Medical thermometer

Medical thermometers are used for measuring human body temperature, with the tip of the thermometer being inserted either into the mouth (oral temperature), under the armpit (axillary temperature), or into the rectum via the anus (rectal temperature).

Additional recommended knowledge

Daily Sensitivity Test

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Essential Laboratory Skills Guide

Classification, by technology

The traditional mercury-filled medical thermometer works in the same way as a meteorological maximum thermometer. The thermometer consists of a bulb containing mercury attached to a small tube.the range of this thermometer is from 89.6^.F to 109.4^.F. As the temperature rises, the mercury expands and flows up the tube. The temperature is obtained by reading the scale inscribed on the side of the thermometer. There is a constriction in the neck close to the bulb. As the temperature rises, the mercury is forced up through the constriction by the force of the expansion. When the temperature falls, the column of mercury breaks at the constriction and cannot return to the bulb, thus remaining stationary in the tube. To reset the thermometer, it must be swung sharply.  

In the 1990s, mercury thermometers were found too risky to handle and have largely been replaced with electronic digital thermometers , or, more rarely, thermometers based on liquids other than mercury ( heat-sensitive liquid crystals) . Beside at the present, we do have some more that are very convienient available such as infrared Digital Infrared contact or Non-Contact Thermometers ( scanner themometers). For eliminating the risk of patient cross-infection, Single-Use Clinical Thermometers and probe covers are made for just one use. In some places, it may be illegal to sell products which contain mercury, such as thermometers. these kinds may be used orally, axillarily, or rectally. others just need to be placed against the forehead or not to be contacted ( one quarter inch away)or to be use as pacifier . Whichever type of thermometer you choose, be sure you know how to use it correctly to get an accurate reading. Keep and follow the manufacturer's recommendations for any thermometer. Remember that the method you choose to take your child's temperature will depend on his or her age and how cooperative your child is.

Basal thermometer

A basal thermometer is a thermometer used to take the basal (base) body temperature, the temperature upon waking. Compared to daytime temperatures, basal body temperatures are much less affected by environmental factors such as exercise and food intake. This allows small changes in body temperature to be detected, such as those caused by ovulation or changes in thyroid function.

Glass fever thermometers have markings every 0.2ºF (0.1ºC). Basal thermometers require accuracy of at least 0.1ºF (0.05ºC), so special glass basal thermometers are sold separately from glass fever thermometers. All digital thermometers generally read to at least 0.1ºF (0.05ºC) and so are suitable for monitoring basal temperatures. Some digital thermometers are marketed as "basal thermometers" and have extra features such as a larger display, expanded memory functions, or beeping to confirm the thermometer is placed properly.

Classification, by location

Oral

Oral temperature may only be taken from a patient who is capable of holding the thermometer in their mouth correctly and securely, which generally excludes small children or people who are overcome by coughing, weak, or vomiting. (This is less of a problem with fast-reacting digital thermometers, but was certainly an issue with mercury thermometers, which took several minutes to register a temperature.) Another counter-indication is if the patient has drunk a hot or cold liquid beforehand, in which case one has to wait or use another method.

Rectal

Rectal temperature-taking, especially if performed by a person other than the patient, should be facilitated with the use of lubricant (such as petroleum jelly (now discouraged) or a water-based personal lubricant). Although rectal temperature is the most accurate, this method may be considered embarrassing in some countries or cultures, especially if used on patients older than young children; and, if not taken the correct way, a rectal temperature-taking can be uncomfortable and in some cases painful for the patient. Rectal temperature-taking is considered the method of choice for infants for the general public; however, the rectal route is desirable in infants from a nursing point of view.^[1]

Ear and forehead

Other kinds of medical thermometers exist, such as the tympanic thermometer that measures the temperature of the tympanum by infrared measurement, and the band thermometer that is applied to the patient's brow.

References

1. ^ Fundamentals of Nursing by Barbara Kozier et al, 7th edition, p. 495