From the Guidelines
End-tidal carbon dioxide (ETCO2) can be a useful indicator in detecting sepsis, though it is not a standalone diagnostic tool. Low ETCO2 levels (typically below 25 mmHg) may suggest sepsis as they reflect metabolic acidosis and poor tissue perfusion that occur during septic shock. This happens because in sepsis, inflammatory mediators cause vasodilation, decreased vascular resistance, and impaired cellular oxygen utilization, leading to lactic acid buildup and reduced carbon dioxide production. ETCO2 monitoring is particularly valuable in emergency and critical care settings as it provides continuous, non-invasive assessment that can detect deterioration before other vital signs change. The gap between arterial CO2 (PaCO2) and ETCO2 also widens during sepsis, with a difference greater than 6 mmHg potentially indicating sepsis 1. However, clinicians should always interpret ETCO2 values alongside other clinical findings, laboratory tests (like lactate levels, white blood cell counts, and blood cultures), and the patient's overall condition, as low ETCO2 can also occur in other conditions such as pulmonary embolism, hypovolemia, or cardiac arrest. Some studies suggest that ETCO2 can be used to predict the outcome of resuscitation efforts, with low ETCO2 levels indicating poor prognosis 1. It is essential to consider the most recent guidelines and recommendations for sepsis management, which emphasize the importance of early recognition and intervention 1. In resource-limited settings, the use of ETCO2 monitoring may be limited, and other clinical signs and symptoms should be used to guide diagnosis and treatment 1. Overall, ETCO2 can be a useful tool in the detection and management of sepsis, but it should be used in conjunction with other clinical and laboratory findings. Key points to consider when using ETCO2 to detect sepsis include:
- Low ETCO2 levels (typically below 25 mmHg) may indicate sepsis
- The gap between PaCO2 and ETCO2 can widen during sepsis
- ETCO2 monitoring should be used alongside other clinical and laboratory findings
- ETCO2 can be used to predict the outcome of resuscitation efforts
- Early recognition and intervention are critical in sepsis management.
From the Research
EtCO2 as an Indicator of Sepsis
- EtCO2 can be used as a tool to predict sepsis and severe sepsis, particularly in prehospital settings 2.
- A study found that low EtCO2 levels were the strongest predictor of sepsis, severe sepsis, and mortality among prehospital variables 2.
- However, another study found that EtCO2 was unlikely to be a useful clinical end point for sepsis resuscitation, although it may be useful as a triage tool in suspected sepsis because baseline values may reflect initial lactate 3.
Relationship between EtCO2 and Sepsis Markers
- There is a correlation between lactate and EtCO2, with a negative correlation found in several studies 2, 4.
- A ROC curve analysis found that an EtCO2 of 25 or less was the best cutoff to predict a high lactate 4.
- EtCO2 predicted the initial ED lactate levels, but did not predict diagnosed infection, admission to the hospital, or ICU admission in one patient population 4.
Clinical Applications of EtCO2 in Sepsis
- EtCO2 can be used as part of a prehospital screening protocol to predict sepsis and severe sepsis 2.
- The use of EtCO2 as a triage tool in suspected sepsis may help expedite initial ED sepsis treatment 4.
- However, the clinical application of EtCO2 in sepsis resuscitation is limited, and its use as a sole indicator of sepsis is not recommended 3, 5, 6.