End-tidal capnography has gained momentum over the years as a standard for monitoring patients undergoing procedural sedation in the emergency department, with a level B recommendation coming out of ACEP’s clinical policy regarding procedural sedation in 2014.1 It can identify hypoventilation earlier than other monitoring tools we have at our disposal in the emergency department, but its utility doesn’t end there. It can quickly and efficiently answer clinical questions beyond that of sufficient ventilation. Are the chest compressions being performed on your cardiac arrest inadequate? Should you stop resuscitation efforts? Is your hyperglycemic diabetic in diabetic ketoacidosis (DKA)? Is that nasogastric tube in the stomach? End-tidal capnography can lend insight to these questions that emergency physicians encounter on a daily basis. End-tidal carbon dioxide (EtCO2) sensibly correlates with the pathophysiology of those and many other disease processes and can help guide decision making on your next shift.
Capnography offers an indirect method to detect metabolic acidosis. EtCO2 measurements have been shown to closely estimate arterial partial pressure of carbon dioxide (pCO2) in healthy patients and also in the presence of metabolic derangements such as acidosis.