Although I'm no longer in ITU, we had Maquet Servoi. We have some still in paediatrics for which I am partly responsible for. They are extremely reliable and very low maintenance. PPM is a doddle. The built in Pre-use test is also the complete post repair / service test procedure and takes 2-3 minutes.
We used to have them, total nightmare! Constantly failing requiring main boards and software uploaded. The nebuliser driver was a frequent fail and as it was part of the above, big bucks to repair. The patient circuits kept failing too.
Then, we bought Drager Evita XL's and the phones stopped ringing at last! No faults, very basic pm once a year. Sorted..