Diagnostic value of end tidal capnography in patients with hyperglycemia in the emergency department

BACKGROUND: Diabetic Ketoacidosis (DKA) is a potentially life-threatening emergency that requires prompt diagnosis and treatment. In paediatric populations an end tidal capnography value greater than 36 mmHg was found to be 100 % sensitive in ruling out DKA. METHODS: A cross sectional observational study of adults ≥ 17 years of age presenting to the emergency department between January 2014 and May 2014 with glucose > 550 mg/dL. In all patients, nasal capnography and venous blood gas analysis were performed prior to any insulin or intravenous fluid administration. The diagnosis of DKA was based on the presence of anion gap metabolic acidosis, hyperglycaemia and ketonemia. The overall diagnostic performance (area under the curve [AUC]), sensitivity, specificity and likelihood ratios at different end tidal CO(2) (ETCO(2)) cut-offs were determined. RESULTS: 71 patients were enrolled in the study of which 21 (30 %) met the diagnosis of DKA. The area under the curve for ETCO(2) was 0.95 with a 95 % CI of 0.91 to 0.99. Test sensitivity for DKA at ETCO(2) level ≥35 mmHg was 100 % (95 % CI, 83.9–100). An ETCO(2) level ≤ 21 mmHg was 100 % specific (95 % CI, 92.9–100.0) for DKA. CONCLUSION: Nasal capnography exhibits favourable diagnostic performance in detecting patients with or without DKA among those who present to the emergency department with a glucometer reading > 550 mg/dL.