Cerebral autoregulation index at high altitude assessed by thigh-cuff and transfer function analysis techniques

Area of Science:

• Physiology
• Altitude Medicine
• Cerebrovascular Regulation

Background:

• Cerebral autoregulation (CA) changes at high altitude are debated, partly due to varying assessment methods.
• Understanding CA is crucial for managing acute mountain sickness (AMS).

Purpose of the Study:

• Compare two common dynamic CA assessment methods at high altitude.
• Investigate if CA is impaired during ascent to 3424m and acclimatization.

Main Methods:

• Studied 11 healthy sea-level residents ascending to 3424m over 13 days.
• Assessed dynamic CA using transfer function analysis (TFA) and thigh-cuff inflation.
• Monitored acute mountain sickness (AMS) symptoms.

Main Results:

• Thigh-cuff CA index (Cuff ARI) decreased significantly at high altitude (P=0.021).
• Transfer function analysis CA index (TFA ARI) remained unaffected by altitude.
• Neither CA method correlated with AMS symptoms.

Conclusions:

• High altitude may impair the brain's ability to buffer abrupt blood pressure changes.
• The capacity to regulate slow blood pressure oscillations appears preserved.
• Discrepancies highlight the need for multiple CA assessment techniques at altitude.