(09-20-2014, 04:00 PM)herbm Wrote: I also think those Pulse Ox tests are better than they are given credit -- there are some issues with them, but when we consider that WITHOUT low saturation events, OSA would probably be pretty irrelevant.
Again, they aren't perfect but they are PROBABLY all that would ever be needed by 99% of the people out there. If you have a lot of desaturations, get a machine, if not (and your symptoms aren't noticeable) what could a machine do?
That's a common misconception, but it's wrong. Your 99% number is WAY too high.
Even with no O2 desats at all, apnea can cause a lot of physiological effects in your body.
Apnea can disturb your sleep. Some people get no REM sleep at all. Some may only get certain stages of sleep. Some are disturbed so often during the night, they're semi-conscious, but it's almost like not sleeping at all.
Imagine how you'd suffer if someone slapped you awake every time you dozed off for several nights. That's one way they torture people.
When you have an apnea, your brain eventually panics. Your heart races. Your glands release adrenaline and other stress hormones. Your heart races. Your blood pressure jumps up. Your breathing muscles start fighting to breathe. Your brain has a psychological response. You may wake up, or at least change sleep stages.
Eventually, you "arouse", get some air and the apnea is over. However, the hormones are still there. Your brain is still disturbed. Your BP and pulse are still elevated.
Some apneacs arouse and start breathing before their SpO2 drops, but there are still a lot of potentially harmful effects of sleep apnea. You don't have to have O2 desats to increase your risk of high BP, stroke, etc.
Doctors tend to emphasize O2 desaturation because it's easy for the apnea patient to understand. It's not the only thing to worry about, maybe not even the most damaging for many patients.
An overnight oximetry is a useful thing because it may give a strong indication of sleep apnea. It's not definitive. It's useful for screening. It's dangerous to assume a good overnight pulseox means you don't have apnea.
Think of an oximetry test as being like snoring. If someone knows they snore, there's a really good chance they have apnea. However, some apneacs don't snore. It would be dangerous to assume no snoring means no apnea.
There are other indications of apnea such as tiredness or not being able to sleep. Quite a few severe apneacs don't have these symptoms.