Hemoglobin exists to carry oxygen from lungs to cells throughout the body. If a patient inhales carbon monoxide, the hemoglobin will be VERY much more likely to latch on to the CO rather than the oxygen and VERY reluctant to let go of it. Therefore saturation levels would be low. Same with apnea, levels would be low because there is no air getting into the lungs and therefore no oxygen is getting into the bloodstream. Cells need oxygen, there are even 'cerebral oxygen monitors' in hospitals to detect low brain oxygen promplty.
Young men suffer a greater damage than do older men.
I really feel the Polysomnography Report I received after my first sleep study was difficut to interpret so I can relate to your questions. I asked for explanations but so much information was flying back and forth that I had difficulty keeping it all straight. My report says I have severe sleep apnea in excess of 1 event per minute with events longer than 50 seconds. I guess my point is that perhaps it's a good idea to ask for copies of all reports - they can come in handy after the fact. It's also helpful to be able to compare reports if you have additional studies.