A near-infrared calibration method suitable for quantification of broadband data in humans

Broadband near-infrared spectroscopy (bNIRS) is a powerful non-invasive technique for the measurement of hemoglobin. bNIRS systems are relatively simple to construct compared with many near-infrared instruments since they operate on the principle of continuous wave. The advantage of the broadband method is the capacity to model the spectra and to use " the second differential method" to quantify deoxyhemoglobin (HHb). An " anoxia pulse" method can be applied to quantify total haemoglobin (tHb) and tissue oxygen saturation (S_tO₂). A disadvantage is that this calibration method is not suitable for application in humans. In this study, we compared the " anoxia pulse" method with " graded hypoxia" method, which can be applied for human studies, to quantify tHb and S_tO₂. The values obtained with the two methods were respectively (tHb=47.8±2.8 and 49.4±7.7μM, mean±S.D., n=8) and (S_tO₂=72.8±3.7% and 73.2±5.7%, mean±S.D., n=8). There was no significant difference (p<0.05) between the two methods, indicating that the graded hypoxia method could be used for quantification of tHb and S_tO₂ in human subjects.