Simple and Easily Interpretable Flap Monitoring Method Using a Commercial Pulse Oximeter and a Widely Used Bedside Patient Monitor

Background Various methods for monitoring after free flap surgery have been reported in the literature. Among them, pulse oximetry shows a sensitive reaction to vascular issues, and it is easy to interpret visually. However, previous reports used special equipment that was less commonly used and difficult to generalize. In this study, we used a commercial pulse oximeter and a widely used bedside patient monitor to monitor transplanted free tissue and lower extremities of healthy subjects with impaired circulation. Methods A reflectance pulse oximeter sensor was attached on the flap after free tissue transplantation. The sensor was connected to a bedside patient monitor, and the flap oxygen saturation (SpO(2)) levels and arterial waveforms were continuously monitored. Additionally, blood circulation disorder was induced in the lower limbs of healthy volunteers using pressure cuff inflation on the thigh, and the waveform and SpO(2) levels on the pulse oximeter attached to the lower leg were monitored. Results Twenty-two patients were included in this study. No postoperative vascular issues were observed in any case. Pulse oximeters showed normal rhythmic wavelengths, and the flap SpO(2) level ranged approximately >90%. The pulse oximeter waveform rapidly disappeared during arterial occlusion in the thigh pressure cuff inflation test, and the waveform flattened and the SpO(2) level decreased slightly during venous congestion. Conclusion Flap monitoring using a commercially available pulse oximeter and a bedside patient monitor is a versatile, easy-to-interpret, and useful method. Changes in waveform and SpO(2) levels appear during arterial and venous circulation disorders, and these changes can be differentiated.