White matter and hypoxic hypobaria in humans

Area of Science:

• Neuroscience
• Environmental Health
• Aerospace Medicine

Background:

• Occupational exposure to hypobaria (low atmospheric pressure) is linked to white matter damage and cognitive decline.
• Understanding the transient effects of hypobaric exposure on cerebral physiology is crucial for aircrew health.

Purpose of the Study:

• To investigate the transient impact of discrete hypobaric exposure on cerebral physiology in healthy aircrew.
• To determine if hypobaric exposure affects white matter integrity, cerebral blood flow, or neurochemical concentrations.

Main Methods:

• Compared 64 aircrew undergoing altitude chamber training to 60 controls.
• Measured cerebral blood flow (CBF), white matter fractional anisotropy, white matter hyperintensity volume, and neurochemicals at baseline, 24 hours, and 72 hours post-exposure.
• Utilized MRI and neurochemical assays to assess cerebral changes.

Main Results:

• Hypobaric exposure significantly increased white matter CBF at 24 hours post-exposure, with a non-significant trend at 72 hours.
• No significant changes were observed in structural white matter measurements or gray matter CBF.
• Higher baseline levels of neuroprotective neurochemicals (glutathione, N-acetylaspartate, glutamate/glutamine) correlated with smaller CBF changes.

Conclusions:

• Discrete hypobaric exposure causes transient alterations in white matter cerebral blood flow.
• Baseline neurochemical concentrations may modulate the cerebral response to hypobaric stress.
• This study provides a model for investigating white matter injury from occupational hypobaric exposure.