Multispectral imaging of post-occlusive skin oxygenation in systemic sclerosis: A feasibility study.

OBJECTIVES: In systemic sclerosis (SSc), hypoxia contributes to pathogenesis. Our aim was to ascertain whether multispectral imaging (MSI) could measure changes in skin oxygenation in response to a dynamic stimulus (finger occlusion) in healthy controls and patients with SSc, and whether responses differed between groups. If so, MSI would have potential as an outcome measure. METHODS: Twenty-five healthy controls and 45 patients with SSc underwent MSI of the hand at baseline (pre-occlusion), after 1.5 min of finger occlusion, at release and 1 and 5 min after release. RESULTS: Changes in oxygenation (arbitrary units) between time-points were significantly different between controls and patients with SSc from 1) baseline to 1.5 min of occlusion (healthy control median[interquartile] change -0.19 [-0.22 to -0.17], SSc -0.16 [-0.19 to -0.12]), p < 0.0001 and 2) 1.5 min of occlusion to release (healthy control change 0.35 [0.28 to 0.37], SSc 0.24 [0.19 to 0.27]), p < 0.0001. The SSc group showed blunted/delayed response upon release. Preliminary feasibility data (n = 3) for inter- and intra-observer reliability were excellent (>0.8) and test retest of occlusion indicated low mean difference (absolute value) of 0.04 arbitrary units. CONCLUSION: MSI was able, in this feasibility study, to identify oxygenation differences between groups; prolonged return to baseline in SSc likely reflects microvascular pathology. MSI is non-invasive and has the potential to monitor skin oxygenation in studies of SSc pathophysiology and treatment response.