Preventing an apache mpm prefork from disk trashing

Hello

I have a wordpress blog running with apache in prefork mode ( all debian
packages ) I have noticed that by traffic peaks ( think reddit ), Apache
starts to swap heavily becauses it creates too much processes according
to the RAM of the machine.

I have been thinking of reducing MaxClients so that MaxClient * ResRAM
apache process < RAM of the server.

Is that the correct way to treat this problem ?

I know there nginx + fastcgi but I am not there yet :)

Emmanuel