Effectiveness of periwound regional oxygen saturation as a wound healing predictor of toes in patients with chronic limb-threatening ischaemia

To verify the utility and accuracy of periwound regional oxygen saturation (rSO2) as a wound healing predictor of toes in patients with chronic limb-threatening ischaemia (CLTI), and compare the results with skin perfusion pressure (SPP) measurements. Patients with hard-to-heal (chronic) toe wounds and CLTI, and who had undergone toe rSO2 (near wound), forefoot rSO2 and SPP measurements, were retrospectively selected. Following the measurements, the patients were treated conservatively, and the progress of wound healing was evaluated 28-91 days after the rSO2/SPP measurements. Toe wounds were classified into two groups: healing and non-healing. Receiver operating characteristic curves were created for rSO2/SPP to evaluate the accuracy of the wound healing prediction index, and the area under the curve (AUC) was also evaluated. A total of 118 toes from 76 limbs were included in the evaluation and analysis. The AUC of periwound rSO2 was 0.938 (cut-off value: 44%; sensitivity: 0.955; specificity: 0.793). The AUC of plantar forefoot rSO2 and SPP were 0.789 and 0.786, respectively. The dorsal forefoot rSO2 and SPP demonstrated lower accuracy as wound healing predictors compared with the plantar side (AUC: 0.551 and 0.758, respectively). In this retrospective study, periwound rSO2 was a highly accurate predictor of toe wound healing in patients with CLTI. Both plantar forefoot rSO2 and SPP demonstrated moderate-to-high accuracy as predictors of toe wound healing, but less than that for periwound rSO2. Prospective studies in controlled populations are required. New devices that can measure periwound perfusion may provide more accurate wound healing predictions.