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Purpose: To investigate the impact of continuous positive airway pressure (CPAP) applied by a full-face fitted mask at 15 cmH₂O on total cerebral blood flow (tCBF), jugular venous flow (tJVF) and cerebrospinal fluid (CSF) flow.

Materials and methods: Axial 2D phase-contrast MRI measurements were acquired at the C2–C3 vertebral level for 23 healthy male awake subjects at baseline (without) and with CPAP applied. CSF flow was quantified within the spinal subarachnoid space and tCBF was quantified based on the summation of blood flow within the left and right internal carotid and vertebral arteries. tJVF was quantified based on the summation of blood flow within the left and right jugular veins. Heart rate, transcutaneous carbon dioxide (PtcCO₂) and oxygen saturation were continuously monitored during the MR protocol.

Results: CPAP decreased the pulse amplitude (PtPPA) of tJVF by 21% (p = 0.004). CSF stroke volume (SV) and PtPPA also decreased by 20% (p = 0.003) and 15% (p = 0.005), respectively. Change in tCBF SV and PtPPA was not significant. However, the timing of maximum systolic tCBF occurred significantly earlier under CPAP. CSF flow and tJVF waveforms showed significant spatial and temporal differences in waveform feature points, and spectral analysis revealed a decrease in the first harmonic of tJVF under CPAP (p = 0.001). Under CPAP, a 5% decrease in PtcCO₂ (p = 0.003) and 9% increase in HR (p = 0.006) were measured. However, these HR and PtcCO₂ changes were not correlated with any changes in arterial, venous or CSF flow dynamics.

Conclusion: Application of CPAP via a full-fitted mask at 15 cm H₂O was found to have a significant effect on intracranial venous outflow and spinal CSF flow at the C2 vertebral level in healthy adult-age awake volunteers. CPAP can be used to non-invasively provoke changes in intracranial and CSF flow dynamics.