Which ETCO2 finding is most commonly associated with diabetic ketoacidosis in a glycemic emergency?

• A. ETCO2 around 60
• B. ETCO2 around 40
• C. ETCO2 less than 20
• D. ETCO2 equal to 30

Answer: (C)

In diabetic ketoacidosis, the body develops metabolic acidosis from ketone buildup, and the respiratory system responds by increasing ventilation to blow off carbon dioxide (Kussmaul breathing). This compensatory hyperventilation lowers the CO2 level at the end of exhalation, so the end-tidal CO2 reading drops well below normal. The most typical finding is an ETCO2 value well under 20 mmHg. Normal ETCO2 around 35–40, or a value around 30, would not reflect this strong compensatory response, and a value around 60 would indicate excessive CO2 retention rather than the expected hyperventilation seen in DKA. ETCO2 helps gauge ventilation and the degree of metabolic acidosis in this emergency.