Hello fellow ventilator and anyone else in the ventilator business that can shed some light on this issue...

I live in a developing country,and I work as a designer for ventilator.As I has worked in this career at most one year,I am not unfamiliar with press support.As my unstanding,i had made use of a test lung accomplishing PSV,but when I change another test lung that the compilance is different,the press platform is disappear.I think I had not find a good arithmetic for psv,please help me!!!
another, please introduce some webs about ventilator to me!!!

I am looking for different attitudes and practice guidelines for psv as well as any reference to valid studies using PSV .
my email: captainyan@etang.com
Your help is greatly appreciated!