Treatment of chronic diabetic and venous ulcers using safe, low frequency (20kHz) and low pressure amplitude (55kPa) ultrasound

Abstract

The primary focus of this study was to assess the clinical efficacy of ultrasound assisted treatment of chronic wounds, such as venous and diabetic ulcers. The treatment was performed with fully wearable applicator, operating at 20 kHz and generating pressure amplitudes near 55 kPa. Over 500,000 patients are treated for venous ulcers annually and with treatment cost of $2,400 per month constitute approximately 1% of total health care costs in the western world. Due to the pain associated with these wounds, many patients are unable to meet their employment requirements after experiencing limited mobility and overall decrease in productivity. Hence, even modest shortening of the time needed for healing may provide substantial healthcare cost savings, and improvement of quality of life. The pilot study included 32 individuals between ages of 18 and 80 having venous (n=23) or diabetic (n= 9) wounds (~ 1cm2 in size) that remained open for a minimum of 8 weeks. In compliance with the IRB study protocol the subjects were randomly assigned to either treatment or control group, with an equal chance of being assigned to receive active ultrasound treatment or sham (current standard care). Treatment sessions lasted 15 minutes and were administered once a week for a period of 12 treatments, or until the wound’s closure. Clinical efficacy was evaluated by measuring the reduction in wound area over time. For both etiologies, i.e. both venous and diabetic wounds the rate of closure was statistically faster (p<.05) in the treated group compared to the control group. The study findings show that the ultrasound treated venous ulcer group had statistically improved (p<0.04) rate of wound size change (reduction of 14.3%/week) compared to the rate of wound size change for the control group (increase of 3.6%/week on average). Diabetic wound closure was achieved typically after 4 sessions for treated wounds, as opposed to 7 sessions for the control group. Time to heal was also statistically faster (p< .05) for treated wounds (~5 weeks) when compared to non-treated wounds (~12 weeks). Overall, the results from this study support the notion that low frequency ultrasound treatment can successfully improve healing outcomes in chronic wounds with different morphology and etiology. The evaluated device used safe levels (<100mW/cm2 ISPTP) of ultrasound energy and featured unique portability, which opens possibility for personalized home treatment of chronic wounds in the future. The secondary goal of this study was to scrutinize statistical information available and develop guidelines to identify the most appropriate parameters suitable for initial (and limited) clinical trials characterized by relatively small sample size (n=32, such as the one discussed here). The outcome of the analysis indicates that minimum number of patients depends on the value of the desirable statistical power. Although this power can be selected by the user, the Food and Drug Administration sets a minimum value at 80% for clinical trials. It was found that most published…