Cardiopulmonary Resuscitation (CPR) uses chest compressions and rescue breathing to maintain a limited flow of oxygenated blood to the brain and heart during cardiac arrest. The effectiveness of this time-sensitive procedure relies on adherence to internationally reviewed guidelines. These guidelines, developed by major resuscitation organizations worldwide, are updated periodically based on the latest medical research. This continuous evaluation ensures that the recommended steps maximize a person’s chance of survival.
Establishing the 30:2 Standard
The definitive shift to the current standard of 30 compressions for every 2 ventilations (30:2) was formally introduced with the publication of the 2005 American Heart Association (AHA) Guidelines for CPR and Emergency Cardiovascular Care. This change was based on the findings from the 2005 International Consensus on Science and Treatment Recommendations (CoSTR), a collaborative effort led by the AHA and the International Liaison Committee on Resuscitation (ILCOR).
The 30:2 ratio was standardized for all single rescuers—both laypeople and healthcare providers—performing CPR on adults, children, and infants (excluding newborns). This unification simplified instruction and improved the retention of CPR skills among the general public. Research showed that a simpler, universal sequence was more likely to be performed correctly. By adopting the 30:2 ratio, the guidelines ensured that rescuers would deliver a greater number of uninterrupted chest compressions per minute.
The Preceding Guidelines
Before the 2005 update, the recommended ratios for CPR were more complex and varied depending on the rescuer’s training level and the victim’s age. The most common standard for professional rescuers performing adult CPR was 15 compressions followed by 2 ventilations (15:2 ratio). Lay rescuers often used 15:2 for adults, but different ratios, such as 5:1, were suggested for infants and children. This variation created confusion and made training segmented, potentially leading to errors during an emergency. The previous emphasis on delivering frequent breaths meant rescuers paused chest compressions more often.
This frequent stopping of chest compressions was identified as a major limitation of the 15:2 protocol. The two-breath sequence following only fifteen compressions caused a longer period of “hands-off time” during the resuscitation attempt. The change to 30:2 was designed to reduce the frequency and duration of these interruptions. This higher-compression ratio prioritized continuous blood flow over immediate oxygen delivery.
Prioritizing Circulation Over Ventilation
The scientific rationale for the shift to 30:2 centered on the understanding that continuous blood flow is the primary determinant of survival in sudden cardiac arrest. Studies revealed that CPR effectiveness is directly tied to the amount of time the rescuer spends actively compressing the chest, known as the “compression fraction.” Maximizing this hands-on time by minimizing pauses became the focus of the new guidelines.
Chest compressions create pressure that pushes blood from the heart to the rest of the body, particularly the brain and the heart muscle. The pressure supplying blood to the heart muscle is called the coronary perfusion pressure, which predicts successful resuscitation. When compressions are paused, this critical pressure drops almost immediately to zero.
It takes several compressions to build the coronary perfusion pressure back to an effective level. Frequent interruptions for rescue breaths severely limit the overall quality of CPR. The 30:2 ratio reduces the number of times a rescuer must stop compressions, allowing the pressure to be sustained for longer periods.
Adults suffering sudden cardiac arrest often have residual oxygen in their bloodstream for the first few minutes. Continuous circulation of this existing oxygenated blood is initially more beneficial than pausing to deliver new breaths. This emphasis on continuous compressions reflects the “pump priming” effect, maintaining blood flow until advanced medical care can take over.