Patent Publication Number: US-2007116089-A1

Title: Electronic thermometer with progress indicator

Description:
BACKGROUND  
      The healthcare field widely uses electronic thermometers for measuring a patient&#39;s body temperature. A typical electronic thermometer has a thermistor or other temperature sensitive element contained within an elongated shaft portion of a probe. In one version, the probe includes a cup-shaped aluminum tip at its free end. A thermistor is placed in thermal contact with the aluminum tip inside the probe. When the free end of the probe is placed in, for example, a patient&#39;s mouth (or rectum or axilla), the tip heats up and the thermistor measures the temperature of the tip to obtain a measurement of the patient&#39;s body temperature. Additional electronics connected to these electronic sensor components may be contained within a base unit connected by wire to the shaft portion or may be contained within a handle of the shaft portion. Electronic components receive input from the sensor components to compute the patient&#39;s temperature. The thermometer typically displays the patient&#39;s temperature on a visual output device, such as a seven segment numerical display device. Additional features of known electronic thermometers include an audible temperature level notification (e.g., a beep or tone alert signal). A disposable cover or sheath is often fitted over the shaft portion and disposed of after each use of the thermometer for sanitary reasons.  
      Electronic thermometers have many advantages over conventional thermometers and have essentially replaced the use of conventional glass thermometers in the healthcare field. One advantage of electronic thermometers over their conventional glass counterparts is the speed at which a temperature reading can be taken. Several procedures are used to promote a rapid measurement of the subject temperature. One technique employed is to use predictive algorithms as part of thermometer logic to extrapolate the temperature measurement from the thermistor in contact with the tip, to arrive at a temperature reading in advance of the tip reaching equilibrium with the body temperature. Another technique that can be employed simultaneously with a predictive algorithm is to heat the probe to near the body temperature, so that the portion of the probe away from the tip does not act as a heat sink. This allows the tip to reach a temperature close to the body temperature more rapidly. Heating with the probe can be accomplished by a resistor placed in contact with the probe. Another thermistor may be placed in contact with the probe to measure the amount of heat provided by the resistor for controlling the heating. It is also known to use an isolator to reduce heat loss from the tip to other parts of the probe. For example, commonly assigned U.S. Pat. No. 6,839,651, the entire disclosure of which is incorporated herein by reference, discloses a prediction type electronic thermometer having an actively controlled heater element thermally isolating the probe tip from the probe shaft.  
      Although most predictive thermometers provide an activity indication during a prediction measurement to indicate that measurement and prediction activity are occurring, there is no way for a user to know how far along the process has progressed. Further, the thermometer can experience interruptions in the data/temperature trend that cause the algorithm to restart, and for which there is no indication. For example, if the probe is moved within the patient&#39;s mouth to a region having a different temperature (e.g., from under the tongue to not under it), the algorithm must restart. Conventional electronic thermometers provide no way for the user to know when anything has interrupted the prediction process.  
     SUMMARY  
      Embodiments of the invention overcome one or more deficiencies in known systems by providing a progress indicator that will visually represent, in real time, how close an electronic thermometer is to producing a temperature reading. For predictive thermometers, aspects of the invention provide an indication of how close the prediction is to completion. In addition, one embodiment of the invention provides visual feedback if the thermometer must restart or reset for some reason. Moreover, the features of the present invention described herein are user friendly and intuitive as well as being economically feasible and commercially practical.  
      Briefly described, an electronic thermometer embodying aspects of the invention has a probe adapted to be heated by a subject for use in measuring the temperature of the subject and at least one temperature sensor for detecting the temperature of the probe during operation. A control circuit responsive to the temperature sensor performs at least one temperature calculation as a function of the detected temperature of the probe and generates a temperature signal representative of the temperature of the subject based on the temperature calculation. In addition, the thermometer includes a progress indicator for visually indicating progress of the control circuit in performing the temperature calculation.  
      According to another aspect of the invention, a method of indicating status of an electronic thermometer includes performing at least one temperature calculation as a function of a detected temperature of a probe, which is adapted to be heated by a subject for use in measuring the temperature of the subject. The method also includes defining a plurality of states, each of which corresponds to an amount of completion of the temperature calculation. The method further includes visually indicating progress of the temperature calculation based on the defined states.  
      Yet another aspect of the invention is directed to a medical device that has a control circuit configured to perform at least one operation over time and a progress indicator for visually indicating progress of the control circuit in performing the operation. 
    
