Using TENS machines for chronic pain – can patients direct the focus of
research?
Pete Gladwell Clinical Specialist Physiotherapist Pain Management Service North Bristol NHS Trust
TENS machines: lightweight, portable, and low risk
Transcutaneous Electrical Nerve Stimulation
Gladwell & Bridson (2005) poster presentation International Association for the Study of Pain
11th World Congress on Pain
Audit of TENS Long Term Users Pain relief Reduced medication Assisting specific activities (e.g. prolonged
sitting such as at a theatre or social events; travelling; housework; prolonged standing; cooking; shopping; walking; gardening).
What if a main benefit of TENS use
is increased sitting tolerance?
None of these measures have an item relating to sitting tolerance:
Roland and Morris Disability Questionnaire Pain Disability Index Brief Pain Inventory (IMMPACT choice) Multidimensional Pain Inventory (IMMPACT choice) SF-36 (IMMPACT choice) Functional Rating Index Health Assessment Questionnaire – Disability Index Low Back Pain Rating Scale
Risk of poorly matched outcome measure selection using a theoretical example
Benefits of TENS for one research participant
Outcomes measured in a trial
Benefit 1 Not represented
Benefit 2 Not represented
Benefit 3 Represented and captured
Not helped for this person Represented
Not applicable for this person
Represented
The primary aim of the investigation:
To explore the range of benefits reported by patients who use TENS devices to
help them to manage chronic musculoskeletal pain, in order to guide the selection of outcome measures to
enhance the sensitivity of future research into the effectiveness of TENS.
Inductive, qualitative research method (descriptive, can lead to theory development)
Focus group then 9 individual interviews Semi-structured interview schedule Chronic musculoskeletal pain Recruitment via posters in the waiting room
of NHS Pain Clinic, South West of England Purposive sampling: patients reporting
benefit from TENS Thematic analysis (Braun and Clarke 2006) Individual case level analysis maintained
Main themes identified from analysis (9 individual interviews; >80 years of combined experience of using TENS)
1 Perceived Benefits of TENS
2 Problems with TENS use
3 Ways of using TENS/ learning to use it
4 Strategies of use, relating to context
5 Limits: problems and context interact
Theme: “Direct benefits” with three sub-themes
Direct benefits
Pain relief Distraction from pain
Help with muscle
tension/spasm
Pain scale data: “Oliver”
45 60 NO PAIN PAIN AS BAD AS POSSIBLE
15mm reduction in pain: less if pain more severe - still helpful to reduce absence from work.
Distraction as a direct benefit, and/or a mechanism?
“it distracts, disguises, um, changes the pain for a while. You get some time off from the pain if you get it right.”
“...turn it up... so it kind of covers up the pain” “It's quite good for the distraction thing apart
from anything else, just sort of having the impulses sort of takes your mind off the pain. But I think it does help with the pain as well.”
Pain scale data: “Moira”
73 NO PAIN PAIN AS BAD AS POSSIBLE
Helpful distraction from pain did not lead Moira to reduce her pain rating
Distraction is challenging to quantify: can we be aware of how unaware we are?
0 100 Not at all Completely aware aware
A special case of the observer effect?
Theme: “Indirect benefits” with four sub-themes
Indirect benefits
Reduction in medication
Reduction in medication side-effects
Enhanced rest
Improved function before and after rest?
Psychological Improved physical function
Activities
Tasks and Participation
Reduction in medication use: only if medication was problematic
“Fran”: “It's like, I work full-time, as you're
aware, if I have to take medication at work the side-effects can affect my ability to do my job: the TENS, there's no side-effects”
Theme: “Indirect benefits” with four sub-themes
Indirect benefits
Reduction in medication
Reduction in medication side-effects
Enhanced rest
Improved function
before and after rest?
Psychological Improved physical function
Activities
Tasks and Participation
TENS as part of a package… linked with planned rest for “Fran”
“Yeah, it's very much a package, that's the way I look at it… …some people may be able to just deal with it with a TENS machine, unfortunately I'm not one of those people, so I do use other things, I use my oils, my aromatherapy, I relax, especially after work, I literally give myself a time period when I get home… I go upstairs like 30 to 45 minutes I just totally, totally relax. I've got my tapes, I've got my burners on, I put my TENS on…”
Theme: “Indirect benefits” with four sub-themes
Indirect benefits
Reduction in medication
Reduction in medication side-effects
Enhanced rest and
relaxation
Improved function
before and after rest?
Psychological Improved physical function
Activities
Tasks and Participation
Theme: “Indirect benefits” with four sub-themes
Indirect benefits
Reduction in medication
Reduction in medication side-effects
Enhanced rest and
relaxation
Improved function
before and after rest?
Psychological Improved physical function
Activities
Tasks and Participation
Theme: “Problems with TENS use” Problems can act to limit benefits
Pads pull off, esp. with larger movements; worse with some skin types/body hair or some pad positions e.g. knees
Wires trail, and can become detached Problems with fitting Problems with portability Problems with sensation and settings Problems with visibility/social stigma
Limits of TENS benefits: interaction between problems and context of use
“Claire”: “…if I'm doing something more active
then I probably won't put it on, in case it comes off or something happens, whereas if I'm just sort of doing something fairly relaxed, then I'll put it on, because it won't matter if anything comes unstuck”
“Sally” only uses TENS for pain relief & distraction during a flare-up
"Yeah, they're awful. Those days I've just… I have said I would rather not be there on my bad days cause they are just awful. They are horrible.“
"Yeah, just busy generally, with my little one, and a new puppy, and Christmas and everyday things that come up, I'm busy thinking about those really, than thinking about, thinking about my TENS machine."
Four strategies of TENS use identified using individual case level analysis
1. Flare-ups: reduced functional benefits 2. Planned rest: linked with pacing and
routines 3. Specific activities which pain limits:
specific to individual/pain 4. General activities: used frequently
during the day
Using TENS to support activity: a goal-focussed strategy.
“I wear my TENS machine to be able to do things. If I am doing my housework then my TENS machine is switched on”
What then happens to the pain relief? Trading off pain relief and activity levels?
Summary
Perceived benefits are modest in size, operating across several domains
Distraction from pain is a possible benefit TENS takes time to learn, including settings,
positioning and strategies (3 months?) Strategy choice depends upon a range of interacting
contextual factors including individual problems with use, variation in pain, and activity plans.
TENS is often used in a goal-focussed manner, with specific functional gains titrated against pain relief
Consequent research challenges and ongoing work
How could we measure distraction from pain? What might be the most appropriate functional
outcome measures? (mapping exercise) Can we account for effect of strategic use? Do we need to individualise outcomes? Will a context - based model of outcome
detection be understood by patients and sensitive to perceived benefits?
Acknowledgements
For Ph.D. supervision: Prof. Shea Palmer, Kathy Badlan, Dr. Fiona
Cramp For their time and support of the research: All focus group and interview participants. For their patience: My colleagues and family.
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