Cardiopulmonary Resuscitation (CPR) is an emergency life-saving technique used when a person’s breathing or heart stops. This intervention involves a rhythmic sequence of chest compressions and rescue breaths designed to artificially maintain circulation and oxygenation until professional medical help arrives. Effective CPR relies on maintaining a precise balance, known as the compression-to-ventilation ratio, between these two actions to maximize the delivery of oxygenated blood to the brain and other vital organs. The established guidelines for this ratio vary depending on the age of the patient and the number of people performing the resuscitation.
Standard Ratios for Adults and Adolescents
For anyone who has reached adolescence or adulthood, a standardized compression-to-ventilation ratio is used for basic life support. The universal standard for this age group is 30 compressions followed by 2 rescue breaths, commonly referred to as a 30:2 ratio. This means the rescuer performs a continuous cycle of thirty chest compressions and then briefly pauses to deliver two breaths, before immediately resuming compressions.
This 30:2 ratio applies in nearly all basic life support scenarios, irrespective of whether a single rescuer or multiple rescuers are present. The rationale behind this high compression focus is that cardiac arrest in adults is typically caused by a primary heart event, such as a sudden electrical malfunction. The blood often retains sufficient oxygen for the first few minutes, making continuous chest compressions the priority to circulate that oxygenated blood.
The two breaths serve to re-oxygenate the blood, but minimizing interruptions to the compressions remains the central focus for survival in adult cardiac emergencies. Adopting this consistent ratio helps ensure a sustained effort to push blood through the circulatory system during the emergency.
Modified Ratios for Children and Infants
The guidelines for pediatric patients, which include infants and children, require modified ratios based on the number of rescuers involved. For a single rescuer treating an infant or child, the ratio remains 30 compressions to 2 breaths. Maintaining the 30:2 ratio for a lone rescuer simplifies the procedure, making it easier to remember and perform during a high-stress situation.
When two or more rescuers are available to perform CPR on a child or infant, the recommended ratio changes significantly to 15 compressions followed by 2 rescue breaths. This 15:2 ratio is designed for team resuscitation, allowing the workload to be shared. The shift to a lower compression number before breathing effectively doubles the frequency of rescue breaths delivered within a given time period compared to the 30:2 ratio.
The clear distinction between the single-rescuer (30:2) and multi-rescuer (15:2) protocols for pediatric patients is a reflection of the different underlying causes of collapse in this age group. This modification ensures that when help is available, the patient receives a higher proportion of breaths, which is often more beneficial for pediatric recovery.
Rationale for Age-Specific Ratio Differences
The primary reason for the altered compression-to-ventilation ratio in pediatric patients lies in the differing causes of cardiac arrest compared to adults. Adult cardiac arrest is most frequently a sudden issue with the heart’s electrical system, meaning the blood is initially oxygenated but not circulating. In contrast, cardiac arrest in children and infants is most often secondary to respiratory failure, resulting from conditions like choking, severe asthma, or drowning.
By the time a child or infant requires CPR, their blood is typically already severely lacking in oxygen. This lack of oxygen, known as hypoxia, necessitates a more frequent delivery of rescue breaths to replenish the body’s oxygen stores. The 15:2 ratio, used with two rescuers, provides this necessary increase in ventilation, offering twice as many breaths compared to the 30:2 ratio over a similar period.
The body of a child or infant is more dependent on immediate and frequent oxygenation to prevent further damage to vital organs. This physiological difference is the scientific basis for the specific pediatric guidelines, aiming to address the underlying respiratory cause of the emergency.
Quality of Delivery: Rate, Depth, and Volume
While the ratio dictates the sequence of compressions and breaths, the effectiveness of CPR also depends heavily on the quality of their delivery. For all age groups—infants, children, and adults—the chest compression rate should be maintained at a consistent speed of 100 to 120 compressions per minute. This rate is designed to mimic the heart’s natural rhythm as closely as possible to provide sufficient blood flow.
The depth of compressions is critical and varies by size. For adults, compressions should be at least 2 inches (5 cm) deep. For children and infants, the depth should be approximately one-third the anterior-posterior diameter of the chest (2 inches/5 cm for children; 1.5 inches/4 cm for infants).
Rescue breaths must be delivered over approximately one second, with only enough volume to cause a visible rise of the patient’s chest. Avoid excessive force or volume, as this can lead to air entering the stomach and cause complications. Allowing the chest to fully recoil after each compression is equally important, as this permits the heart to refill with blood before the next compression pushes it out.