How the Pain Scale Works

Observational Measurements
Doctors have to rely on observations of pain-related behavior in patients -- like this upset baby -- who can't communicate their pain any other way.
Doctors have to rely on observations of pain-related behavior in patients -- like this upset baby -- who can't communicate their pain any other way.
Jose Luis Pelaez Inc/Blend Images/Thinkstock

If doctors can't rely on a patient to give them an accurate pain report — or any report at all — then they have to look at how the body is responding to pain. How? Think about the way you acted last time you were in pain. You probably made some sort of grimace and maybe groaned a little. If it was bad enough, perhaps you began sweating or your heartbeat increased. Those are exactly the kinds of things doctors are looking for.

The body's reactions to pain generally can be placed into two categories: behavioral and physiological. Behavioral responses are sometimes vocal, causing a person to talk about the pain or simply moan, whimper or cry. They can also manifest themselves in facial expressions like grimacing, which is characterized by movements like brow lowering, nose wrinkling and eye narrowing [source: Turk and Melzack]. Body language is a key indicator too: Movements like bracing, rocking, rubbing or guarding a specific area are all potential symptoms of pain. Physiological responses, on the other hand, have to do with changes in the normal function of your body and organs. This could mean an increase in heart rate, respiratory rate or blood pressure, in addition to sweating, nausea and pupil dilation.

Often doctors simply take these qualities into consideration when making a diagnosis, but sometimes they will score them using scales. Infant pain, for example, can be estimated using the CRIES tool, which takes into account crying, oxygen saturation, vital signs, facial expressions and sleep patterns. Each of these categories receives a rating between 0 and 2, and if the sum of the ratings is greater than four, the pain likely demands medication.

Other tools are specifically designed for use with elderly people exhibiting dementia. The Abbey Pain Scale, for instance, rates pain based on six categories, each rated between 0 and 3. These include vocalization, facial expression, change in body language, behavioral change, physiological change and physical changes. A score under 2 is considered "no pain," while one above 14 rates "severe pain." Still, these are only estimates, and the pain intensity of a patient who can't self-report is still considered unknown [source: Pasero and McCaffery].

Author's Note: How the Pain Scale Works

My experience with pain scales stems from a short hospital stay for a collapsed lung. Aside from the tube in my side, there wasn't much to complain about, so my standard answer when asked to rate my pain from "0" to "10" was "2." But I was awake and able to communicate, so when it started to hurt a little more I said so and they gave me some medicine. While writing this article, however, I realized that a lot of hospital patients don't have the ability to speak up when they hurt. Doctors can only guess whether they're in pain and try to medicate accordingly. That's certainly a sobering thought. But thankfully there's a lot of research out there to help doctors estimate pain as best they can — at least until the day a Star Trek-y pain meter takes the mystery out of it.

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More Great Links


  • Abbey, J. et al. "Abbey Pain Scale." JH & JD Gunn Medical Research Foundation. (March 12, 2015)
  • Baker, Connie M. "FACES History." Wong-Baker FACES Foundation. (March 11, 2015)
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  • Bildner, Judy. "CRIES Instrument: Assessment Tool of Pain in Neonates." City of Hope Pain/Palliative Case Resource Center. 1997. (March 13, 2015)
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  • Radiolab. "Inside 'Ouch!'" National Public Radio. Aug. 27, 2012. (March 12, 2015)
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