Feasibility Study to Evaluate Cycloidal Vibration Therapy for the Symptomatic Treatment of Intermittent Claudication Due to Peripheral Arterial Disease

Introduction:

Peripheral arterial disease (PAD) is a strong prognostic indicator of poor long-term survival (Norgren et al., 2007). A symptom of PAD is intermittent claudication which affects 5% of the adult population aged over 55 years (Fowkes et al., 2013). Intermittent claudication (IC) occurs during ambulation when the peripheral circulation is inadequate to meet the metabolic requirement of the active leg muscle, resulting in severe pain (Gardner et al., 2008). Consequently, patients suffering from IC find that the ambulatory dysfunction limits daily physical activity and negatively affects health-related quality of life. Current recommended first-line treatment for IC is for the patient to undertake a supervised exercise programme (NICE, 2012), supervised exercise is designed to improve symptoms by improving rate of formation of new blood vessels and establishing collateral flow. However, there are limitations with supervised exercise. These limitations include: difficulties with accessing exercise programmes (Stewart et al., 2008, Shalhoub et al., 2009, Harwood et al., 2016), poor completion rates/high dropout rates (Kruidenier et al., 2009, Treat-Jacobson et al., 2009, Nicolai et al., 2010), high number of patients unsuitable to participate due to concomitant disease (Suzuki and Iso, 2015, Kruidenier et al., 2009), and lack of patient motivation/willingness to undertake exercise therapy (Muller-Buhl et al., 2012, Stewart et al., 2008). Due to these limitations there is a need to investigate alternative treatments to help improve patients’ symptoms of intermittent claudication. One potential option is cycloidal vibration therapy (CVT).

CVT has been shown to increase blood flow (Maloney-Hinds et al., 2009, Button et al., 2007): it is hypothesised that improvement in blood flow would positively impact on patients’ symptoms of IC. This prospective feasibility study explored whether there is an association between CVT and patients’ symptoms of experiencing IC, measuring changes in pain free walking time and maximum walking time. Focusing on evaluating the research protocol and assessing the feasibility of undertaking a large study in this area and providing detailed information about the variability of the primary outcome measures to facilitate the design of future randomised controlled trial.

Methods:

A feasibility study was designed and undertaken. National Health Service (NHS) research and ethical approval was obtained. Patients reporting intermittent claudication were identified from vascular out-patients clinics within Mid Yorkshire NHS Trust. They were screened to ensure they met the inclusion/exclusion criteria for this study, and if suitable were approached to be included within the study. The patients were than consented and recruited into the study based on sample of convenience.

CVT if provided through a portable machine called Vibropulse (Vibrant Medical) which is designed to be used by the patient at home. The device is a rectangular soft pillow style pad, approximately the size of the lower leg, which is connected to a transformer powered via mains electricity. The machine is fully portable and comes within its own carrying case. The CVT was self-applied at home for 30 minutes twice a day over a 12-week period. Participants were reviewed at weeks 4, 8 and 12, then again at weeks 24 and 36 to assess whether any changes were sustained. Primary outcomes were: change from baseline of both pain free walking time and maximum walking time. Secondary outcome measures were: ankle brachial pressure index (ABPI), limb systolic pressure, mental health component summary score and physical component summary score of the SF-36 quality of life questionnaire, treatment compliance and patients’ ease of use of product assessed via a simple questionnaire.

Results:

Thirty-four participants with IC were recruited, of which 30 (88%) were male and four (12%) were female. Mean age of all participants was 68 years (IQR 60-75 years). After 12 weeks, 29 participants improved their pain free walking time, with an average improvement of 215% from baseline, (range of -8% to 1005%). Comparison of differences in time to event (event being pain onset) showed a statistically significant difference, between comparison time points at baseline and week 12 (2(1)=25.6; p<0.001).

Furthermore, at week 12, 23 participants recorded improvement in their maximum walking time, with an average improvement of 161%. Comparison of differences in time to event (event being termination of walking due to pain) showed that there was a statistically significant difference between comparison time points at baseline and week 12 (2(1)=15.36; p<0.001).

Analysis of the results showed that improvements in participants’ pain free walking time and maximum walking time were most pronounced within the first eight weeks of CVT treatment. Additionally, the long-term follow-up results showed that the improvements seen in pain free walking time and maximum walking time within the treatment phase were sustained once the CVT therapy had been discontinued.

Assessment of changes in participants’ lower limb perfusion showed evidence of a statistically significant difference between ABPI at baseline and at the end of week 12 (t29=-2.008, p=0.046). Furthermore, statistically significant changes were seen in the treated leg when comparing systolic leg pressure at baseline and week 12 (t31=-2.273, p=0.03). However, in the untreated leg there was no evidence of a statistically significant difference (t31=-0.597, p=0.555).

The results showed a positive improvement in participants’ quality of life, with their overall physical functioning scores improvement from 35.34 (SD 8.93) at baseline increasing at the end of active therapy to 44.52 (SD 9.11). During the follow-up period there was a decline in scores; however, at week 36 the physical functioning scores were 39.55 (SD 12.37), which is an increase from the starting baseline.

Conclusion:

Following 12 weeks of CVT there was statistically significant improvement in pain free walking time and maximum walking time in participants experiencing IC, with improvements being most pronounced within the first eight weeks of treatment. On average, participants’ pain free walking time increased by 215% from baseline, this level of improvement is comparable to improvements seen from other treatment options such as supervised exercise (Stewart et al., 2002). This improved walking ability resulted in improved quality of life, measured by physical functioning scores. Additionally, participants’ lower limb perfusion had increased, both ABPI and systolic leg pressure showed statistical evidence of improvements, and these changes in lower limb perfusion were not seen in the untreated limb.

This is the first study investigating the feasibility of using CVT as a treatment for IC and has provided novel information relating to duration/positioning of treatment, sample size, number of potential eligible participants and potential association between CVT and improved symptoms. Additionally, it has established that CVT treatment is highly acceptable, as indicated by no participant drop out in the treatment phase, and may potentially offer an alternative treatment option for patients experiencing IC. Furthermore, this study has assessed the variability of the primary outcome measure which provides vital information needed to calculate sample sizes for any future studies. In conclusion, this study has established the feasibility of using CVT to improve patients’ symptoms of IC and provides essential information which will contribute to the design of any future investigations.