pain models

Pain model – helping to target change


In my recent post on behavioural approaches to pain management, I had a number of commentators ask why do it, why not focus on pain intensity, and aren’t I invalidating a person’s experience if I target a person’s response to their experience. Today’s post will explore some of these points.

I suppose my first point needs to distinguish between pain as an experience, and pain behaviour – or what we do when we experience pain. I like to use a pretty old “model” or diagram to help untangle these concepts. It’s drawn from Loeser’s “Onion ring” model, and he wrote about this way back in the early 1980’s. This is my interpretation of that way of thinking about the person experiencing pain. It’s not intended to represent Truth – but to help us to get our heads around an individual’s truth, or their experience. It’s one way to consider the factors we’ve learned are associated with human pain. It should be evaluated in terms of its utility and practical usefulness for a person experiencing pain, and for clinicians hoping to help them.

The “BIO”

Firstly, we have all the neurobiological processes involved in transmitting nociceptive information throughout the body. Much of this information never reaches conscious awareness – activity in nociceptors occurs all the time, and we have rapid reflexive responses to this such as blinking, shifting in a chair, swaying while standing and so on. A whole lot of neurobiological activity occurs as this information reaches conscious awareness – much of this activity occurs above the brainstem. In fact, if we look carefully at neurobiological activity, much of the reason we never notice reflex responses to nociception is because we have a pretty effective inhibitory system that’s operating constantly to limit how much nociceptive activity hits consciousness. That’s all part of cortical and brainstem (yeah – BRAIN) processes. If anyone learns neurobiology of pain and doesn’t include attention, motivation, emotion, expectations then they’re missing an enormous chunk of what nociception and pain are about.

Added to this neurobiological information are another whole bunch of physiological and hormonal responses – and these are incredibly complex and often omitted from our discussions. For example, men and women differ in their hormone production, and this means more women experience persistent pain, women have lower pain tolerance, and respond to nociceptive information more quickly and at lower thresholds than men.

Suffice to say, there are a whole bunch of biological processes that are integral to our experience of pain and to nociceptive transmission, transduction and perception. So if anyone should suggest that a “biopsychosocial” model of pain does not include BIO – go wash your mouth out please.

Pain-the-experience

The next aspect of pain that Loeser included was “pain-the-experience” – the subjective, personal, unshareable “what it is like to experience pain” part. This encompasses the qualia – the sensory qualities of pain, and includes intensity and location. Pain is always experienced as having a negative or aversive quality, so we know that the urge to avoid or take action to reduce, and indeed our tendency to attend to this experience is part of a human experience of pain. Note that Loeser (and I) don’t include appraisal at this point! In other words, this is the “ouch” that a baby feels when we perform a Guthrie heel prick test. It’s that moment when scalding coffee hits your lap, before you’ve realised you’ve spilled your coffee.

But just to complicate things here – unless we’re newborns, we’re always aware of context and pretty much once we learn language, we’re interpreting when/where/how/why events are happening. This means that factors such as expectations, past learning, predictions we make about “what next” always inform “pain-the-experience”. Even before we’re consciously aware of these influences! So technically, as soon as we recognise “ouch” we’re already invoking a whole bunch of higher cortical processes into our experience. This matters because pain is a conscious experience, and requires perception before it can be experienced.

Judgement or appraisal

The next “ring” of Loeser’s model was called “suffering” – I’ve translated this into a cognitive process of “appraisal” because while pain is inherently tainted with negative emotional valence and a motivational urge to avoid, it’s also possible to view our experience of pain in different ways. Some commonplace examples are the jab from a vaccination – many of us will welcome that nociceptive input, and judge the pain to be negligible. Others who may be less comfortable with a vaccination might view it more negatively and be more aware of that pain. People who run or train in a gym might appraise the pain from working hard “feel the burn” as a sign that they’ve done enough to make performance gains. And some of us who live with persistent pain such as fibromyalgia might notice pain and consider it to be “just a nuisance”.

