cvp (central venous pressure) monitoring comes under the category of hemodynamic monitoring. the central venous catheter is connected to a tall thin manometer. when a cvp reading is desired, the base of the manometer is held at the level of the atrium of the patient's heart. a stopcock on the iv line is turned so that the iv fluids are stopped and there is only connection between the manometer and the distal end of the catheter which is in the patient's right atrium. the pressure in the right atrium of the heart will cause iv fluid to backflow into the manometer and stop when it is equalized with the pressure in the right atrium. the nurse watches to see where the fluid level stays stationary in the manometer and is helped by a small ball floating at the top of the fluid in the manometer. this is the cvp reading. it is relatively easy to do. here are some sites that have information about central venous pressure (right atrial pressure) monitoring and the physiology behind this and what a cvp reading means:
does the patient have to be disconnected from the mech vent when taking cvp? because i see some nurses practice it and others don't. i once asked what the rationale behind that and i was told that the mech vent increases the cvp reading. i tried looking at the skills manual but there isn't anything mentioned there about disconnecting the patient from the mech vent while reading cvp. please enlighten me on this. thank you very much.
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.
In my ICU rotation we do not disconnect the patient from the vent when recording CVP, Instead, we just account for the vent adding about 3 mm Hg. Instead of the normal value being 4-7, we like it a little higher if the patient is on a vent. We record CVPs every hour and are mostly looking for the trend.
thank you so much live to learn and june 2009!!! i will ask our charge nurses if the normal range that we use is applicable to patients on mech vent.. if the values they use aren't adjusted, then i'd just disconnect when reading cvp unless contraindicated. thank you again!