• cephalic
• pressure

Cephalic fluid shifts occur with exposure to microgravity and is associated with minor subjective discomfort resulting from tissue swelling (increased blood volume) including the nasal mucosa - precipitating ‘space sniffles’. However, recently a number of astronauts upon return from long duration ISS missions have been identified to have occular damage indicative of increased intra-occular pressure (IOP) and suggestive of intra-cranial pressure (ICP) elevation.
Chronic ICP and IOP elevation is associated with cognitive decline (dementia) and occular pathology (including glaucoma) respectively.
Whilst fluid shifts associated with re-orientation and/or microgravity have been modelled for various anatomical compartments, the head has been relatively neglected. This in part relates to the complexity of the tissues and their pressure-flow relationships which is compounded by the paucity of appropariate non-invasive measurement techniques.
The determinants of ICP and IOP are particular unclear. We seek to test the hypothesis that non-invasive (infrared) recording of nasal mucosa blood volume (Rhinolux, Rhinos, Germany) may act as a predictor of ICP and IOP.
Thus, we sought to model pressure-flow-volume relationships in various head compartments ultilizing multiple 5-element Windkessel models developed in MATLAB run and within Simulink (MathWorks, USA).
Having created a model that was consistent with published data we sought to test its validity in predicting nasal blood volume changes associated with rapid 60° head up tilt and 10° head down tilt from concurrent arterial blood pressure, stroke volume, cardiac output and total peripheral resistance (Finometer, FMS, Netherlands).
Thus, our aim is to validate non-invasive recording of nasal mucosa blood volume as a potential proxy of IOP and ICP within a constrained cephalic fluid shift model.