Figure 3
Mean CSF and venous flow. Color-coded mean flow rates (ml s−1) of CSF and venous blood averaged across subjects at all locations during the 90 s breathing protocol (bottom). The procedure largely removes the cardiac component. Note the different scaling for the various ROIs. Normal breathing (0–40 s): low CSF flow with cardiac pulsatility. Venous flow in C3-EV and IJV remains constantly negative (blue). IVC shows upward (red) flow. Mean L3-EV flow is close to zero with a tendency towards the downward direction (light blue). Forced breathing (40–80 s): synchronous flow of CSF and venous blood following respiratory modulations. CSF moves upwards with IN in all ROIs (red) and downwards during EX (blue). Venous blood in the vessels at C3 shows downward flow with only small modulations. In L3-IVC flow modulations are more pronounced i.e. assuming a decrease during IN and an increase during EX. Flow in L3-EV yields a similar behavior. Normal breathing (80–90 s): rapid return of CSF and blood flow to the initial pattern. Aqd = aqueduct, C3 = cervical level 3, L3 = lumbar level 3, EV = epidural veins, IJV = internal jugular vein, IVC = inferior vena cava, IN = inspiration, EX = expiration.
