thermometer

Introduction

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

Clinical significance

• clinically acceptable error +/- 0.5 degrees C
  • peripheral thermometers thus not acceptable*

* several caveats not discussed in

• 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, but ref lumps them all together (from differences described in ref, this would not seem like a good idea)

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
• peripheral thermometers read 1.4 degrees C lower than central thermometers in patients with fever & 2.0 degrees C lower in patients with hypothermia
• 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

Notes

Ear & temporal thermometers cost $30-$50 (2007)

More general terms

• laboratory instrument

Additional terms

• body temperature
• device (medical device)