Mapleson capnograms

Capnography can help titrate the appropriate fresh gas flow when using a Mapleson breathing circuit, and can indicate a leaking or detached fresh gas hose.
(A) With very high fresh gas flow rates, there may be little or no rebreathing and the capnogram will look "normal". However, the fresh gas flow is higher than it needs to be in this case.
(B) When the fresh gas flow is optimal, there will be some inspired CO₂, but the end-tidal CO₂ will be normal with modest hyperventilation. The distinctive shape shown in panel B is from a Mapleson D (Bain) circuit, where fresh gas is inhaled followed by some exhaled gas.
(C) When the fresh gas flow is too low, or when the fresh gas hose is broken or disconnected, there will be high inspired CO₂ and no amount of hyperventilation will prevent hypercarbia.