Triage
Simply measuring an initial EtCO2 as a triage vital sign may have added benefit to the EP, and consideration could be made for making this a policy in your ED. One study demonstrated that abnormal initial EtCO2 (outside of 35-45 mm Hg) was predictive of admisison (RR 2.5, 95% CI 1.5-4.0).67 An abnormal EtCO2 (outside of 31-41 mm Hg for this study) was 93% sensitive (95% CI 79-98%), with expectedly low specificity of 44% (95% CI 41-48%) for mortality prior to discharge.47 This potential vital sign may be treated similarly to tachycardia; while an abnormal heart rate should increase a clinician’s concern for a pathological condition, it needs to be taken in context of the situation to accurately interpret it.
Summary
Capnography has numerous uses in the ED in both intubated and spontaneously breathing patients. Quantitative capnography is the standard of care for confirming endotracheal intubation. It is recommended as an aide in maximizing chest compressions during cardiac arrest and can assist in prognostication. It rapidly identifies hypoventilation during procedural sedation. It also has many more potential applications that continue to be explored in areas such as respiratory distress, sepsis, trauma, DKA, and PE. Ultimately, capnography should always be used in association with the remainder of the clinical assessment.