Flap monitoring with near-infrared spectroscopy (NIRS) facilitates early detection of vascular compromise. However, standard NIRS devices that employ two wavelengths of light to assess tissue oxygenation (StO2) are susceptible to artifact from background noise and demonstrate significant variability in the clinical setting. As the number of wavelengths detected by a NIRS device is increased, the precision of StO2 measurements can be improved and additional chromophores other than oxyhemoglobin and deoxyhemoglobin can be measured. A three-wavelength light emitting diode NIRS device (Artinis, Zetten, the Netherlands) that also detects cytochrome aa3, a measure of intracellular oxygen demand, was compared with the standard two-wavelength device commonly used for flap monitoring (ViOptix device, ViOptix Inc., Freemont, CA) to determine if there is an improvement in the precision of tissue oxygen measurements.Methods
ViOptix and Artinis were applied to the forearms of human volunteers (n = 15) and a blood pressure cuff was placed around the upper arm to occlude arterial and venous flow. StO2 measurements were obtained from both devices. Artinis also yielded cytochrome aa3 oxidation state measurements.Results
StO2 measurements from both devices were proportionate during ischemia (R2 = 0.79, p < 0.01). Monte Carlo stimulation showed Artinis outperformed ViOptix (p < 0.01) as a measure of change in StO2 during ischemia. Artinis did not detect a reduction in cytochrome aa3 associated with the decrease in StO2 during ischemia.Conclusion
The addition of a third wavelength to NIRS monitoring may improve the precision of StO2 trend monitoring. However, the three-wavelength device lacked the sensitivity to reliably measure changes in cytochrome aa3.