A rise in end-tidal CO2 above 50 mmHg is typically associated with which condition?

A rise in end-tidal CO2 above 50 mmHg is typically associated with which condition?

• A. Hypoventilation
• B. Hyperventilation
• C. Anaphylaxis
• D. Pulmonary edema

Answer: (D)

End-tidal CO2 reflects how well the lungs are ventilating relative to CO2 production. When ventilation drops while CO2 production stays the same, CO2 accumulates in the alveoli and ETCO2 rises, often to 50 mmHg or higher. This is the classic sign of hypoventilation, such as from respiratory depression, airway obstruction, or a faulty ventilator circuit. Hyperventilation, by contrast, blows off CO2 faster than it’s produced, so ETCO2 drops. Anaphylaxis can cause airway compromise and redistribution of blood flow, but it doesn’t inherently produce a rise in ETCO2 as a typical feature. Pulmonary edema impairs gas exchange, mainly affecting oxygenation; CO2 may not rise unless ventilation becomes inadequate due to fatigue or severe respiratory distress, so it’s not the most direct association with a high ETCO2.

End-tidal CO2 reflects how well the lungs are ventilating relative to CO2 production. When ventilation drops while CO2 production stays the same, CO2 accumulates in the alveoli and ETCO2 rises, often to 50 mmHg or higher. This is the classic sign of hypoventilation, such as from respiratory depression, airway obstruction, or a faulty ventilator circuit.

Hyperventilation, by contrast, blows off CO2 faster than it’s produced, so ETCO2 drops. Anaphylaxis can cause airway compromise and redistribution of blood flow, but it doesn’t inherently produce a rise in ETCO2 as a typical feature. Pulmonary edema impairs gas exchange, mainly affecting oxygenation; CO2 may not rise unless ventilation becomes inadequate due to fatigue or severe respiratory distress, so it’s not the most direct association with a high ETCO2.