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Patients are often asked to rate their level of pain. Usually, I have found that these questions come without instructions as to what constitutes the maximum on this scale (maximum pain you can imagine? maximum pain you ever felt?).
What are ways pain can be quantified in these situations? Are there any "objective" (as objective as this can be) measures to help patients with this?
Please note that the pain scale is usually used to evaluate the efficacy of treatment. As long as the pain is responding to treatment, there need not be objectivity per se.
Was it a '7' on arrival? is it a '2' after a couple of doses of an analgesic? (if so, Great! Can we safely get it to a '1' or '0'? Did it spike to a '5' today? Why might that be? Is there something the team is missing that is causing the pain to be poorly controlled?)
This is the goal of the pain scale. For this reason, there is no need for objectivity.
Can pain be objectively measured, therefore reported?
The intensity of pain (as you have mentioned) is often left to the patient to describe on a scale of 1-10, or a visual analogue of faces. There is nothing objective about these methods, nor can there be, because pain is not objective; it is subjective.
Pain is subjective
Pain is a subjective experience; you cannot tell with certainty how much pain your fellow human is experiencing, which is why we ask people; they then can tell us. Pain relief (both physical and emotional) is a significant part of medicine, yet we still have "pain scales" for self-reported pain, one of the more common ones being the Wong-Baker Faces Pain Rating Scale:
To try to accurately assess pain (which is still subjective), a patient's scale should be interpreted by a caregiver using examples appropriate to that patient (If the person has had severe kidney stones, for example, the examiner can use that as a "10".)
...the worst pain I ever had was a kidney infection where I eventually passed out. If I take that as a 10, very few things even get to a 7 ;-) which is why I am asking. So you're basically saying physicians expect a high number much earlier than that?
No, we don't expect a lot of 8/9/10s on the scale. We hope it will be used exactly as you have described: in many cases, 10 is described by a caregiver as "the worst pain you ever had." If the patient has never had severe pain before (kidney stones, childbirth [for most], etc.) the pain has to be imagined.
Left to their own devices, a patient might look like a 6, but be reporting a 10. In this case, a nurse must try to ascertain their actual level of their pain. But still, it is their pain, and how it is felt differs from person to person, which is why no objective criteria can be assigned the pain scale.
The subjective experience of pain: Where expectations become reality
The Numerical Rating Scale (NRS - 11) may be the easiest one to relate to. Between ranges can be looked at pretty objectively, but within ranges is more subjective.
Rating: Pain Level
ADLs are activities of daily living.
I'll give two perspectives: 1) human factors engineer and 2) chronic pain patient.
1) When trying to objectify a subjective item like pain, a common set of tasks are applied to level the field and serve as a reference against which to measure. A common scale is called the Cooper-Harper scale. I have used it to quantify a pilot's ability to complete tasks like landing, hovering around an airport and turning. In the case of pain, neerajit mentions activities of daily living, and those would include dressing, urinating and having bowel movements, maintaining communications, having a stable mood, eating, drinking, etc. When assessing pain, a 4-6 might interfere with the ability to do the task even significantly, but it probably would not cause deterioration of the patient's health. These scales work much better for acute pain or how pain responds to treatment in an acute setting to treatment. For chronic pain, a scale is applied like this one, Scamahorn's Pain Scale, but it is applied more to how much the pain interferes with activities over say the previous two weeks overall. How does it affect overall quality of life, relationships, ability to work, walk, do housework, socialize, etc. This brings me to perspective #2.
2) Pain and experiencing the sensation of pain can be scary for someone who never experiences; the same can be true for the opposite. What I mean by that is people who are in pain and who experience it regularly do not necessarily know that their experience is different, and they learn to work within the experience of pain.
To measure my experience of being in pain and experience too strong of sensations, I had to have people point out to me that what I experience is not what everyone else experience. I do NOT experience it the same way. In my case, this awareness was realized because I felt so much frustration in the amount of effort it took in order to accomplish similar work compared to what I used to be able to do or as compared to my colleagues. This measure is also relative because it is only against a small subset.
Another measure that I use for my own pain is the amount of discomfort that I see my colleagues or even my own doctors in when they watch me in pain. I personally find this fascinating because most of the time, I am really just trying to get something done while pushing through. I can be just as distracting or more for them as it is for me.
These are my two different ways to attempt to objectify a very subjective experience. A good post-script attempt to this objectification would be to somehow quantify via black-white contrast the patient's pain experience through them drawing it. When I look at Pain Art, it tends to be very raw with high contrast, and the ultimate measure for a 10 on a 0-10 scale would be no drawing at all because the patient couldn't do it. That is my afterthought.
