Jugular and Portal Vein Volume, Middle Cerebral Vein Velocity, and Intracranial Pressure in Dry Immersion

BACKGROUND The objective was to determine if short term exposure to dry immersion (DI) results in a cephalic fluid shift similar to what has been observed with spaceflight. METHODS Data were collected from 10 individuals at rest and during the first 2 h of dry immersion. Jugular vein (JV), portal vein (PV), and thyroid volume were measured using 3D echography. Middle cerebral vein velocity (MCVv) was determined using transcranial Doppler ultrasound. The cochlear response to audio stimulation was used to derive an estimate of intracranial pressure (dICP). RESULTS After 2 h of DI, there was a significant increase (mean ± SD) in JV (2.21 ± 1.10 mL), PV (1.05 ± 0.48 mL), and thyroid (0.428 ± 0.313 mL) volume. MCVv was also significantly increased with DI (3.90 ± 5.03 cm · s-1). There was no change in dICP with DI in part due to large individual variability. The range of dICP changes appeared to be related to MCVv, with participants with the largest increase in MCVv also showing increased dICP. DISCUSSION The results suggest that DI induces a significant cephalic fluid shift similar to what is observed with spaceflight. The increased thyroid volume suggests that cerebral tissue may also be subjected to similar fluid filtration, with implications for changes in intracranial pressure. However, despite all participants having an increase in JV and thyroid volume, only half showed an increase in dICP, suggesting that increased venous pooling alone is not sufficient to cause increased intracranial pressure.Arbeille P, Avan P, Treffel L, Zuj K, Normand H, Denise P. Jugular and portal vein volume, middle cerebral vein velocity, and intracranial pressure in dry immersion. Aerosp Med Hum Perform. 2017; 88(5):457-462.