Optical technique for continuous monitoring of flap viability in plastic surgery

The application of free tissue grafts is well established in plastic surgery. Some 10% of transplanted flaps fail in the first 48 hours. Salvage rates for these failing flaps can be as high as 83% with immediate surgical correction. A reliable monitor of flap vitality is therefore required which should be continuous and easily interpreted. A system has been developed based on a standard pulse oximeter using a modified neonatal probe and a laptop computer. The probe was modified by removing the emitters and detector which were then mounted on a 0.8 mm thick stainless steel backing strip and encapsulated in clear epoxy resin. The temperature characteristics of the probe were assessed to confirm that thermal damage to tissue would not occur in long term use. Circuitry was constructed to isolate the oximeter from the computer