P165 A pilot study of oxygenation and perfusion in systemic sclerosis-related digital ulcers

Background Up to 50% of patients with systemic sclerosis (SSc) will develop digital (finger/toe) ulcers (DU). DUs can be chronic and difficult to treat and have a huge effect on patients’ quality of life and hand function. DUs are difficult to measure and to define, which is a problem in terms of outcome measures for clinical trials. Whilst relatively little is known about the pathophysiology of SSc-related DU, it has been shown recently that both fingertip and extensor surface ulcers are ischaemic. The objective of this study was to use non-invasive imaging techniques to gain further insight (in a pilot study) into the pathophysiology (including level of oxygenation) of SSc-related finger ulcers. The hypothesis was that digital ulcers are hypoxic as well as ischaemic. Methods Nine patients with SSc-related DU (1 male, 8 female, median age 62 [IQR 60 to 69] years, onset of first non-Raynaud’s feature 17 [12 to 22] years, duration of Raynaud’s 18 [12 to 27] years) underwent imaging of DU. Measurements of oxygenation (multispectral imaging), perfusion (laser speckle imaging, laser Doppler imaging [LDI], and thermography), and vessel size (LDI) were performed at the site of ulceration to include skin from an adjacent (unaffected) site. Results Eight fingertip DUs and one extensor DU were imaged; one DU from each patient. Oxygenation was decreased in the ulcer vs. adjacent site but was not statistically significant, p = 0.083 [0.035 to 0.193] vs. 0.145 [0.002 to 0.254]. Perfusion as measured by laser speckle and LDI and showed significant decreases at the ulcer site as compared to the adjacent site: laser speckle, 170 [104 to 210] vs. 443 [234 to 790] PU, p < 0.01; LDI, ulcer median 215 [IQR 97 to 507] vs. adjacent 344 [222 to 1071] arbitrary perfusion units (PU), p < 0.05;. Thermal imaging did not identify differences in perfusion, 31.9 [28.2 to 33.2] vs.31.9 [28.3 to 33.2]oC, non-significant. The mean lesion area was 3.4 [3.25 to 4.95] cm2. Oxygenation was associated with LDI perfusion (r = 0.83, p < 0.01). Conclusion Supporting our hypothesis, oxygenation was reduced at the ulcer site (although not significantly; however, we acknowledge that the number of ulcers studies was small). Laser speckle and LDI were both sensitive to differences in perfusion between the ulcer site and the adjacent area. That thermography was not, may be due to its lower resolution and also to the fact that thermal imaging obtains its signal from deeper within the tissue as well as more superficially; deeper tissue is likely unaffected. Oxygenation showed a strong relationship to perfusion as measured by LDI, indicating that the ulcers imaged were both hypoxic and ischaemic. As well as providing more insight into pathogenesis, measuring ulcer oxygenation and perfusion may provide a biomarker of ulcer healing. Disclosures J.B. Manning None. E. Marjanovic None. T.L. Moore None. G. Dinsdale None. S. Wilkinson None. M.R. Dickinson None. A.L. Herrick None. A.K. Murray None.