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(t)O(2)). 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(t)O(2). The values obtained with the two methods were respectively (tHb=47.8+/-2.8 and 49.4+/-7.7 microM, mean+/-S.D., n=8) and (S(t)O(2)=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(t)O(2) in human subjects.