Abstract:
An oral thermometer including a probe for insertion into the mouth of a user. The probe includes and an elongate first stem, a joint stem extending the first stem and disposed at a first angle to the first stem, and an elongate second stem extending from the joint stem and disposed at a second angle to the joint stem. The first angle open down and the second angle open up. The second stem includes a probe tip at a distal end thereof that is configured to be inserted into the mouth of a user. In operation the thermometer is operable to heat the probe tip to a pre-warmed temperature, detect an elevated temperature higher than the pre-warmed temperature when inserted in a user&#39;s mouth, and initiate a temperature reading upon detecting the elevated temperature.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to devices for measuring temperature, and specifically relates to thermometers primarily intended for medical applications. 
       DESCRIPTION OF PRIOR ART 
       [0002]    A contact medical thermometer is a device capable of measuring temperature through physical contact with the object of measurement. Typically, the probe of an oral thermometer is placed inside the patient&#39;s mouth in a sublingual pocket. The measurement is done by detecting the response of a temperature sensor that is built into the probe. 
         [0003]    Oral thermometers are well known and their designs range from the glass tube filled with liquid as exemplified by U.S. Pat. No. 3,780,586 issued to Donofrio, to liquid crystal probes as exemplified by U.S. Pat. No. 4,779,995 issued to Santacaterina et al, to a plastic tube with a metal sensing tip as exemplified by U.S. Pat. No. 4,813,790 issued to Frankel et al. 
         [0004]    To improve the thermal coupling between the temperature sensitive probe and the sublingual pocket tissues, a resilient pacifier probe has been proposed as exemplified by U.S. Pat. No. 5,176,704 issued to Bernd and a flexible probe as described by U.S. Pat. No. 5,013,161 issued to Zaragoza et al. A stem of the probe may be given a permanent bend to facilitate a better thermal contact with the patient&#39;s lip as taught by U.S. Pat. No. 7,036,984 issued to Penney et al. 
         [0005]    Response speed is a major issue with any contact thermometer and specifically with oral thermometers. When a colder (e.g., room temperature) probe is placed in the patient&#39;s mouth, it alters the oral tissue temperature so much that a substantial time is required to re-warm the oral tissue to a pre-insertion level. Typically, this time may range from 6 seconds to a minute. If the re-warming time is ignored, accuracy may be compromised. One way to minimize this thermal drag by a cooler probe is to pre- warm the probe to a temperature that is substantially close to the oral anticipated temperature. This approach is exemplified by U.S. Pat. No. 5,632,555 issued to Gregory et al. and U.S. Pat. No. 6,109,784 issued to Weiss. 
         [0006]    Due to talking and breathing, many spots in the mouth, even in a sublingual pocket, may have lower temperatures than that of the inner (core) body. A preferred place for the oral temperature measurement is an area near the root of the tongue in the sublingual pocket which is well shielded from the outside. This area has a more consistent and stable temperature. 
         [0007]    Conventional probes have several drawbacks, such as poor coupling between the probe and the root of the tongue which reduces accuracy and prolongs the measurement time. Another limitation of conventional heated probes is the need for a manual initiation of measurement upon inserting the probe into the patient&#39;s mouth. Yet another limitation is the ease of placing the probe in the wrong spot inside the mouth by an inexperienced operator. 
         [0008]    Thus, there is a need for an oral probe design that facilitates an intuitive self-guidance toward the root of the tongue when placed in the mouth. Moreover, there is a need for a probe that increases thermal contact between the probe body and the tissue of interest, has a fast response speed and requires only limited control by the operator. 
