Phase Change Material for Thermotherapy of Buruli Ulcer: A Prospective Observational Single Centre Proof-of-Principle Trial

Abstract

BackgroundBuruli ulcer (BU) is an infection of the subcutaneous tissue leading to chronic necrotizing skin ulcers. The causative pathogen, Mycobacterium ulcerans, grows best at 30°C–33°C and not above 37°C. We explored the safety, tolerability and efficacy of phase change material (PCM), a novel heat application system for thermotherapy of BU.Methodology/Principal FindingsIn a prospective observational single centre proof-of-principle trial in Ayos/Cameroon, six laboratory reconfirmed patients with ulcerative Buruli lesions received 28–31 (ulcers ≤2 cm) or 50–55 (ulcers >2 cm) days of thermotherapy with the PCM sodium acetate trihydrate as heat application system. This PCM is widely used in commercial pocket heat pads, it is easy to apply, rechargeable in hot water, non-toxic and non-hazardous to the environment. All patients enrolled in the trial completed treatment. Being completely mobile during the well-tolerated heat application, acceptability of the PCM bandages was very high. In patients with smaller ulcers, wounds healed completely without further intervention. Patients with large defects had skin grafting after successful heat treatment. Heat treatment was not associated with marked increases in local inflammation or the development of ectopic lymphoid tissue. One and a half years after completion of treatment, all patients are relapse-free.Conclusions/SignificanceOur reusable PCM-based heat application device appears perfectly suited to treat BU in endemic countries with limited resources and infrastructure.Trial RegistrationControlled-Trials.com ISRCTN88392614

Development of thermal energy storage materials for biomedical applications

“…The thermal model allowed the prediction of skin surface temperatures and an optimization of the amount of PCM with respect to discharge time. The result obtained from the model matched well with the first prototype developed and used in a proof of principal trail in Cameroon [10]. For the human body, the maximum skin temperature which can be tolerated is $42 C. The PCM embedded bandages keep the skin surface temperature at $40 C for 4-5 h due to their specific thermo-physical properties.…”

“…The prototype device developed using PCMs has also been considered for thermotherapy, i.e. application in medical treatments such as buruli ulcer [9,10] and arthritis [11]. Some heating/cooling pads have been commercialized too, but with limited success due to high cost and lesser awareness.…”

The contribution of community health workers to the control of Buruli ulcer in the Ngoantet area, Cameroon

“…There are currently close to 6000 cases in Cameroon [12]. Only 30% of these patients benefit from medical treatment with antibiotics [12].…”

Phase change material for thermotherapy of Buruli ulcer: modelling as an aid to implementation

“…In six of the seven patients the clinical diagnosis of Buruli ulcer was reconfirmed in the laboratory. The results of the trial which was funded by the Volkswagen Foundation, Germany, are very promising with all ulcers healed and no relapses after 18 months of follow-up [10]. The set-up consisted of sterile bandages as inner insulation, 3 cm flexible outer insulation, and usually one pcm pack as heat source.…”

“…With the technical properties described and the very positive results of a proof-of-principle study conducted in Cameroon [10], pcm-based heat application devices show great promise as a treatment modality for Buruli ulcer patients. A further and more intensive study to refine the heat treatment has already been initiated.…”