Look at three of the four deepest drops in the ox line - drop 1, 2 and 4. Just before each of these drops, you see a drop in pulse measurement. When you are TRULY having an apnea, your pulse will go up, not down. Your pulse measurement is probably dropping due to a loss in contact as Pugsy explained. Then immediately following, the ox measurement catches up and records a drop.
I am not a fan of patient analyzed pulse-ox reports for two reasons. One, you get this kind of confusion and fretting because the patient does not know how to read the report. Two, a good pulse-ox report does not mean the patient is cleared of having a very unhealthy sleep-disordered breathing (SDB) condition ---->
Pugsy wrote: pulse oximetry reports aren't alarming but that doesn't mean that there's no sleep apnea or no sleep disordered breathing. All it means is that the oxygen levels aren't alarming. We can still have sleep breathing problems or arousals that can cause problems without there being any alarming drop in oxygen levels.
One of those situations where a negative pulse ox report doesn't mean no problems...just means the oxygen levels aren't alarming...and further evaluation in other areas possibly needs to be done.