Figure 2.

Average normalized CSF velocity in the aqueduct over the cardiac cycle, averaged over both repeated measurements and all subjects, during expiration (blue), inspiration (orange), and no gating (yellow). The CSF flow curves were interpolated (using cubic interpolation with the MatLab function interp1) to 100 timepoints (0–100% of the cardiac cycle). As triggering was performed using a peripheral pulse oximeter, the cardiac cycle starts around peak‐systole. The cardiac cycle duration varied between 857–1090 msec. The line represents the average CSF velocity, the transparent band represents the SEM. The normalization was performed per subject, by dividing by the maximum absolute velocity of any of the six measurements (three respiratory conditions, each measured twice).