Confirming backups

Ok, in a multimode couchDB distributed database si there anyway to get a consistent backup? I understand that if you take a backup on a specific node that when you recover that backup the other nodes will bring it up to speed, but, what about the case where something has contaminated the entire database with bad data and you want to restore to a point in time? Is there any way, without shutting down all the nodes but one, to take a consistent backup? Can you quiesce and resolve for example so everything is current? I have searched for commands to quiesce the database but haven’t found anything and also is there a command to force the db to be consistent for a given point in time?