Respiration related question -UNI

[Physiofriend]

Don't really know where to start with this past paper question. Any tips would be appreciated.

Describe what you would expect to observe and what you might record in the circumstances below:

A healthy adult is switched, just after normal expiration, from breathing air to rebreathing in and out of a bag which initially contains 6L of 100% oxygen.

He is switched, just after normal expiration, from breathing room air to rebreathing in a closed circuit from a spirometer which incorporates a CO2 absorber on the expiratory side. The spirometer initially contains 6L of air.