Suffering is an interesting concept, and I prefer to take Erik Cassel’s definition of it: suffering refers to the loss of a sense of self. A paper cut typically doesn’t lead to a loss of sense of self, while low back pain that remains for many months might be far more likely to erode that sense of “who I am and what I can do”.

Judgements and appraisals are influenced by a whole lot of factors – socio-cultural norms (I’m in a rugby-mad country, if a rugby player experiences pain on the field, he or she may well grit teeth and keep going, believing that it’s not OK to “give in” to pain – the appraisal might be “this isn’t so bad, I can still keep going”. Socio-cultural norms are often implicit – we absorb them effortlessly within our own cultural context, and we’re quite capable of holding different implicit norms depending on our current proximity to our social group. Consider the rugby player who will brush off an on-the-field injury but when getting a splinter might feel a little sick. The meanings we attribute to our pain influence how willing we are to go with them – tattoos and body piercings and body suspensions are really good examples of times when we’re OK to experience pain in the pursuit of something else, similarly post-surgical pain after joint arthroplasty.

When appraisals are unhelpful is when we get tripped up. When a person holds an inaccurate understanding of what’s happening – thinking, perhaps, that this back pain is a sign of cancer metastasising, or the end of a career as a sportsman, or an indication of some dire outcome, then a couple of things happen. Firstly, negative emotions are likely to rise, along with sympathetic arousal (the two systems are linked in the experience of pain), and then what we do about pain also begin to turn to short-term over long-term outcomes.

Pain behaviours

Pain behaviours are what we do when we experience pain, and they’re shaped both by evolution and by socio-cultural norms, as well as what we think is going on. I wrote about pain behaviour recently – click

Pain behaviours are the only part of “what it is like to experience pain” that we can observe.

Let me say that again – what we do about pain is the only part of the pain experience that a person who is NOT The Person In Pain that we can share.

Pain behaviour includes everything a person does and says in relation to their pain, both reflexive and automatic actions that we’re not aware of, as well as those we are aware of. Some of the behaviours we do are reflex responses (blinking and tearing up), some of them are not. Some of them are well-learned – we’ve been doing them since we were tiny kids. Others are things we’ve learned to do, perhaps on the advice of someone else, or because we’ve observed someone else, or because we think it might help or it’s worked once before.

The thing is – pain behaviours are malleable. They can and do change. Again, read my earlier post on how pain behaviours can be changed, and know that just because a behaviour has changed, the person’s experience of pain may not. In other words, while I move pretty normally, and to many onlookers I don’t appear to have pain – I still do.

Social context

I’ve already alluded to the influence of contextual factors. Things we’re aware of – prevailing attitudes in our immediate social group, our community, our spouse, our treatment providers. Things we’re often less aware – of implicit attitudes about gender, ethnicity, socio-economic status, supposed pain mechanisms, visibility of tissue damage and so on. And we are ALL influenced by these implicit socially constructed attitudes and beliefs, people with pain and their clinicians and their families and their communities….

I often use this way of exploring factors involved in why a person is presenting in this way at this time, and what might be done to reduce distress and disability. I might package the conversation in various ways – perhaps more complex if I expand on some aspects, perhaps less so if the person doesn’t want or need to explore something (often this is the neurobiological part). While it’s imperfect remember that the purpose of a model like this is contextual. I am not hoping to represent Truth as a universal law about “how pain works”. I AM hoping to explore useful elements for a particular purpose. One purpose might be to demonstrate that emotions and appraisals influence pain behaviour. Another might be to introduce medical students to the complex factors that might be involved in their interpretation of a patient’s distress. And another to help someone understand why he avoids a movement in one context but not in another. And even another might be to help someone know why she has such a panicky feeling when she’s in the middle of a flare-up.

