How can you increase chest compression fraction during a code?
Charge the defibrillator before the rhythm check, about 15 seconds ahead, so compressions continue right up to the moment of analysis and can resume instantly. This minimizes hands-off pauses, keeping chest compression fraction (CCF) high, ideally above 60-80%.
The answer
The most effective way to increase chest compression fraction (CCF) during a code is to charge the defibrillator before the rhythm check (roughly 15 seconds ahead) so that compressions continue until the very last moment and resume immediately after any shock. CCF is the percentage of the total resuscitation time that compressions are actually being delivered. Every pause, for rhythm analysis, charging, shocking, pulse checks, or rescuer changes, is "hands-off" time that lowers CCF and reduces the blood flow reaching the brain and heart.
By pre-charging the defibrillator while compressions are ongoing, you shrink the biggest recurring pause in the cycle. When it is time to analyze the rhythm, the device is already charged; you clear the patient for a two-second check, deliver the shock (or not), and get hands back on the chest immediately. This can trim the peri-shock pause from many seconds down to under five.
Why minimizing interruptions matters
During cardiac arrest, chest compressions are the only thing generating blood flow. It takes several compressions after any pause just to rebuild the pressure that perfuses the coronary and cerebral arteries, so every interruption forces you to start that build-up over again. Research behind the ACLS guidelines links higher CCF to better survival and neurological outcomes. The target is a CCF of at least 60%, and high-performing teams aim for 80% or more.
Other ways to keep CCF high
Pre-charging is the headline technique, but a coordinated team stacks several habits:
- Continue compressions during charging. Never stop compressions just to charge, charge with hands on the chest.
- Limit pauses to under 10 seconds for any rhythm or pulse check; aim for even less.
- Switch compressors every 2 minutes (or every 5 cycles) to prevent fatigue-related shallow compressions, and do the swap during the rhythm check so it costs no extra hands-off time.
- Anticipate and pre-position. The next compressor is ready at the opposite side of the chest before the switch is called.
- Have the team leader call out CCF and coach in real time, using a metronome and feedback device.
- Minimize pulse checks, only during rhythm analysis, and keep ventilation from interrupting compressions once an advanced airway is in place (compress continuously, ventilate asynchronously).
High-quality CPR metrics to protect
While driving CCF up, do not sacrifice the other pillars of high-quality CPR: a rate of 100-120/min, a depth of at least 2 inches (5 cm) in adults, full chest recoil between compressions, and avoiding excessive ventilation. Charging early, swapping smoothly, and keeping every pause short together keep hands on the chest, which is what CCF ultimately measures and what saves lives.
- 1
Continue compressions
Keep delivering high-quality compressions at 100-120/min without interruption while the cycle runs.
- 2
Pre-charge the defibrillator
About 15 seconds before the 2-minute rhythm check, charge the defibrillator with hands still on the chest.
- 3
Brief rhythm check
Pause compressions only for a 2-second clear-and-analyze; the device is already charged.
- 4
Shock and resume instantly
Deliver the shock if indicated and immediately restart compressions, keeping the peri-shock pause under 5 seconds.
- 5
Swap compressors on the check
Rotate compressors every 2 minutes during the rhythm check so the switch adds no extra hands-off time.
Frequently asked
What is a good chest compression fraction?
Aim for a chest compression fraction of at least 60%, meaning compressions are delivered at least 60% of the resuscitation time. High-performing resuscitation teams target 80% or higher, since more hands-on time correlates with better survival.
Why is minimizing interruptions important in CPR?
Compressions are the only thing pumping blood during arrest, and it takes several compressions after each pause to rebuild the pressure that perfuses the heart and brain. Frequent or long pauses drop that perfusion and worsen outcomes.
How often should compressors switch during a code?
Switch compressors roughly every 2 minutes, or every 5 cycles, to prevent fatigue that makes compressions shallow. Perform the swap during the rhythm check so it does not add extra hands-off time.
What does charging the defibrillator early accomplish?
Charging about 15 seconds before the rhythm check lets compressions continue until the last moment and resume immediately after the shock. This shortens the peri-shock pause, often to under 5 seconds, keeping the chest compression fraction high.
What is the target CCF in ACLS?
ACLS guidance sets a minimum chest compression fraction of 60%, with a goal of 80% or more for optimal outcomes. It is one of several high-quality CPR metrics alongside adequate rate, depth, and full recoil.