From the Guidelines
A sudden and sustained rise in end-tidal CO₂ during CPR is a reliable indicator of return of spontaneous circulation (ROSC), even in the absence of ECG evidence, as it reflects restored pulmonary blood flow and cardiac output. This is supported by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care, which state that an abrupt sustained increase in PETCO2 during CPR is an indicator of ROSC 1. When effective circulation resumes, more CO₂ from cellular metabolism is transported to the lungs, causing end-tidal CO₂ levels to increase rapidly from typical CPR values to normal ranges.
Key Points to Consider
- The correlation between PETCO2 and cardiac output during CPR makes end-tidal CO₂ monitoring a valuable tool for assessing the effectiveness of resuscitation efforts 1.
- A transient rise in PETCO2 after sodium bicarbonate therapy should not be misinterpreted as an improvement in quality of CPR or a sign of ROSC, as it is expected due to the conversion of bicarbonate to water and CO₂ 1.
- Vasopressor therapy can alter the correlation of PETCO2 with cardiac output, and a small decrease in PETCO2 after vasopressor therapy should not be misinterpreted as a decrease in CPR quality 1.
- Monitoring PETCO2 trends during CPR has the potential to guide individual optimization of compression depth and rate and to detect fatigue in the provider performing compressions 1.
Clinical Implications
- If a sudden and sustained rise in end-tidal CO₂ is observed during CPR, the resuscitation team should immediately check for pulses and blood pressure while continuing ventilation.
- If ROSC is confirmed, post-cardiac arrest care should begin, including optimizing oxygenation, maintaining normocapnia, securing the airway if not already done, and initiating hemodynamic support as needed.
- Continuous end-tidal CO₂ monitoring should be maintained throughout resuscitation efforts, as it provides feedback on CPR quality and can indicate when exhaustion is occurring if values begin to decline.
From the Research
Indicators of Return of Spontaneous Circulation (ROSC)
- A sudden and sustained rise in end-tidal CO₂ during CPR can indicate return of spontaneous circulation (ROSC), even in the absence of ECG evidence 2, 3, 4, 5
- Studies have shown that end-tidal CO₂ (ETCO₂) values are significantly higher in patients who achieve ROSC compared to those who do not 2, 3, 4
- The mean ETCO₂ value in participants with ROSC was found to be 25.8 ± 9.8 mm Hg, compared to 13.1 ± 8.2 mm Hg in those without ROSC 3
Predictive Value of End-Tidal CO₂
- End-tidal CO₂ has been shown to be a reasonable predictor of ROSC in cardiac arrest patients, with a sudden increase in ETCO₂ exceeding 10 mm Hg indicating the possibility of ROSC 4
- The change in ETCO₂ (delta ETCO₂) during resuscitation has been found to be predictive of future ROSC in patients with pulseless electrical activity (PEA) arrests 5
- A positive linear relationship between delta ETCO₂ and ROSC has been observed, with values of delta ETCO₂ > 20 mm Hg being highly specific for ROSC in PEA patients 5
Comparison with Other Predictors
- Cerebral oximetry (CerOx) has been found to be superior to ETCO₂ in predicting ROSC, with a higher area under the curve (AUC) for CerOx compared to ETCO₂ 6
- However, both ETCO₂ and CerOx have been shown to be good predictors of ROSC, with ETCO₂ being a simpler and more non-invasive method of measurement 6