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.
Therefore, the hypoxic drive theory is debunked! And even if you are unconvinced that this is the case, the hypoxic drive only starts to theoretically be affected when the patientâs oxygen saturations are more than 90%. So if your COPD patient has low oxygen saturations, put oxygen on them until they have an oxygen saturation at least 90%.