Figure 5
From: Evidence that large vessels do affect near infrared spectroscopy
Original traces from a single subject showing the responses to two subsequent short lasting venous occlusions (30 and 60 mmHg, respectively). From top to bottom: cuff pressure; Cross-sectional area of brachial vein and basilic vein; tHb signals from the vein (blue) and muscle (red) probes. At the bottom, single frames of US imaging of blood vessels underneath the NIRSV probe (as indicated in Fig. 1b) are displayed, with superimposed coloured shadings indicating the extent of collapse/dilatation of the brachial (BrV) and basilic (BV) veins. The brachial artery (BrA) is also indicated. Note the unusual 2-steps increase in tHbV in response to the second occlusion, which is explained by the delayed dilatation of the basilic vein. The fact that the increase in venous size is delayed, compared to tHbV is due to the NIRS sample volume extending proximally to the US insonation site (during venous occlusion, venous pressure increases earlier at proximal than at distal sites, in the raised arm). Vertical dashed lines indicate start of cuff inflation and deflation.
