About 5% of British males over 50 years develop peripheral arterial occlusive disease. Of these about 2% ultimately require lower limb amputation. In 1995 we proposed a new technique using lightguide spectrophotometry to measure the oxygen saturation level of haemoglobin (SO2) in the skin as a method for predicting tissue viability. This technique, in combination with thermographic imaging, was compared with skin blood flow measurements using the (I125) 4-lodoantipyrine (IAP) clearance technique. The optical techniques gave a sensitivity and selectivity of 1.0 for the prediction of successful outcome of a below knee amputation compared with a specificity of 93% using the "traditional" IAP technique at a below knee to above knee amputation ratio (BKA:AKA) of 75%.
The present study assesses the routine clinical application of these optical techniques. The study is ongoing, but the data to date comprises 22 patients. 4 patients were recommended for above knee amputation (AKA) and 18 patients for below knee amputation on the basis of thermographic and tissue SO2 measurements. All but one of the predicted BKA amputations healed. The study to date produces evidence of 94% healing rate (specificity) for a BKA:AKA ratio of 82%. This compares favourably with the previous figures given above.
Hanson JM, Harrison DK, Hawthorn IE. Tissue spectrophotometry and thermographic imaging applied to routine clinical prediction of amputation level viability. Functional Monitoring and Drug-Tissue Interaction, Kessler MD, Müller GJ, (Eds), Proceedings of SPIE Vol. 4623 (2002).
Dr. David K. Harrison, Durham Unit, Durham. Tel: +44 (0)191-333-2215.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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