Changes in cerebral hemodynamics associated with interval hypoxia-hyperoxia in healthy volunteers

Intermittent hypoxia-hyperoxia (IHH) is considered a method for inducing an organ-protective phenotype and acute stress response. The effect of short IHH on cerebral blood flow remains poorly studied. Objective. To examine the short-term impact of intermittent hypoxia-hyperoxia on cerebral hemodynamic parameters using ultrasound data. Materials and methods. The study included 20 volunteers aged 60—74 years. Individuals in the study group (n=10) underwent IHH sessions, while those in the control group (n=10) received a placebo. Ultrasound examination of the cerebral vessels was performed before the first procedure and 24 hours after the last. Hemodynamic assessment was done at rest, during a hypercapnic test and after IHH using B-mode, color and pulsed wave Doppler mapping. All participants underwent magnetic resonance imaging and magnetic resonance angiography. Results. In the study group, two subgroups were identified: with a positive reaction (n=7; increase in the reactivity index (RI) to 1.3—1.4) and a paradoxical reaction (n=3; decrease in RI to 0.8—0.9). All participants experienced reductions in systolic and diastolic blood pressure and heart rate; venous and central venous pressure remained unchanged. In a positive reaction, a statistically significant increase in the venous outflow velocity was observed, while in a paradoxical reaction, a decrease was noted. Arterial inflow parameters did not change significantly, and RI remained positive. No changes in the studied indicators were detected in the control group. Conclusion. Intermittent hypoxia-hyperoxia improves venous outflow in the majority of elderly patients without severe somatic pathology. Short-term assessment of the impact of this method on cerebral hemodynamics may be important for monitoring during intermittent hypoxia-hyperoxia sessions.