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.

Next, there are glass thermometers that are common in households but are uncommon in health care settings since they can break, creating a safety hazard.

They should never be used with a patient who may bite down on it, like a toddler or someone who’s confused. Glass thermometers have a bulb containing a red liquid alloy that expands when in contact with body heat, and you’ll need to leave the thermometer in place for up to five minutes to allow enough time for the liquid to expand.

The temperature is measured by noting how far the liquid reaches as it expands along the numbered scale on the outside of the thermometer.

Then there are disposable, single-use thermometers, which come in either a temperature-sensitive tape that can be placed on the forehead or abdomen, or a plastic probe with dots that can be used for axillary or oral temperatures.

They are commonly used for newborns or patients who are on transmission-based precautions. The temperature is measured by noting the change in color from body heat; and the results typically display within two minutes.

Now, before you take your patient’s temperature, determine the route and type of thermometer to use. When taking an oral temperature, be sure your patient has finished eating, drinking, smoking, or chewing gum for at least 15 minutes, to avoid inaccurate readings.

Then, ask them to open their mouth and place the thermometer probe into the posterior sublingual pocket at the base of the tongue, instructing them to keep their lips closed until the reading is complete.

To measure a tympanic temperature, pull the pinna of their ear back and up, for an adult, and down and back for a child under the age of two.

Then insert the temperature probe into their ear canal, aiming it towards their nose. For an axillary temperature, make sure your patient’s axilla is clear from any lotions, antiperspirants, or moisture to avoid erroneous readings.

Then, place the probe into their armpit while they fold their arm over their chest. Next, to measure temperature from the temporal artery, place the thermometer sensor over the skin on your patient’s forehead and slide it steadily along the artery until results are registered.

Temporal artery readings can be inaccurate if your patient’s forehead is sweaty, or if their skin is cold. Lastly, to take a rectal temperature, begin by providing privacy and assisting your patient to roll onto their left side with their knees bent.

Lubricate the tip of the probe and insert it into their rectum about 3 centimeters, or around 1 inch, angling it slightly towards the umbilicus.

Afterwards, be sure to clean the probe appropriately and wipe lubricant or stool from your patient, as needed. Rectal temperatures should be avoided in patients who’ve undergone rectal surgery or have cardiac conditions, since it can stimulate the vagus nerve and decrease heart rate.

They should also be avoided in uncooperative patients, since damage can occur to the rectum if they move during measurement.

Alright, as a quick recap… 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.