One of my favorite tools in the field is capnography. This technology has been around since the 1970s and has been used in operating rooms by anesthesiologists as a standard of care since 1991. EMS has taken this technology and incorporated it into the prehospital setting with more uses than just endotracheal tube (ETT) placement confirmation - although, initially, that was its primary purpose for paramedics. What is so amazing about this tool is that it not only gives you feedback on the ventilatory status of your patient, if you understand the physiology of the body, you can interpret their circulatory and metabolic processes as well.
In short, capnography gives you feedback on ventilation, circulation AND the metabolic status of your patient. And it does so, continuously, immediately, basically… breath for breath!
This picture shows the "normal" waveform of a capnograph.
With capnography, you can recognize if either metabolism, circulation, or ventilation changes - and you will note it before blood pressure or oxygen saturation variations occur. Heck, we can even tell when return of spontaneous circulation (ROSC) occurs during a cardiac arrest with this tool. And now, research is suggesting it can be used as a noninvasive diagnostic tool for metabolic emergencies such as gastroenteritis, diabetic ketoacidosis and more.
To sum up this “new topic” that I will dedicate a few posts to, start by knowing that capnography is simply the measurement of exhaled carbon dioxide. Today’s technology provides a numerical value and a waveform that is important in the diagnostic process of your patient. And the key to using capnography to its fullest potential is recognizing that it provides us with feedback on ventilation, metabolism, and circulation.
How about that!
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