diver's position in the water

[FM1520]

When reading reviews on regulators sometimes they mention the performance in reference to the position of the diver - upside down. I don't understand how the position of the diver could make any difference in how a regulator will perform. Help me understand, thanks.

 

[USCScubaboy]

Here a link to another thread that deals with the issue.

Regulator breathes much harder when inverted [Archive] - ScubaBoard