Yes, positive pressure vent will increase CVP around 3-5 mm H2O. I will explain why this occurs as best I can. When a spontaneously breathing person inhales, the pressure in the lining around the heart and the lungs (pericardium and pleura) decreases, and these pressures affect the pressure in the right atrium, making it less. This is the opposite when we give a positive pressure breath; we are raising these pressures as we deliver a breath to the patient. In both patients, the pressure at the end of exhalation is around that of the atmosphere, so the patient can exhale the breath. This is why that's the best time to take a CVP pressure. Our facility policy is to disconnect during the reading, unless otherwise ordered for this reason. You also want to look at the patient's trend over time, not just one isolated reading. There are a lot of other things that influence a patient's CVP (ex- how well the right side of the pt's heart works, how compliant the heart is), this is just one thing that does.