  can be set anywhere between 25 BPM and 235 BPM, with a 5 BPM step size. The low alarm limits  1120 ,  1140  always have to be set below the corresponding high alarm limits  1110 ,  1130 . When a high alarm limit  1110 ,  1130  is set below the corresponding low alarm limit  1120 ,  1140 , the low alarm limit  1120 ,  1140  will automatically adjust to the next setting below the newly entered high alarm limit  1110 ,  1130 . 
     As shown in FIGS. 11A-B, the alarms menu  1100  also has alarm limit type  1150 , silence  1160 , volume  1170  and delay  1180  settings. The instrument stores three alarm limit types  1150  including adult, neo and custom limits. Adult and neo limits are preset and cannot be changed by the user. Table 1 outlines the default values of the preset and custom alarm limit types  1150 . 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 TYPES 
                 SpO 2  HIGH 
                 SpO 2  LOW 
                 PR HIGH 
                 PR LOW 
               
               
                   
               
             
             
               
                 Adult 
                 Off 
                 90% 
                 140 BPM 
                  50 BPM 
               
               
                 Neo 
                 100% 
                 90% 
                 180 BPM 
                 100  BPM 
               
               
                 Custom 
                 Off 
                 90%  
                 140 BPM 
                  50 BPM 
               
               
                   
               
             
          
         
       
     
