Effects of transcutaneous nerve stimulation on the microcirculation in chronic leg ulcers.

The purpose of this study was to find out to what extent transcutaneous electrical nerve stimulation (TENS) affects the blood flow in and around chronic lower leg ulcers, as measured with a new technique, laser Doppler imaging (LDI). Fifteen patients, mean age 73 years (range 38-85) with chronic leg ulcers of various causes participated in the study. The duration of the ulcers ranged from 3 months to 16 years. Low-frequency (2 Hz; 10-45 mA) TENS was given for 60 minutes. The changes in blood flow were measured every 5 minutes by LDI. After 60 minutes, mean blood flow had increased in the ulcer by 35%, and in the intact skin surrounding the ulcer by 15%. Even 15 minutes after the TENS had finished there was still a mean blood flow increase of 29% in the ulcer and 9% in the skin. The present results show that TENS has a stimulating effect on local blood circulation in and around chronic ulcers.

Effect of transcutaneous nerve stimulation on microcirculation in intact skin and blister wounds in healthy volunteers.

Healthy non-smoking volunteers participated in two experimental studies in which the circulatory changes induced by transcutaneous nerve stimulation (TENS) were quantified by two different methods. In experimental series 1 (intact skin), nine volunteers were given TENS on the left lower leg for 60 minutes on three occasions at different frequencies each time (2 Hz, 100 Hz, and sham). Changes in blood flow were assessed by laser Doppler imaging technique every five minutes. The mean blood flow increased by 40% during low frequency TENS and by 12% during high frequency TENS. There was no change in mean blood flow during sham stimulation. In experimental series 2 (blister wound), the circulatory changes induced by TENS were studied by intravital video microscopy and computerised image analysis in standard blister wounds on the lower leg. The microcirculatory blood flow, measured as red blood cell velocity (RBC-V) in 5-14 individual capillaries in each wound, was assessed before and during 45 minutes of TENS (2 Hz and 100 Hz). Mean RBC-V increased by 23% during low frequency TENS (n = 6) and by 17% during high frequency TENS (n = 8). The results show that: laser Doppler imaging and intravital video microscopy techniques can be used to study events at the microcirculatory level; the blister wound is an interesting new standard wound for use in clinical studies; and TENS stimulates the peripheral circulation.