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thermometer
An instrument for measuring temperature by means of expansion or contraction of mercury or alcohol as indicated by its rise or fall in a thin glass tube.
Also measured by an electronic sensor without the use of mercury.
[Greek, therme = heat; thermos = warm or hot; metron = measure
Procedure:
For measurements of body temperature:
- peripheral thermometers (oral, ear, axillary, temporal artery)
- central thermometers (rectal, pulmonary artery, urinary bladder, esophageal)
- central (rectal) thermometers are the most reliable
- oral thermometer ok for older children & adults
- oral temperatures read 0.5-1 degree F lower than rectal temperature [2]
- peripheral thermometers read 1.4 degrees C lower than central thermometers in patients with fever & 2.0 degrees C lower in patients with hypothermia [3]
- ear thermometers, useful when oral temperatures not practical - earwax can interfere do not use if ear infection
- temporal thermometer uses infrared technology to read temperature while scanning the forehead
- axillary temperatures are least accurate
Clinical significance:
- clinically acceptable error +/- 0.5 degrees C
- peripheral thermometers thus not acceptable [3]*
* several caveats not discussed in [3]
- assuming the temperature measured with a central thermometer is the gold standard, is the difference in temperature meausured with a peripheral thermometer consistently low? i.e. is this a systematic error where the core temperature can be calculated by applying a correction factor?
- differences in the different types of peripheral thermometers are considered in ref [2], but ref [3] lumps them all together (from differences described in ref [2], this would not seem like a good idea)
Notes:
Ear & temporal thermometers cost $30-$50 (2007)
Related
body temperature
device (medical device)
General
laboratory instrument
References
- Stedman's Medical Dictionary 27th ed, Williams &
Wilkins, Baltimore, 1999.
- Prescriber's Letter 14(10): 2007
Chart Comparing Thermometers
Detail-Document#: 231006
(subscription needed) http://www.prescribersletter.com
- Niven DJ, Gaudet JE, Laupland KB et al
Accuracy of Peripheral Thermometers for Estimating Temperature:
A Systematic Review and Meta-analysis.
Ann Intern Med. 2015;163(10):768-777
http://annals.org/article.aspx?articleid=2470325