    
      Other features will be in part apparent and in part pointed out hereinafter.  
      This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.  
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective of an electronic thermometer according to embodiments of the invention.  
       FIG. 2  is an exemplary progress indicator according to an embodiment of the invention.  
       FIG. 3  is an exemplary progress indicator according to another embodiment of the invention.  
       FIG. 4  is an exemplary flow diagram illustrating a progress determination of a temperature prediction process according to an embodiment of the invention.  
       FIG. 5  and  FIG. 6  are exemplary flow diagrams illustrating a stability variance determination of a temperature prediction process according to another embodiment of the invention. 
    
    
      Corresponding reference characters indicate corresponding parts throughout the drawings.  
     DETAILED DESCRIPTION  
      Referring now to the drawings and in particular to  FIG. 1 , an electronic thermometer constructed according to the principles of the present invention is indicated generally at  11 . The electronic thermometer comprises a temperature control circuit or unit, indicated generally at  13 , that is sized and shaped to be held comfortably in the hand H. The control unit  13  (broadly, “a base unit”) is connected by a helical cord  15  to a probe  17  (the reference numerals indicating their subjects generally). The probe  17  is constructed for contacting the subject (e.g., a patient) and sending signals to the control unit  13  representative of the temperature. The control unit  13  receives the signals from probe  17  and uses them to calculate the temperature. Suitable circuitry for performing these calculations is contained within a housing  19  of the control unit  13 . The logic in the circuitry may include a predictive algorithm for rapidly ascertaining a final temperature of the patient. The circuitry makes the calculated temperature appear on a LCD display  21  on the front of the housing  19 . Other information desirably can appear on the display  21 , as will be appreciated by those of ordinary skill in the art. A panel  21 A of buttons for operating the thermometer  11  is located just above the display  21 . In the embodiment of  FIG. 1 , display  21  includes a progress indicator  23 .  
      Those skilled in the art are familiar with various user interfaces for displaying information to a user and receiving user input. As an example, display  21  may be a graphical user interface having a touch screen by which the user can provide input. In this example, the panel  21 A could be embodied on display  21  itself.  
      The housing  19  includes a compartment (not shown) generally at the rear of the housing that can receive a distal portion of the probe  17  into the housing for holding the probe and isolating the distal portion from the environment when not in use.  FIG. 1  illustrates probe  17  being pulled by the other hand H 1  from the compartment in preparation for use. The housing  19  also has a receptacle  25  that receives a suitable container such as a carton C of probe covers (not shown). In use, the top of the carton C is removed, exposing open ends of the probe covers. The distal portion of probe  17  can be inserted into the open end of the carton C and one of the probe covers can be captured (e.g., snapped into) an annular recess. The probe  17  may be protected from contamination by the cover when a user inserts the distal portion of a probe shaft  35  into, for example, a patient&#39;s mouth. When depressed, a button  37  on the probe handle  33  causes pushers located at the junction of the probe shaft  35  and a handle  33  of probe  17  to move for releasing the probe cover from probe shaft  35 . Subsequent to use, the probe cover is discarded. Other ways of capturing and releasing probe covers may be used without departing from the scope of the present invention.  
      An aluminum tip at the distal end of probe shaft  35  is heated up by the patient and the temperature of the tip is detected, as will be described more fully hereinafter. The probe cover is preferably made of highly thermally conductive material, at least at the portion covering the tip, so that the tip can be rapidly heated by the patient. Batteries (not shown) may be used to power a tip thermistor (not shown), separator thermistor (not shown), and/or resistor (not shown) preferably located in the housing  19  of thermometer  11 . It will be understood that other suitable power sources could be employed. The power source need not be located in the control unit housing  19 . In general, the tip thermistor generates a signal that is representative of the temperature of the tip. The signal is transmitted by one or more electrical conductors to the circuitry in housing  19 . As described above, the resistor is powered by the batteries and heats a separator (not shown) so that the aluminum tip can reach the temperature of the patient more rapidly. Monitoring the temperature of the separator with the separator thermistor allows the heating of the resistor to be controlled to achieve optimum results. For instance, the separator can be initially rapidly heated, but then heated intermittently as the separator nears or reaches a preselected temperature. The function and operation of these components are known to those of ordinary skill in the art. It will be appreciated that various electrical components (not shown) and other arrangements and numbers of components may be used without departing from the scope of the present invention.  
      For example, commonly assigned U.S. Pat. No. 6,634,789, U.S. Pat. No. 6,839,651, and U.S. patent application Ser. No. 11/266,548, and U.S. patent application Ser. No. 11/265,984, the entire disclosures of which are incorporated herein by reference, disclose electronic thermometers.  
