Can ETCO2 Help Detect Sepsis? Before you wait on a lactate, or start fluid boluses based on a gut feeling, there’s a tool right under your nose that can help you detect sepsis earlier and more accurately, your ETCO2 monitor. The Physiology of ETCO2 in Sepsis ETCO2 reflects cardiac output, ventilation, and metabolism. In sepsis, especially as shock begins to develop, perfusion drops. Less blood reaches the lungs, less CO₂ gets delivered to the alveoli, ETCO2 falls, even though the patient is brea