This here graph looks like what -SWS described as "breath stacking". Maybe some of you can confirm or correct that appellation. There's a nice French word so brain_trust will drool instead of being irritated. Note the flow graph at the bottom. During the inhale phase, there are two peaks with a zero between and no exhale, so I think it is breath stacking. And for those of you not used to reading my charts (why, that would be everybody but me), this occurred right at the start of the first REM period for the night. (See the Tidal Volume for REM identification. Don't need no stinking Zeo with a chart this clear.)

If you have an example like that, or another oddball graph, post it.