I'v been searching hardly these past days in how to use CouchDB in the 2-tier, I haven't found a properly documented and useful resource (Doctrine's CouchDB ODM seems very vague I think), so the question is: How are you using CouchDB in your app, obfuscating the access to the users? I really don't think that is wise to use CouchDB on the first tier! I found some packages on Packagist but with little to none documentation about the usage.
I'd recommend checking out Sag: http://www.saggingcouch.com/
It's a deliberately simplistic PHP (with a matching JS) client library for interfacing with CouchDB. It doesn't (by design) provide ORM or extra "magic" preferring to give you simple access to the CouchDB API.
Hope that helps.