White Mountain Expedition 2019: Peaks and Valleys - Oscillatory cerebral blood flow at high altitude




Rickards, Caroline
Anderson, Garen K.
Barnes, Haley
Rosenberg, Alexander
Bird, Jordan
Pentz, Brandon
Byman, Britta
Jendzjowsky, Nicholas
Wilson, Richard
Day, Trevor


0000-0002-1013-3478 (Anderson, Garen K.)

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An oscillatory pattern in cerebral blood flow (at ~0.1 Hz) protects cerebral tissue oxygen saturation (ScO2) under conditions of cerebral hypoperfusion. In this study, we hypothesized that inducing oscillations in cerebral blood flow at 0.1 Hz would protect cerebral blood flow and ScO2 during exposure to combined simulated hemorrhage and sustained hypobaric hypoxia. Eight healthy human subjects (4 M, 24.7 ± 4.1 y; 4 F, 34.3 ± 8.3 y) participated in two lower body negative pressure (LBNP) experiments (simulating hemorrhage) at high altitude (3800 m): 1) 0 Hz control condition (CTRL) and 2) 0.1 Hz oscillatory LBNP (OLBNP) condition. Measurements included internal carotid artery (ICA) blood flow via duplex Doppler ultrasound, middle cerebral artery velocity (MCAv) via transcranial Doppler ultrasound, and ScO2 via near-infrared spectroscopy. Mean MCAv waveforms were fast Fourier transformed to verify oscillations were generated at ~0.1 Hz. Low frequency power (0.07-0.15 Hz) in mean MCAv increased during OLBNP vs. CTRL (P = 0.02). OLBNP did not protect ICA flow (OLBNP: -32.5±4.5 Δ%; CTRL: -19.9±8.9 Δ%; P = 0.18) or mean MCAv (OLBNP: -18.5±3.4 Δ%; CTRL: -15.3±5.4 Δ%; P = 0.58), but ScO2 was protected (OLBNP: -0.67±1.0 Δ%; CTRL: -4.07±2.0 Δ%; P = 0.004). These results support our hypothesis that inducing oscillatory blood flow leads to protection of cerebral tissue oxygenation, despite no differences in ICA blood flow or mean MCAv. Overall, these data suggest that therapies using oscillatory perfusion may help preserve cerebral tissue oxygen saturation under conditions of reduced oxygen delivery.