Spectroscopic assessment of cutaneous hemodynamics in the presence of high epidermal melanin concentration.

BACKGROUND For individuals with lightly pigmented skin, early stage pressure ulcers appear as areas of redness, which have compromised microcirculation and do not blanch in response to pressure. The lack of a visible blanch (hemodynamic response) to pressure is a convenient diagnostic test for stage I sores. However, the blanch response is not visually apparent in people with highly pigmented skin color due to the overwhelming contribution of melanin to the reflectance of skin. METHODS A simple least squares projection operator method is described, which can separate the reflectance contributions from melanin and hemoglobin. The methodology was tested in a study population of 20 subjects with healthy skin. The study population was evenly divided into a lightly pigmented skin group (visible blanch response) and a highly pigmented skin group (no visible blanch response). RESULTS The hemodynamic response to pressure being applied to the skin could clearly be distinguished spectroscopically in both groups at a high level of statistical significance. CONCLUSION The specific aim of this work was directed towards developing a spectroscopic basis for distinguishing the healthy blanch response in a manner that was independent of skin pigmentation. However, the technique has a general application when optical hemodynamic measurements are being made over a diverse patient population or under conditions of varying pigmentation such as the seasonal changes in skin color.