Chronic venous insufficiency (CVI), defined as impaired venous return to the heart, is a factor in 60% to 90% of all lower extremity ulcers according to studies from 1997 to 2012.1-7 Approximately 9.4% of individuals in the US are diagnosed with CVI.1 According to a review,8 patients with CVI can exhibit a variety of leg symptoms, including achiness, heaviness, sensations of swelling, and skin irritation. Expeditious wound closure in patients with CVI is important to avoid infections, medical complications, and costly hospital admissions.9 In the US alone, care for ulcers due to CVI resulted in annual treatment costs between $3 million and $750 million in 2006,1,6 or 2% to 3% of the US healthcare budget.10 Many treatment options are available for CVI and include surgery, medications, ultrasound, compression stockings, electrical stimulation, and wound debridement.5
When granulation and wound bed epithelialization are inhibited due to the presence of necrotic tissue, debridement of nonviable tissue is a common practice, regardless of the wound etiology.11 Sharp debridement is among the quickest ways to remove nonviable tissue3 and is widely accepted as the gold standard for optimal healing in diabetic foot ulcers,12 an accepted practice in “good wound care,”13,14 and “may help expedite healing in chronic venous ulcers.”15 In addition, sharp debridement utilizes few tools and is inexpensive, making it a commonly used treatment option.1,3,5,13,14 In a concurrently controlled, prospective study3 conducted over 12 months with two patient cohorts, sharp debridement (with calcium alginate dressings to control blood loss) in combination with general ulcer management (compression dressings and pain relief as needed) was found to completely heal four chronic venous ulcers (16%) in 8 to 20 weeks, compared to one healed ulcer (4.3%) in the control group that received only general ulcer management. However, the reduction in surface area between the groups over the entire study period did not achieve statistical significance.3 Although it may expedite the healing process for patients with CVI, sharp debridement is not considered the mainstay of venous ulcer management,15 and its effectiveness has not been fully evaluated on patients with CVI.3 Sharp debridement requires a competent practitioner with specialized training,11,16 may be risky in wounds located in the gaiter region of the leg due to post-debridement hemorrhage,7,11 and may require the use of mild analgesics if the patient experiences pain.11 Newly developed technologies are beginning to challenge more traditional methods of wound debridement (eg, sharp debridement), but further evidence is needed to make these techniques more widely accepted.16
Ultrasound for wound care. Ultrasound has been used in medicine as a diagnostic tool (eg, Doppler blood flow studies) for approximately 50 years; more recently, it has served as a therapeutic device (eg, wound care).17 The two main types of therapeutic ultrasound are high-frequency ultrasound, which oscillates between 1 and 3 MHz (one to three million times per second) and is absorbed into tissue creating heat18; and low-frequency ultrasound (LFU), which oscillates between 30 and 40 kHz (30,000 to 40,000 times per second) and is commonly used to stimulate the tissue beds of chronic wounds.17 The authors of several literature reviews reported that both forms of ultrasound (high- and low-frequency) produce mechanical effects, including cavitation and acoustic streaming (thought to alter cell membrane activity), improve diffusion rates, enhance membrane permeability, fragment necrotic tissue, loosen slough, and destroy bacteria and biofilms on the wound surface.19,20 However, LFU may be reflected at the skin or wound surface, leaving little of the energy from the machine to reach deeper tissue layers.17
A number of studies utilizing LFU have been published; the results are mixed. A 2003 literature review18 examined 15 studies (meta-analyses, quasi-randomized, or randomized control trials) that utilized LFU on patients with chronic venous leg ulcers, trophic ulcerations, infected wounds, infected diabetic foot ulcers, or pressure ulcers. The reviewers concluded the benefit of LFU was not convincing. A 2011 meta-analysis9 involving 444 patients treated with noncontact, low-frequency ultrasound (NLFU) reported on the results of eight studies (one randomized, double-blind sham-controlled trial, five retrospective analyses, and two prospective, nonrandomized studies). The primary indications for treatment were ulcers due to diabetes mellitus, venous insufficiency, arterial insufficiency, and pressure. The authors concluded NLFU was associated with consistent wound size reduction, alleviation of wound pain, and favorable wound healing results. Over the course of treatment, approximately 85% reduction in wound area was noted over 7 weeks, 80% reduction in wound volume over 12 weeks, and 79% reduction in wound pain (no timeline given). A Cochrane review10 that specifically examined therapeutic ultrasound on patients with venous leg ulcers and utilized the results of eight randomized, controlled trials found no strong evidence for the benefit of LFU on venous ulcer healing. However, because the quality of the evidence was low, a beneficial effect of ultrasound could not be ruled out.
