End-Tidal CO₂ Monitoring in Critical Illness: Applications in Resuscitation, Shock, and Ventilation

BackgroundContinuous end tidal carbon dioxide (ETCO₂) monitoring provides a noninvasive, real-time assessment of ventilation, pulmonary perfusion, and indirectly cardiac output. Although historically limited to anesthetic practice, capnography has emerged as an increasingly valuable physiologic monitoring tool in critical care settings.MethodsA review was conducted using MEDLINE/PubMed and the Cochrane Library from 1988 to 2025 to evaluate the clinical applications of ETCO₂ monitoring in critically ill patients. Eighteen studies met predefined inclusion criteria after screening and were included. Data were narratively synthesized.ResultsETCO₂ monitoring reliably reflects cardiopulmonary resuscitation quality and return of spontaneous circulation. In shock states, low ETCO₂ correlates with elevated lactate, transfusion requirements, and mortality, serving as a rapid bedside marker of systemic hypoperfusion. Dynamic changes in ETCO₂ during passive leg raising may predict fluid responsiveness in septic and cardiogenic shock. In ventilated or sedated patients, capnography enables earlier detection of hypoventilation and airway compromise.ConclusionsETCO₂ monitoring is a physiologically informative, underutilized tool in critical care. When integrated in clinical context, capnography may enhance resuscitation quality, guide hemodynamic management, and improve ventilatory safety. Further prospective studies are needed to establish standardized ETCO₂-guided resuscitation protocols.