Oxygen is vital to many organs and performance of physiological functions; the brain requires about 20% of the body’s oxygen supply which is met by the blood. When deprived of oxygen the brain can’t metabolize glucose and convert it into energy leading to localized injuries or lasting brain damage depending on the duration of hypoxia.
Effects of hypoxia on the brain have been extensively studied, while the effects of hyperoxia have not, leading the researchers from the University of Alberta to anesthetize naturally sleeping rats and administer high levels of oxygen to them, while using electroencephalography to record brain wave pattern to interpret effects.
When comparing effects of different levels of oxygen increasing the amount of oxygen by 100% prolonged the time rats spent in SWS, while in this state animal heart respiration rate decreased. When carbon dioxide was introduced and concentration was increased to 5% the animal’s time in SWS decreased; reducing oxygen concentration also caused a steady decrease of time spent in SWS. When lowered to less than normal levels animal brains were observed to remain in active sleep; doing this right after hyperoxia resulted in a rebound effect which caused the brain to go back into SWS for a longer duration afterwards. This was considered to be an favorable discovery as it further demonstrated elevated oxygen levels can encourage the brain to remain in or revert to deep sleep. Findings are believed to highlight clinical potential of oxygen therapy to help people with sleeping disorders get enough sleep.
SWS is known as stage 3 and 4 non-rapid eye movement sleep that is characterized in EEG by slow high voltage delta waves. Slow wave sleep is part of NREM, it is a dreamless sleep where eye movement, breathing, and heartbeat are relatively stable and quiet. REM sleep is active sleep where dreaming occurs typically accompanied by rapid eye movement, vocalizations, body movements, and irregular breathing.
Humans in the state of SWS are said to be in deep, restorative sleep as SWS is known to promote brain recovery and restoration, as well as playing a role in memory consolidation. Staying in slow wave sleep for a longer period of time may be beneficial to brain health for these reasons. “This seems to be the stage where metabolites are cleared from the brain, muscles grow, and proteins reform,” according to the researchers.
