Low frequency transcutaneous sensory nerve stimulation (LF-SNS) [International Patent PCT/AU2004/001079:“nerve function and tissue healing” (Khalil, Z.)] improves sensory nerve function and accelerates wound healing of older animals. Intervention: Double blind, placebo controlled randomised trial of LF-SNS for 5 minutes, twice daily for up to 12 weeks, on healing of chronic venous leg ulcers in older people. Four layer compression bandaging was the standard therapy. Outcome measures (methods): Wound healing and the rate of epithelialisation (calculated from serial wound area estimation), microvascular blood flow (measured using LASER Doppler flowmetry), transcutaneous oxygen tension (measured using a transcutaneous oxygen monitor, TCM Radiometer). Sensory nerve activity (assessed via measuring electrical cutaneous perception threshold using the Neurometer®CPT and the flare response to 5% capsaicin (a selective activator of C fibres). Participants: 14 older people with chronic venous ulcers randomly allocated to active (mean age 74.8±2.3 years) and 15 to Sham nerve stimulation (mean age 76.5±2.6 years). Results: Microvascular blood flow improved in all participants. A high proportion of wounds healed (∼ 60%). There were trends for better C-fibre function and faster healing rates in the Active group (1.1±0.3 cm2/wk) compared to the Sham group (0.6±0.2 cm2/wk) but failed to reach statistical significance due to the small sample size. Conclusions: The improvement in microvascular blood flow in both groups was an unexpected finding that has not previously been described. Most likely this was due to the four layer compression bandaging provided to all participants. Improved microvascular blood flow may be a significant contributor to wound healing. The observed trends to increased healing rates and improvements in C-fibre function in the actively stimulated group compared to the sham group warrant further studies of LF-SNS as an adjunct therapy for chronic venous leg ulcers. An exploration of the possibility that LFSNS induced-improvement in C-fibre function could protect against future ulceration is also warranted.
Keywords: Sensory nerve stimulation, four layer compression bandaging and venous ulcers