FAMILY MEDICINE® COLUMN
By John C. Wolf, D.O.
Associate Professor of Family Medicine®
Ohio University College of Osteopathic Medicine

NEW "IN THE EAR" THERMOMETERS ACCURATE, BUT EXPENSIVE

Question: I've seen advertisements for new thermometers that take the temperature in the ear. Are they as good as the old-fashioned thermometers?

Answer: Elevation of body temperature occurs with infection or other types of illness. The magnitude of elevation above normal is a fair indication of the condition's severity. Therefore, you should measure the temperature when you, your children, or other adults in the family are ill. I mention this obvious fact because while parents routinely take the temperature of their sick children, adults rarely take their own temperature when they are ill.

The body has a number of protective responses that help keep us alive despite the changing threats from the environment. The important response for this discussion is the body's "homeostatic thermoregulating" mechanisms. In plain language this means that the body implements many subtle changes in circulation, perspiration and muscle activity to keep the temperature of the brain, heart, lungs and digestive system at a constant temperature. Illness can cause these normal mechanisms to work improperly or the body may be unable to cope with the extra demands placed on it by the disease process. The end result is that the body temperature goes up.

The body systems try to maintain a constant temperature in the "core" areas of the head, neck, chest and abdomen to keep the vital organs within them working most efficiently. Measuring the temperature in any of these areas should give a value that is close to the temperature in the remainder of them. Temperature measured at the hands or feet can be several degrees cooler, so they aren't used to determine if a fever is present.

Measuring temperature with a rectal thermometer is considered the most accurate method and therefore, it is the standard against which other methods are compared but it isn't very convenient. Measuring the temperature in the mouth is quite common, but it is often inaccurate when compared to the core temperature reading obtained with a rectal thermometer. The most common reason for this inaccuracy is the heating or cooling of the mouth by food, drink or mouth breathing. Despite these possible sources of inaccuracy, oral temperature is often used because it is convenient and socially acceptable.

Placing a thermometer under the arm also produces a reliable temperature reading. The temperature obtained in this way called axillary temperature in doctor language is consistently 1.5 degrees below a rectal temperature. So adding 1.5 degrees to an axillary temperature gives an accurate guess, usually within 1 degree, of the actual core temperature.

Several years ago, fever strip thermometers those liquid crystal strips that are held against the forehead became available. These thermometers can have an error of up to two degrees, and the inaccuracy is greater the higher the person's temperature. Therefore, I don't recommend them to my patients.

The newer "in the ear" thermometers measure the temperature of the eardrum which is deep inside the head at the end of the ear canal. Its temperature is very close to the "core" reading. These thermometers are accurate within 1/2 degree and are also fast. I think they are great for use in hospitals and clinics where many temperatures are taken. And, there is nothing wrong with their use at home, but a simple and very inexpensive thermometer will do the same job.

Family Medicine® is a weekly column. To submit questions, write to John C. Wolf, D.O., Ohio University College of Osteopathic Medicine, Grosvenor Hall, Athens, Ohio 45701.