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

Systemic sclerosis (SSc) causes functional and structural microcirculatory dysfunction, affecting also distal extremities. Optical Near-InfraRed Spectroscopy (NIRS) of blood HbO2 saturation (stO2) is able to evaluate O2 delivery/consumption balance in the explored tissue. The NIRS-sensitive camera non-invasively detects stO2 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.

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.

A significant difference was found between controls and SSc patients in basal stO2 (84.3 ± 7.5 vs. 75.4 ± 10.9%, p < 0.001), minimum stO2 (65.2 ± 8.0 vs. 53.4 ± 10.1%, p < 0.001) and time to maximum stO2 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.

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.