Figure 4

Difference of flow between normal and forced respiration. Paired t-test results at Aqd C3 (CSF, EV, IJV) and at L3 (CSF, EV, IVC). Each data point represents mean magnitude flow across all 320 time frames. Note the significant increase in CSF flow between normal and forced respiration at all location. Venous flow in lower body (L3-IVC) increases significantly with forced respiration while in upper body (C3-IJV) it decreases. In C3- and L3-EV no significant differences in flow can be detected. Aqd = aqueduct, C3 = cervical level 3, L3 = lumbar level 3, EV = epidural veins, IJV = internal jugular vein, IVC = inferior vena cava, R/C = respiration/cardiac, NB = normal breathing, FB = forced breathing, ns = not significant.