What is a Capnometer?

Jamie M. Burkitt, DVM, DACVECC, assistant professor of clinical surgical and radiological sciences at the University of California, Davis, explains what a capnometer is and a few its most common uses.

"A capnometer evaluates end-tidal carbon dioxide concentration or partial pressure. So basically it tells you how much carbon dioxide you're exhaling. The thing that's tough about this technology, is that for the most part a patient has to have an endotracheal tube in place and actually be intubated in order to get that information on your capnometer. End-tidal co2 can of course be used to monitor ventilation in a patient who is under anesthesia but it also has a huge role during CPR.

So during CPR, we actually use it as a monitor of pulmonary perfusion in that animals that are receiving chest compressions as the way that they are moving blood around their circulation, if you are not moving very much blood not very much new carbon dioxide is being delivered to the lung, and so the carbon dioxide value that comes out—the amount of carbon dioxide that comes out that's sampled by your capnometer equipment—that co2 is going to be quite low. But if you are doing really effective compressions and you have really nice blood flow through your lungs, then you're gonna get a higher and higher co2 as that carbon dioxide comes back from the tissues to the right side of the heart and through that pulmonary circulation. So while in the alive animal under anesthesia where oftentimes using a co2 to evaluate ventilation, so how well an animal is ventilating, while they are undergoing CPR we're actually evaluating the efficacy of the team's compression efforts. So it's a really valuable tool that way."