Reliability of near-infrared spectroscopy in people with dark skin pigmentation

Near-infrared spectroscopy (NIRS) is a promising non-invasive technique for the continuous monitoring of tissue oxygen delivery. NIRS detects light absorbance of haemoglobin chromophores to determine tissue oxygen saturation (StO2). As skin colour is also determined by the presence of chromophores, it is plausible that NIRS signal quality may be affected by dark skin pigmentation.

Tissue saturation in the anterior compartment of the lower leg during isometric contraction was measured using NIRS in 17 volunteers with dark skin pigmentation. Measurements were continued until StO2 was zero percent or until the signal disappeared.

The NIRS device failed to register tissue saturation values at some point in nine of seventeen volunteers. This occurred more often in individuals with darker skin.

In patients with a dark pigmented skin, NIRS StO2 measurements should be interpreted with caution, as melanin clearly interferes with the quality of the reflected NIRS signal.