Key result
Mild hypoxia reduces prefrontal oxyhemoglobin ~38% while increasing very low frequency oxygenation oscillations.
Why the study?
The study was designed to investigate the effects of mild cerebral hypoxia on haemoglobin oxygenation, cerebrospinal fluid dynamics, and cardiovascular physiology.
Does mild poikilocapnic hypoxia alter haemoglobin oxygenation oscillations and subarachnoid space width in healthy volunteers?
Does mild poikilocapnic hypoxia alter haemoglobin oxygenation oscillations and subarachnoid space width in healthy volunteers?
Mild poikilocapnic hypoxia increases very low frequency prefrontal cortex haemoglobin oxygenation oscillations and decreases subarachnoid space fluctuations, suggesting local brain mechanisms adapt to mild hypoxia.
Should not change practice; leaves open cerebral oxygenation dynamics in hypoxia for prospective validation.
The aim of the study was to investigate the effect of mild cerebral hypoxia on haemoglobin oxygenation (HbO2), cerebrospinal fluid dynamics and cardiovascular physiology. To achieve this goal, four signals were recorded simultaneously: blood pressure, ECG, HbO2 from right hemisphere and changes of SAS width from left hemisphere. Signals were registered from 30 healthy, young participants (2 females and 28 males, BMI = 24.5 ± 2.3 kg/m2, age 30.8 ± 13.4 years). We analysed the recorded signals using wavelet transform (WT). We demonstrated for the first time that in healthy subjects exposed to mild poikilokapnic hypoxia that there were increases in very low frequency HbO2 oscillations (< 0.052 Hz) in prefrontal cortex. Additionally, SAS fluctuation diminishes in the whole frequency range which could be explained by brain oedema. Consequently the study provides insight into mechanisms governing brain response to a mild hypoxic challenge. Our study supports the notion that HbO2 and SAS width monitoring might be beneficial for patients with acute lung disease, including SARS-CoV-2.
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Gruszecka et al. (2021) studied Healthy volunteers (n=30). Mild poikilocapnic hypoxia vs. Normal room air (19.8% O2) was evaluated on Relative changes in prefrontal cortex oxyhaemoglobin (HbO2 RIGHT) [%O2] (p=<0.001). Mild poikilocapnic hypoxia significantly decreased overall prefrontal oxyhaemoglobin levels (0.45% vs 0.72%, p<0.001) while increasing very low frequency haemoglobin oxygenation oscillations.
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