As a pragmatist, and basing my practice on approaches that might help this person achieve a specific something in this moment, I use models like these to build therapeutic alliance, to enable the person to be willing to play with new ways of being, and to help them recognise that the target for change might not be what they initially think is relevant.

Loeser, JD. (1980). Perspectives on pain. In P. Turner (Ed.), Clinical Pharmay & Therapeutics (pp. 313-316). London: Macmillan.

Loeser, JD. (1982). Concepts of pain. In M. Stanton-Hicks & R. Boas (Eds.), Chronic low back pain (pp. 145-148). New York: Raven Press.

Explaining pain to people with chronic pain


One of the most challenging jobs we do in chronic pain management is help people get their heads around what chronic pain is…without giving them the idea that we think they’re imagining it, they’re mentally unwell, they’re ‘pretending’, ‘malingering’ or otherwise ‘not coping’.

While I can’t say I’ve got the answer, after explaining what pain is for a few years (not telling how many!), there are some things I find work better than others…

The first thing is to have a bunch of examples of everyday pain (mainly acute pain) to act as examples – mine include getting a flu jab, sunburn, a stubbed toe, sports bruises, and shark bites!  This helps people understand that pain is a normal, everyday experience that is understable.  Challenging, but understandable!

I use two different models of pain to help give people a bit of an understanding of their pain.  The first is a biopsychosocial model – so I have three circles, and while I’m talking with the person and getting them to tell me what their pain is like and how it’s affecting them.  The three circles are the ‘bio’ or biophysical factors, ‘psycho’ or psychological factors, and ‘social’ which includes social and cultural factors.

I find that working from what people already agree about (ie what they identify for themselves) and working with that to develop an explanation using a framework, like the one above, avoids saying which comes first (the pain or the irritability), and helps people acknowledge that each part influences the other.

Another option is to use Loeser’s ‘onion rings’ model.  This is a model that helps place the pain experience in context – it helps put the biophysical factors in the centre (whether as initiator or maintainer of the pain), while ensuring that the other aspects of pain such as the behaviour and context are also in place.

At the centre of the ‘onion’ is nociception – today we might instead think about neuromatrix dysfunction – which initiates and probably maintains the biophysical aspects of the pain experience.  But without the next few components, the pain experience does not actually exist.  We need to attend to or judge the meaning of the information being transmitted to the brain before it can be experienced…

So the next part is the actual quality or experience of pain – this is the part we can’t share with another, no matter how much we want to.  This is directly influenced by the nociception/neuromatrix part, but is also influenced by the next layer – which is our judgement of the meaning of that experience.  Loeser describes this as ‘suffering’ – but while experiencing pain may not be optional, suffering certainly is!

Suffering is all about how we interpret the sensations we become aware of, arising from the neuromatrix or nociceptors.  Suffering includes our predictions of the implications of the pain, what we think the pain means (something serious? something that will mean we can avoid something unpleasant? something to worry about…).  Some pain we can interpret as good – the pain after exercising, or the pain of childbirth (really!), while other pain we are concerned about (is it cancer? am I dying?).

What we do about pain is action, or behaviour.  Pain behaviours are directly influenced by what we think is going on – we run away if we think it’s something harmful, if we think it’s helpful we’re more likely to tolerate it (think about the flu jab compared with being jabbed with a dirty syringe in a dark alley).  At the same time, pain behaviours are influenced by our social setting – we do different things depending on who is around us, and where we are!

So the final ring is the social context – where we are at the time, the response of other people, our culture and even the legislative setting in which we live and work – these all make a difference to our pain behaviour (think of the response to stubbing your toe in your garage compared with your response to stubbing your toe on a pew at a funeral).

Working from what the person tells us, to a framework or model, seems to help people understand that we know what’s going on for them, we understand they’re not going nuts, and that we do know what we’re talking about.  A bit of reflective listening doesn’t hurt either.

I’ve also attached this description if you want something more complex…simple-explanation-of-cp

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