Who's woken me up!
Now let me see ...
Don't do it! Remember your schoolboy Physics (damned if I can, did I do Physics?). Fill the space in your keg with 100% Nitrogen and the 100% Carbon Dioxide dissolved in your beer will think ... "I'm not having that" ... and will start coming out of solution in an attempt to make the concentration in solution comply with the concentration of CO2 in the space above, i.e. equilibrium in accordance with the laws of partial pressure and ...

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I know ... let's just say 'the beer'll go "flat"'? At which point you won't want to wait for your wife to do the job and you will top yourself.