Different Types of Body Thermometers

There are many different types of body thermometers and their usage is varied; greatly in some instances. These include the following:

1. The conventional glass thermometer which used to use mercury to rise and fall on a scale, now uses a colored alcohol formula to accomplish the same thing. The glass thermometer is used orally, which is the most accurate way; rectally, which is accurate, but you must subtract one degree in order to get the correct temperature; and axillary, in which the thermometer is placed under the arm. One degree is added to an axillary temperature in order to get the proper temperature; however, not many physicians will accept an axillary temperature because of it's inaccuracy. The axillary temperature, does not touch any mucous membranes. This is believed to contribute to it's nonacceptance as an accurate method of determining temperature.

2. The digital thermometer is used essentially the same way as the glass, except the readout is digital, and the temperature is achieved faster. Plastic probe covers are used to maintain a clean environment between patients. There is usually a digital thermometer dedicated for rectal use. I must explain the necessity for a rectal use thermometer. A small child will usually be crying because of discomfort, or unable to understand the need to hold the thermometer under their tongue; therefore, a rectal temp. will be required. The glass or digital is only inserted about 3/4 inch into the rectum for minimal discomfort.

3. The tympanic thermometer is used much like an otoscope, in that it is inserted into the ear, and reflects the temperature off the eardrum, or tympanic membrane. This is probably the most accurate of thermometers because the tympanic membrane shares the same blood supply as the hypothalamus. This is the part of the brain which regulates body temperature, thus the hypothalamus sharing it's blood supply with the tympanic membrane would give the most accurate temp., simply because the T.M. would be heated or cooled to a normal temp. by blood circulation.

In order to accurately reflect off the tympanic membrane, the Pinna, or external ear should be pulled up and back to straighten the canal in an adult. It should be pulled down and back to straighten the canal in children.

4. The forehead tape thermometer was tried for a short while, but discontinued due to inaccuracy and it's inability to adhere to the forehead. This type thermometer was a one use, throw away type. It had a covering that was peeled away exposing a mild adhesive. This, in theory, stuck to the forehead, and a type of phosphorescent reading gave you the temperature after a specified time. It was a flop. It would not stay adhered and the temperature itself was inaccurate.

At this time, there are constant experimentation with medical devices, and one that is more accurate than others may be in the planning stage now. However, of all listed above, it is the authors opinion that the tympanic thermometer far surpasses the others; even the "old reliable" glass thermometer.