      The response time of electronic thermometers has also been improved by methods that do not involve heating the probe shaft or tip. Predictive type thermometers are known, for example, wherein a set of early temperature measurements are read by the electronics of the thermometer and a mathematical algorithm is applied to extrapolate to a final estimated equilibrium temperature. Various prediction type thermometers are known that improve response time and provide accurate temperature estimations. Still other methods of improving the response time of electronic thermometers are known which combine heating methods with prediction methods. Using predictive techniques, the patient&#39;s temperature reading is taken in a significantly shorter time period, for example thirty seconds, compared to several minutes required for conventional Mercury thermometers.  
      Predictive thermometers use a numerical algorithm to accelerate the speed with which a patient&#39;s body temperature is acquired. The algorithm uses the temperature history of the thermometer&#39;s probe and projects where the final temperature reading will be. In order for the software to be satisfied that an accurate temperature has been predicted, a certain number of final temperature projections must fall within a certain range or tolerance of each other.  
      Despite the response time improvements over glass thermometers, typical electronic thermometers can still have unacceptably long response times. Delay in providing a temperature reading often results from the patient inadvertently repositioning probe  17  during the measurement. For example, if the patient moves the probe to a region having a different temperature (e.g., from under the tongue to not under it) the algorithm may need to restart. This may also be the case if the patient draws in a breath of air over the probe. As described above, conventional predictive thermometers at most provide an activity indication during a prediction measurement to indicate that measurement and prediction activity are occurring. But there is no way for a user of a conventional thermometer to know how far along the process has progressed. Further, if the thermometer experiences interruptions in the data/temperature trend that cause the algorithm to restart, there is no indication by a conventional thermometer. Thus, users desire progress information.  
      According to aspects of the invention, the progress indicator  23  provides a user friendly, visual indication of relative completion of the prediction. As shown in the examples of  FIGS. 2 and 3 , progress indicator  23  may take the form of any type of visual indication or display, such as a progress bar (oriented horizontally or vertically on the display screen  21 ) (see  FIG. 2 ) or a pie graph (see  FIG. 3 ). For example, indicator  23  may be a series of icons or segments  41  forming a bar, a segmented single bar, a continuous bar that is progressively filled in or illuminated, or a continuous bar of variable length, all within the scope of the present invention. In these exemplary embodiments, indicator  23  essentially takes the form of a variable length bar that provides a visual characteristic for indicating a relative amount of completion of the temperature calculations. In an alternative embodiment, indicator  23  may be a pie graph or “pin wheel” having pieces  43  that are progressively filled in piece-by-piece as thermometer  11  performs the temperature calculations. Similarly to a bar-type indicator, the pie graph may also be filled in progressively in a continuous manner. Those skilled in the art are familiar with generating graphical user interface components for displaying symbols such as those contemplated herein on an LCD screen or other type of display in color, gray scale, or monochrome.  
      In one embodiment, display  21  displays the temperature as estimated during the operation of progress indicator  23 . This temperature may be updated as progress continues. In the alternative, thermometer  11  waits until completion of the temperature calculations to display the temperature reading.  
      Referring now to the exemplary embodiment of  FIG. 2 , indicator  23 , in the form of a variable length or segmented bar, “marches” along as the sequence of ongoing predictions start to converge to an answer (i.e., the trend flattens out and becomes more consistent). As shown in  FIG. 2 ( a ), progress indicator  23  has a single segment  41  filled in, which indicates that the temperature calculations are just beginning. It is to be understood that each segment  41  may be embodied by an LED, a shaded or colored icon or portion of the bar, a bright or illuminated icon or portion of the bar, a blinking or solid icon or portion of the bar, or the like to visually distinguish itself from the remainder of the bar. Moreover, segments  41  may abut each other or be separated and may be grouped or boxed to indicate the full length of the bar.  FIG. 2 ( b ) illustrate that thermometer  11  has completed about half of the necessary calculations for rendering a final temperature.  FIG. 2 ( c ) illustrates that an interruption to the temperature calculations may have occurred, resulting in a fall back in progress. In other words, if the trend is interrupted for any reason and the prediction must restart, progress indicator  23  provides such an indication by becoming less filled in and resets as appropriate. Conversely, an immediate full bar may be used to indicate an error (e.g., bad placement). At  FIG. 2 ( d ), only the last segment  41  remains to indicate the thermometer  11  is nearing completion of its temperature calculations. In this embodiment, segment  41 A may be blinking or otherwise visually distinguishable from the other filled in segments  41  to indicate the current relative status of completion.  
      As shown in the exemplary flow diagram of  FIG. 4 , in one embodiment of the invention, control unit  13  continuously samples the temperature thermistor at  47  during a prediction determination and generates progress indicator  23  as a function of the patient thermistor. Using a software loop, control unit  13  saves and compares the last several samples at  49  for determining the trend toward a final temperature measurement. In other words, variables can be used to see if consecutive thermistor readings are getting closer together. For example, control unit  13  uses the following at  51 :
 