Based on the results of controlled clinical trials only, the application of NLFU has been shown to be effective in decreasing the size of chronic ulcers and, in some cases, shortening healing times. In one study,4 participants randomly assigned to conventional wound therapy and NLFU delivered by a foot bath (n = 19) were found to have a significant reduction in chronic venous ulcer size when compared to participants randomly assigned to conventional therapy alone (n = 18) (P <0.05). Over a period of 8 weeks, the NLFU-treated participants experienced a 41% reduction in ulcer size compared to an 11% reduction in the conventional treatment group. In another study,21 participants were randomly assigned to receive standard wound care (n = 35) or standard wound care plus ultrasound delivered by a NLFU system (MIST Therapy System, Celleration, Inc, Eden Prairie, MN) (n = 35) that utilized a 40-kHz transducer. The participants had a variety of wound etiologies including diabetes, chronic renal failure, prior vascular reconstructive surgery, and osteomyelitis. At 12 weeks, a significant number of wounds were more than 50% healed in the study group (63% of wounds) compared to the control group (29% of wounds) (P <0.001). A randomized, double-blind, sham-controlled study22 reported similar findings among participants with diabetic foot ulcers. Twenty-seven (27) participants received NLFU, while 28 received treatment with a sham device. A significant difference was seen in the 12-week healing rates of the two groups; 41% of wounds treated with ultrasound healed completely versus 14.3% of wounds in the control group (P = 0.0366, Fisher’s exact test). Mean healing time also significantly differed between the two groups (9.12 weeks for the ultrasound group compared to 11.74 for the sham treatment group; log rank P <0.0144). A prospective, single-arm study23 using historical controls examined healing in wounds of a variety of etiologies (diabetic, venous, ischemic, pressure, postoperative, and inflammation); although the overall percentage of wounds healed during the 8-month study was comparable between participants (69% NLFU participants versus 72% historical controls), the healing times were different. Participants treated with NLFU were healed in a median time of 7 weeks compared to 10 weeks in historical controls. Furthermore, NLFU-treated wounds that healed completely began to respond to the treatment within 4 weeks of treatment initiation, a timeframe that may serve as an indicator for responders to the treatment.
The Sonica 185 (Soring Gmbh, Soring, Inc, Germany) LFU device operates at a fixed frequency of 25 kHz. Treatment can be provided with either direct contact to the wound bed through a probe or by holding the transducer above the wound bed (noncontact).24 A prospective, pilot study25 in 2005 examined the effects of this device on 17 patients with a variety of wound etiologies, including venous ulcers, foot wounds in persons with diabetes mellitus, pressure, arterial insufficiency, and other nonhealing/surgical wounds. Over a period of 3 to 8 months, 53% of the wounds healed primarily or with the aid of a skin graft, while 35% of the remaining wounds healed at least 50%. A prospective, pilot study by Tan et al5 examined the effect of this same device on 18 patients with ulcers (average initial size 4.72 cm2) due to venous insufficiency (n = 13), rheumatoid (n = 3), or sickle cell (n = 2). After 12 weeks, 38.9% of the ulcers were completely healed. The average number of treatments was 5.7. In a randomized clinical trial26 published in 2013, 40 patients were randomly assigned to either a standard wound care group (n = 20) or standard wound care plus LFU delivered by this device (n = 20). After 2 months, a significant difference was seen in the percent of wound size reduction between the two groups (63.6% ultrasound, 39.3% control, P = 0.01). The significance continued at 3 months (78% ultrasound, 55.7% control, P = 0.02). However, at 6 months no significant differences in wound size reduction were seen between the two groups (87.9% ultrasound, 82.4% control).
The Qoustic Wound Therapy System (Arobella Medical, LLC, Minnetonka, MN) LFU device received US Food and Drug Administration (FDA) clearance for marketing in 2006. This device combines an ultrasound transducer set at 35 kHz with a special curette designed to scrape away devitalized tissue the ultrasound waves are thought to fragment and soften.27 Karau et al28 reported the system was able to effectively kill planktonic bacteria and decrease biofilm in vitro. In vitro, bacterial counts decreased by a mean of 5.10 (Pseudomonas aeruginosa), 4.99 (Staphylococcus epidermidis), and 5.22 (S. aureus) log 10 colony-forming units/mL. Mean decreases in biofilm were 1.34 (P. aeruginosa), 1.46 (S. epidermidis), and 1.02 (S. aureus) log 10 colony forming units/mL. Conner-Kerr et al29 found the system reduced colony forming units of bacteria, punctured and fractured bacterial cell walls, and altered colonial characteristics of methicillin-resistant S. aureus (MRSA) in vitro.
Although other LFU devices (MIST therapy, Sonica 185) have been researched with patient populations, the literature review did not find any studies that utilized the Qoustic Wound Therapy system on patients with any wound etiology.
The purpose of this case study was to evaluate the use of the Qoustic Wound Therapy System in patients with wounds due to CVI.