The efficacy of low-frequency ultrasonic debridement (LFUD) and Polyhexamethylene Biguanide (PHMB) combination therapy for adults with chronic wounds; a randomised controlled trial

Each participant will receive ultrasonic debridement on their wound weekly for six weeks in a specified specialist wound clinic in the University Health Clinics. The ultrasonic procedure involves the use of a low-frequency ultrasound machine using the Sonoca 185 by Soring. This machine operates at 25kHz and is applied for 20 seconds per 1 cm2 of tissue to attain adequate bacterial kill, at 60-80% intensity, or at 40% and double the time. The use of LMX4 topical anaesthetic cream can be used prior to debridement if required to minimise discomfort. A wound swab will be taken prior to debridement, post debridement, and, post antiseptic soak (if in the intervention group). A small piece of tissue scraping can be taken during debridement treatment if able, at week 1, 3, 6 & 12 as well as the wound swab culture. Those in the intervention group will receive the application of antiseptic PHMB post ultrasonic debridement and in a sustained primary dressing. The antiseptic solution Prontosan contains the active ingredient PHMB and is applied as per the manufacturer guidelines for 15 mins in a soaked sterile gauze square. The dressing product that contains PHMB will be left on the wound until next dressing change. Frequency of dressing change will be determined by exudate amount. Those that require dressing changes between weekly clinic visits will require strict adherence to the regime of the Prontosan soak and continual application of the PHMB dressing product, if in the intervention group. The debridement therapy will be performed by the Chief investigator/Clinician/Registered Nurse or the Podiatrist in the Wound Clinic who has been trained with the ultrasonic device and debridement techniques. The Registered Nurse has up to 3 years experience with this debridement method and 17 years as a Registered Nurse working with chronic wounds. The participants will be followed weekly for a further six weeks post the six weeks of ultrasonic therapy, with either the antiseptic solution and medicated dressing product with PHMB, or if in the control group, a non-medicated dressing, for a total of 12 weeks. To assess intervention fidelity, the participant and carer (if applicable) must first understand the importance of adhering to the particular regime and agree to attend weekly clinic visits for 12 weeks. Carers or nurses who will attend to the dressings during the week will be advised and provided with a clear written plan of the dressing trial regime and the importance of adherence. The main clinician in the clinic will ask the participant each week if the correct product was applied and check during the participant's visit. The contact details for the clinician is supplied to the participant, carer and nurses if any queries arise about the trial between clinic visits. Any violation in the protocol will involve cessation of the trial for that participant, When the participant cannot attend a weekly visit due to illness or other event, nine out of 12 visits will be considered acceptable, and will not result in cessation of the trial for that participant. All data will be included, using the intention to treat policy,