Right now this results in slightly confusing graphs, since sometimes
the IPAP/EPAP data for a machine is primarily reported by its settings
events, and for other machines by its statistics events. Also, the
"average" pressure on F0 looks like it might be effectivley EPAP in
single-pressure mode rather than the true average in bi-level mode.
Once we decide on the best presentation, we can either update the importer
or the display to show the most helpful channels for a given session.
