A new electrode design to improve outcomes in the treatment of chronic non-healing wounds in diabetes.

BACKGROUND: Chronic wounds are life-threatening in people with diabetes. Some studies show that electrical stimulation (ES) can help wounds heal, while others do not. But, ES is usually applied using a two-electrode system, where current distribution is greatest in the center line between the electrodes. In the present study, a three-electrode system (three-channel ES) was developed. Current dispersion on the skin and in the quadriceps muscle was compared between the conventional two-electrode and three-electrode systems in controls and tested for its ability to heal chronic wounds in people with diabetes. METHODS: In controls, current was delivered via a biphasic sine wave at a frequency of 30 Hz and pulse width of 100 microseconds. Stimulation electrodes 5 cm x 5 cm and 5 cm x 10 cm were placed at 10 cm and 15 cm separation distances above the quadriceps muscle. Skin currents were measured using five pairs of surface electrodes positioned in five separate locations on the skin. Muscle currents were measured using three pairs of needle electrodes positioned in three different locations in the muscle belly. In chronic wounds in eight subjects with diabetes, stimulation was applied for 1 month, and healing and blood flow were measured. RESULTS: Current during three-channel ES was dispersed more evenly and more deeply than with conventional two-channel ES (P < 0.05). In wounds, there was almost complete healing in 1 month, and current was uniform in the wound. CONCLUSIONS: Three-channel ES is more effective than two-channel ES in terms of better current dispersion across the skin and penetration into tissue and will probably be better for wound healing.

Interrelationships between body fat and skin blood flow and the current required for electrical stimulation of human muscle.

There is variability between individuals in the current needed to elicit a contraction in human muscle with surface electrodes. To understand what might be causing some of this variability, 25 subjects whose average age was 24.4+/-2.3 years, whose height was 165.5+/-9.5 cm, and whose average weight was 70.3+/-21 kg were examined. Electrical stimulation was applied above the motor point of the quadriceps, biceps, and lateral gastrocnemius muscles. To assess body fat, 2D ultrasound was used with a 1cm stand off. Electrical stimulation was applied with sine wave stimulation at 100 micros pulse width and at a frequency of 30 Hz. To alter skin blood flow, aside from the natural difference in skin blood flow at rest, hot packs and cold packs were used for 5 min. The average fat thickness below the quadriceps and gastrocnemius muscles was 0.75+/-0.13 cm and under the biceps was 0.48+/-0.16 cm. Without the use of hot or cold packs, the currents for the quadriceps and gastrocnemius muscles were significantly higher than that of the biceps (p<0.01). While there was some relationship between stimulation current and blood flow without the application of hot or cold packs, when hot packs were applied, skin blood flow increased as did the current required to stimulate muscle to threshold. When cold packs were applied, there was a decrease in the current required to stimulate these muscles. In conclusion, there is a causal relationship between skin blood flow, the thickness of the fat layer below the skin, and the current required to stimulate the muscle.

Comparison of different heat modalities for treating delayed-onset muscle soreness in people with diabetes.

BACKGROUND: Delayed-onset muscle soreness (DOMS) is a serious problem for people who do not exercise on a regular basis. Although the best preventive measure for diabetes and for maintaining a low hemoglobin A1c is exercise, muscle soreness is common in people with diabetes. For people with diabetes, DOMS is rarely reported in exercise studies. RESEARCH DESIGN: One hundred twenty subjects participated in three groups (young, older, and type 2 diabetes) and were examined to evaluate the soreness in the abdominal muscles after a matched exercise bout using a p90x exercise video (Beachbody LLC, Los Angeles, CA) for core fitness. Next, three heating modalities were assessed on how well they could reduce muscle soreness: ThermaCare(®) (Pfizer Consumer Healthcare, Richmond, VA) heat wraps, hydrocollator heat wraps, and a chemical moist heat wrap. RESULTS: The results showed that people with diabetes were significantly sorer than age-matched controls (P < 0.05). On a 100-mm VAS (100 mm = sorest), the average soreness for the people with diabetes was 73.3 ± 16.2 mm, for the older group was 56.1 ± 15.1 mm, and for the younger group was 41.5 ± 9.3 mm; these differences were significant (analysis of variance, P < 0.05). The greatest reduction in soreness after applying the modalities was using moist heat, both immediately after the modality and up to 2 days after the exercise. Right after the modality, moist heat reduced pain by 52.3% in the older subjects compared with 30.5% in the subjects with diabetes and 33.3% in the younger subjects. Skin blood flow in the abdominal area before exercise was greatest in the younger subjects and lower in the subjects with diabetes after heat application. Skin temperature at rest and after exercise was greatest in the diabetes group. CONCLUSIONS: Muscle soreness following exercise was greatest in people with diabetes, and the best modality of the three studied to reduce this type of soreness was chemical moist heat.

