Fig. 1

Observed intracranial air volumes and simulated ICP changes. These represent the observed post-surgery intracranial air volumes, with simulated decrease in cabin pressure (to 0.74 atm or 8000 ft altitude) during flight ascent. In (a), starting ICP is 5 mmHg. A clinical treatment target of ICP under 20 mmHg is shown as the red line on the ICP axis. Even with low starting ICP, one can note that with larger starting IC air volumes, ICP is expected to rise quickly even during early flight phases (climbing to cruising altitude). In (b), the starting is ICP 10 mmHg. It is notable that in this model, when there are larger amounts of air, and with ‘ascending’ altitude, that the estimated intracranial pressure rises quite quickly, within the first 3000 ft ascent. In (c), the starting ICP is 15 mmHg. With higher starting ICP, even subjects with small amounts of intracranial air volume can have air expansion and intracranial pressure increases well above a safe level of 20 mmHg