Quarterly QA Audits...Help Please

In your agency does the individual staff audit a complete chart on a quarterly basis or do they just audit the area they are involved with. For example does the Physical Therapist audit nursing, Speech etc (the complete chart)or do they just audit the Physical Therapy care plans, notes etc.. This in a big area of debate in our agency right now and as I've never worked anywhere else I would love some feedback as to how other agencies manage this and what is considered compliant with the conditions of participation.. Thanks!