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{{BioPsy}} |
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| − | Body temperature varies both within individual organism and between species. [[Cold-blooded]] and [[warm-blooded]] animals differ in their methods of [[thermoregulation (body)| thermoregulation]]. |
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| − | [[Image:1911 Animal heat.png|thumb|400 px|Diurnal variation in body temperature, (from the 1911 [[Encyclopædia Britannica Eleventh Edition]]) ranging from about 37.5 °C from 10 a.m. to 6 p.m., and falling to about 36.3 °C from 2 a.m. to 6 a.m.]] |
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| − | '''Normal human body temperature''', also known as normothermia or euthermia, is a concept that depends upon the place in the [[human body|body]] at which the measurement is made. The value of 36.8 °C ±0.7 °C, or 98.2 °F ±1.3 °F is the common oral measurement.<ref name=Mac>{{Cite journal |
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| − | | doi = 10.1001/jama.268.12.1578 |
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| − | | volume = 268 |
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| − | | issue = 12 |
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| − | | pages = 1578–1580 |
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| − | | last = Mackowiak |
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| − | | first = P. A. |
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| − | | coauthors = S. S. Wasserman, M. M. Levine |
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| − | | title = A critical appraisal of 98.6 degrees F, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August Wunderlich |
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| − | | journal = JAMA |
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| − | | accessdate = 2007-08-22 |
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| − | | date = 1992-09-23 |
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| − | | url = http://jama.ama-assn.org/cgi/content/abstract/268/12/1578 |
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| − | }}</ref><ref name="Elert2005">{{Cite web |
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| − | | last = Elert |
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| − | | first = Glenn |
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| − | | title = Temperature of a Healthy Human (Body Temperature) |
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| − | | work = The Physics Factbook |
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| − | | accessdate = 2007-08-22 |
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| − | | year = 2005 |
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| − | | url = http://hypertextbook.com/facts/LenaWong.shtml |
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| − | }}</ref> Rectal measurements, or measurements taken directly inside the body cavity, are typically about a half degree Celsius (1 °F) higher. The core body temperature of an individual also tends to vary during the day and with activity level, with the lowest value in the second half of the sleep cycle; this low point, called nadir, is one of the primary markers for [[circadian rhythm]]s. |
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| − | ==History== |
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| − | In 1861, [[Carl Reinhold August Wunderlich]] claimed to measure the temperatures of one million people, and reported the average to be 37 °C.<ref name=Mac /> In the [[United States]], normal human body temperature is commonly quoted as 98.6 °F, which is an [[Significant figures|inappropriately exact]] conversion of Wunderlich's 19th century announcement that the human body temperature is 37 °C.<ref name="Elert2005"/> In [[Russia]] and former Soviet countries, the commonly quoted value is {{convert|36.6|°C|°F}}, based on an armpit reading. |
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| − | ==Variations== |
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| − | Temperature control ([[thermoregulation]]) is part of a [[homeostatic]] mechanism that keeps the organism at optimum operating temperature, as it affects the rate of [[chemical reaction]]s. In [[human]]s the average temperature is {{convert|36.8|C|lk=on}}, though it varies among individuals, as well as cycling regularly through the day, as controlled by one's [[circadian rhythm]]s with the lowest temperature occurring about two hours before one normally wakes up. |
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| − | Body temperature normally fluctuates over the day, with the lowest levels around 4 a.m. and the highest in the late afternoon, between 4:00 and 6:00 p.m.<ref name=Mac /><ref>[http://www.webmd.com/a-to-z-guides/body-temperature Body Temperature] at WebMD</ref> (assuming the person sleeps at night and stays awake during the day). Therefore, an oral temperature of 37.2 °C (99.0 °F) would, strictly speaking, be normal in the afternoon but not in the morning. An individual's body temperature typically changes by about 0.5 °C (0.9 °F) between its highest and lowest points each day.<ref name=Mac /> |
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| − | Temperature is increased after eating, and psychological factors also influence body temperature. |
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| − | Many outside factors affect the measured temperature as well. "Normal" values are generally given for an otherwise healthy, non-fasting adult, dressed comfortably, indoors, in a room that is kept at a normal room temperature (22.7 to 24.4°C or 73 to 76 °F), during the morning, but not shortly after arising from sleep. Furthermore, for oral temperatures, the subject must not have eaten, drunk, or smoked anything in at least the previous fifteen to twenty minutes, as the temperature of the food, drink, or smoke can dramatically affect the reading. |
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| − | Children develop higher temperatures with activities like playing, but this is not fever because their set-point is normal. Elderly patients may have a decreased ability to generate body heat during a fever, so even a [[Low-grade fever|low-grade fever]] can have serious underlying causes in [[geriatrics]]. |
