Network oscillatory dynamics accompany cerebral bioenergetic defence in hypoxia.
A network physiology framework investigated how coordinated interactions among multiple organ systems collectively support the preservation of cerebral bioenergetic function and better distinguish adaptive from maladaptive responses to hypoxia. Twelve healthy males were passively exposed to 6 h of normoxia (21% O2) and hypoxia (12% O2) in a randomised, single-blind, crossover design. Venous blood was assayed for oxidative-nitrosative stress (OXNOS, spectroscopy/chemiluminescence) and neurovascular unit (hs-ELISA) biomarkers. Global cerebral delivery of O2 and glucose were determined by duplex ultrasound. Clinical acute mountain sickness (AMS+) was diagnosed in five participants. Cerebral substrate delivery was well maintained in both hypoxia and AMS+ (p < 0.05 vs normoxia and AMS-) despite marked arterial hypoxemia. Bioenergetic defence coincided with pronounced elevations in the spectral amplitude and phase synchronisation of very low-frequency oscillations (VLFOs, 0.03-0.06 Hz), which were evident across multiple organ systems and most prominent within the cerebral network. Systemic VLFOs were further exaggerated and more functionally connected in AMS+ in the absence of exaggerated systemic OXNOS or structural damage/destabilisation of the neurovascular unit (both p < 0.05 vs normoxia and AMS-). Collectively, these findings suggest that AMS, while characterised by debilitating symptomatology, may reflect a neuroprotective adaptive as opposed to pathologically maladaptive phenotype.