     The custom limits are set to the values listed in the table at the factory. Once the values are changed, the new values are retained after a power cycle. 
     The alarm menu  1100  allows the user to set an alarm silence duration  1160 . An alarm is silenced by pressing the alarm silence button  230  (FIG. 2A) on the front panel. The alarm silence duration  1160  can be virtually any amount of time. However, in a preferred embodiment, the duration  1160  is set as 30, 60, 90 and 120 seconds. As an indicator that the alarm system is silenced, the alarm status indicator  436  (FIG. 4) is shown as a bell with a slash through it. A timer is shown next to the bell indicating the remaining alarm silence duration. The alarm silence duration  1160  is reset to 120 seconds upon a power cycle, except for when the instrument is set to operate in the home mode. In an all mute mode, all patient alarm conditions are silenced. Only system alarms will be indicated by an audible alarm. As an indicator that the system is set to all mute, the alarm status indicator  436  (FIG. 4) is shown as a flashing bell with a slash through it. In an all mute with audible reminder mode, all patient alarm conditions are silenced. Only system alarms will be indicated by an audible alarm. As a reminder, a single audible alarm will occur every three minutes. 
     Also shown in FIGS. 11A-B, the alarm menu  1100  allows the user to set the alarm volume  1170 . According to one embodiment, four levels are available, with level  1  being the softest and level  4  being the loudest. The instrument retains the alarm volume  1170  setting upon a power cycle. For home use, the alarm level to typically set to level 4. If an alarm condition occurs while the alarm silence period is set to all mute, the only alarm indications will be visual displays and symbols related to the alarm condition. No alarm tone will sound. 
     FIG. 12 illustrates the display menu  1200  having display view  1210 , contrast  1220  and language  1230  items. The display view item  1210  allows selection of one of the three display views including pleth  400  (FIG.  4 ), pleth and signal quality  500  (FIGS. 5A-B) and numeric  600  (FIG.  6 ), described above. The contrast item  1220  allows the user to set the display contrast. According to one embodiment, contrast ranges from 1 to 64. The contrast can also be set by pressing and holding the backlight/contrast key  240  (FIG. 2A) on the front panel. The language item  1230  allows the user to select the display language. 
     FIG. 13 illustrates a general menu  1300  having averaging time  1310 , FastSat  1320 , home use  1330 , interface alarms  1340 , SatShare numbers  1350  and power save  1360  items. Averaging time  1310  is the signal averaging time of the instrument, which can be set to include 2, 4, 8, 10, 12, 14 and 16 seconds. FastSat  1320 , when set to “yes,” activates a fast signal processing algorithm, such as described in U.S. patent application Ser. No. 09/586,845 referenced above. In the 2 and 4 seconds averaging mode, the fast signal processing algorithm is automatically enabled. With fast signal processing, the averaging time is dependent on the input signal. For the 2 and 4 second settings, the averaging times may range from 2-4 and 4-6 seconds, respectively. 
     As shown in FIG. 13, home use  1330 , when set to “yes,” places the instrument in the home mode, where it remains until the “no” setting is selected. A password is required to activate or deactive this mode. Home use operation is described further with respect to FIG. 18, below. Interface alarms  1340  allows audible alarms to be enabled or disabled. SatShare numbers  1350  is set to “yes” to display saturation and pulse rate measurements during upgrade operation, as described with respect to FIG. 1C, above. 
     Also shown in FIG. 13, power save  1360  can be set to “yes” or “no,” to adjust battery-operating time of the instrument while powered by the handheld battery or optional docking station battery. Selecting “yes” disables docking station functions such as the interface cable, serial and analog outputs. Selecting “no” activates these docking station functions while operating on battery power. While operating in the power save mode, a power cycle of the instrument may be required to activate the docking station again after it has been disabled. 
     FIG. 14 illustrates a clock menu  1400  having time  1410 , time format  1420 , date  1430  and date format  1440  items. The time item  1410  sets the hour and minutes. The time format item  1420  sets the time display in 12 hour (default) and 24 hour format. The date item  1430  sets the day, month and year. The date format item  1440  sets the date display in mm/dd/yyyy (default) and dd/mm/yyyy format. 
     FIG. 15 illustrates the about screen  1500 . The about screen  1500  simply displays the copyright and software versions of the handheld  101  (FIG. 1A) and the docking station  103  (FIG.  1 B). 
     FIG. 16 illustrates the output menu  1600  having serial  1610 , analog  1620  and nurse call  1630  output modes. The output menu selections are available when the handheld  101  (FIG. 1A) is interfaced to the docking station  103  (FIG.  1 B). The serial item  1610  allows a user to specify various serial output modes, which, according to one embodiment, are RS-232 based. In ASCII 1 mode, for example, ASCII text data is sent to the serial interface at one-second intervals. The ASCII text includes date and time stamp, SpO 2  pulse rate, PI, and alarm and exception values. All text is single line followed by a line feed character and a carriage return. In ASCII 2 mode, ASCII text data is sent to the serial interface following a query from the connecting computer. 
     The analog items  1620  specify the docking station analog outputs. In 0%-100% mode, the saturation measurement is scaled with 0% being equal to 0 volts and 100% equal to 1 volt. In 50%-100% mode, the saturation measurement is scaled with 50% being equal to 0 volts and 100% equal to 1 volt. In the 0V mode, a 0 volts calibration signal is mapped onto the analog outputs. This signal is used for calibration of recording devices, where 0 volts represent a saturation of 0% and a pulse rate of 0 bpm. In the 1V mode, a 1 volt calibration signal is mapped onto the analog outputs. This signal is also used for calibration of recording devices, where 1 volt represents a saturation of 100% and a pulse rate of 250 bpm. In pleth mode, the pulse waveform is scaled with 1 volt being equal to 100% full scale. In signal IQ mode, 1 volt is equal to maximum signal quality. The nurse call item  1630  can specify alarms and low signal quality as generating a nurse call. 
     FIG. 17 illustrates a service menu  1700  having handheld battery discharge  1710  and docking station (DS) battery discharge  1720  items. The service menu  1700  selections are only available when the handheld  101  (FIG. 1A) is interfaced to the docking station  103  (FIG.  1 B). Each of these items  1710 ,  1720 , when selected, causes the instrument to perform a deep discharge the respective handheld or docking station battery. The discharge cycle will take approximately 16 hours to complete for the handheld battery and approximately 30 hours to complete for the docking station battery. A message will appear in the service screen when the discharge cycle is complete. The batteries will be fully charged after completion of the cycle. 
     FIG. 18 illustrates a password entry display  1800 . A password is entered using the password soft key icons  1810  and pressing in a particular sequence the corresponding soft key buttons  260  (FIG. 2A) to the right or bottom of the display. In a home mode, a password is required to access the menu system and the soft key buttons and icons. When the instrument is set to operate in the home mode, the default values that the instrument reverts to after a power cycle are set according to a predetermined setting with the exception of the alarm silence setting, which is set to the pre-power down setting. The instrument can be placed into the home mode to protect unqualified users from changing the alarm settings and operation. Entering a password does not automatically reset the instrument to a normal operating mode. To return to a normal operating mode, the home use parameter  1330  (FIG. 13) is set to “No” in the general menu  1300  (FIG.  13 ). 
     FIG. 19 illustrates a trend setup menu  1900  having %SpO 2  max and min  1910 , BPM max and min  1920 , default view  1930 , trend action  1940  and trend period  1950  items. The trend setup menu  1900  allows the user to set the default trend settings and to clear the trend data or download the trend data to the serial port. The default settings are used to scale the trend graphs when the trend data icon  864  (FIG. 8B) is selected. %SpO 2  max and min  1910  set the high and low scale, respectively, of the SpO 2  trend graph  1030  (FIG.  10 ). BPM max and min  1920  set the high scale, respectively, of the pulse rate trend graph  1050  (FIG.  10 ). Default view  1930  selects the default time scale of the trend view  1000  (FIG.  10 ). This setting only selects the time scale of the trend view  1000  (FIG. 10) when the trend data is initially displayed, (i.e. when the trend data is initially accessed). According to one embodiment, the selections include 24 hrs, 12 hrs, 8 hrs, 4 hrs, 2 hrs, 1 hr, 30 minutes, 10 minutes, 1 minute and 20 seconds. 
     As shown in FIG. 19, trend action  1940  has serial dump, analog dump and print options. The serial dump option sends all the data that is stored in trend memory to the serial port and is used to communicate the stored data set to trend graphing software applications. The analog dump option sends all the data that is stored in the trend memory to the analog output and is used to print the trend information on an analog chart recorder. The print option prints the trend data that is shown in the trend view  1000  (FIG.  10 ). The trend data is first printed in histogram format, followed by a table of data that shows the time and date stamp of a trend record and the SpO 2  and pulse rate measurement. Each trend record is printed on a single line, followed by a carriage return and line feed character. 
     Also shown in FIG. 19, trend period  1950  determines how often a set of SpO 2  and pulse rate data points is stored in trend memory. A setting of 2, for example, sets the instrument to store one set of SpO 2  and pulse rate measurements every 2 seconds, resulting in a minimum trend capacity of 72 hours. A setting of 10, for example, sets the instrument to store one set of data points every 10 seconds, resulting in a typical trend storage capacity of 30 days. Because of data compression, the actual trend capacity is dependent on the type of data that is collected. 
     A pulse oximetry user interface 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 from the disclosure herein any variations and modifications. 
     Additionally, all publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.