Your respiratory drive is related to things other than just low oxygen levels. There is a pacemaker in your medulla that integrates a bunch of data, including carbon dioxide levels, strain, airway narrowing, lung expansion etc.For instance with OSA there are often respiratory effort-related arousals (RERAs) caused by partial airway obstruction. These increase the effort needed to take a breath, but do not cause hypoxemia. They do cause awakening because of the increased work of breathing and the muscle strain sends and alarm signal to higher centers involved in the sleep-wake cycle.So oxygen doesn't cure sleep apnea because this isn't the only reason that there are awakenings. In addition if there is complete airway obstruction then no amount of oxygen is going to help.
Right, so basically you're suggesting that the fact that I am noticing improvement despite feeling sleepy can be accounted for by my sleep deprivation being nonetheless less severe in comparison to before I got started on CPAP, even if I haven't been sleeping well for other reasons recently? That can make sense.Are Spo2 drops to the level that I described harmful to the brain? How about the effects of CO2 buildup itself (independent of the fact that it causes you to wake up periodically)?