ACCS Practice Exam 2026 – Complete Test Preparation Guide

A reading of 4% end tidal CO2 (ETCO2) in an intubated patient suggests normal carbon dioxide levels that indicate proper ventilation. Typically, end tidal CO2 values in a healthy individual during normal ventilation range from approximately 35 to 45 mmHg, which correlates to about 5% to 6% when measured as a percentage.

When an intubated patient shows a 4% reading, it can be interpreted as a sign of potential hypoventilation, or insufficient ventilation that might lead to increasing levels of carbon dioxide in the body. However, a reading that is significantly lower than the normal range can better suggest a problem with ventilation, such as the endotracheal tube being misplaced, possibly in the esophagus instead of the trachea, which would eliminate proper gas exchange and lead to inadequate CO2 elimination.

This indicates that a 4% reading of ETCO2 warrants evaluation of the patient's positioning and ventilation status, emphasizing the importance of continuous monitoring in critical care settings.