How do temporal artery thermometers work?
January 5, 2011 7:29 PM   Subscribe

How do temporal artery thermometers work?

A friend of mine just had a baby and got a new thermometer. The directions indicate to slide it across the forehead and down around behind the ear, ending just behind the earlobe. I found some info about temporal artery thermometers on Google, but the info was about a specific brand (Exergen) and did not explain why you have to slide it. Why can't it get a reading being stationary on the forehead? I know that when I was little, my mom had a black strip of plastic thermometer she'd hold in one place on my forehead for a reading.

The info also didn't mention why a forehead thermometer would end up behind your earlobe, nor did the demonstration videos show this. I'm not sure what brand thermometer my friend had, but the directions specifically called for this. A quick search of Wikipedia shows the temporal artery going in front of the ear, so I'm not sure it's measuring that artery there.

Bonus: Are there any drugstores/department stores where I can dispose of an old glass and mercury thermometer? Google led me to my state's website says to specially pack it in sand, seal it, and take it to the landfill but that's a really long drive for me. I don't mind keeping an old-style thermometer around but I feel more comfortable using an alcohol-based one.
posted by IndigoRain to Health & Fitness (3 answers total)
It works in a very similar way to hardware store infrared thermometers, I believe... except it takes a LOT of readings, over the course of a few seconds, and averages 'em. The company explains it a lil' more here.

BTW: when I had a baby, a half-decade ago, I was told that I HAD to use The Icky Method (rectal temp) until WeeThumbscrew was six months old or so... not sure if this still holds, but just an FYI.
posted by julthumbscrew at 8:50 PM on January 5, 2011

Describing a particular thermometer, Suleman et al. explain that device "consists of an infrared scanner that detects the highest temperature on the skin of the forehead and temporal region. From this value, the device estimates Tcore using a proprietary algorithm that incorporates a compensation for ambient temperature (Tst). This system thus differs from conventional skin-temperature measurements (i.e., liquid crystal strips) in searching for the highest forehead temperature and compensating for ambient temperature."

Suleman et al., "Insufficiency in a new temporal-artery thermometer for adult and pediatric patients", Anesthesia and Analgesia 95(1):67-71.

Based on more poking around with Google Scholar, the reason you have to slide the scanner is that the highest skin temperature depends on several things, including the sweatiness of the skin, the proximity of the artery to the skin's surface, and the thickness of the subcutaneous fat layer. So sliding is the way you get the maximum. I'm pretty sure the reason to go behind the ear instead of in front is the depth of the artery - the branch of the carotid that runs behind the ear is smaller but it's right up against the bone and the skin over it is super-thin.
posted by gingerest at 8:59 PM on January 5, 2011

Oh, from julthumbscrew's link:

"If sweating, the temperature on the neck behind the ear lobe becomes the overriding temperature, and since this area is not quite as stable as the temporal artery, it can easily cooled be by the thermometer in taking multiple readings. Remember, the probe of thermometer will be at room temperature, and is about 30 degrees Fahrenheit (17 degrees Celsius) cooler than body temperature."

Thanks everyone!
posted by IndigoRain at 10:58 PM on January 5, 2011

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