Near-infrared spectroscopic imaging of the whole hand: A new tool to assess tissue perfusion and peripheral microcirculation in scleroderma

Objectives: Systemic sclerosis (SSc) causes functional and structural microcirculatory dysfunction, affecting also distal extremities. Optical Near-InfraRed Spectroscopy (NIRS) of blood HbO 2 saturation (stO 2 ) is able to evaluate O 2 delivery/consumption balance in the explored tissue. The NIRS-sensitive camera non-invasively detects stO 2 values in superficial tissues, automatically generating 2D-imaging maps in real time. We aimed at testing whether NIRS hand imaging may evaluate peripheral microcirculatory dysfunction and its spatial heterogeneity in SSc patients compared to controls. Methods: Forty SSc patients (aged 55.1 ± 15.6 years) and twenty-one healthy controls (aged 54.3 ± 14.5years, p = 0.89) were studied by palmar hand NIRS-2D imaging. A blood pressure cuff was applied to the forearm and 3 min ischemia was induced. Images were acquired at basal conditions and every 10 seconds during 3 minutes of ischemia and 5 minutes of reperfusion. Five regions of interest were positioned on each fingertip, from the second to the fifth finger and one on the thenar eminence. Results: A significant difference was found between controls and SSc patients in basal stO 2 (84.3 ± 7.5 vs. 75.4 ± 10.9%, p < 0.001), minimum stO 2 (65.2 ± 8.0 vs. 53.4 ± 10.1%, p < 0.001) and time to maximum stO 2 during hyperemia (63 ± 38 vs. 85 ± 49 s, p < 0.05). Among clinical characteristics, anti-Scl70 antibody positivity, digital ulcers history and smoke exposure affected NIRS parameters, as well as sildenafil and statins therapy. Conversely, no significant differences were found in NIRS-2D values between different nailfold-videocapillaroscopy patterns. Conclusion: NIRS-2D imaging is a simple, automated tool to non-invasively detect regional microcirculatory impairment in SSc, which seems to add significant functional information to the morphological picture of nailfold-videocapillaroscopy.