02-02-2016, 02:59 PM
(This post was last modified: 02-02-2016, 03:00 PM by PoolQ.)
Well this will be fun. IMHO it does not matter, because it is not exact. Let me try and explain.
When you are asleep it is not O2 that is the main concern, it is the CO2 that triggers everything. You do not want CO2 to build up in your system while you are asleep. Because of this the people that set limits on what an apnea is are trying to decide on when a person is most likely not clearing the CO2 from their system and not really when the airway is fully closed. Of course if the airway is fully closed you are not clearing CO2, but it does not have to be fully closed to not clear CO2.
Now how the heck did they figure what level they are going to use? They could have put masks on people, monitor their blood gases, and restricted their air flow. I doubt that. They could have gotten a group or people with known breathing issues and tested them at different times to see what was happening when their CO2 levels rose.
And then someone looked at all the data they got and put a margin of error on top of that and said "when sleeping, a reduction of air flow of xx% or more needs to be addressed"
They don't at this point care if it's obstructive or central, just that the restriction has reached the target level. They then decide if it's obstructive or central to figure what to do about it if anything and depending on what kind of machine they have, CPAP, APCP, BiPAP, ASV.
HOW what kind of apnea detected is with the pulses or pressure spikes. This has to do with impedance or the air way. So you have two cases 1) a long tube that is closed at the end and 2) a long tube with a fairly large drum at the end. If you try and increase the pressure in both of these cases you have 1) very little air to compress so the pressure rises quickly and 2) LOTS of air to compress so the pressure rises slowly if at all.
1) is obstructive (passage to the lungs is closed off)
2) is central (passage to the lungs is open)