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.