[IPVI]
Non-invasive assessment of intracranial pressure for space flight and related visual impairment

RESEARCH OVERVIEW

• Very recently, medical doctors found that some crew members on the ISS seem to be at risk for impairments of the eye (e.g. optic disc edema). This may be due to elevations in intracranial pressure induced by long-duration spaceflight. This experiment investigates “intracranial pressure" on crew members, by using multiple indexes that can be obtained non-invasively.
• Non-invasive assessment of intracranial pressure for space flight and related visual impairment (IPVI for 1YM) non-invasively estimates the changes in intracranial pressure and brain circulation before, and after long-duration spaceflights, by analyzing the “arterial blood pressure waveform” and the “brain blood flow waveform". In addition, the investigation team hopes to confirm that abnormalities of the eye occur among the crew members whose intracranial pressure has increased.
• The major impact of this research seeks to advance the understanding of human pathophysiology during spaceflight. Moreover, it is hoped that this investigation method leads to a screening examination for elevated intracranial pressure on crew members. The non-invasive method may be appropriate for the monitoring of space-related intracranial alterations, and can be used for preventing visual impairments (e.g. optic disc edema).

DESCRIPTION

The primary objective of the Non-invasive assessment of intracranial pressure for space flight and related visual impairment (IPVI for 1YM) is to non-invasively estimate the changes in intracranial pressure and cerebral circulation induced by long-duration spaceflight, by analyzing the arterial blood pressure (ABP) and the cerebral blood flow velocity (CBFV) waveforms before and after long-duration spaceflight. In addition, the research team seeks to confirm that abnormal visual function and/or ocular structure (e.g. optic disc edema) occurs among the subjects whose intracranial pressure has increased.

The Investigators have reported changes in cerebral autoregulation by analyzing ABP and CBFV in middle cerebral artery by non-invasive ABP monitor, and transcranial Doppler sonography during a variety of environments, including spaceflight. Recently, an analysis method was developed by using high resolution waveforms, with increased sampling frequency, to estimate intracranial pressure. Intracranial pressure can be estimated non-invasively by this method.

Before and after ISS-flight, ABP and CBFV waveforms are recorded simultaneously in a supine position at rest and/or while doing a 15 sec Valsalva maneuver. The analysis of changes in intracranial pressure and cerebral circulation are performed offline.

Currently, this is the only study that relates to optic disc edema looking at “intracranial pressure”, by using non-invasively obtained multiple indexes. It is hoped that this study method leads to the development of a screening examination. The non-invasive methods developed and validated during space flight of six months will most likely be found appropriate for the monitoring of space-related intracranial alterations.

SPACE APPLICATIONS

Recent studies have shown some crew members on the ISS experience swelling of the optic nerve, which can affect their vision. This may be because of elevated intracranial pressure, or pressure inside the head, which happens in microgravity. The investigation aims to confirm that eye abnormalities, such as swelling of the optic nerve, happen in crew members whose cranial pressure has increased. The investigation’s non-invasive measurement methods could be used for early detection of this pressure change.

EARTH APPLICATIONS

Physicians currently use invasive procedures to measure intracranial pressure, including inserting a needle in a person’s spine. The IPVI for 1YM investigation uses a non-invasive method instead, gauging intracranial pressure by combining arterial blood pressure and brain blood flow. Results from this investigation can benefit patients on Earth who need to be tested for high intracranial pressure, or who need other measurements for ailments such as fluid on the brain, brain swelling, or low intracranial pressure.

OPERATIONAL REQUIREMENTS AND PROTOCOLS

Constraints for subjects:

• Crews whose ABP and CBFV wave form can be measured (check at screening or #1pre-BDC)
• No maximal exercise including VO2 Max, and NBL within 12 hours before each BDC session.
• More than 6 hours should elapse after nitroglycerin, and more than 1 hour should elapse after catecholamines, etc.
• No caffeine, nicotine, or alcohol for 12 hours prior to testing.
• No heavy meals within last 4 hours. Light snack of complex carbohydrates are OK within 2 hours of testing.
• Other medicine and exercise logs of subjects for 6 hours prior to testing are required if acceptable.