What term is used to describe the duration from the onset of cardiac arrest until CPR is initiated?

The correct term to describe the duration from the onset of cardiac arrest until CPR is initiated is "downtime." This term specifically refers to the elapsed time between the event of cardiac arrest and the start of effective medical intervention, such as CPR. Understanding this timeframe is crucial in emergency medical care because the chances of survival decrease significantly with each passing minute without resuscitation efforts. In emergency medical situations, minimizing downtime is vital, as it greatly impacts patient outcomes and survival rates.

Other terms in the question may refer to related concepts, but they do not specifically capture the essence of the duration leading to the initiation of CPR. For instance, "response time" often refers to the time it takes for emergency services to arrive on the scene, and "critical interval" could imply a broader time frame concerning different medical emergencies, rather than just focusing on cardiac arrest. "Rescue period" could suggest the entire duration of rescue efforts, which also doesn't pinpoint the moment between cardiac arrest and the start of CPR. Thus, "downtime" is the most precise term for this critical time interval.