CA vs OA? How to tell?

Looking at my data in Sleepyhead, I'm wondering how the software knows whether an event is an OA or a CA? When I compare the flow rate chart of each, I don't see any significant difference. Both look like I stopped breathing, usually for 15-20 sec. How does it know/decide?

Here's an example. Event 1 is CA, 2 is OA:

Your Resmed S9 AutoSet uses the same FOT technique described in this document:
http://www.resmed.com/us/assets/documen ... -paper.pdf

Hence those short but squiggly lines you see in the graph above during your apneas.

nifty, thanks for the link.

i've felt the FOT pulsing before when playing w the machine by holding my breath. nice to know what it's for.