Oxygen saturation (SHB) and concentration (CHB) of dermal hemoglobin are important parameters for the supply of the skin. They may be non-invasively assessed by means of reflection photometry as hemoglobin is predominantly contributing to the skin reflection spectrum.
Dermal reflection spectra from the middle of the forefoot and from the tip of the toe of 20 healthy subjects and 61 patients suffering from peripheral arterial occlusive disease (PAOD) were recorded and compared to transcutaneous oxygen pressure (tcPO2). SHB, and tcPO2 were significantly higher in controls: compared to patients (ankle pressure (AP) > 50 mmHg) SHB in the skin of the forefoot was 63.8 vs. 54.5% (p < 0.05), CHB was 0.89 vs. 0.62 aU (p < 0.01). In the great toe SHB was 92.9 vs. 59.9% (p < 0.001), CHB was 2.21 vs. 0.92 aU (p < 0.001). Heating the skin of the forefoot to 44 degrees C yields local dermal vascular reserve capacity: SHB and CHB increased in all healthy subjects (96.4%; 1.44 aU, respectively). SHB decreased at the forefoot in 14 and at the toe in 18 of 21 patients with AP < 50 mmHg. At the toe decrease was found in 50 of 61 patients (sensitivity 82%, specificity 100%).
Local vascular reserve capacity of dermal perfusion is reduced in patients with PAOD, depending on AP. It should be determined preferably in patients with severe PAOD.