Patent Application
20130023785
This invention relates to devices for measuring temperature, more specifically to medical thermometers.
A contact medical thermometer is a device capable for measuring temperature by means of a physical contact with the object of measurement. Medical thermometers are known in art for over 150 years. Their designs range from a 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. All the above patents are incorporated herein as references.
Depending on medical reasons and cultural preferences, noninvasive temperature from a patient is typically measured by an axillary (under-the-armpit) probe, by an oral probe in a sublingual pocket, by a rectal probe in the anus, by an ear canal infrared probe, by a contact probe behind the ear lobe, by an infrared probe from the forehead, etc. Invasive (internal) temperatures are measured by an esophageal probe, a Swan-Ganz catheter, etc. In all cases, for a quality measurement it is essential to achieve a good thermal coupling between the temperature sensor inside the probe and the patient's body site of measurement, for example, the forehead skin or sublingual tissue. This invention concerns with an oral probe. The probe is part of a contact thermometer that shall come in a physical contact with the sublingual tissue in the mouth of a patient, preferably in the vicinity of a sublingual artery.
Due to a possible talking, sneezing, coughing and breathing by a patient, many areas in the mouth, even in a sublingual pocket, may have lower temperatures than that of the inner (core) body. It can be shown anatomically that the best place for the oral temperature measurements is the area in a mouth under the tongue where the sublingual artery passes near the root of a tongue. This area has a stable temperature because it's well thermally shielded from the outside and is closer a carotid artery.
To improve a thermal coupling between the temperature sensitive tip and the sublingual pocket tissues, a resilient pacifier probes were proposed as exemplified by U.S. Pat. No. 5,176,704 issued to Bernd and a flexible probe as taught by U.S. Pat. No. 5,013,161 issued to Zaragoza et al. The probe has a bend to facilitate a better thermal contact with the sublingual area as taught by the U.S. Pat. No. 7,036,984 issued to Penney et al. Another embodiment with a bent probe is taught by the U.S. Pat. No. D525,542 issued to Russak et al. All the above patents are incorporated herein as references.
A speed response is a major issue with any contact thermometer and with the oral thermometers specifically. When a colder probe (initially at a room temperature, e.g.) is placed into the patient mouth, it alters the oral tissue temperature so much that a substantial time is required to re-warm the oral tissue to the pre-insertion temperature level. Typically, this time may range from 6 seconds to a minute. If the re-warming time is ignored, accuracy is compromised. One way to minimize a 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 a U.S. Pat. No. 5,632,555 issued to Gregory et al. and U.S. Pat. No. 6,109,784 issued to Weiss. The above patents are incorporated herein as references.
The prior art oral probes have several drawbacks, such as a poor coupling between the probe and the root of a tongue. A poor coupling reduces accuracy and prolongs the measurement time. Another limitation of the prior art that teaches the heated oral probes is a need for a manual initiation of the measurement upon inserting the probe into the patient's mouth. And another limitation is placing the probe in a wrong spot inside the mouth by an inexperienced operator.
Thus, the goal of this invention is to offer an oral temperature probe that would facilitate an intuitive self-guidance of the probe tip toward the root of the tongue, when placed in the mouth.
An additional goal of the invention is to increase a thermal contact between the probe temperature sensor and the root of a tongue.
Another goal of this invention is providing a fast speed response of the probe,
And additional goal is to make the oral thermometer operation requiring a minimal control by the operator. Attainment of these and other goals will be apparent from the foregoing description of the invention.
A shape of the oral temperature probe is sculptured to facilitate its self-guidance toward the root of the tongue. The probe body consists of two distinct sections—the stem and curved sections. The curved section allows the probe to go around the teeth of a lower jaw and to position the stem section under the tongue in order to direct the temperature sensing tip toward the root of the tongue. To speed up the probe temperature response, before inserting the probe into a mouth, the probe tip is preheated to a temperature that is cooler than the lowest expected temperature of the patient.
The new and improved probe for an oral contact thermometer is illustrated in
A typical radius R of the curved axis 14 ranges between 10 and 25 mm. This was selected to accommodate sizes of the human teeth and lower jaws. In some designs, it may be desirable to make radius R variable, that is to fabricate elbow 9 of a pliant material capable of retaining its shape after been manually bent to increase or decrease radius R. When radius R changes, the joint angle a will also change.
Length of stem 8 is selected to assure that when placed in the mouth under the tongue 13 (see
Both sections of the probe, elbow 9 and stem 8, should be fabricated of a material having low thermal conductivity and easy cleanable. An example of the material is ABS resin. A cross-sectional profile of the probe may have any practical shape—round, oval, rectangular, etc. This is illustrated in
As it was indicated above, tip 6 comprises a temperature sensor. Examples of such sensor are a thermistor, thermocouple junction, resistive temperature device (RTD) and semiconductor p-n junction.
The outer shell 25 of the tip 6 (
The heating element 26 should be turned on/off in a prescribed manner. Also, a signal produced by the temperature sensor 28 should be processed in a specific timing relationship with the heater 26 operation.
At the first instant 30, the thermometer is turned on and the electronic control circuit starts supplying electric power to the heater 26 to elevate its temperature to the predetermined level of a pre-warmed temperature tH. This set temperature tH of the heater is close and preferably lower than the lowest anticipated patient temperature tp-min=34° C. For example, we may select tH=33° C. For most practical purposes, the offset Δ between these two temperatures should be 0.5-2.0° C. When the temperature sensor 28 reaches the pre-warmed temperature set tH at the second instant 31, this temperature of the tip 6 is stabilized and maintained by the feedback control loop of the electronic circuit for as long as needed to place the probe into the mouth of the patient.
The operator places the probe into the patient's mouth so that a tip 6 of the probe is pressed against the root of the tongue at the third instant 32. This quickly elevates the sensor 28 temperature above the tH level. This “jump” in temperature is detected by the electronic circuit when its value 35 reaches the predetermined threshold at the fourth instant 33. Note that the jump threshold value (tH+δ) should be less or equal to the lowest possible oral temperature tp-min.
At this fourth instant 33, electric power to the heater 26 is turned off and temperature of the tip 6 is allowed to evolve to the actual patient temperature tp, which is reached at the fifth instant 34 when the tip temperature has the end value 36. At this fifth instant 34 the tip 6 and the sublingual surface 10 are in a thermal equilibrium, the measurement is over and the end value 36 temperature or its equivalent signal is sent to the output element 18, for example a display. Since the temperature tH is much closer to the final temperature tp than the initial temperature ta, the measurement time (between instances 32 and 34) is drastically reduced. Experimentally it was shown the time is between 1 and 3 s.
One of the important innovations of this invention is control of electric power supplied to the heart by a “jump” is a signal communicated by the temperature sensor. This innovation 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.
In cases when the initial temperature ta is already warm, meaning it's equal or higher than the heater set temperature tH, the heater is never turned on and the cup 6 allowed to equilibrate with the patient tp temperature, just as in the conventional equilibrium thermometers known in art.
In other embodiments, the heater 26 is not employed and no probe pre-warming performed. Then, the measurement time is either accepted as being slower or it may be shortened by some other methods, such as one of several predictive algorithms known in art. A predictive algorithm predicts or anticipates patient temperature from a rate of change in temperature of a temperature sensor. Yet, even without a heating or prediction, a probe that is the subject of this invention would still provide a more accurate measurement due to more consistent and reliable coupling between the tip and the patient at the root of the tongue.
The invention has been described in connection with preferred embodiments, 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.
