The Science Behind Chest Compressions

Matthew Sholl, MD MPH, FACEP

Maine Medical Center/MaineHealth

Curr Op Crit Care 2004;10:208-212

Excellent Chest Compressions are the Foundation of Survival!

Recent Changes in ACLS?

• Most recent AHA changes (2005/2010)attempted to highlight the importance of uninterrupted chest compressions and limited the positive pressure ventilation rate to 8 – 12 breaths per minute

Why focus on minimally interrupted chest compressions and limiting positive pressure

ventilation?

What’s The Big Deal?Do Chest Compressions Really Work?

• While in early phases of OHCA (< 5 min), no benefit to bystander CPR existed

• As time to shock increased, see increasing survival benefit of bystander CPR

• No survivors seen if collapse to shock interval > 15 minutes

The Most Important Treatment You Offer…

• … is effective chest compressions• Effective means:

– Right rate (at least 100)– Right depth (2.5 inches or 5 cm)– Relax – allow for recoil– NO interruptions– Avoid excessive ventilations

• Despite our best ALS capabilities, our BLS skills are what appears to be most important

Cardio-cerebral Resuscitation (CCR)

• Based on the Three Phase Model of resuscitation• Generated in AZ –the AZ Sarver Heart Center

Goals:1. Minimize interruptions of chest compression2. Provide immediate post-shock chest

compressions for prolonged VF– Why is that important?

3. Delay or eliminate endotracheal intubation 4. Minimize all positive pressure ventilation 5. Decrease the time interval to IV Epinephrine

Benbrow, B –6th Annual Symposium on Neurologic Emergencies and Neurocritical Care , June 2009, NYC, NY

A New Horizon for OHCA…

• Two new thoughts on OHCA:

1.Primary and Secondary Injury– Primary injury – cardiac arrest– Secondary injury – brain injury

• Even if we can obtain ROSC – still see large numbers of deaths

• These deaths predominantly due to hypoxic brain injury

– Target of therapeutic hypothermia

2.Three Phase Model for Resuscitation…

Three Phase Model of Resuscitation

Minimizing Positive Pressure Ventilation

• Old Paradigm:– ABC’s – M2M/BVM/ETT to deliver high flow O2

• New Concepts:– Positive pressure ventilation increases intrathoracic

pressure– Increased intrathoracic pressure decreases venous return– Resultant decrease in coronary and cerebral blood flow

• SO… AHA has recommended RR of 8 – 12 breaths/minute

The Message may Not Have Been Received….

• Observational study of EMS practitioners performing CPR

• Measured ventilation rate• Average rate = 37 +/- 3 per

minute– Range 15-49– Recall: BLS/ACLS

recommends 8-12• Second part of the study….

Disadvantages to Ventilations During CPR

• Delays/Interrupts chest compressions

• Complicated

• Stops bystanders from doing CPR

• Gastric inflation – aspiration

• Increases intrathoracic pressure– Reducing coronary/cerebral perfusion

• Animal models show worse outocme

What Have We Learned So Far?

• OHCA happens to a lot of people!!– One of the top causes of death

• There remain opportunities to save lives– Especially through engaging laypersons and

both PAD programs as well as by-stander CPR• New ACLS/BLS protocols attempted to improve

well preformed, continuous chest compressions with minimal interruptions

• Despite these recommendations, still see many interruptions and too aggressive ventilation

Questions?

Thank You