The effect of the moisture content of a local heat source on the blood flow response of the skin.

Numerous studies have examined the effect of local and global heating of the body on skin blood flow. However, the effect of the moisture content of the heat source on the skin blood flow response has not been examined. Thirty-three subjects, without diabetes or cardiovascular disease, between the ages of 22 and 32 were examined to determine the relationship between the effects of dry vs. moist heat applied for the same length of time and with the skin clamped at the same skin temperature on the blood flow response of the skin. The skin, heated with an infrared heat lamp (skin temperature monitored with a thermocouple) to 40 degrees C for 15 min, was either kept moist with wet towels or, in a separate experiment, kept dry with Drierite (a desiccant) between the towels to remove any moisture. Before and after heat exposure of the forearm, blood pressure, heart rate, skin moisture content, skin temperature, and skin blood flow were recorded. The results of the experiment showed that there was no change in skin moisture after 15 min exposure to dry heat at 40 degrees C. However, with moist heat, skin moisture increased by 43.7%, a significant increase (P < 0.05). With dry heat, blood flow increased from the resting value by 282.3% whereas with moist heat, blood flow increased by 386% over rest, a significant increase over dry heat (P < 0.05). Thus, with a set increase in skin temperature, moist heat was a better heating modality than dry heat. The reason may be linked to moisture sensitivity in calcium channels in the vascular endothelial cell.

Estimation of the distribution of intramuscular current during electrical stimulation of the quadriceps muscle.

Electrical stimulation is commonly used for strengthening muscle but little evidence exists as to the optimal electrode size, waveform, or frequency to apply. Three male and three female subjects (22-40 years old) were examined during electrical stimulation of the quadriceps muscle. Two self adhesive electrode sizes were examined, 2 cm x 2 cm and 2 cm x 4 cm. Electrical stimulation was applied with square and sine waveforms, currents of 5, 10 and 15 mA, and pulse widths of 100-500 micros above the quadriceps muscle. Frequencies of stimulation were 20, 30, and 50 Hz. Current on the skin above the quadriceps muscle was measured with surface electrodes at five positions and at three positions with needle electrodes in the same muscle. Altering pulse width in the range of 100-500 micros, the frequency over a range of 20-50 Hz, or current from 5 to 15 mA had no effect on current dispersion either in the skin or within muscle. In contrast, the distance separating the electrodes caused large changes in current dispersion on the skin or into muscle. The most significant finding in the present investigation was that, while on the surface of the skin current dispersion was not different between sine and square wave stimulation, significantly more current was transferred deep in the muscle with sine versus square wave stimulation. The use of sine wave stimulation with electrode separation distances of less then 15 cm is recommended for electrical stimulation with a sine wave to achieve deep muscle stimulation.

The interrelationships between electrical stimulation, the environment surrounding the vascular endothelial cells of the skin, and the role of nitric oxide in mediating the blood flow response to electrical stimulation.

BACKGROUND: Electrical stimulation (ES) is a commonly used modality in physical therapy for treating wounds such as diabetic ulcers and pressure sores but the mechanism of its effect on skin blood flow (BF) has not been determined. MATERIAL/METHODS: Ten subjects were examined during ES of the skin above the quadriceps muscle with biphasic sine wave stimulation at a frequency of 30 Hertz, pulse width 250 microseconds. BF was measured between the electrodes with a Laser Doppler Flow meter. In one series of experiments, N-Nitro-L-Arginine Methyl Ester (L-NAME) was infused to determine the effect of blocking nitric oxide production on the blood flow response to ES. In another series, acetylcholine and epinephrine were infused to determine the effects of the initial blood flow prior to stimulation on the magnitude of the BF response to ES. RESULTS: The apparent mechanism of the increase in blood flow during electrical stimulation seems to be mediated by nitric oxide since the increase in blood flow as a result of stimulation was blocked by L-NAME. Modulation of the vasoconstrictor or vasodilator tone of the skin blood vessels altered the magnitude of the BF response to electrical stimulation; epinephrine blocked the response and acetylcholine increased the response. CONCLUSIONS: The BF response to ES is caused by NO and can be modulated by changing the environment of the vascular endothelial cell.