In those cases, the spread between the bid & ask goes to the market maker as compensation for making a market in a stock. For a liquid stock that is easy for the market maker to turn around and buy/sell to somebody else, the spread is small (narrow).
In cerebral hypoxia, sometimes only the oxygen supply is interrupted. Brain cells are extremely sensitive to a lack of oxygen. Some brain cells start dying less than 5 minutes after their oxygen supply disappears. As a result, brain hypoxia can rapidly cause severe brain damage or death.
Your goal is to increase the amount of time it takes for the patient to become critically hypoxic (less than 70% oxygen saturation) in case there are problems with intubation.(3) In a 2010 study, apneic oxygenation was shown to increase the time until an obese patient started to become hypoxic by about 2.5 minutes.(4)