Evaluating SnapshotNIR for Tissue Oxygenation Measurement Across Skin Types After Mastectomy

Accurate monitoring of mastectomy skin flap (MSF) perfusion is critical, especially in patients with darker skin pigmentation at higher risk of misdiagnosed tissue ischemia. Near-infrared spectroscopy (NIRS) devices, such as SnapshotNIR, offer real-time tissue oxygen saturation measurements (StO₂), but their accuracy across skin pigmentation levels remains unexplored. This quasi-experimental study included 33 patients undergoing mastectomy. MSF edge ΔStO₂, defined as preoperative minus postoperative StO_2, was measured using SnapshotNIR device (Kent Imaging, Calgary, AB, Canada) pre- and post-mastectomy. By definition, a positive ΔStO₂ indicates a decrease in tissue oxygenation, while a negative ΔStO₂ indicates an increase relative to baseline. ΔStO₂ was analyzed against Fitzpatrick scores to assess skin pigmentation impact on measurement accuracy. ΔStO₂ (mean ± SD) progressively decreased with increasing Fitzpatrick score: 14.0 ± 22.98 for score 1, 6.87 ± 17.45 for score 2, -3.13 ± 6.89 for score 3, and -40.75 ± 22.27 for score 5, indicating a shift from positive to negative O₂ change. Fitzpatrick scores significantly correlated with ΔStO₂ (ρ = -0.392, p = 0.016). ANOVA confirmed differences (p = 0.008), with Tukey's post hoc testing showing significant differences between Fitzpatrick scores 1 and 5 (p = 0.022), and 2 and 5 (p = 0.006). SnapshotNIR technology demonstrated measurable sensitivity for detecting changes in StO₂ and predicting ischemia; however, NIRS-based devices may overestimate oxygenation in darker skin pigmentation, highlighting a need for device calibration to improve accuracy across skin tones.