Cognitive Performance During Acute Hypoxia Is Associated with Cerebral Oxygenation and Blood Flow.

INTRODUCTION

Acute hypoxia can impair cognitive performance, yet the underlying systemic and cerebral physiological mechanisms remain unclear. The objective of this study was to elucidate the systemic and cerebral physiological responses associated with changes in cognitive performance during acute hypoxia.

METHODS

There were 11 healthy subjects (5 females) who completed a cognitive test during baseline normoxia (21% fraction of inspired oxygen, FIO2) followed by 2 randomized hypoxia trials: 11.8% FIO2 (moderate hypoxia) and 7.7% FIO2 (severe hypoxia). Subjects were instrumented with an arterial catheter, transcranial doppler ultrasound, and near-infrared spectroscopy to measure systemic (arterial O2 saturation) and cerebral oxygenation (cerebrovascular conductance and cerebral tissue saturation).

RESULTS

Moderate hypoxia reduced arterial O2 saturation and cerebral tissue saturation, with no change in cerebrovascular conductance. Severe hypoxia decreased arterial O2 saturation, cerebrovascular conductance, and cerebral tissue saturation. Cognitive performance did not differ from baseline during either hypoxia condition (omission rate, errors/min: baseline 0 ± 1 vs. moderate hypoxia 1 ± 1; baseline 1 ± 1 vs. severe hypoxia 1 ± 1). No associations were observed between physiological changes and cognitive performance during moderate hypoxia. During severe hypoxia, smaller declines in arterial O2 saturation (r = 0.643) and greater declines in cerebrovascular conductance (r = -0.651) were associated with increased omission rates.

DISCUSSION: Cognitive performance during acute severe hypoxia correlated with cerebral oxygenation and blood flow. Associations differed between moderate and severe hypoxia, suggesting that both duration and severity of hypoxia influence the relationship between physiological responses and cognitive performance.