Measuring Temperature

Temperature reflects the body’s ability to regulate body heat, a process called thermoregulation. As the nurse you’ll consider factors that affect your patient’s temperature and measure their temperature using the most appropriate route and thermometer type based on their developmental level and condition.

Now, factors that affect body temperature include age, biological processes, and illness.

A normal adult temperature varies between 97.5 to 99.5 F, or 36.4 to 37.5 C, whereas in infants and children, the range can be wider because their thermoregulatory mechanisms are less effective. In older adults, baseline temperature is often slightly lower due to decreased amounts of subcutaneous fat and slower metabolic rate.

Illness can also be reflected in temperature readings. For instance, body temperature typically increases above normal in patients with an infection or inflammation, which can cause a fever; or it can decrease in patients experiencing excessive heat loss related to conditions like frostbite or hypothermia.

Keep in mind that changes in your patient’s temperature should always be compared with their baseline readings, and any abnormalities should be reported to the registered nurse.

You can measure your patient’s temperature from a variety of routes, including the temporal artery; tympanic membrane or eardrum; oral cavity; axilla or armpit; or rectum. The most accurate route is the rectum due to its proximity to core body temperature, and it’s typically about 1 degree F or 0.5 degree C higher than oral readings.

The least accurate site is the axilla due to its distance from the core, and its typically about 1 degree F or 0.5 degree C lower than oral readings. For most stable and cooperative patients, you can use the tympanic membrane, temporal artery, or oral cavity; whereas, if your patient is clinically unstable, the rectal route is often used. For patients who are confused, uncooperative, or unable to follow commands, like infants, you can use the axilla, tympanic membrane, or temporal artery.

Once you’ve identified the appropriate route for temperature measurement, you’ll select the type of thermometer to use, which can be electronic, glass, or disposable.

First, electronic thermometers are battery-operated devices that are most often used to measure temperature. They come in a variety of designs and can measure temperature from any route. Once the device has measured the patient’s temperature, there will be an audible chime, and the result will appear on the display screen.