Early identification of diabetic ketoacidosis (DKA) may improve clinical outcomes. Prior studies suggest exhaled end tidal carbon dioxide (ETCO2) provides a non-invasive, real-time method to screen for DKA in the emergency department (ED).

This a retrospective cohort study among patients who activated Emergency Medical Services (EMS) during a one-year period. Initial out-of-hospital vital signs documented by EMS personnel, including ETCO2 and first recorded blood glucose level (BGL), as well as in-hospital records, including laboratory values and diagnosis, were collected. The main outcome was the association between ETCO2 and the diagnosis of DKA.

Of the 118 patients transported with hyperglycemia (defined by BGL >200), six (5%) were diagnosed with DKA. The mean level of ETCO2 in those without DKA was 35mmHg (95% CI, 33-38mmHg) compared to mean levels of 15mmHg (95% CI, 8-21mmHg) in those with DKA (P <.001). The Area Under the Receiver Operating Characteristics (ROC) Curve (AUC) for ETCO2 identifying DKA was 0.96 (95% CI, 0.92-1.00). The correlation coefficient between ETCO2 and serum bicarbonate (HCO3) was 0.436 (P <.001) and the correlation coefficient between ETCO2 and anion gap was -0.397 (P <.001).

Among patients with hyperglycemia, prehospital levels of ETCO2 were significantly lower in patients with DKA compared to those without and were predictive of the diagnosis of DKA. Furthermore, out-of-hospital ETCO2 was significantly correlated with measures of metabolic acidosis.