An angiosome-centred approach for TcpO2 electrode positioning

Background: The latest guidelines propose a TcpO2 value of 30 mmHg to help to confirm the diagnosis of chronic limb threatening ischemia. However, placement of electrodes is not standardised. The relevance of an "angiosome-centred" approach for TcpO2 electrode positioning has never been evaluated. We therefore retrospectively analysed our TcpO2 results to study the impact of electrode placement on the different angiosomes of the foot. Patients and methods: Patients consulting the vascular medicine department laboratory for suspicion of CLTI using TcpO2 electrodes placement on the different angiosome arteries of the foot (first inter metatarsal space, lateral edge of the foot and plantar side of the foot) were included. As the mean intra-individual variation is reported to be 8 mmHg, a variation of mean TcpO2 for the 3 locations ≤8 mmHg was considered to be not clinically significant. Results: Thirty-four patients (34 ischemic legs) were analysed. The mean TcpO2 was higher at the lateral edge of the foot (55 mmHg) and plantar side of the foot (65 mmHg) than at the first intermetatarsal space (48 mmHg). There was no clinically significant variation of mean TcpO2 according to anterior/posterior tibial artery patency and fibular artery patency. This was present when stratifying on the number of patent arteries. Conclusions: The present study suggests that multi-electrode TcpO2 is not useful to assess tissue oxygenation in the different angiosomes of the foot to guide surgical decision; first intermetatarsal electrode alone would be preferred. TcpO2 seems rather to evaluate overall tissue oxygenation of the foot. Electrode location on the plantar side of the foot may overestimate results and lead to misinterpretation.