Adult Critical Care Specialty (ACCS) Practice Exam

When monitoring end tidal CO2 in an intubated patient, a reading of 4% suggests?

1. Proper ventilation

2. Hypoventilation

3. ET tube misplacement

4. Normal carbon dioxide levels

The correct answer is: ET tube misplacement

A reading of 4% end-tidal CO2 (ETCO2) in an intubated patient typically indicates that there is insufficient carbon dioxide being exhaled, which could suggest problems such as hypoventilation or further complications like misplacement of the endotracheal (ET) tube. When the ETCO2 is at this level, it often reflects inadequate ventilation, where carbon dioxide accumulates or is not being effectively expelled from the lungs. The expected normal range of ETCO2 for a well-ventilated patient is usually between 35-45 mmHg or approximately 5-6% in volume. Since the reading is only 4%, it may imply either a misconnection, a malfunction, or indeed that the tube may be positioned poorly, potentially in the esophagus or another site that does not allow for proper gas exchange. Therefore, this low reading of ETCO2 signals the need for immediate evaluation of the airway and ventilation status. The patient's ventilatory efficacy is compromised, and corrective measures should be taken promptly to ensure that the ET tube is in the correct position and that ventilation is optimized.