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| − | Normal body temperature may differ as much as 1.0 °F between individuals or from day to day. |
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| − | ==Specific temperature concepts== |
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| − | ===Fever=== |
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| − | {{Main|fever}} |
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| − | A temperature setpoint is the level at which the body attempts to maintain its temperature. When the setpoint is raised, the result is a fever. Most fevers are caused by [[infectious disease]]. |
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| − | If temperature is raised, but the setpoint is not raised, then the result is [[hyperthermia]], which can result in [[heat stroke]] or related conditions. |
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| − | An organism at optimum temperature is considered ''afebrile'' or ''apyrexic'', meaning "without fever". |
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| − | ===Hyperthermia=== |
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| − | {{Main| Hyperthermia}} |
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| − | Hyperthermia is an acute condition which occurs when the body produces or absorbs more heat than it can dissipate. It is usually caused by prolonged exposure to high temperatures. The heat-regulating mechanisms of the body eventually become overwhelmed and unable to effectively deal with the heat, causing the body temperature to climb uncontrollably. Hyperthermia at or above about 40 °C (104 °F) is a life-threatening medical emergency and requires immediate treatment. Common symptoms include headache, confusion, and fatigue. If sweating has resulted in dehydration, then the affected person may have dry, red skin. |
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| − | In a medical setting, mild hyperthermia is commonly referred to as heat exhaustion or heat prostration; severe hyperthermia is called heat stroke. Heat stroke may come on suddenly, but it usually follows the untreated milder stages. Treatment involves cooling and rehydrating the body. This may be done through moving out of direct sunlight to a cooler and shaded environment, drinking water, removing clothing that might keep heat close to the body, or sitting in front of a fan. Bathing in tepid or cool water, or even just washing the face and other exposed areas of the skin, can be helpful. |
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| − | With fever, the body raises the core temperature to a higher temperature through the action of the part of the brain that controls the body temperature; with hyperthermia, the body temperature is raised without the consent of the heat control centers. |
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| − | ===Hypothermia=== |
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| − | {{Main|Hypothermia}} |
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| − | In hypothermia, the body temperature drops below that required for normal metabolism and bodily functions. In humans, this is usually due to excessive exposure to cold air or water, but it can be [[Therapeutic hypothermia|deliberately induced as a medical treatment]]. Symptoms usually appear when the body's core temperature drops by 1-2°C (1.8-3.6°F) below normal temperature. |
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| − | {{Main|Basal body temperature}} |
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| − | Basal body temperature is the lowest temperature attained by the body during rest (usually during sleep). It is generally measured immediately after awakening and before any physical activity has been undertaken, although the temperature measured at that time is somewhat higher than the true basal body temperature. In women, temperature differs at various points in the [[menstrual cycle]], and this can be used for [[fertility awareness|family planning]]. |
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| − | ===Core temperature=== |
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| − | '''Core temperature''', also called '''core body temperature''', is the operating [[temperature]] of an [[organism]], specifically in deep structures of the body such as the [[liver]], in comparison to temperatures of peripheral tissues. Core temperature is normally maintained within a narrow range so that essential enzymatic reactions can occur. Prolonged core temperature elevation ([[hyperthermia]]) or depression ([[hypothermia]]) is incompatible with life. |
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| − | Temperature examination in the [[rectum]] is the traditional [[gold standard (test)|gold standard]] measurement used to estimate core temperature (oral temperature is affected by hot or cold drinks and mouth-breathing). Rectal temperature is expected to be approximately one Fahrenheit degree higher than an oral temperature taken on the same person at the same time. Ear thermometers measure eardrum temperature using [[infrared]] sensors. The blood supply to the [[tympanic membrane]] is shared with the [[brain]]. However, this method of measuring body temperature is not as accurate as rectal measurement and has a low sensitivity for fevers, missing three or four out of every ten fevers in children.<ref>{{cite journal |author=Dodd SR, Lancaster GA, Craig JV, Smyth RL, Williamson PR |title=In a systematic review, infrared ear thermometry for fever diagnosis in children finds poor sensitivity |journal=J Clin Epidemiol |volume=59 |issue=4 |pages=354–7 |year=2006 |month=April |pmid=16549256 |doi=10.1016/j.jclinepi.2005.10.004 |url=}}</ref> Ear temperature measurement may be acceptable for observing trends in body temperature but is less useful in consistently identifying fevers. |