PatientCountLast=PatientCountNow
 
PatientCountNow=ThermistorValueNow
 
PatientDiff3=PatientDiff2
 
PatientDiff2=PatientDiff1
 
PatientDiff1=PatientCountNow−PatientCountLast
 
PatientDiffAve=(PatientDiff3+PatientDiff2+PatientDiff1)/3
 
      The value PatientDiffAve in this example is the average of the last three sets of differences accumulated.  
      As described above, progress indicator  23  may be any number of discrete pieces and may take many different shapes or appearances. The bar shown in  FIG. 2  provides a suitable implementation of progress indicator  23  because users are familiar with the use of a bar in the context of many computer applications to indicate “busy” or “activity.” For this example, seven segments  41  are used to define a complete bar. The various states of completion of progress indicator  23  are numbered 0-6 in this example where the state number represents the number of pieces or segments  41  that are “on” during that state. For example, in state 0 there are no segments turned on; in state 1 there is one segment turned on; and so forth. Thus, a progress bar begins at state 0 and sequentially progresses to state 1, 2, 3, 4, 5, and 6. At state 6, a complete bar indicates that the activity is substantially 100% complete. In one embodiment, the states are defined as a function of temperature, time, etc.  
      According to aspects of the invention, there may be many ways to determine when and how the states progress from 0 to 6. For example, if an activity is expected to take a relatively consistent amount of time, the states might progress based on a time interval (with the final state being slightly delayed until the activity is complete). In an alternative embodiment, state progression may be defined according to the PatientDiffAve value described above. Referring again to  FIG. 4 , exemplary states are defined at  53  as follows:
 
