1/13/2010 09:23:00 AM

How good is End Tidal CO2 monitoring?

The following is the definition per Wikipedia "Capnography is the monitoring of the concentration or partial pressure of carbon dioxide (CO2) in the respiratory gases. Its main development has been as a monitoring tool for use during anesthesia and intensive care. It is usually presented as a graph of expiratory CO2 plotted against time, or, less commonly, but more usefully, expired volume. The plot may also show the inspired CO2, which is of interest when rebreathing systems are being used.

The capnogram is a direct monitor of the inhaled and exhaled concentration or partial pressure of CO2, and an indirect monitor of the CO2 partial pressure in the arterial blood. In healthy individuals, the difference between arterial blood and expired gas CO2 partial pressures is very small, and is probably zero in children. In the presence of most forms of lung disease, and some forms of congenital heart disease (the cyanotic lesions) the difference between arterial blood and expired gas increases and can exceed 1 kPa.

During anesthesia, there is interplay between two components: the patient and the anesthesia administration device (which is usually a breathing circuit and a ventilator or respirator). The critical connection between the two components is either an endotracheal tube or a mask, and CO2 is typically monitored at this junction. Capnography directly reflects the elimination of CO2 by the lungs to the anesthesia device. Indirectly, it reflects the production of CO2 by tissues and the circulatory transport of CO2 to the lungs.

When expired CO2 is related to expired volume rather than time, the area beneath the curve represents the volume of CO2 in the breath, and thus over the course of a minute, this method can yield the CO2 minute elimination, an important measure of metabolism. Sudden changes in CO2 elimination during lung or heart surgery usually imply important changes in cardiorespiratory function."

Capnography has been an up and coming measure of function in the human body for some time now though it has gradually become more frequently used as technological advances permit it and as we learn how incredibly valuable it can be as a tool to predict, before it presents outwardly, what is going on at the cellular level and overall as well. It should be noted that Capnography is of greatest value when both good wave form and numeric readout are used. It has been my experience that how useful this is to us in the prehospital environment is largely the result of how knowledgeable we are about Capnography as well as our ability to accurately interpret the wave forms and the numeric readings too.
Generally speaking the care provider can get a very good picture of what is happening in their patient, with respect to perfusion and function at the cellular level. We all should know and understand that without adequate perfusion and function at the cellular level, our patients will not do well. Our ability to accurately recognize not only what is happening but WHY it is happening is the first step in correcting the prevailing issues. Surely nobody can argue that the single most important attribute of any care provider is Good Assessment. It is with this thought in mind that that I suggest we in the care provider professions aggressively pursue and become proficient at using Capnography. Of the many avenues available to us that assist us in diagnosing the issues with our patients Capnography is probably one of the best tools to help us get ahead of the curve and stay there. It should go without saying that this is also in the best interests of those that call for our service.
I was first advised of Dr. Baruch Krauss, MD many years ago who at the time (and I believe this is still true) a very well informed and strong advocate of Capnography. More about Dr. Krauss by following this link. http://www.childrenshospital.org/cfapps/research/data_admin/Site2625/mainpageS2625P0.html
I had the benefit of viewing some of his lectures on Capnography and was amazed at the wealth of information that could be gleaned from this technology.
If you are interested in being a great care provider, I would strongly encourage you to do some research on capnography. Become proficient and see the remarkable results.
For more information as provided by "Capnography.com" check out the following link; http://www.capnography.com/outside/911.htm and here too is search results that also has a lot of additional information.
Google Search Results for Capnography

Thank you for your time. Stop by my website at www.rcmedic.com

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