LAUSR

tissue disease. This study was a first step in determining the feasibility of measuring oxygenation at the nailfold, using adapted nailfold capillaroscopy, a well-established technique for measuring characteristic vascular structural changes in SSc. Methods: Capillaroscopy was performed with two optically filtered cameras (at two wavelengths) simultaneously. Filters were chosen to enable combined images to show changes in oxygenation. Single frame images (rather than panoramas), allowed oxygenation measurement at single vessels only. Participants underwent imaging before, during and after finger occlusion. Images were taken at baseline, one minute after finger occlusion (two mins, 200 mmHg), upon cuff release and at one minute after release. A two-sample t-test with unequal variances was used to compare baseline capillary level oxygenation between patients with SSc and healthy controls (HC) and changes between time-points. The share of individuals recovering their baseline level of the outcome variable after release was compared between groups using Fisher’s exact test. Results: Forty participants took part (20 HC and 20 SSc). Movement artefacts within images led to loss of capillaries between time-points or low contrast due to poorly visualised capillaries and made identification difficult in some images. Twenty (of 40) sets of images could not be analysed for oxygenation, leaving twenty sets of images that were analysed: seven (35%) from HC and 13 (65%) from patients with SSc. At baseline, the mean oxygenation (single vessel) was 2.8 (SD 8.9) arbitrary units in HC and -0.6 (SD 8.4) in SSc (p1⁄40.416). At occlusion, oxygenation dropped in all except for one HC. The mean change was 12.1 (SD 8.1) for HC and -14.4 (SD 6.3) for SSc (p1⁄40.522). At release, oxygenation increased for all participants and 4/7 (57.1%) HC recovered their baseline level vs. 6/13 (46.2%) SSc (p1⁄41.000). The change upon release had a mean of 14.2 (SD 2.9) for HC and 13.7 (SD 6.8) for SSc patients (p1⁄4 0.840). Conclusion: This feasibility study confirms that the system is sensitive enough to measure, in individual capillaries, changes in oxygenation due to occlusion. Panoramic mosaic images or lower magnification (enabling a larger field of view) would ensure the same field of vessels is captured through all time-points; and enable oxygenation at multiple vessels in the nailfold to be captured. In this small study, no differences could be detected between HC and patients with SSc. Groups started at similar levels of oxygenation. At occlusion, oxygenation dropped for all (but one) and increased for all at release. At release and one-minute post-release, a similar rate had recovered their baseline levels. Ongoing work is required to establish whether oxygenation varies in enlarged or angiogenic vessels in SSc. Disclosures: A.K.M. has received honoraria from GSK and Actelion Pharmaceuticals Ltd and has received funding for research from Actelion Pharmaceuticals Ltd. M.B., G.D., S.P., T.M., J.M., S.L., J.M., J.C., C.C., C.T., M.D. and A.H. have declared no conflicts of interest.