Early prediction of skin viability using visible diffuse reflectance spectroscopy and autofluorescence spectroscopy

BACKGROUND:: Accurate and early prediction of skin flap viability is vitally important in reconstructive surgery. To the best of the authors' knowledge, this is the first pilot study to evaluate the simultaneous use of both visible diffuse reflectance and autofluorescence spectroscopy on a reverse MacFarlane rat dorsal skin flap model in the early prediction of skin viability. METHODS:: A total of 62 flap measurement sites from 11 Sprague-Dawley rats were monitored for 72 hours. Both statistical analysis using measured spectra and quantification of physiologically relevant tissue parameters using empirical methods were performed. RESULTS:: The statistical analysis results suggest that either visible diffuse reflectance spectroscopy or autofluorescence spectroscopy alone can predict the skin viability accurately; however, autofluorescence spectroscopy is more sensitive to tissue changes in the first 2 hours after induction of ischemia. The pilot study shows that it is feasible to predict flap failures in the first 2 hours when using autofluorescence spectroscopy alone; moreover, it is possible to predict flap failures even in the first 15 minutes with high accuracy when using diffuse reflectance and autofluorescence spectroscopy simultaneously. Meanwhile, several physiologically relevant parameters including hemoglobin oxygenation, total hemoglobin concentration, and redox ratio indicators estimated from diffuse reflectance and autofluorescence spectra show distinctively different trends over time for nonviable and viable skin. CONCLUSIONS:: These findings will be helpful to clinicians for making a precise judgment on flap viability. Furthermore, the authors' results highlight the advantage of using autofluorescence spectroscopy in the early prediction of skin flap viability relative to diffuse reflectance spectroscopy.