if (PatientDiffAve*2≧200) then State=0
 
if (PatientDiffAve*2≧50 and &lt;200) then State=1
 
if (PatientDiffAve*2≧30 and &lt;50) then State=2
 
if (PatientDiffAve*2≧25 and &lt;30) then State=3
 
if (PatientDiffAve*2≧20 and &lt;25) then State=4
 
if (PatientDiffAve*2≧8 and &lt;20) then State=5
 
if (PatientDiffAve*2≧8) then State=6
 
      Proceeding to the operation illustrated in  FIG. 4  at  55 , progress indicator  23  displays a visual indication of the progress of the temperature calculation based on the defined state. Different ranges may be selected to cause progress indicator  23  to behave differently as PatientDiffAve changes. Likewise, many combinations or calculations based on PatientDiff1, PatientDiff2, PatientDiff3, PatientDiffAve, PatientCountNow and PatientCountLast may be used. Moreover, one embodiment of progress indicator  23  does not display progress unless certain threshold conditions are met (e.g., sensing that the probe  17  of thermometer  11  has been placed in the patient; the thermistor reading is greater than a certain baseline value; and/or the last several readings have all been increasing).  
      In an alternative embodiment, a different intermediate variable within the prediction algorithm may be used in manner similar to PatientDiffAve. For example, a stability calculation may be continuously made during the prediction algorithm similarly to PatientDiffAve. Replacing PatientDiffAve with this stability factor, or using it in a generally similar manner to determine progress bar state is contemplated by the invention. For reference, an exemplary variance stability prediction flowchart is shown in  FIGS. 5 and 6 .  
      Referring now to  FIG. 5 , control unit  13  computes a moving variance of patient temperatures. If the variance is low enough, it reports the temperature as is (without doing any predictions). In one embodiment, control unit  13  calculates a moving standard deviation to determine if a temperature is stable. However, to save execution time, taking the square root as would normally be done for the standard deviation may be omitted. Instead, the constant that is used for comparison is squared. Hence, the term variance instead of standard deviation is used. Beginning at  59 , control unit  13  increment its buffer address pointer and inserts a new reading into the buffer. Proceeding to  61 , control unit  13  reads an AutoDetection Flag and checks whether the buffer is full. If so, control unit  13  sets a flag at  63  to indicate that the buffer is full. If the buffer is full, as determined at  65 , control unit  13  calculates the variance. If not, operations pause at  69  to remain synchronized and the variance is set to indicate that it is unstable or that the buffer needs more data. Then, if variance is less than zero at  71 , the variance is set to stable at  73 .  
      Proceeding to  FIG. 6 , if the AutoDetection flag is set to one at  75 , the variance is less than 1600, and the temperature is greater than or equal to 36.6° C., control unit  13  determines at  77  whether the last two patient thermistor temperature readings are within 0.87, for example, of each other. On the other hand, if each of the three conditions is not met at  75 , control unit  13  proceeds to  79 . Continuing at  81 , if the last two temperature readings differ by less than 0.87, control unit  13  determines at  81  that a temperature prediction has been made. If not, operations proceed to  79  but otherwise continue at  83  to determine if the patient thermistor temperature readings are within an acceptable range (e.g., 28° C. to 44° C.). If the readings are outside of this range, control unit  13  considers them to be invalid at  85 ; if the readings are within this range, control unit  13  considers them to be valid predictions.  
      Although described primarily in the context of a predictive thermometer, aspects of the invention also apply to a direct measurement mode where the predictive algorithm is turned off. In this situation, progress indicator  23  similarly shows relative completion of stabilization of the measured temperature. The direct measurement mode examines, for example, the convergence of actual temperature rather than predicted temperature.  
      In operation, thermometer  11  indicates its status by performing at least one temperature calculation as a function of a detected temperature of probe. The probe  17  is adapted to be heated by a subject for use in measuring the temperature of the subject. By defining plurality of states, each of the states corresponding to an amount of completion of the temperature calculation, thermometer  11  is able to indicate progress of the temperature calculation. In one embodiment, each of the defined states corresponds to one or more successive operations performed in the temperature calculation. Advantageously, thermometer  11  visually indicates progress by displaying progress indicator  23  to a user. The progress indicator  23  may be a progress bar having a variable length indicative of a percentage of completion of the temperature calculation. Likewise, progress indicator  23  may have a plurality of segments  41  or  43  that correspond to the defined states and that have a visual characteristic representing the amount of completion of the temperature calculation.  
      It is to be understood that aspects of the present invention may be applied to medical devices generally. For example, a progress bar may be used in conjunction with a pump to indicate the progress of the delivery of a desired volume of fluid.  
      The order of execution or performance of the methods illustrated and described herein is not essential, unless otherwise specified. That is, it is contemplated by the inventors that elements of the methods may be performed in any order, unless otherwise specified, and that the methods may include more or less elements than those disclosed herein. For example, it is contemplated that executing or performing a particular element before, contemporaneously with, or after another element is within the scope of the invention.  
      When introducing elements of the present invention or the embodiments thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.  
      In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.  
      As various changes could be made in the above constructions and methods without departing from the scope of embodiments of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.