Here is a pretty good article (2018) on pain measurement and calibration.
While the early research in pain concentrated on developing a calibrated scale by managing all the variables (environment, mood, stress, language, etc.) and working with external stimuli that could be most precisely varied (heat, electric), it seems that more recent work is trying to measure our physiological reaction to pain stimuli to see if a common scale can be derived from the measurements.
The article talks about brain imaging as a measurement of pain (and, to its credit, describes the drawbacks). Another paper I ran across measured the biochemical reaction of pain receptors (they produce a chemical signal in response to pain stimuli).
The article also points out the recent efforts to address chronic pain calibration, which is different than pain from a traumatic event. Most of the early studies (and recent studies) try to calibrate response to immediate pain stimuli. But does this correspond to calibration of ongoing chronic pain from disease or debilitating conditions? Calibration of chronic pain is arguably much more important than calibrating pain from a single trauma to the body.
I watch a fly-on-the-wall ambulance programme. They go to all kinds of accidents and a common trope is that farmers are tough. A big muscular biker with a broken ankle will be incoherent and need plenty of ketamine before they can straighten it out. He will be claiming a 9 on the scale. A farmer would fell off a roof and impaled himself on some machinery will wave off the meds and tell the medics that he can walk to the ambulance.
Six years ago I woke up with horrible pain in my chest. I got out of bed and made my way to the couch, afraid I’d moan or scream and wake up my gf.
I thought I was dying and accepted that it was the end. Then the pain stopped. I was drenched in perspiration. Because I was alive, I assumed it wasn’t my heart and I immediately began thinking what a pussy I’d been over some heartburn or GERD.
A few nights later it happened again. Again I scoffed at what a baby I was over a little pain. I purchase Maalox and began drinking some before bed.
LongStoryShort, turns out I had unstable angina and at least one of the episodes was actually a heart attack. I learned this over a month after my first pain, when I finally went to my doctor (who was gobsmacked). A stent fixed me.
Pain is a personal, subjective experience. That doesn’t mean a statistical description of people’s pain reporting is meaningless.
Somewhere there is a back story as to why you are likely to be given pain meds if you have a 13 mm kidney stone, and not if you have a splinter, over and above your reporting of it. This is a gray area, but it still has significance.
Complicating the topic is the instance where a person claims to be in pain as a ruse to get a prescription for an opioid. Are there any data on how often this occurs?
On a personal note, many years ago I had kidney stones. My doc ordered a CT scan which verified the existence of the stones. She sent me home and said her staff would call in a prescription for pain meds, and got me an appointment with a urologist for the next morning. She also said that if I got sick to call her.
Well, her staff screwed up and did not call in the prescription. I took tylenol but ended up puking. By this time it was after office hours. When I reached her, she told me to go the ER and that she was calling in an order for morphine.
The ER staff insisted I wait my turn to be seen. Twice I went to the desk and begged for the shot she’d called in, telling them that the diagnosis of kidney stones was made that afternoon by the radiology staff at that very hospital.
Nope. Wait your turn.
I was pretty sure they thought I might be faking the pain to get drugs.
(When I finally got in the see the ER doctor, they confirmed that I did in fact have kidney stones, gave me two shots of morphine, and admitted me. It all worked out, but I hope I never again have to spend a couple of hours puling and moaning in the corner of the ER waiting room.)
There is also the concept of secondary gain. At least some persons derive some benefit from presenting themselves as “special”, and deserving of accommodations/special treatment.
The only thing I could envision would be a statistical method, with lots of correspondents reporting their perceived pain indices for a “standard” set of pain stimuli. Then statistical analysis to derive “best” values for each stimulus.
That experimental design would have insurmountable real-world problems, starting with inflicting a standard set of pain stimuli.
It seems like any method of quantifying by relation to real-world injuries would be complicated by the fact that not only are there differences among individuals, but with the same individual across separate occasions. I’ve had a fair number of needles in my arms over the years–lots of blood tests and blood donations, lots of vaccines-- and the pain variability is astonishing. Sometimes I hardly feel it; other times it’s agony. I’ve also had differing levels of pain from bee stings, sunburns of seemingly the same intensity and in the same place (in terms of how red they got, how fast they peeled, how long it took to recover), and pizza burns to the roof of my mouth. It seems like there might be multiple factors affecting the subjective experience.
It is possible to perceive pain from limbs that have been amputated and are not there. Emergency doctors might interpret pain far out of proportion to what is expected as due to ischemia, where cells have insufficient oxygen, but it can also be due to bizarre and poorly understood entities like reflex sympathetic dystrophy - possibly a global nervous system dysfunction.
Before studying anatomy, medical students study embryology. It is fascinating how much we have in common with some other animals. The nervous system develops in a systematic way. You do not necessarily want to have a lot of sensation in the gut - you do not want to feel every squeeze as food works its way from gum to bum. This does not mean there are not nerves in the bowel; one third of nerves in the body are there to keep things moving. But it does mean internal hemorrhoids do not hurt (same sensory nerves as bowel), but thrombosis external hemorrhoids can be excruciating (same nerve supply as skin).
