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Assessment Techniques

The following clinically relevant parameters are routinely assessed - studies can be tailored to meet clients requirements.

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Rate of wound Closure

The impact of agents on wound closure is assessed using excisional wound models. Wound closure, which is measured by computer-assisted planimetry from calibrated images taken at intervals during the study, can be differentiated into its components:-Wound Re-epithelialisation & Wound Contraction (see below)

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Wound PlanimetryDiagram showing wound planimetry measurements in a normal (non-impaired) wound healing model.

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Data showing % wound area remaining (relative to the original wound area on day 0) ± s.e.m. for a non-impaired wound healing model with and without a developmental active topical wound therapy.

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The relative contribution of % wound contraction and % wound re-epithelialisation to overall wound closure are displayed.

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Data showing % wound area remaining (relative to the original wound area on day 0) ± s.e.m. for a diabetes impaired wound healing model with and without a developmental active topical wound therapy. 

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Note that untreated wounds remain open at 20 days

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Wound Colour Profile

Wound colour  is a useful parameter by which to monitor wound maturation.

Surface colour measurements of wounds are made using a Ci64 Sphere spectrophotometer (X-Rite Pantone) and CIELAB: an industry wide, internationally recognised numerical colour notation system.

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Ci64 Sphere spectrophptometer (X-Rite, Pantone)

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CIELAB colour space: an industry wide, internationally recognised numerical colour notation system.

This provides: “absolute” and “difference” (e.g. change over time) measurements Isolation of different colour attributes such as level of red/green, blue/yellow, dark/light, hue & chroma. un-biased quantitative colour data Coloration assessments can be made at regular intervals - up to a maximum of 12 months (e.g. for scar maturation investigations

Case Study

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  • Client wanted to examine the possibility of unwanted skin staining with a novel silver dressing .

  • Colour analysis revealed short-term discoloration due to presence of silver

  • Colour analysis also demonstrated reduced wound “redness” (reduced inflammation/angiogenesis) as an unexpected effect of treatment (see below for graphed data examples of wound appearance)

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Treated

Control

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Example wound images Day 14

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Repair Of The Epidermis - TEWL measurements

Trans-epidermal water loss (TEWL), the loss of water vapour via the epidermis, can be used to measure the health status of normal skin and restoration of the epidermis after injury.

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  • Trans-epidermal water loss (TEWL), the loss of water vapour via the epidermis, can be used to measure the health status of normal skin and the restoration the epidermis after injury.

  • Measured using a Tewameter® TM 300 (Courage & Khazaka electronic GmbH, Germany) the most accepted device by which to assess TEWL.

  • The Tewameter is an open-chamber device that can measure TEWL continuously without influencing the microenvironment.

  • Typically used in porcine wound healing studies – where TEWL is assessed at regular intervals after injury - up to a maximum of 1 month (when barrier function of skin wound sites has normally returned to that of  normal skin).

  • Measures progression of re-epithelialisation & restoration of barrier function. TEWL is elevated after injury to the skin;  as wounds heal, and the epidermal barrier is gradually restored, TEWL falls back to normal.

  • Can also be used to assess the impact of ‘agents’ on the condition of  undamaged and peri-wound skin.

Case Study

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  • Client wanted to examine the impact of a novel topical wound therapy on the healing of split-thickness (donor site) wounds - with a view to it use in the clinical setting.

  • Therapy was applied tp partial-thickness (skin graft donor site). TEWL measurements (of wounds and normal skin) were taken on post-wounding days 6 and 12.

  • TEWL was elevated after wounding, and was found to reduce over time. The novel wound therapy was found to accelerate the rate at which TEWL returned to normal – i.e. the rate of restoration of normal epidermal barrier function (see below).

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Wound & skin perfusion measurements

Wounds and surrounding peri-wound skin can be assessed in terms of tissue perfusion using a moorFLPI-2 blood flow imager (Moor Instruments) - enquire for further details

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