So no idea what "Ao" (That's big A, little letter o) stands for, and neither does anybody I've asked.
It's sensor is attached to the the vent's tubing right before it hooks to the ett. It's a mostly flat line that has upward deflection in regards to breathing. We use it to determine where to average the CVP.
I figured the descriptors would help incase it's not referred to "Ao" elsewhere. I must have my curiosity satisfied! Thanks in advance