Measuring pain

 

Karoly (1985) - we should focus on all of the factors that contribute to pain

  1. 1.      Sensory - intensity, duration, threshold, tolerance, location, etc
  2. 2.      Neurophysiological - brainwave activity, heart rate, etc
  3. 3.      Emotional and motivational - anxiety, anger, depression, resentment, etc
  4. 4.      Behavioural - avoidance of exercise, pain complaints, etc
  5. 5.      Impact on lifestyle - marital distress, changes in sexual behaviour
  6. 6.      Information processing - problem solving skills, coping styles, health beliefs

Techniques used to collect data.

  1. 1.      interviews - advantage - it can cover Karoly's 6 points
  2. 2.      behavioural observations
  3. 3.      psychometric measures
  4. 4.      medical records
  5. 5.       physiological measures

Physiological measures of pain

Muscle tension is associated with painful conditions such as headaches and lower backache, and it can be measured using an electromyograph (EMG). This apparatus measures electrical activity in the muscles, which is a sign of how tense they are. Some link has been established between headaches and EMG patterns, but EMG recordings do not generally correlate with pain perception (Chapman et al 1985) and EMG measurements have not been shown to be a useful way of measuring pain.

Another approach has been to relate pain to autonomic arousal. By taking measures of pulse rate, skin conductance and skin temperature, it may be possible to measure the physiological arousal caused by experiencing pain. Finally, since pain is perceived within the brain, it may he possible to measure brain activity, using an electroencephalograph (EEG), in order to determine the extent to which an individual is experiencing pain. It has been shown that subjective reports of pain do correlate with electrical changes that show up as peaks in EEG recordings. Moreover, when analgesics are given, both pain report and waveform amplitude on the EEG are decreased (Chapman et al, 1985).

Evaluation

The advantage of the physiological measures of pain described above is that they are objective (that is, not subject to bias by the person whose pain is being measured, or by the person measuring the pain). On the other hand, they involve the use of expensive machinery and trained personnel. Their main disadvantage, however, is that they are not valid (that is, they do not measure what they say they are measuring). For example, autonomic arousal can occur in the absence of pain being wired up to a machine may be stressful and can cause a person’s heart rate to increase. If someone is very anxious about the process of having his or her pain assessed, or else is worried about the meaning of the pain, this will cause physiological changes not necessarily related to the intensity of the pain being experienced.  Autonomic responses can be affected by many other factors such as diet, alcohol consumption and infection. E.g. infection present can get increased pulse rate. Better used as a signal for the presence of pain rather than as a direct indices of pain.

 

Observations of pain behaviours

People tend to behave in certain ways when they are in pain; observing such behaviour could provide a means of assessing pain.

Turk, Wack and Kerns (1985) have provided a classification of observable pain behaviours.

 

•        Facial /audible expression of distress: grimacing and teeth clenching; moaning and sighing.

•        Distorted ambulation or posture: limping or walking with a stoop; moving slowly or carefully to protect an injury; supporting, rubbing or holding a painful spot; frequently shifting position.

•        Negative affect: feeling irritable; asking for help in walking, or to be excused from activities; asking questions like ‘Why did this happen to me?’

•        Avoidance of activity: lying down frequently; avoiding physical activity; using a prosthetic device.

 

One way to assess pain behaviours is to observe them in a clinical setting (although pain is also assessed in a natural setting as the patient goes about his or her everyday activities). Keefe and Williams (1992) have identified five elements that need to be considered when preparing to assess any form of behaviour through this type of observation.

 

•        A rationale for observation: it is important for clinicians to know why they are observing pain behaviours. One reason is to identify ‘problem’ behaviours that the patient may be reluctant to report, such as pain when swallowing, so that treatment can be given. Another is to monitor the progress of a course of treatment.

•        A method for sampling pain behaviour techniques for sampling and recording behaviour include continuous observation, measuring duration (how long the patient takes to complete a task), frequency counts (the number of times a target behaviour occurs) and time sampling (for example, observing the patient for five minutes every hour).

•        Definitions of the behaviour: observers need to be completely clear as to what behaviours they are looking for.

•        Observer training: in most clinical situations, there will be different observers at different times and it is important that they are consistent.

•        Reliability and validity: the most useful measure of consistency in observation methods is inter-rater reliability, but test-retest reliability can also be useful. Three types of validity that could be assessed are: concurrent validity (are the results of the observation consistent with another measure of the same behaviour?), construct validity (are the behaviours being recorded really signs of pain?) and discriminant validity (do the observation records discriminate between patients with and without pain?).

 

A commonly used example of an observation tool for, assessing pain behaviour is the UAB Pain Behaviour Scale designed by Richards et al (1982). This scale consists of ten target behaviours and observers have to rate how frequently each occurs.

The UAB is easy to use and quick to score; it has scored well on inter-rater and test-retest reliability.

However, correlation between scores on the UAB and on the McGill Pain Questionnaire is low indicating that the relationship between observable pain behaviour and the self-reports of the subjective experience of pain is not a close one. Turk et al (1983) describe techniques that someone living with the patient (the observer) can use to provide a record of their pain behaviour. These include asking the observer to keep a pain diary, which includes a record of when the patient is in pain and for how long, how the observer recognized the pain, what the observer thought and felt at the time, and how the observer attempted to help the patient alleviate the pain. Other techniques are to interview the observer, or to ask the observer to complete a questionnaire containing questions about how much the pain interferes with the patient’s normal activities and social life, the effect of the pain on family relationships and on the moods of both patient and observer.

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Commentary

•        Behavioural assessment is less objective than taking physiological measurements, because it relies on the observer’s interpretation of the patient’s pain behaviours (although, in practice, this can be partly dealt with by using clearly defined checklists of behaviour and carrying out inter-rater reliability that is, using two independent observers and comparing their findings).

•        An individual may be displaying a great deal of pain behaviour, not because that individual is in severe pain but because he or she is receiving social reinforcement for the pain behaviour (for example, attention, sympathy and time off work). A by Gil et al (1988) ...

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