       SUMMARY OF INVENTION 
       [0009]    In an embodiment, the present invention provides an oral temperature probe having a shape that is sculptured to facilitate self-guidance toward the root of the tongue. The probe body has at least two bends in opposite directions so it resembles a letter Z. This shape allows the probe to curve around the teeth and direct the sensing tip toward the root of the tongue. The shape of the tip may be formed such that the area contacting the tissue is larger than the side area of the tip that is not intended for touching the tissue. The probe tip may be preheated to a temperature that is cooler than the lowest expected temperature of the patient and the measurement cycle may be initiated when the tip temperature approaches the lowest expected temperature of a patient. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]    Exemplary embodiments of the present invention are described in more detail below with reference to the drawings, in which: 
           [0011]      FIG. 1  is a representative view of a medical oral thermometer inserted into a sublingual pocket; 
           [0012]      FIG. 2  shows a view of the probe having two bends; 
           [0013]      FIG. 3  illustrates a cross-sectional view of the probe tip with the temperature sensor and heater; and 
           [0014]      FIG. 4  is a timing diagram of the thermometer operation. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       [0015]      FIG. 1  illustrates a probe  8  of an oral thermometer  5  inserted into a sublingual pocket  4  of patient  1 . The probe tip  15  makes thermal contact with the tongue root  3 . The thermometer  5  inside or on its housing  40  contains an output element  7  that may be a visual display, audio speaker, wired or wireless transmitter, etc. The output temperature is the result of a signal processing performed by an electronic circuit and software residing inside the thermometer housing  40 . The probe  8  is sculptured or formed in a Z-shape having the first stem  9 , second stem  10  and joint stem  11 . The Z-shape is facilitated by two bends in the probe: first bend  13  and second bend  12 . The tip  15  may be separated from the second stem  10  by a thermal insulator  14 . This thermal insulator may be needed when the second stem  10  has higher thermal conductivity, for example, when it is fabricated of metal. During the measurement, the second stem  10  is positioned under the tongue  2  in such a manner as to make reliable contact with the tongue root  3 . Often, when measuring oral temperatures, patients place probes randomly in the oral cavity, either missing the sublingual pocket  4  or not pressing the probe tip against the tongue root. The Z-shape allows for an intuitive placement of the probe  8  inside the sublingual pocket  4  with the tip being forced to touch the tongue root. Any other position of the probe will likely be uncomfortable and thus, intuitively avoidable. 
         [0016]      FIG. 2  depicts probe  8  with two bends  13  and  12  formed in the opposite directions. This creates a Z-shape of the probe. The first, second and joint stems ( 9 ,  10  and  11 , respectively) may be the hollow tubes of any suitable cross-section, such as round, oval, etc. Each stem has its own axis. That is, the first stem  9  is disposed along the first axis  16 , the second stem  10  is disposed along the second axis  17 , while the joint stem  11  is disposed along the joint axis  18 . These three axes sequentially cross each other, wherein the first and joint axes make an angle A, while the joint and second axes make an angle B. In an embodiment, each of the angles A and B may range from 45 to 135 degrees. Typically, the second stem  10  may have a length (along second axis  17 ) of about 25 mm, but no less than 10 mm. This allows positioning the second stem  10  behind the teeth and creates a reliable thermal contact between the tip  15  and the tongue root  3  for most patients. The second stem  10  may be fabricated either from a rigid or flexible/resilient material, so it will be able to accommodate variations in a distance between the patient&#39;s teeth and the tongue root  3 . The area where the first stem  9  is attached to the housing  40  of the thermometer  5  may be made as a pivot  27 , allowing for the probe  8  to rotate toward the case  40  during storage and away from the case  40  during operation. Inside the case  40 , there may be an electric switch that signals the electronic circuit on the rotation (closing and opening) of probe  8 , so that electric power may be turned off and on accordingly. 
         [0017]    The joint stem  11  may have a length (along second axis  18 ) of about 15 mm to accommodate for the height of human teeth and gums, but the length is typically no less than 8 mm. The length of the first stem  9  may be any suitable length, depending of a particular thermometer design. The first and joint stems  9  and  11  may be fabricated of any suitable rigid material. A low thermal conductivity plastic may be used for the second stem  10 . However, if the second stem  10  is fabricated of a material having relatively high thermal conductivity, a low thermal conductivity (thermal insulator) insert  14  can be positioned between the second stem  10  and the tip  15 . 
         [0018]    The tip  15  may be fabricated with a metal cup  6 . Inside the cup  6 , temperature sensor  20  is positioned. Sensor  20  can be of any suitable nature, such as a thermistor, thermocouple, RTD, etc. For a higher speed response, the tip  15  also may contain a heater  21 . The sensor  20 , heater  21  and the cup  6  are connected to the electronic circuit by conductors  19 . The cup  6  may be gold plated. 
