Optimizing Chronic Wound Treatment Through Near-Infrared Spectroscopy (NIRS) Imaging-Guided Non-Contact, Low-Frequency Ultrasound Therapy

Introduction: Chronic wounds often fail to heal due to various factors, including poor tissue oxygenation. Improving tissue oxygenation has been a central tenet of promoting wound healing since the early 1900’s. Low intensity non-contact non-thermal energy as delivered by non-contact low frequency ultrasound (NCLF) has been shown to stimulate angiogenesis from existing blood vessels in the wound bed, improving microcirculation and delivery of nutrients and oxygen to the regenerating tissue. Near-Infrared Spectroscopy (NIRS) imaging can distinguish viable from non-viable tissue and quantify tissue oxygen saturation (StO2) in the wound bed and surrounding tissues. NIRS objectively measures the free oxygen diffused to the tissue’s surface from the underlying vessels. Using NIRS, we sought to identify areas of poor tissue oxygenation to be targeted by NCLF ultrasound with the goal of stimulating angiogenesis and achieving a measurable increase in post treatment StO2.Methods:A chronic non-healing unstageable pressure injury on the left ischium was treated with NCLF ultrasound therapy for four-minute sessions, based on the size of the wound, three times a week for seven weeks. Prior to initiating the treatment, both the wound and surrounding tissue were visually assessed and scanned using a non-contact NIRS device. Tissue oxygenation was automatically calculated as a percentage (%), using the ratio of oxyhemoglobin to total hemoglobin. NCLF ultrasound therapy was focused on the wound area with the lowest oxygenation levels followed by a repeat NIRS scan post treatment to assess for any significant increase in StO2. Results:The wound was initially treated medically, including intermittent sharp debridement, for five weeks.  NCLF ultrasound was then added using NIRS imaging to guide the treatment towards the tissue with the lowest oxygen reading. On average, tissue oxygenation increased by 12-16% after each NCLF ultrasound treatment.  After 21 sessions, wound contraction reached 99%, with full closure anticipated.Discussion: NCLF ultrasound therapy is an effective tool in managing chronic wounds. It favorably impacts wound healing by significantly enhancing post treatment tissue oxygenation and angiogenesis in the wound bed.References:Dormand EL, Banwell PE, Goodacre TE. Radiotherapy and wound healing. Int Wound J. 2005;2(2):112-127. doi:10.1111/j.1742-4801.2005.00079.x