Final answer:
The ETCO2 concentration reflects changes in cardiac output during invasive CPR when oxygen consumption, arterial oxygen saturation, and hemoglobin are constant. This measure is useful for monitoring the effectiveness of chest compressions in real-time without interrupting the process, as high-quality compressions should maintain or increase ETCO2 levels.
Step-by-step explanation:
The invasive CPR performance measure that reflects changes in cardiac output due to chest compressions when oxygen consumption, arterial oxygen saturation, and hemoglobin remain constant is the end-tidal carbon dioxide (ETCO2) concentration. The ETCO2 measurement is an indirect method of assessing cardiac output during CPR because it is influenced by the pulmonary blood flow, which in turn is determined by the effectiveness of chest compressions in generating cardiac output.
As performing CPR, compressions on the chest are meant to manually pump blood when the heart fails to do so. If myocardial function is absent, the only blood flow is generated by the chest compressions. Therefore, monitoring ETCO2 values can provide feedback on the quality of the CPR being administered, as adequate compressions should lead to the maintenance or increase in the ETCO2 readings, indicating that blood is indeed being circulated. Since this measurement is taken from the patient's exhaled breath, it is non-invasive and can be continuously monitored without interrupting chest compressions.
CPR effectiveness is paramount and is the focus of current resuscitation guidelines which emphasize the importance of high-quality chest compressions. Hence, ETCO2 is a valuable measurement because it helps in the real-time assessment of resuscitation efforts without impeding the ongoing emergency procedures. Consistent monitoring of ETCO2 can inform rescuers whether the chest compressions are adequate enough to sustain minimum circulation, specifically to vital organs such as the brain and heart.