Non‐invasive assessment of negative pressure wound therapy using high frequency diagnostic ultrasound: oedema reduction and new tissue accumulation

Abstract

Tissue oedema plays an important role in the pathology of chronic and traumatic wounds. Negative pressure wound therapy (NPWT) is thought to contribute to active oedema reduction, yet few studies have showed this effect. In this study, high frequency diagnostic ultrasound at 20 MHz with an axial resolution of 60 µm was used to assess the effect of NPWT at - 80 mmHg on pressure ulcers and the surrounding tissue. Wounds were monitored in four patients over a 3-month period during which changes in oedema and wound bed thickness (granulation tissue) were measured non-invasively. The results showed a rapid reduction of periwound tissue oedema in all patients with levels falling by a mean of 43% after 4 days of therapy. A 20% increase in the thickness of the wound bed was observed after 7 days due to new granulation tissue formation. Ultrasound scans through the in situ gauze NPWT filler also revealed the existence of macrodeformation in the tissue produced by the negative pressure. These preliminary studies suggest that non-invasive assessment using high frequency diagnostic ultrasound could be a valuable tool in clinical studies of NPWT.

Systematic review and evidence based recommendations for the use of Negative Pressure Wound Therapy in the open abdomen

“…Although this has not been confirmed clinically in the open abdomen, an NPWT-mediated reduction in oedema has been observed in other indications [24].…”

High frequency ultrasound sacral images in the critically ill: Tissue characteristics versus visual evaluation

“…Other authors have reported pixel distribution analysis using the ratio of low echogenic pixels (LEP) to total pixels (TP) to reflect changes in dermal water content. 5,6,38 Use of this ratio may reduce the variability found we found in dermal density. Other have used HFUS image evaluation comparison to photography and use of neural networks decision systems in guinea pigs 27 to detect pressure ulcer phases, although both HFUS and photographs must be available for this methods.…”

Ultrasound and dermatology: basic principles and main applications in dermatologic research

“…HFUS has been employed in the evaluation of different wound types, especially pressure ulcers [85,86] and leg ulcers [87]. An US and histological study conducted using artificially induced wounds in pigs has demonstrated that both techniques are comparable in their ability to reveal wound healing parameters, such as wound depth, collagen accumulation and granulation tissue deposition [88].…”

“…Some devices may also allow the visualization of the underlying bone. The thickness of the tissue overlying the bone can be measured during treatment to assess quantitatively the rate of new tissue formation in the wound bed [85]. Even better sore healing assessment is achieved if it is combined to photography [89].…”