SPECTRAL-ANALYSIS OF PHOTOPLETHYSMOGRAMS FROM RADIAL FOREARM FREE FLAPS

Objective: Photoplethysmography utilizes a green-light-emitting diode to transmit light into a tissue, Reflected light from hemoglobin in de rmal capillary red blood cells is received by a photo detector and is analyzed as light intensity along a frequency spectrum, This method of analysis allows for the removal of ''noise'' above (stray light and a lternating current [AC]) and below (room vibrations and respiratory mo tion) the peak signal (1 to 2 Hz) and results in a means to distinguis h between perfused and nonperfused tissues. Methods: Twenty-two of 30 consecutive radial forearm free flap (RFFF) patients were enrolled in an approved human studies protocol to collect descriptive data for RFP Ps that were perfused, arterial occluded, and venous occluded The prot ocol was performed following completion of flap elevation and prior to pedicle ligation, flap inset, and microvascular anastomose. Six 90-se cond measurements per flap were obtained (n = 132), processed by fast Fourier transform (FFT), and analyzed by blinded reviewers to determin e their state of perfusion. Signal was collected 5 minutes after the o nset or release of individual vessel occlusion, Results: The reviewers ' interpretations were compared with the status of the pedicle and ana lyzed for sensitivity (0.96), specificity (0.95), and positive predict ive Value (0.98), Conclusions: FFT analysis of photoplethysmograms fro m RFFF patients provides an accurate and rapid means for determining R FFF pedicle vessel patency, Photoplethysmography may provide a clinica lly useful tool for postoperative perfusion monitoring of free flaps i n the future.