I believe the closest we can currently get to quantifying pain may be with this new technique of merging PET and MRI scans. While this may correlate pretty closely to qualifying pain, there’s no way to measure exactly how an individual perceives that pain. One person’s qualia may differ significantly from that of someone else, just like one’s perception of the color red may differ from that of someone else. Luckily, you don’t need 100% accuracy for effective pain management, or to appreciate a red sunset.
Before physicians can begin to accurately quantify pain, they need to stop denying that it exists, i.e. cease referring to their procedures as causing “discomfort”.
No medical intervention can be accurately described as resulting in “discomfort”. It’s pain. It may be only mild pain, but it still hurts.
Aside from that aside, people’s experiences and thresholds are way too variable to be able to measure pain in absolute terms.
I WISH that would become the standard. I never know what to say when asked to rank my option on a scale from 1-10. And i have a good imagination, so i never hit the top of that scale, even when i was delivering a breech baby and thought, “now i know how you can die from pain”. But if you ask me, “does this pain interfere with my self-care? Does it distract me from work? Does it prevent me from walking?” I can answer all of those. And i feel like my answers aren’t going to vary from day to day based on my mood.
It is remarkable how varied the pain caused by a procedure can be, but patients should not feel they have been deceived. Ideally, the person doing the procedure would fully explain both the principle common and serious sequelae.
Improving function is a more useful measure than an arbitrary number. However, this is a longer term goal. If someone comes into the emergency room in pain requiring treatment, in good faith, a treatment should be supplied. There is considerable literature suggesting an improvement of the arbitrary value by at least fifty percent is a reasonable goal for short term relief. However, too often this is the end of the story. This analysis suffers the limitations of any overgeneralized discussion, including that it can be harder to improve function than it is to intervene briefly.
This. Back pain in particular tends to be difficult to appropriately diagnose and treat. Back when I was in medical school one of my attending physicians cited a rough statistic that only 1/2 of people who undergo back surgery for pain relief end up feeling better. I’m not a surgeon, but do take care of such patients postoperatively. IME this number is about right. Here’s what I think is happening.
Many people have some kind of abnormalities to their back that will be found on MRI. However, a lot of people have such findings and do not have any pain at all. My guess is that the people who don’t get better after surgery don’t improve because the source of their pain wasn’t some slightly herniated disc or a vertebrae that was a little misaligned. Rather, their pain is likely due to abnormalities in the way their brain perceives pain. Back surgery, of course, isn’t going to fix that.
My wife and I clearly recall the day she delivered our oldest daughter, 33 years ago.
There had not been sufficient time for an epidural. The placenta did not deliver, and before he went in after it, the doc said, “You may experience some pressure.”
My wife’s first comment that was intelligible and somewhat suitable for public consumption was, “I’m gonna buy that SoB a dictionary!”
fwiw, my typical experience with the dentist does not involve any pain, but I usually do feel some pressure. On the other hand, when I had an IUD inserted, my first comment was, “I wish you’d warned me it would hurt so much.”
As said above ‘pain’ can’t be compared to color. Color is an objective characteristic of objects, while pain is the personal experience of some event (injury), so there is always the personal element. Is there any other personal experience that we can objectively quantify? This is not a rhetorical question.
I also wonder whether looking only at the appearance of the injury is sufficient for comparison. Sticking a needle in your sole may not hurt at all, or a lot, depending on whether you hit a nerve. But from the outside it all looks the same. Even absent personal sensitivity I could well imagine that particular injuries could hurt much more than usual or very little because of particularities that are not immediately clear.
My thought would be that any objective test would suffice in pretty much the same way that, say, a blood panel for cholesterol might? A patient can’t tell you, with their mouth, anything useful about their cholesterol - high nor low - but it doesn’t matter because you can directly measure it and compare it to a baseline. Getting a person into a healthy range - based on taking averages and backtracking from large groups of people who had good health and no reported issues - is really all you need to accomplish to know that you’re going the right direction?
It would seem like if we’ve locked in on every biochemical, reaction, and neuro-signal that the body can send out when something painful hits it, then paying any attention at all to the patient’s view of their pain level is just self-defeating. Like it you can measure their body weight, why would you ever ask them what they think their bodyweight is, and - even more so - why would you ever even think of trying to reconcile the measurement and the self-reported number or give preference to the self-reported weight?
Sure, approached in that way you might end up with some stoic patient who doesn’t interpret their every day existence as being one of agony and pain, despite measuring off the scale compared to almost everyone else, but I suspect that they’d still find themselves feeling better if you happened to bring them into the normal range. I doubt that they’d feel like you’d done nothing good.
It seems likely to me that we do have ways to measure pain in a fairly consistent and reliable way, from what all things I’ve read about over the years. My suspicion would be that it’s just cumbersome, expensive, and poorly calibrated at the moment, with no good baselines. And that because, as Qadgop points out, the ability to function is the big metric and that’s easy enough to test, through questions and asking them to perform some tasks, that it’s just not worth breaking out the space age scanning devices at $1m a pop.
