Body Temperature
Body Temperature
Definition
Purpose
Demographics
Description
Preparation
Aftercare
Risks
Normal results
Morbidity and mortality rates
Alternatives
Definition
Temperature is a measure of an organism’s ability to generate and get rid of heat. The human body has mechanisms to maintain its internal temperature within a relatively narrow, safe range despite relatively large variations in temperatures in which the body exists.
Purpose
The purpose of maintaining body temperature within a relatively narrow range is to promote and sustain life.
Demographics
Thermometers are used to measure body temperature. They are calibrated in either degrees Fahrenheit (°F) or degrees Celsius (°C). Temperatures in the United States are typically measured in degrees Fahrenheit. The standard in most countries of the world is degrees Celsius.
Description
When humans become too warm, blood vessels in the skin increase in diameter (dilate). The purpose is to carry the excess heat to the surface of the skin. In turn, this causes the body to begin to perspire. As the perspiration evaporates, it helps to cool the body. When the body becomes too cold, the blood vessels decrease in diameter (contract) so that blood flow to the skin is reduced in an attempt to conserve body heat. This often causes people to start shivering. This involves rapid, involuntary contractions of muscles. Shivering helps to generate additional heat through muscle activity. Under normal conditions, these activities maintain human body temperature within a narrow range that is healthy for the organism.
Body temperature can be measured in many locations. The mouth, ear, armpit, and rectum are the most commonly used places. Temperature can also be measured on the forehead.
Body temperature is checked for several reasons.
- To detect fever.
- To document an abnormally low body temperature(hypothermia) in people who have been exposed tocold.
- To document an abnormally high body temperature(hyperthermia) in people who have been exposed toheat.
- To monitor the effectiveness of a fever-reducing medicine (antipyretic).
- To determine when a female is ovulating, thereby increasing the probability of becoming pregnant.
Preparation
Preparation for taking a body temperature consists of ensuring that the thermometer is clean and disinfected.
Aftercare
Aftercare consists of ensuring that a thermometer is clean and disinfected. Electronic thermometers must be turned off to conserve their batteries.
Risks
Taking a body temperature involves little risk. Inserting a thermometer into the rectum can occasionally be painful. Breaking a thermometer that contains mercury causes exposure to a toxic substance (mercury).
Normal results
Most people consider a normal body temperature to be an oral temperature of 98.6 degrees Fahrenheit. This is more correctly an average of body temperatures. A person’s body temperature varies during each 24 hour period. A normal range encompasses temperatures that are 1°F (0.6°C) above or below 98.6 degrees F. Some variation is due to fluctuations in physiology nd cellular metabolism. Bodily activities (or lack) can temporarily increase (or decrease) body temperature. Body temperature is very sensitive to hormone levels and may be higher or lower when a female is ovulating during her menstrual cycle.
A rectal or ear (tympanic membrane) temperature reading is 0.5 to 1 degree F (0.3 to 0.6 degrees C) higher than an oral temperature reading. A temperature taken in the armpit is 0.5 to 1 degree F (0.3 to 0.6 degrees C) lower than an oral temperature reading.
In adults, an oral temperature above 100 degrees F or a rectal or ear temperature above 101 degrees F is considered to be a fever. Children are considered to have a fever when their rectal temperature is 100.4 degrees F or higher.
Abnormally low body temperature is called hypothermia. It is always serious and can be life-threatening. Hypothermia can occur after exposure to cold, when a person is in shock, or after alcohol or drug usage. Metabolic disorders, such as hypothyroidism or diabetes can trigger hypothermia. An infection involving the entire body (sepsis) can cause hypothermia. Infections in older adults, newborn infants or other frail persons may be accompanied by hypothermia.
Morbidity and mortality rates
Perforations of the colon due to inserting a rectal thermometer too far have been reported. These are uncommon. The number of deaths associated with taking a temperature is essentially zero.
Alternatives
There are no alternatives to obtaining a body temperature.
KEY TERMS
Fever— An abnormally elevated body temperature, usually defined as being 101 degrees Fahrenheit or more
Hypothermia— An abnormally low body temperature, usually defined as being 90 degrees Fahrenheit or less
Sepsis— An infection involving the entire body
Resources
BOOKS
Bickley, L. S., and P. G. Szilagyi. Bates’ Guide to Physical Examination and History Taking. 9th ed. Philadelphia: Lippincott Williams and Wilkins, 2007.
Jarvis, C. Physical Examination and Health Assessment. 5th ed. Philadelphia: Saunders, 2007.
Seidel. H. M., J. Ball, J. Dains, and W. Bennedict. Mosby’s Physical Examination Handbook. 6th ed. St. Louis: MOsby, 2006.
Swartz, M. H. Textbook of Physical Diagnosis: History and Examination. 5th ed. Philadelphia: Saunders, 2005.
PERIODICALS
Bruel, C., J. J. Parienti, W. Marie et al. “Mild hypothermia during advanced life support: a preliminary study in out-of-hospital cardiac arrest.” Critical Care 12, no. 1 (2008): R31–R41.
Gunn, A. J., T. Hoehn, G. Hansmann et al. Hypothermia: an evolving treatment for neonatal hypoxic ischemic encephalopathy.” Pediatrics 121, no. 3 (2008): 648–650.
Mance, M. J. “Keeping Infants Warm: Challenges of Hypothermia.” Advances in Neonatal Care 8, no. 1 (2008): 6–12.
Salerian, A. J., and N. G. Saleri. “Cooling core body temperature may slow down neurodegeneration.” CNS Spectrums 13, no. 3 (2008): 227–229.
ORGANIZATIONS
American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 906-6000. E-mail: [email protected]. http://www.aafp.org.
American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 434-4000, Fax: (847) 434-8000. E-mail: [email protected]. http://www.aap.org/default.htm.
American College of Physicians. 190 N. Independence Mall West, Philadelphia, PA 19106-1572. (800) 523-1546, x2600, or (215) 351-2600. http://www.acponline.org.
American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. http://www.ama-assn.org.
OTHER
HyperTextbook. “Information about body temperature.” 2008 [cited February 24, 2008]. http://hypertextbook.com/facts/LenaWong.shtml.
Kid’s Health. “Information about adolescent body temperature.” 2008 [cited February 24, 2008]. http://www.kidshealth.org/parent/general/body/fever.html.
Mayo Clinic. Information about low body temperature. 2008 [cited February 25, 2008]. http://www.mayoclinic.com/health/body-temperature/AN01513.
National Library of Medicine. “Information about body temperature.” 2008 [cited February 22, 2008]. http://www.nlm.nih.gov/medlineplus/ency/article/001982.htm.
L. Fleming Fallon, Jr, MD, DrPH