CIEMT Emergency Medical Technician (EMT) Practice Exam 2026 - Free EMT Practice Questions and Study Guide

The respiratory center in the brainstem is responsible. Central chemoreceptors in the medulla monitor changes in hydrogen ion concentration that result from CO2 crossing into the CSF. When CO2 levels rise, the pH of the CSF drops, signaling the respiratory center to increase the rate and depth of breathing to blow off CO2 and restore pH. This ties the detection of CO2 directly to the brainstem’s control of ventilation. The other centers—cardiac, vasomotor, and reticular activating—do not monitor CO2 or regulate breathing, so they aren’t the ones detecting CO2 levels.