Out of interest, does using an auto CPAP increase your tidal volume?
I have only been using an auto machine for three days and now that I can see my data (at long last!) I see my tidal volume is increasing slightly.
Pretty sure my sleep has increased as well by about an hour since changing machines (S8 escape to S9 autset).
To the extent that positive pressure can open airways, it may help a bit with tidal volume. Bilevel therapy and to some extent EPR (exhale pressure relief) can definitely increase tidal volume by increasing pressure during inhalation and decreasing pressure during exhale. The ability of bilevel to improve ventilation is one of the strategies used for patients that require that benefit.