ETCO2 measures cardiac output. The better the CPR, the higher the cardiac output. The higher the cardiac output, the higher the ETCO2.
While the American Heart Association recommends you switch compressors every two minutes during a cardiac arrest to prevent compressor fatigue. A fatigued compressor can't maintain consistent CPR. The compressor tires, the cardiac output declines. Time to switch compressors. Or so the AHA suggests.
I would accept this if you have two compressors of equal ability and talent at CPR,. If on the other hand, you have two compressors of different strengths, go with the compressor who can achieve the highest ETCO2. I challenge my partners to do their best CPR and get the ETCO2 up as high as they can. Even if one compressor grows tired, if he is consistently hitting 28, while the fresh compressor can only get to 24, keep the strong one on the chest.
Use the ETCO2 level as your marker not an artificial two minute limit.