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| − | Direct measurement of core body temperature would require invasive insertion of a probe and is not clinically possible, so a variety of indirect methods are used. Whilst the '''[[rectum|rectal]] temperature''' is generally considered to give the most accurate assessment of core body temperature, particularly in hypothermia, though its recording is disliked by patients and medical staff alike. |
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| − | ==Methods of measurement== |
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| − | [[Image:Clinical thermometer 38.7.JPG|thumb|right|A [[Medical thermometer|medical/clinical thermometer]] showing the temperature of 38.7 °C]] |
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| − | Taking a patient's [[temperature]] is an initial part of a full [[clinical examination]]. |
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| − | The temperature reading depends on which part of the body is being measured. Measurements are commonly taken in the mouth, the ear, the [[anus]], or the armpit. In females, the [[vagina]] can also be used. The median daytime temperature among healthy adults are as follows: |
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| − | * Temperature in the anus (rectum/rectal), vagina, or in the ear (otic) is about 37.6 °C (99.6 °F)<ref name="Elert2005" /> |
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| − | * Temperature in the mouth (oral) is about 36.8 °C (98.2 °F)<ref name=Mac /> |
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| − | * Temperature under the arm (axillary) is about 36.4 °C (97.6 °F) <ref name="Elert2005" /> |
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| − | Normal human body temperature varies slightly from person to person and by the time of day. Consequently, each type of measurement has a range of normal temperatures. The range for normal human body temperatures, taken orally, is 36.8±0.7 °C (98.2±1.3 °F).<ref name=Mac /> This means that any oral temperature between 36.1 and 37.5 °C (96.9 and 99.5 °F) is likely to be normal. |
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| − | '''Problems of various measurements''' |
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| − | It is claimed that changes in core body temperature are reflected sooner and more accurately in the ear than at other sites. |
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| − | Influencing factors on other areas where temperatures are taken: |
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| − | * Oral temperatures are influenced by drinking, eating and breathing. |
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| − | * Rectal temperatures lag behind changes in core body temperature and there is a risk of cross-contamination. |
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| − | * Skin temperatures, measured under the arm or at the forehead, are not always reliable indicators of core body temperature, especially during those critical times when core body temperature is increasing or decreasing. This is because the skin is a tool the body uses to control core body temperature. For example, when fever is increasing people are likely to react by shivering and drawing in heat from the increased core body temperature. Skin temperatures are further influenced by factors such as fever-lowering medication, clothing and external temperature. |
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| − | ==Measurement devices== |
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| − | There is a risk of injury from cracking the original glass thermometers if too much force is applied by the teeth to hold them in place and the [[alcohol]] or [[mercury (element)|mercury]] contents are poisonous. This is avoided by the use of '''electronic thermometers''' which are made from solid plastic and use a metal ([[thermocouple]]) sensor. |
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| − | A '''plastic thermometer strip''' placed on the [[forehead]] gives an approximate local reading, which depends to a great extent on ambient air temperature and local circulation effects. Using a thermometer to record the temperature under the '''armpit''' is less affected by surrounding air temperature, but is still prone to diverge from true core temperature if there are alterations in blood circulation. |
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| − | Recently small '''ear thermometers''' have become available and it is thought that the [[eardrum]] closely mirrors core temperature values. These work by detecting the [[infrared]] heat emission from the [[tympanic membrane]] and a measurement is quickly taken within one second making them popular for use with children. Whilst the electronic display of the temperature value is easier to read than interpreting the graduation marks on a thermometer, there are some concerns for the accuracy of ear thermometers in home use.<ref name="pmid15644134">{{cite journal |author=Robinson JL, Jou H, Spady DW |title=Accuracy of parents in measuring body temperature with a tympanic thermometer |journal=BMC Fam Pract |volume=6 |issue=1 |pages=3 |year=2005 |month=January |pmid=15644134 |pmc=545063 |doi=10.1186/1471-2296-6-3 |url=}}</ref> |
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| − | ==Diurnal variation in body temperature== |
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| − | ==Body temperature and ovulation== |
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| − | *[[Ectotherm]] |
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| − | *[[Cold blooded]] |
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| − | *[[Gigantothermy]] |
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| − | *[[Poikilotherm]] |
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| − | *[[Warm bloodied]] |
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| − | ==See also== |
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| − | *[[Hypothermia]] |
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| − | ==References== |
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| − | [[Category:Body temperature]] |
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| − | [[Category:Physiology]] |
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The term body temperature may refer to :