## 3 Results
### Blood Pressure Testing Using SCISCCO on Forearm  
The authors of [39] reported using an SC system for CCO measurements in a blood pressure test, where the SC source was a commercial SC source based on mode-locked lasers. Consequently, as a first step toward validating our system, we wanted to confirm that our new SCISCCO system obtained comparable results to those reported in the literature. The approximate set-up and protocol for the blood pressure test are illustrated in Figure 7. A blood pressure cuff was wrapped on the upper arm, and then the probe from Figure 5b and the SCISCCO system from Figure 5a were applied to the forearm on the same side. The test protocol was that the healthy human participant was in a normal state (deflated cuff) for about 3 min, and then the cuff was inflated to above 100 mmHg of pressure for 4 min, after which the pressure was released for about 4 min. The spectrum of the diffusely reflected light was measured continuously through the test, with each complete spectrum measurement requiring about 30 s due to the speed of the mechanical rotation of the grating in the spectrometer in Figure 5a. (Note that in the attention test reported later in this paper, we optimized the data collection to reduce the scan time to \(\sim\)17 s.)  
Exemplary results for the change in HbO (red stars and lines), HbR (blue squares and lines), and CCO (yellow circles and lines) for the blood pressure test are illustrated in Figure 8 from our SCISCCO measurements. In particular, the HbR increased after applying the cuff pressure, the HbO decreased, and the CCO remained relatively unchanged (within the noise of the measurement). The results in Figure 8 are similar to those obtained in [39], thereby validating that our SCISCCO system matched the previously reported literature measurements for CCO using different kinds of super-continuum light sources. In particular, Figure 13 in [39] shows the same trends in HbR (increasing during cuff occlusion), HbO (rising at first, and then falling during cuff occlusion), and CCO (basically remaining approximately the same during cuff occlusion) as we saw in our results of  
Figure 6: Flow chart or block diagram of algorithm used to extract HbO, HbR, and CCO from the wavelength-dependent measurements (following [37; 38]).  
Figure 8. However, the magnitudes of the changes and the relative changes between different parameters were different from those in [39] and our experiments, probably because they were performed on different participants and the precise protocol and cuff occlusion may have been different. For example, in [39], the HbR changed from \(\sim\)0 to \(\sim\)20, the HbO went up to \(\sim\)5 and down to \(\sim\)\(-\)5, and the CCO changed by less than \(\sim\)2 (numbers should be considered relative to each other). On the other hand, in Figure 8, which is plotted in arbitrary units, the HbR changed from \(\sim\)0 to \(\sim\)2.1, the HbO went up to \(\sim\)0.3 and down to \(\sim\)\(-\)0.3, and the CCO changed by less than \(\sim\)0.15. Thus, the qualitative behavior matched, but the quantitative numbers were not the same due to different experimental conditions. We believe that the CCO did not change in the forearm for several reasons. First, the forearm muscles have a relatively low level of CCO compared, for example, with the brain. Second, for only a 4-min tightening of pressure, there is blood constriction, but there is not expected to be a significant change in the metabolism of the muscles, since muscle is less affected by oxygen deprivation.  
Figure 8. Measured changes in HbO, HbR, and the redox state of CCO during a blood pressure test.  
Figure 7. Set-up and protocol for blood pressure tests.