         [0019]      FIG. 3  shows an embodiment of the tip  15  with a flexible strip  22  that carries the sensor  20  and, possibly, heater  21 . The strip  22  also carries the electrical conductors. The strip  22 , sensor  20  and heater  21  may be attached to the inner surface of the cup  6  by a thermally conductive epoxy  23 . Thus, the cup  6 , sensor  20  and heater  21  will be in an intimate thermal coupling with each other. Besides, these components, the inner space  24  of the cup  6  may be void of any material (with a possible exception of air), thus a thermal coupling between the sensor  20  and other components positioned outside the cup  6  will be minimized. The cup  6  has side walls  28  disposed substantially parallel to the second axis  17  and the end wall  29  being substantially perpendicular to the second axis  17 . The end wall  29  is intended for contacting the measured tissue. Even if the cup has a hemi-spherical shape, the corresponding tangents to the surface (side and end) are situated in the above described manner. It should be noted that the area of the end wall  29  can be as large as practical for an acceptable response speed, while side  28  area may be minimized. Hence, the length x (along the second axis  17 ) should be minimized while the dimension y (normal to the second axis  17 ) should be maximized. For most practical cases, length x may be between 1 and 3 mm, while dimension y may be 4 mm or larger. 
         [0020]    To assure ease of operation and fast speed response, heater  21  may be turned on/off in a prescribed manner. Also, a signal produced by the sensor  20  can be processed in relationship with the heater operation.  FIG. 4  illustrates an embodiment of the relationships between various temperatures of the cup  6  and thermometer actions. At first, the cup  6  has initial temperature t a  which may be room temperature. Patient oral temperature in a sublingual pocket is t p , while the lowest possible temperature of the sublingual pocket is t p−min . For example, it may be assumed that the patient particular temperature is t p 32 39.4° C., while the lowest oral temperature of any human subject is t p-min =34° C. 
         [0021]    At first time instant  30 , the thermometer is turned on and the electronic control circuit supplies electric energy to the heater to elevate its temperature to a level of pre-warmed temperature t H  that is lower than the lowest patient temperature t p−min =34° C. For example, t H =33° C. For most practical purposes, the difference D between these two temperatures can be at least 0.5° C. When the sensor  20  reaches the pre-warmed temperature t H  at the second time instant  31 , this temperature is maintained by the feedback loop of the electronic circuit for as long as needed to place the probe into the mouth of the patient. 
         [0022]    The operator places the probe into the patient&#39;s mouth and at the third time instant  32 , the cup  6  contacts the tongue root  3  which quickly elevates the sensor  20  temperature above the t H  level. This “jump” in temperature is detected by the electronic circuit when its value  35  reaches a preset threshold at the fourth time instant  33 . It should be noted that the jump threshold value (t H +d) should be less than or equal to expected t p−min . 
         [0023]    At this fourth time instant  33 , the heater  21  is turned off and temperature of the cup  6  is allowed to continue rising up to the patient temperature t p , which is reached at the fifth time instant  34  when the cup temperature has the end value  36 . At this fifth time instant  34  the cup  6  and the tongue root  3  are in a thermal equilibrium, the measurement is over and the end value  36  temperature is provided by the output element  7 . Since the time interval between time instants  33  and  34  is much shorter than the time interval between time instants  30  and  34 , the time from placing the probe in the mouth ( 32 ) and the end of measurement at the fifth time instant  33  is drastically reduced. Typically, it is less than three seconds. 
         [0024]    One aspect of this invention is that the pre-warmed temperature t H  is cooler than the patient&#39;s minimum temperature (t H &lt;t p−min ) and the measurement cycle is initiated when the tip temperature approaches the patient&#39;s minimum temperature t p−min . This allows for an automatic detection of the probe placement in the mouth and thus eliminates a need for a manual control of the temperature taking cycle. 
         [0025]    In cases when the initial temperature t a  is already warm, that is it is equal or higher than the patient minimum temperature t p−min , the heater is never turned on and the cup  6  allowed to equilibrate with the patient t p  temperature, just as in conventional equilibrium thermometers. 
         [0026]    In other embodiments, the heater  21  is not employed and no probe pre-warming performed. In such an embodiment, the measurement time is either accepted as being slower or it may be shortened by using one of several known predictive algorithms. 
         [0027]    The invention has been described in connection with a preferred embodiment, but the invention is greater than and not intended to be limited to the particular form set forth. The invention is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0028]    All patents and other documents referred to herein are incorporated by reference in their entirety.