Efficacy of Transcutaneous Oxygen Measurement in Flap Monitorning

Abstract

Background Early detection of vascular compromise is critical to microsurgical free flap survival. Although non-invasive tissue oximetry platforms are already used in flap monitoring, transcutaneous oxygen measurement (TCOM), a dermal oxygen tension (transcutaneous oxygen tension [PtcO2])-based method widely established in wound and vascular surgery, has not been systematically validated for flap surveillance with standardized diagnostic thresholds.

Methods Twenty-one anesthetized volunteers underwent sequential cuff-induced venous (50 mm Hg) and arterial occlusion (systolic pressure + 30 mm Hg), with three TCOM probes recording PtcO2 changes over 1–15 min. Thresholds were derived using Youden’s index and clinically assessed in eight free flap reconstructions.

Results Arterial occlusion caused rapid TCOM decline: −51.6% at 1 min, −90.1% at 2 min, and −96.1% at 5 min (all p < 0.0001), with excellent accuracy (area under the receiver operating characteristic curve [AUC] 0.997–1.000). A −41.4% threshold at 2 min yielded 95.2% sensitivity and 100% specificity. Venous obstruction produced smaller, slower changes; the best cutoff, −5.2% at 10 min, had limited diagnostic value (AUC 0.620). Clinically, TCOM identified arterial failure and supported salvage in one borderline flap after revision.

Conclusion TCOM detected arterial compromise rapidly and objectively within 2 min but failed to reliably detect venous obstruction in this cuff-occlusion model. Because venous compromise is a common cause of free flap failure, these findings argue against TCOM as a standalone comprehensive flap monitoring modality and suggest that it is likely inferior to technologies capable of detecting both arterial and venous compromise when used alone. Its potential role, if any, is best limited to an adjunctive arterial inflow sentinel within a broader surveillance strategy.