Which statement about ETCO2 levels is true?

Which statement about ETCO2 levels is true?

• A. ETCO2 is not related to ventilation
• B. Normal ETCO2 is 35-45 mmHg
• C. High ETCO2 indicates hypoventilation
• D. Low ETCO2 indicates hyperventilation

Answer: (C)

End-tidal CO2 shows how effectively CO2 is being eliminated by ventilation. When ventilation is reduced (hypoventilation), CO2 builds up in the lungs and blood, so the amount of CO2 exhaled at the end of a breath rises. That makes a high ETCO2 a direct indicator that ventilation is insufficient. In healthy adults, ETCO2 is typically about 35–45 mmHg, with values generally a bit lower than arterial CO2 due to the slight ventilation–perfusion gradient. In practice, ETCO2 helps us gauge ventilation during airway management and ongoing breathing support; rising ETCO2 suggests hypoventilation, while falling ETCO2 would suggest over-ventilation or other factors lowering CO2 delivery to the lungs. So the statement that high ETCO2 indicates hypoventilation is the best takeaway, because it directly links reduced air exchange to a measurable rise in end-tidal CO2.

End-tidal CO2 shows how effectively CO2 is being eliminated by ventilation. When ventilation is reduced (hypoventilation), CO2 builds up in the lungs and blood, so the amount of CO2 exhaled at the end of a breath rises. That makes a high ETCO2 a direct indicator that ventilation is insufficient.

In healthy adults, ETCO2 is typically about 35–45 mmHg, with values generally a bit lower than arterial CO2 due to the slight ventilation–perfusion gradient. In practice, ETCO2 helps us gauge ventilation during airway management and ongoing breathing support; rising ETCO2 suggests hypoventilation, while falling ETCO2 would suggest over-ventilation or other factors lowering CO2 delivery to the lungs.

So the statement that high ETCO2 indicates hypoventilation is the best takeaway, because it directly links reduced air exchange to a measurable rise in end-tidal CO2.