Evaluation of clinical effectiveness of MIST ultrasound therapy for the healing of chronic wounds.

OBJECTIVES: (1) To determine the incidence of wound closure for chronic nonhealing lower extremity wounds of various etiologies using MIST ultrasound therapy, a 510(K)-approved, low-frequency, noncontact ultrasound device indicated for the cleansing and debridement of chronic wounds. (2) To determine the optimum treatment duration for therapy with this low-frequency, noncontact ultrasound device, quantifying end points that correlate with a maximal clinical response and identifying potential synergistic therapies that could be used in conjunction with this therapy. (3) To analyze the impact of low-frequency noncontact ultrasound therapy on the microcirculatory flow patterns within the wound bed.

DESIGN: A noncomparative clinical outcomes trial utilizing low-frequency, noncontact ultrasound.

SETTING: A tertiary-referral hospital-based wound clinic.

PATIENTS: Twenty-three patients from a single tertiary-referral hospital-based wound clinic. Control data were obtained from a previously published, prospectively collected database from the same clinic.

INTERVENTIONS: During an 8-month period, a total of 29 lower extremity wounds in 23 patients who met criteria for inclusion were treated with low-frequency, noncontact ultrasound therapy. Standard of care was provided for 2 weeks for all wounds screened for the study. A failure to achieve an area reduction greater than 15% qualified the patient for enrollment to the trial and the addition of low-frequency, noncontact ultrasound therapy to the current treatment regimen.

MAIN OUTCOME MEASURES: Wound healing, area and volume reduction, and laser Doppler-derived mean voltage (a marker for microcirculatory flow) are the main outcome measures for the study.

RESULTS: Overall, 69% of the wounds in the study were healed using an intent-to-treat model. When low-frequency, noncontact ultrasound was used as a stand-alone device, median time to healing was 7 weeks. Historic controls were healed with a median time to healing of 10 weeks; however, a statistically significant number of these patients required wound-related hospitalization and surgical procedures to achieve closure compared with the wounds in the present study.

CONCLUSIONS: Treatment with low-frequency, noncontact ultrasound achieved healing in chronic wounds when used as a stand-alone device or in combination with moist wound care in 69% of cases. Response to low-frequency, noncontact ultrasound was evident within 4 weeks of therapy. Earlier transition to secondary procedures and decreased utilization of inpatient care might result in more cost-effective wound healing than the current standard of care. A well-designed health economic-based trial is warranted to assess this technology.